DE102022133262A1 - flight profile - Google Patents

Abstract

A method (2050) of operating an aircraft, the aircraft having a gas turbine engine and a fuel tank arranged to supply fuel to the gas turbine engine, comprising the steps of: determining (2052) at least one fuel attribute of the fuel supplied to the gas turbine engine becomes; and proposing or initiating a change (2054) to a flight profile of the aircraft based on the at least one fuel attribute. For example, the intended flight path and/or flight altitude of the aircraft may be changed based on the one or more fuel characteristics.

Description

The present disclosure relates to aircraft propulsion systems and to methods for operating aircraft, which include the management of fuels of different types, including the detection of fuel properties and measures to improve aircraft performance based on the data obtained, as well as methods for modifying aircraft, to enable such procedures to be carried out.

The aviation industry is expected to trend towards using fuels other than the conventional kerosene-based jet fuels now in general use. These fuels may have other fuel characteristics, e.g. B. a lower aromatic content or a lower sulfur content compared to petroleum based hydrocarbon fuels.

Therefore, in view of the greater possibility of variation, the fuel properties must be taken into account and the control and management of aircraft propulsion systems and fuel supply must be adapted to these new fuels.

• Ermittlung einer oder mehrerer Kraftstoffmerkmale des bereits im Kraftstofftank vorhandenen Kraftstoffs vor dem Betanken;
• Bestimmung einer oder mehrerer Kraftstoffmerkmale eines Kraftstoffs, der dem Kraftstofftank beim Tanken zugeführt wird; und
• Berechnung einer oder mehrerer Kraftstoffmerkmale des resultierenden, nach dem Tanken im Kraftstofftank befindlichen Kraftstoffs.

According to a first aspect, there is provided a method for identifying a fuel contained in a fuel tank of an aircraft and arranged to power a gas turbine engine of the aircraft. The method is performed by aircraft processing circuitry and includes:

• determining one or more fuel characteristics of the fuel already in the fuel tank prior to refueling;
• determining one or more fuel characteristics of a fuel supplied to the fuel tank during refueling; and
• Calculation of one or more fuel characteristics of the resulting fuel in the fuel tank after refueling.

This approach can be referred to as an active infinite summation approach, since measures are taken to create and continuously update a record of fuel onboard an aircraft. The method may be performed for any one of a plurality of aircraft fuel tanks or for all fuel on board the aircraft, regardless of which tank it is in.

The determination of one or more fuel characteristics of a fuel that is already in the fuel tank before refueling can consist in retrieving these characteristics from a computer memory, acquiring them directly or determining them from other acquired parameters.

The step of determining one or more fuel characteristics of a fuel already in the fuel tank prior to refueling may include determining one or more compositional properties of the fuel already in the fuel tank.

The step of determining one or more fuel characteristics of a fuel already present in the fuel tank prior to refueling may comprise the result of a previous determination made using the method of identifying a fuel described above for this first aspect.

The step of determining one or more fuel characteristics of a fuel already in the fuel tank prior to refueling may include maintaining current fuel characteristics data by updating the fuel characteristics of the fuel in the tank after each refueling of the aircraft.

The step of determining one or more fuel characteristics of the fuel added to the fuel tank at refueling may include reading a bar code associated with the provided fuel.

1. i. den prozentualen Anteil an nachhaltigem Flugbenzin im Kraftstoff;
2. ii. den Gehalt an aromatischen Kohlenwasserstoffen im Kraftstoff;
3. iii. den Gehalt an multiaromatischen Kohlenwasserstoffen im Kraftstoff;
4. iv. der prozentuale Anteil der stickstoffhaltigen Spezies im Kraftstoff;
5. v. das Vorhandensein oder der prozentuale Anteil einer Tracer-Spezies oder eines Spurenelements im Kraftstoff (z. B. eine im Kraftstoff inhärent vorhandene Spurensubstanz, die von Kraftstoff zu Kraftstoff variieren und so zur Identifizierung eines Kraftstoffs verwendet werden kann, und/oder eine absichtlich zugesetzte Substanz, die als Tracer wirkt);
6. vi. das Wasserstoff-Kohlenstoff-Verhältnis (H/C) des Kraftstoffs;
7. vii. die Kohlenwasserstoffverteilung des Kraftstoffs;
8. viii. das Niveau der Emissionen nichtflüchtiger Partikel (nvPM) bei der Verbrennung (z. B. bei der Verbrennung für eine bestimmte Brennkammerkonstruktion unter bestimmten Betriebsbedingungen);
9. ix. Naphthalin-Gehalt des Kraftstoffs;
10. x. Schwefelgehalt des Kraftstoffs;
11. xi. Cycloparaffingehalt des Kraftstoffs;
12. xii. Sauerstoffgehalt des Kraftstoffs;
13. xiii. thermische Stabilität des Kraftstoffs (z. B. thermische Durchbruchstemperatur);
14. xiv. Grad der Verkokung des Kraftstoffs;
15. xv. die Angabe, dass es sich bei dem Kraftstoff um einen fossilen Kraftstoff handelt, z. B. fossiles Kerosin; und
16. xvi. eine oder mehrere Eigenschaften wie Dichte, Viskosität, Heizwert und/oder Wärmekapazität.

The fuel characteristics may be or may include parameters of the fuel's hydrocarbon distribution. The fuel characteristics may be or include:

1. i. the percentage of sustainable aviation fuel in the fuel;
2. ii. the content of aromatic hydrocarbons in the fuel;
3. iii. the content of multiaromatic hydrocarbons in the fuel;
4. IV. the percentage of nitrogenous species in the fuel;
5. v. the presence or percentage of a tracer species or trace element in the fuel (e.g. a trace substance inherent in the fuel that varies from fuel to fuel and can thus be used to identify a fuel, and/or an intentionally added substance , which acts as a tracer);
6. vi. the hydrogen to carbon ratio (H/C) of the fuel;
7. vii. the hydrocarbon distribution of the fuel;
8. viii. the level of non-volatile particulate matter (nvPM) emissions during combustion (e.g. during combustion for a given combustor design under given operating conditions);
9. ix. naphthalene content of the fuel;
10. x. fuel sulfur content;
11. xi. cycloparaffin content of the fuel;
12. xiii. fuel oxygen content;
13. xiii. thermal stability of the fuel (e.g. thermal breakdown temperature);
14. xiv. degree of fuel coking;
15. xv. the indication that the fuel is a fossil fuel, e.g. B. fossil kerosene; and
16. xv. one or more properties such as density, viscosity, calorific value and/or heat capacity.

The method may further include chemically or physically sensing one or more parameters of the resulting fuel in the fuel tank after refueling and verifying one or more of the calculated fuel characteristics based on the one or more sensed parameters. The sensed parameters may be fuel characteristics, or they may be used to calculate or derive fuel characteristics - for example, the sensed parameters may be shaft speed and fuel mass flow rate, from which the heating value (a fuel characteristic) may be determined, or the sensed parameters may be fuel density and/or the presence of a tracer, both of which are fuel characteristics.

Determining the one or more fuel characteristics of a fuel already present in the fuel tank prior to refueling may include determining stored fuel characteristics. The method may further include chemically or physically sensing one or more parameters of a fuel already in the fuel tank prior to refueling and validating the input to the calculating step based on the one or more sensed parameters.

The method may further include chemically and/or physically determining one or more parameters of the fuel in the fuel tank and using the determined values to substitute the stored fuel characteristics for the fuel in the fuel tank.

The chemical and/or physical determination of one or more parameters of the fuel in the fuel tank can take place by taking a sample of the fuel from the fuel tank for off-wing testing.

1. i. einen Schwellenwert für die Zeit, die seit einer früheren chemischen und/oder physikalischen Bestimmung des einen oder der mehreren Parameter des Kraftstoffs im Kraftstofftank verstrichen ist;
2. ii. eine Schwellenzahl von Betankungsvorgängen und/oder Flügen, die seit einer vorherigen Bestimmung des einen oder der mehreren Parameter des Kraftstoffs im Kraftstofftank erreicht wurde; und/oder
3. iii. eine Diskrepanz zwischen einem oder mehreren der berechneten Merkmale und einem erkannten Parameter, die einen Schwellenwert überschreitet.

The chemical and/or physical determination of one or more parameters of the fuel in the fuel tank and the use of the determined values to replace the stored fuel characteristics for the fuel in the fuel tank may be performed in response to a trigger event, such as:

1. i. a threshold for the time elapsed since a previous chemical and/or physical determination of the one or more parameters of the fuel in the fuel tank;
2. ii. a threshold number of fuelings and/or flights achieved since a previous determination of the one or more parameters of the fuel in the fuel tank; and or
3. iii. a discrepancy between one or more of the calculated features and a detected parameter that exceeds a threshold.

The method may further include controlling the power system based on the calculated one or more fuel characteristics of the resulting fuel in the fuel tank after refueling, for example as described below in relation to the fourth and fifth aspects.

The method may further comprise proposing or initiating a change in the flight profile based on the one or more fuel characteristics of the fuel in the fuel tank after refueling, for example as described below in relation to the sixth and seventh aspects.

• Ermittlung einer oder mehrerer Kraftstoffmerkmale des bereits im Kraftstofftank vorhandenen Kraftstoffs vor dem Betanken;
• Bestimmung einer oder mehrerer Kraftstoffmerkmale eines Kraftstoffs, der dem Kraftstofftank beim Tanken zugeführt wird;
• Berechnung einer oder mehrerer Kraftstoffmerkmale des resultierenden Kraftstoffs im Kraftstofftank nach der Betankung; und
• Steuerung des Antriebssystems auf der Grundlage der berechneten einen oder mehreren Kraftstoffmerkmale des resultierenden Kraftstoffs im Kraftstofftank nach der Betankung.

According to a second aspect there is provided a method of controlling a propulsion system of an aircraft, the propulsion system comprising a gas turbine engine and a fuel tank arranged to supply fuel to the gas turbine engine, the method comprising:

• determining one or more fuel characteristics of the fuel already in the fuel tank prior to refueling;
• determining one or more fuel characteristics of a fuel supplied to the fuel tank during refueling;
• calculating one or more fuel characteristics of the resulting fuel in the fuel tank after refueling; and
• Controlling the propulsion system based on the calculated one or more fuel characteristics of the resulting fuel in the fuel tank after refueling.

• (i) Erfassen eines oder mehrerer Merkmale der Zusammensetzung des bereits im Kraftstofftank vorhandenen Kraftstoffs; oder
• (ii) Erhalten des Ergebnisses einer früheren Bestimmung, die mit dem Verfahren des ersten Aspekts durchgeführt wurde.

Determining one or more fuel characteristics of a fuel already in the fuel tank prior to refueling may include:

• (i) detecting one or more characteristics of the composition of the fuel already present in the fuel tank; or
• (ii) Obtaining the result of a previous determination made with the method of the first aspect.

• ein Gasturbinentriebwerk, wobei das Gasturbinentriebwerk optional umfasst:
  • einen Triebwerkskern mit einer Turbine, einem Verdichter und einer Kernwelle, die die Turbine mit dem Verdichter verbindet; und
  • einen Fan, der stromaufwärts des Triebwerkskerns angeordnet ist, wobei der Fan eine Vielzahl von Fanschaufeln umfasst und so angeordnet ist, dass er durch einen Abtrieb von der Kernwelle angetrieben wird;
• einen Kraftstofftank, der so angeordnet ist, dass er einen Kraftstoff zum Antrieb der Gasturbine enthält; und
• einen Kraftstoffzusammensetzungs-Tracker, der dazu vorgesehen ist:
  • aktuelle Kraftstoffmerkmale zu speichern, wobei die Kraftstoffmerkmale eine oder mehrere Kraftstoffmerkmale des im Kraftstofftank vorhandenen Kraftstoffs umfassen;
  • eine oder mehrere Kraftstoffmerkmale eines beim Tanken in den Kraftstofftank eingefüllten Kraftstoffs zu erhalten; und
  • aktualisierte Werte für das eine oder die mehreren Kraftstoffmerkmale des Kraftstoffs im Kraftstofftank nach dem Betanken zu berechnen.

According to a third aspect, there is provided a propulsion system for an aircraft, comprising:

• a gas turbine engine, the gas turbine engine optionally comprising:
  • an engine core having a turbine, a compressor, and a core shaft connecting the turbine to the compressor; and
  • a fan positioned upstream of the engine core, the fan including a plurality of fan blades and arranged to be driven by an output from the core shaft;
• a fuel tank arranged to contain fuel for driving the gas turbine; and
• a fuel composition tracker designed to:
  • store current fuel characteristics, the fuel characteristics including one or more fuel characteristics of the fuel present in the fuel tank;
  • obtain one or more fuel characteristics of a fuel filled into the fuel tank during refueling; and
  • calculate updated values for the one or more fuel characteristics of the fuel in the fuel tank after refueling.

The updated values can then replace the stored values and be used in future iterations of the steps performed by the fuel composition tracker.

The fuel characteristics may be fuel composition data including one or more fuel hydrocarbon distribution parameters.

According to a further aspect there is provided a non-transitory computer readable medium storing instructions which when executed by a processor cause the processor to perform the method of the first and/or second aspect. The processor may be or be part of an aircraft electronic engine control unit.

• Bestimmen einer oder mehrerer Kraftstoffcharakteristiken des Kraftstoffs, der dem Gasturbinentriebwerk zugeführt werden soll; und
• Vorschlagen oder Einleiten einer Änderung des Flugprofils des Luftfahrzeugs auf der Grundlage der einen oder mehreren Kraftstoffmerkmale.

According to a fourth aspect there is provided a method of operating an aircraft comprising a gas turbine engine and a fuel tank arranged to supply fuel to the gas turbine engine, the method comprising:

• determining one or more fuel characteristics of the fuel to be delivered to the gas turbine engine; and
• Proposing or initiating a change in the flight profile of the aircraft based on the one or more fuel characteristics.

The implementation of this aspect may therefore allow environmental benefits (e.g. reduced or tailored contrail formation) and/or operational benefits (e.g. improved fuel burn) to be achieved based on knowledge of the fuel burned.

In some examples, the method may include automatically initiating the modification of the flight profile based on the determined characteristics. In some examples, the method may include notifying a pilot of the proposed flight profile change based on the determined characteristics and providing the pilot with an opportunity to confirm or reject the change. In some implementations, either example may be performed depending on the nature of the change.

The one or more fuel attributes of the fuel may include at least one of the fuel attributes listed above.

• (i) eine Änderung der vorgesehenen Flughöhe; und
• (ii) eine Änderung der geplanten Route.

Flight profile modification based on fuel characteristics may include at least one of the following:

• (i) a change in intended flight altitude; and
• (ii) a change in planned route.

• Ermittlung einer oder mehrerer Kraftstoffmerkmale des bereits im Kraftstofftank vorhandenen Kraftstoffs vor dem Betanken;
• Bestimmung einer oder mehrerer Kraftstoffmerkmale eines Kraftstoffs, der dem Kraftstofftank beim Tanken zugeführt wird; und
• Berechnung einer oder mehrerer Kraftstoffmerkmale des nach dem Tanken im Kraftstofftank befindlichen Kraftstoffs.

Determining one or more fuel characteristics of the fuel may include performing the method of the first aspect, in particular by:

• determining one or more fuel characteristics of the fuel already in the fuel tank prior to refueling;
• determining one or more fuel characteristics of a fuel supplied to the fuel tank during refueling; and
• Calculation of one or more fuel characteristics of the fuel in the fuel tank after refuelling.

The method may further include receiving weather forecasts for a planned route of the aircraft. The received forecast weather conditions can be used to influence the changes in planned route and/or altitude.

The determination of the one or more fuel characteristics may be based on the detection of one or more fuel properties. The detection can take place on the wing.

The determination of the one or more fuel characteristics may be based on received fuel composition data, e.g. B. based on data electronically transmitted to the aircraft by a third party or entered via a user interface on board the aircraft. Fuel composition data may be made available to the aircraft during refueling.

The one or more fuel characteristics may be determined for fuel in one or more fuel tanks of the aircraft.

One or more of the fuel characteristics, e.g. B. the heating value, can be derived from the performance of the gas turbine engine during the warm-up phase of the engine, taxi, take-off and climb of the aircraft. The planned in-cruise flight profile may be modified or updated based on the one or more derived fuel characteristics.

• ein Gasturbinentriebwerk, wobei das Gasturbinentriebwerk optional umfasst:
  • einen Triebwerkskern mit einer Turbine, einem Verdichter und einer Kernwelle, die die Turbine mit dem Verdichter verbindet; und
  • einen Fan, der stromaufwärts des Triebwerkskerns angeordnet ist, wobei der Fan eine Vielzahl von Fanschaufeln umfasst und so angeordnet ist, dass er durch einen Abtrieb von der Kernwelle angetrieben wird;
• einen Kraftstofftank, der so angeordnet ist, dass er einen Kraftstoff zum Antrieb der Gasturbine enthält; und
• ein Modul zur Bestimmung der Kraftstoffzusammensetzung, das dazu dient:
  • eine oder mehrere Kraftstoffcharakteristiken des dem Gasturbinentriebwerk zuzuführenden Kraftstoffs zu bestimmen; und
• eine Flugprofil-Einstellvorrichtung, die dazu dient:
  • eine Änderung des Flugprofils des Luftfahrzeugs auf der Grundlage der einen oder mehreren Kraftstoffmerkmale des Kraftstoffs vorzuschlagen oder einzuleiten.

According to a fifth aspect, there is provided a propulsion system for an aircraft, comprising:

• a gas turbine engine, the gas turbine engine optionally comprising:
  • an engine core having a turbine, a compressor, and a core shaft connecting the turbine to the compressor; and
  • a fan positioned upstream of the engine core, the fan including a plurality of fan blades and arranged to be driven by an output from the core shaft;
• a fuel tank arranged to contain fuel for driving the gas turbine; and
• a fuel composition determination module that is used to:
  • determine one or more fuel characteristics of fuel to be delivered to the gas turbine engine; and
• a flight profile setting device designed to:
  • propose or initiate a change in the flight profile of the aircraft based on the one or more fuel characteristics of the fuel.

• (i) eine Änderung der vorgesehenen Flughöhe; und
• (ii) eine Änderung der geplanten Route.

The flight profile setting device may be arranged to initiate or suggest at least one of the following actions based on the fuel characteristics:

• (i) a change in intended flight altitude; and
• (ii) a change in planned route.

The drive system can be set up in such a way that it carries out the method described in the fourth aspect.

• Bestimmen einer oder mehrerer Kraftstoffmerkmale des Kraftstoffs, der dem Gasturbinentriebwerk zugeführt werden soll; und
• Steuern des Antriebssystems auf der Grundlage der einen oder mehreren Kraftstoffmerkmale.

According to a sixth aspect, there is provided a method of operating an aircraft having a propulsion system, the propulsion system comprising a gas turbine engine and a fuel tank arranged to supply fuel to the gas turbine engine, the method comprising:

• determining one or more fuel characteristics of the fuel to be supplied to the gas turbine engine; and
• Controlling the power system based on the one or more fuel characteristics.

The implementation of this aspect may therefore allow environmental benefits (e.g. reduced or tailored contrail formation) and/or operational benefits (e.g. improved fuel combustion efficiency) to be achieved based on knowledge of the fuel burned.

In some examples, the method may include controlling the propulsion system based on the determined characteristics without seeking pilot input or approval. In some examples, the method may include notifying a pilot of the proposed change to control of the propulsion system based on the identified characteristics and providing the pilot with an opportunity to confirm or reject the change. In some implementations, either example may be performed depending on the nature of the change. The control can therefore take place directly or after the check.

The method can be performed iteratively during flight, e.g. B. due to changes in fueling of the gas turbine engine and/or changes in conditions and phase of flight.

The one or more fuel attributes of the fuel may include one or more of the attributes listed above.

The method may further include receiving weather data relating to weather conditions in the vicinity of the aircraft or along a planned route of the aircraft. The received weather data can be used to influence the control of the propulsion system.

The method may further include detecting weather conditions in the vicinity of the aircraft during flight. The detected weather conditions can be used to influence the control of the propulsion system.

• • Ein Betriebsparameter eines Wärmemanagementsystems des Luftfahrzeugs (z. B. eines Kraftstoff-Öl-Wärmetauschers) kann geändert werden, oder die Temperatur des einer Brennkammer des Triebwerks zugeführten Kraftstoffs kann geändert werden.
• • Wenn an Bord eines Luftfahrzeugs mehr als ein Kraftstoff gelagert wird, kann die Auswahl des zu verwendenden Kraftstoffs für bestimmte Betriebsarten (z. B. für den Betrieb am Boden im Gegensatz zum Flug, für das Anlassen bei niedrigen Temperaturen oder für Betriebsarten mit unterschiedlichen Schubanforderungen) auf der Grundlage von Kraftstoffmerkmalen wie dem Anteil an nachhaltigem Flugkraftstoff („Sustainabie Aviation Fuel“ - SAF), dem Potenzial zur Bildung von nichtflüchtigem Feinstaub (nvPM), der Viskosität und dem Heizwert getroffen werden. Ein Kraftstoffzufuhrsystem kann daher auf der Grundlage der Kraftstoffmerkmale angemessen gesteuert werden.
• • Eine oder mehrere Flugsteuerungsflächen des Luftfahrzeugs können so eingestellt werden, dass die Flugroute und/oder die Flughöhe aufgrund der Kenntnis des Kraftstoffs geändert wird.
• • Der Überlaufprozentsatz einer Kraftstoffpumpe (d. h. der Anteil des gepumpten Kraftstoffs, der zurückgeführt wird, anstatt der Verbrennungsanlage zugeführt zu werden) basiert auf dem %SAF des Kraftstoffs. Die Pumpe und/oder ein oder mehrere Ventile können daher auf der Grundlage der Kraftstoffmerkmale entsprechend gesteuert werden.
• • Die Einstellung der Leitschaufeln mit variablem Einlass (VIGVs) kann auf der Grundlage der Kraftstoffmerkmale geändert werden. Die VIGVs können daher je nach den Kraftstoffmerkmalen verschoben werden oder eine Bewegung der VIGVs kann aufgehoben werden.

Propulsion system control based on fuel characteristics may include in-flight changes to one or more of the following:

• • An operational parameter of an aircraft's thermal management system (eg, a fuel-to-oil heat exchanger) may be changed, or the temperature of fuel supplied to an engine's combustor may be changed.
• • When more than one fuel is stored on board an aircraft, the choice of fuel to use for specific modes of operation (e.g. for operations on the ground versus in flight, for low temperature starting, or for modes of operation with different thrust requirements ) based on fuel characteristics such as Sustainable Aviation Fuel (SAF) content, non-volatile particulate matter (nvPM) formation potential, viscosity and calorific value. A fuel supply system can therefore be appropriately controlled based on the fuel characteristics.
• • One or more of the aircraft's flight control surfaces can be set to change flight path and/or altitude based on knowledge of fuel.
• • A fuel pump's spill percentage (ie, the proportion of pumped fuel that is returned rather than sent to the incinerator) is based on the %SAF of the fuel. The pump and/or one or more valves can therefore be controlled accordingly based on the fuel characteristics.
• • Variable Inlet Guide Vanes (VIGVs) can be tuned based on fuel characteristics. The VIGVs can therefore be moved or a movement of the VIGVs can be canceled depending on the fuel characteristics.

These options can be referred to as control examples because they are examples of how the power system can be controlled based on the fuel characteristics.

(The Sustainable Aviation Fuel Percentage (%SAF) of a fuel can be expressed gravimetrically or volumetrically - it is known that there are frequent - generally small - differences in density between SAF and traditional jet fuels such as Jet A).

The determination of the one or more fuel characteristics may be based on the detection of one or more fuel properties. The detection can take place on the wing.

The determination of the one or more fuel characteristics may be based on received fuel composition data. The data on the fuel composition can be transmitted to the aircraft when refueling.

The one or more fuel characteristics may be determined for fuel in one or more fuel tanks of the aircraft.

The one or more fuel characteristics may be determined for each of a plurality of fuels stored onboard the aircraft.

The one or more fuel characteristics may be determined for fuel just before entering a combustor of the gas turbine engine. The determination of the one or more fuel characteristics of the fuel just prior to entry into the combustor of the gas turbine engine may be performed multiple times during flight to account for changes in fuel composition.

The one or more fuel characteristics may be derived from performance of the gas turbine engine during engine warm-up, taxiing, takeoff, and aircraft climb. The propulsion system may be controlled during cruise based on the one or more inferred fuel characteristics.

• Ermittlung einer oder mehrerer Kraftstoffmerkmale des bereits im Kraftstofftank vorhandenen Kraftstoffs vor dem Betanken;
• Bestimmung einer oder mehrerer Kraftstoffmerkmale eines Kraftstoffs, der dem Kraftstofftank beim Tanken zugeführt wird; und
• Berechnung einer oder mehrerer Kraftstoffmerkmale des nach dem Tanken im Kraftstofftank befindlichen Kraftstoffs.

Determining the one or more fuel characteristics of the fuel can include performing the method of the first aspect, in particular:

• determining one or more fuel characteristics of the fuel already in the fuel tank prior to refueling;
• determining one or more fuel characteristics of a fuel supplied to the fuel tank during refueling; and
• Calculation of one or more fuel characteristics of the fuel in the fuel tank after refuelling.

• ein Gasturbinentriebwerk, wobei das Gasturbinentriebwerk optional einen Triebwerkskern umfasst, der eine Turbine, einen Verdichter und eine Kernwelle umfasst, die die Turbine mit dem Verdichter verbindet; und einen stromaufwärts des Triebwerkskerns angeordneten Bläser, wobei der Bläser eine Vielzahl von Bläserschaufeln umfasst und so angeordnet ist, dass er durch einen Ausgang von der Kernwelle angetrieben wird;
• einen Kraftstofftank zur Aufnahme des Kraftstoffs für den Antrieb der Gasturbine;
• ein Modul zur Bestimmung der Kraftstoffzusammensetzung, das so beschaffen ist, dass es eine oder mehrere Kraftstoffmerkmale des Kraftstoffs bestimmt, der dem Gasturbinentriebwerk zugeführt werden soll; und
• eine Steuerung des Antriebssystems, die so angeordnet ist, dass sie das Antriebssystem auf der Grundlage der einen oder mehreren Kraftstoffmerkmale des Kraftstoffs steuert.

According to a seventh aspect, there is provided a propulsion system for an aircraft, comprising:

• a gas turbine engine, the gas turbine engine optionally including an engine core including a turbine, a compressor, and a core shaft connecting the turbine to the compressor; and a fan positioned upstream of the engine core, the fan including a plurality of fan blades and arranged to be driven by an output from the core shaft;
• a fuel tank for storing fuel for driving the gas turbine;
• a fuel composition determination module arranged to determine one or more fuel characteristics of the fuel to be supplied to the gas turbine engine; and
• a powertrain controller arranged to control the powertrain based on the one or more fuel characteristics of the fuel.

The fuel composition determination module may include a receiver configured to receive fuel composition data. The fuel composition determination module may be configured to determine one or more fuel characteristics based on the received data.

The fuel composition determination module may include one or more sensors arranged to provide data relating to one or more fuel characteristics. The fuel composition determination module may be configured to determine one or more fuel characteristics based on the sensor data.

The power system may include a plurality of fuel tanks arranged to contain various fuels for powering the gas turbine engine. The fuel composition determination module may be configured to determine at least one fuel attribute for each different fuel.

The drive system can be arranged in such a way that it carries out the method described under the sixth aspect.

• ein Gasturbinentriebwerk, wobei das Gasturbinentriebwerk optional umfasst:
  • einen Triebwerkskern mit einer Turbine, einem Verdichter und einer Kernwelle, die die Turbine mit dem Verdichter verbindet; und
  • einen Fan, der stromaufwärts des Triebwerkskerns angeordnet ist, wobei der Fan eine Vielzahl von Fanschaufeln umfasst und so angeordnet ist, dass er durch einen Abtrieb von der Kernwelle angetrieben wird;
• eine Vielzahl von Kraftstofftanks, die jeweils so angeordnet sind, dass sie einen unterschiedlichen Kraftstoff enthalten, der zum Antrieb des Gasturbinentriebwerks verwendet werden soll, wobei die Kraftstoffe unterschiedliche Heizwerte haben; und
• einen Kraftstoffmanager, der so angeordnet ist, dass er Informationen über den in jedem Kraftstofftank enthaltenen Kraftstoff speichert und die Kraftstoffzufuhr zum Gasturbinentriebwerk im Betrieb (optional nur im Flug) durch Auswahl eines bestimmten Kraftstoffs oder einer bestimmten Kraftstoffkombination aus einem oder mehreren der mehreren Kraftstofftanks auf der Grundlage des Schubbedarfs des Gasturbinentriebwerks steuert, so dass dem Gasturbinentriebwerk bei geringerem Schubbedarf ein Kraftstoff mit einem niedrigeren Heizwert zugeführt wird.

According to an eighth aspect, there is provided a propulsion system for an aircraft, comprising:

• a gas turbine engine, the gas turbine engine optionally comprising:
  • an engine core having a turbine, a compressor, and a core shaft connecting the turbine to the compressor; and
  • a fan positioned upstream of the engine core, the fan including a plurality of fan blades and arranged to be driven by an output from the core shaft;
• a plurality of fuel tanks each arranged to contain a different fuel to be used to power the gas turbine engine, where the fuels have different calorific values; and
• a fuel manager arranged to store information about the fuel contained in each fuel tank and fuel delivery to the gas turbine engine in operation (optionally only in flight) by selecting a specific fuel or fuel combination from one or more of the multiple fuel tanks on the Controls the basis of the thrust requirement of the gas turbine engine, so that the gas turbine engine is supplied with a fuel having a lower calorific value when the thrust requirement is lower.

It is understood that the propulsion system may include additional fuel tanks containing the same fuels in addition to a plurality of fuel tanks containing different fuels; in the implementation of this aspect, at least two different fuels are provided on board the aircraft.

Varying the calorific value of the fuel according to the thrust demand may enable the maintenance of a more constant fuel flow rate during at least one flight segment (e.g. at cruise or for a constant altitude segment of cruise) and/or smoother operation of the fuel pump and spill over during flight during at least one leg of the flight. In addition, the minimum required fuel flow can be increased at key points (e.g. at very low thrust operating points) by switching to a lower calorific value fuel, thereby raising the overall minimum flow and keeping the throughput in a tighter range throughout the flight range is held.

Executions of this aspect may therefore allow a higher fuel mass flow to be maintained with less thrust demand than if a fuel were not selected on the basis of calorific value, thereby facilitating the use of the fuel as a heat transfer medium (provided that the lower calorific value fuel in question does not have a correspondingly lower heat capacity), the lubrication is improved and/or the risk of fuel overheating is reduced. This can be particularly useful when the engine is running at low idle boost. Likewise, when there is a higher demand for thrust, the use of a fuel with a higher calorific value can make it easier to meet that demand without burdening the fuel flow control system. The implementation of the present aspect can therefore mean that when the demand for thrust is reduced, the fuel flow does not have to be reduced as much as would otherwise be necessary.

Each fuel tank may be arranged to contain a fuel of a different type or proportion of sustainable aviation fuel.

A first fuel tank of the plurality of fuel tanks may be arranged to contain only one fuel that is a sustainable aviation fuel. The sustainable aviation fuel in the first fuel tank can be selected in such a way that the propulsion system can only be operated with this fuel.

The fuel manager can be set up to provide different controls for operation on the ground than in flight. For example, sustainable aviation fuel may be used in the primary fuel tank or a high percentage SAF blend for aircraft propulsion when the aircraft performs at least most of its ground operations, regardless of the thrust demand or heating value of that fuel.

The fuel manager may be configured such that all fuel used for ground operations is drawn from the first fuel tank and/or all fuel used for ground operations is SAF or the highest %SAF blend available to the aircraft.

The fuel manager can be set up to supply the gas turbine engine with a lower calorific value fuel during cruise than during climb.

The fuel manager may be arranged to supply the gas turbine engine with fuel having a lower calorific value at low idle than at high idle.

A first fuel tank of the plurality of fuel tanks may contain a higher percentage of sustainable aviation fuel (e.g., 100%) than a second fuel tank of the plurality of fuel tanks. In some cases, more fuel can be used from the second fuel tank when cruising and more fuel from the first tank at operating points with higher power requirements. The fuel with the higher %SAF may have a higher calorific value.

The first and second fuel tanks of the plurality of fuel tanks may contain different compositions of sustainable aviation fuels.

The fan can have a diameter of at least 330 cm.

• Anordnen jedes Kraftstofftanks der mehreren Kraftstofftanks, um einen anderen Kraftstoff zu enthalten, der zum Antrieb des Gasturbinentriebwerks verwendet werden soll, wobei die Kraftstoffe unterschiedliche Heizwerte haben;
• Speichern von Informationen über den in jedem Kraftstofftank enthaltenen Kraftstoff; und
• Steuern der Kraftstoffzufuhr zum Gasturbinentriebwerk im Betrieb (optional nur im Flug) durch Auswahl eines bestimmten Kraftstoffs oder einer bestimmten Kraftstoffkombination aus einem oder mehreren der mehreren Kraftstofftanks auf der Grundlage des Schubbedarfs des Gasturbinentriebwerks, so dass dem Gasturbinentriebwerk bei geringerem Schubbedarf ein Kraftstoff mit einem niedrigeren Heizwert zugeführt wird.

According to a ninth aspect, there is provided a method of operating an aircraft including a gas turbine engine and a plurality of fuel tanks arranged to store fuel for powering the gas turbine engine, the method comprising:

• arranging each fuel tank of the plurality of fuel tanks to contain a different fuel to be used to power the gas turbine engine, the fuels having different heating values;
• storing information about the fuel contained in each fuel tank; and
• Controlling fuel delivery to the gas turbine engine during operation (optional only in flight) by selecting a specific fuel or fuel combination from one or more of the plurality of fuel tanks based on the thrust demand of the gas turbine engine such that the gas turbine engine can use fuel with a lower calorific value when the thrust demand is lower is supplied.

Arranging each fuel tank to contain a different fuel may include supplying each fuel tank with a different sustainable aviation fuel and/or with a fuel blend containing a different type or proportion of sustainable aviation fuel.

Controlling fuel delivery to the gas turbine engine based on thrust demand can only be done in flight. The fuel supply can be controlled differently for operation on the ground.

• Anordnen jedes Kraftstofftanks, um einen anderen Kraftstoff zu enthalten, der zum Antrieb des Gasturbinentriebwerks verwendet werden soll, wobei die Kraftstoffe unterschiedliche Heizwerte haben; und
• Bereitstellen eines Kraftstoffmanagers, der so angeordnet ist, dass er Informationen über den in jedem Kraftstofftank enthaltenen Kraftstoff speichert und die Kraftstoffzufuhr zum Gasturbinentriebwerk im Betrieb (optional nur im Flug) durch Auswahl eines bestimmten Kraftstoffs oder einer bestimmten Kraftstoffkombination aus einem oder mehreren der mehreren Kraftstofftanks auf der Grundlage des Schubbedarfs des Gasturbinentriebwerks steuert, so dass dem Gasturbinentriebwerk bei geringerem Schubbedarf ein Kraftstoff mit einem niedrigeren Heizwert zugeführt wird.

According to a tenth aspect, there is provided a method of modifying an aircraft that includes a gas turbine engine and a plurality of fuel tanks arranged to store fuel for powering the gas turbine engine, the method comprising:

• arranging each fuel tank to contain a different fuel to be used to power the gas turbine engine, the fuels having different heating values; and
• providing a fuel manager arranged to store information about the fuel contained in each fuel tank and fuel delivery to the gas turbine engine in operation (optionally only in flight) by selecting a particular fuel or fuel combination from one or more of the plurality of fuel tanks based on the thrust demand of the gas turbine engine such that a fuel having a lower calorific value is supplied to the gas turbine engine when the thrust demand is lower.

Arranging each fuel tank to contain a different fuel may include supplying each fuel tank with a different sustainable aviation fuel and/or with a fuel blend containing a different type or proportion of sustainable aviation fuel.

Arranging each fuel tank to receive a different fuel may include adjusting at least one valve to fluidically isolate two or more fuel tanks from one another to provide separate containers for different fuels.

The fuel manager may be arranged to provide different controls for operation on the ground than in flight. Controlling fuel delivery to the gas turbine engine based on thrust demand can only be done in flight. The fuel supply can therefore be controlled differently for operation on the ground, e.g. B. by selecting SAF (or a higher percentage SAF blend) independently of calorific value when choosing between it and a fossil-based fuel (or a lower percentage SAF blend).

• ein Gasturbinentriebwerk, das so angeordnet ist, dass es einen Kraftstoff verbrennt, um das Luftfahrzeug mit Energie zu versorgen;
• eine Vielzahl von Kraftstofftanks, von denen jeder so angeordnet ist, dass er einen Kraftstoff enthält, der verwendet wird, um das Luftfahrzeug mit Energie zu versorgen, wobei mindestens zwei Tanks der Vielzahl von Kraftstofftanks unterschiedliche Kraftstoffe enthalten, und wobei ein oder mehrere Tanks der Vielzahl von Kraftstofftanks so angeordnet sind, dass sie nur einen Kraftstoff enthalten, der ein nachhaltiger Flugkraftstoff ist; und
• einen Kraftstoffmanager, der so eingerichtet ist, dass er Informationen über den in jedem Kraftstofftank enthaltenen Kraftstoff speichert und die Kraftstoffzufuhr so steuert, dass nur der nachhaltige Flugkraftstoff entnommen wird, um zumindest den Großteil des Betriebs am Boden zu betreiben.

According to an eleventh aspect, there is provided a propulsion system for an aircraft, comprising:

• a gas turbine engine arranged to combust a fuel to power the aircraft;
• a plurality of fuel tanks each arranged to contain a fuel used to power the aircraft, at least two tanks of the plurality of fuel tanks containing different fuels, and one or more tanks of the plurality fuel tanks are arranged to contain only fuel that is sustainable aviation fuel; and
• a fuel manager arranged to store information about the fuel contained in each fuel tank and to control the fuel supply so that only the sustainable aviation fuel is taken to power at least the majority of the operations on the ground.

In some examples, only sustainable aviation fuel may be used for the operation of aircraft on the ground, such that all ground-based activities are operated with sustainable aviation fuel.

In other examples, most but not all fuel used for ground operations is sustainable aviation fuel, with only small amounts used from other sources (e.g. less than 10% or less than 5% of fuel consumption and/or operating time of the ground operations).

In some examples, particularly examples where the sustainable aviation fuel has a higher viscosity at a given temperature than the fuel in another fuel tank, the fuel from the other fuel tank can be used to start the engine, and the fuel source can then be switched to the be switched to sustainable aviation fuel when the engine is running, e.g. B. when a certain temperature is reached. The fuel in the tank used for starting may be optimized for low temperature use and/or other characteristics of the starting operation. In such examples, sustainable aviation fuel may be used for all ground operations other than engine starting if the fuel in the starter tank is not also SAF, and SAF (optionally various SAFs) may be used for all ground operations if it is SAF.

A gas turbine engine of the one or more gas turbine engines may be an auxiliary power unit (APU) gas turbine engine. The APU may be designed to be active primarily or only during ground operations.

A first fuel tank of the one or more tanks may be configured to contain sustainable aviation fuel and may be dedicated to the APU such that the sustainable aviation fuel from the first fuel tank is not supplied to any other aircraft gas turbine engine. A fuel that is not approved for use as aviation fuel can therefore be stored in the first fuel tank.

A first fuel tank of the one or more tanks may be arranged to contain sustainable aviation fuel and may be arranged to fuel the APU when operating on the ground and to serve as a trim tank in flight .

The APU shall not provide propulsion power to the aircraft.

• einen Triebwerkskern mit einer Turbine, einem Verdichter und einer Kernwelle, die die Turbine mit dem Verdichter verbindet; und
• einen Fan, der stromaufwärts des Triebwerkskerns angeordnet ist, wobei der Fan eine Vielzahl von Fanschaufeln umfasst und so angeordnet ist, dass er durch einen Abtrieb von der Kernwelle angetrieben wird.

The gas turbine engine may be arranged to provide motive power to the aircraft and may include:

• an engine core having a turbine, a compressor, and a core shaft connecting the turbine to the compressor; and
• a fan positioned upstream of the engine core, the fan including a plurality of fan blades and arranged to be driven by an output from the core shaft.

• ein Gasturbinentriebwerk, wobei das Gasturbinentriebwerk optional umfasst:
  • einen Triebwerkskern mit einer Turbine, einem Verdichter und einer Kernwelle, die die Turbine mit dem Verdichter verbindet; und
  • einen Fan, der stromaufwärts des Triebwerkskerns angeordnet ist, wobei der Fan eine Vielzahl von Fanschaufeln umfasst und so angeordnet ist, dass er durch einen Abtrieb von der Kernwelle angetrieben wird;
• eine Vielzahl von Kraftstofftanks, die jeweils so angeordnet sind, dass sie einen Kraftstoff enthalten, der verwendet wird, um das Luftfahrzeug mit Energie zu versorgen, wobei mindestens zwei Tanks der Vielzahl von Kraftstofftanks unterschiedliche Kraftstoffe enthalten und wobei ein oder mehrere Tanks der Vielzahl von Kraftstofftanks so angeordnet sind, dass sie nur einen Kraftstoff enthalten, der ein nachhaltiger Flugkraftstoff ist; und
• einen Kraftstoffmanager, der so angeordnet ist, dass er Informationen über den in jedem Kraftstofftank enthaltenen Kraftstoff speichert und die Kraftstoffzufuhr zum Gasturbinentriebwerk so steuert, dass nur der nachhaltige Flugkraftstoff verwendet wird, wenn das Luftfahrzeug zumindest den Großteil des Betriebs am Boden durchführt.

According to a twelfth aspect, there is provided a propulsion system for an aircraft, comprising:

• a gas turbine engine, the gas turbine engine optionally comprising:
  • an engine core having a turbine, a compressor, and a core shaft connecting the turbine to the compressor; and
  • a fan positioned upstream of the engine core, the fan including a plurality of fan blades and arranged to be driven by an output from the core shaft;
• a plurality of fuel tanks each arranged to contain a fuel used to power the aircraft, at least two tanks of the plurality of fuel tanks containing different fuels and one or more tanks of the plurality of fuel tanks arranged to contain only one fuel that is a sustainable aviation fuel; and
• a fuel manager arranged to store information about the fuel contained in each fuel tank and to control the fuel supply to the gas turbine engine so that only the sustainable aviation fuel is used when the aircraft is performing at least the majority of its operations on the ground.

Each fuel tank may be arranged to contain fuel with a different type and/or proportion of sustainable aviation fuel. In some implementations, two or more tanks may contain the same fuel.

The sustainable aviation fuel in at least a first fuel tank of the one or more tanks containing sustainable aviation fuel contained can be selected so that the drive system can be operated with this fuel alone.

The fuel manager may be arranged to control in-flight fuel delivery to the gas turbine engine by selecting a particular fuel or fuel combination from one or more of the plurality of fuel tanks.

The fuel in the one or more tanks containing sustainable aviation fuel for use in ground operations may have a lower calorific value than any fuel stored in another fuel tank of the plurality of fuel tanks. The fuel in the one or more tanks containing sustainable aviation fuel for use in ground-based operations may have lower nvPM emissions than any fuel stored in another fuel tank of the plurality of fuel tanks. The fuel selected for ground operations may be optimized for ground operations that have, in part or in whole, relatively low energy requirements compared to average flight operations and that are required in part or in whole to meet more stringent emission criteria due to regulations.

A first fuel tank of the one or more tanks containing sustainable aviation fuel may be smaller than the one or more other fuel tanks. The first fuel tank may be arranged to be used exclusively for ground operation of the aircraft. This arrangement may be as described in the sixteenth to twentieth aspects below. The fuel in the first fuel tank may be selected to have a lower calorific value than fuel stored in another fuel tank of the plurality of fuel tanks.

The sustainable aviation fuel can be used for all aircraft ground operations.

• Anordnen von mindestens zwei Kraftstofftanks aus der Vielzahl von Kraftstofftanks zum Speichern unterschiedlicher Kraftstoffe, wobei ein oder mehrere Tanks aus der Vielzahl von Kraftstofftanks so angeordnet sind, dass sie nur einen Kraftstoff enthalten, der ein nachhaltiger Flugkraftstoff ist;
• Steuern der Kraftstoffzufuhr derart, dass nur nachhaltiges Flugbenzin verwendet wird, wenn das Luftfahrzeug zumindest den größten Teil des Betriebs am Boden durchführt.

According to a thirteenth aspect there is provided a method of operating an aircraft including a gas turbine engine and a plurality of fuel tanks arranged to store fuel for powering the gas turbine engine, the method comprising:

• arranging at least two fuel tanks of the plurality of fuel tanks to store different fuels, wherein one or more of the plurality of fuel tanks are arranged to contain only one fuel that is a sustainable aviation fuel;
• Controlling fueling so that only sustainable aviation fuel is used when the aircraft is conducting at least most of its ground operations.

The method may further include storing information about the fuel contained in each fuel tank. The control can be carried out on the basis of the stored information.

• einen Triebwerkskern mit einer Turbine, einem Verdichter und einer Kernwelle, die die Turbine mit dem Verdichter verbindet; und
• einen Fan, der stromaufwärts des Triebwerkskerns angeordnet ist, wobei der Fan eine Vielzahl von Fanschaufeln umfasst und so angeordnet ist, dass er durch einen Abtrieb von der Kernwelle angetrieben wird.

The gas turbine engine may be arranged to provide motive power to the aircraft and may include:

• an engine core having a turbine, a compressor, and a core shaft connecting the turbine to the compressor; and
• a fan positioned upstream of the engine core, the fan including a plurality of fan blades and arranged to be driven by an output from the core shaft.

The gas turbine engine may be a gas turbine engine of an auxiliary power unit (APU) of the aircraft.

A first fuel tank of the one or more sustainable aviation fuel tanks may be an aircraft trim tank. The sustainable aviation fuel in the primary fuel tank may be arranged to be consumed (at least substantially) in the performance of the ground operations such that the primary fuel tank is at least substantially empty and available to receive fuel used during the flight is pumped in.

• Anordnen von mindestens zwei Kraftstofftanks der Vielzahl von Kraftstofftanks, um jeweils einen anderen Kraftstoff zu speichern, wobei ein oder mehrere Tanks der Vielzahl von Kraftstofftanks so angeordnet sind, dass sie nur einen Kraftstoff enthalten, der ein nachhaltiger Flugkraftstoff ist; und
• Bereitstellung eines Kraftstoffmanagers, der die Kraftstoffzufuhr so steuert, dass nur nachhaltiger Flugkraftstoff verwendet wird, wenn das Luftfahrzeug zumindest den Großteil des Betriebs am Boden durchführt.

According to a fourteenth aspect, there is provided a method of modifying an aircraft that includes a gas turbine engine and a plurality of fuel tanks arranged to store fuel for powering the gas turbine engine, the method comprising:

• arranging at least two fuel tanks of the plurality of fuel tanks to each store a different fuel, wherein one or more tanks of the plurality of fuel tanks are arranged to contain only one fuel that is a sustainable aviation fuel; and
• Provision of a fuel manager that controls the fuel supply in such a way that only sustainable aviation fuel is used when the aircraft performs at least the majority of operations on the ground.

The fuel manager may be configured to store information about the fuel contained in each fuel tank. The fuel manager may be configured to control fuel delivery based on the stored information.

• einen Triebwerkskern mit einer Turbine, einem Verdichter und einer Kernwelle, die die Turbine mit dem Verdichter verbindet; und
• einen Fan, der stromaufwärts des Triebwerkkerns angeordnet ist, wobei der Fan eine Vielzahl von Fanschaufeln umfasst und so angeordnet ist, dass er durch einen Abtrieb von der Kernwelle angetrieben wird.

The gas turbine engine may be arranged to provide motive power to the aircraft and may include:

• an engine core having a turbine, a compressor, and a core shaft connecting the turbine to the compressor; and
• a fan positioned upstream of the engine core, the fan including a plurality of fan blades and arranged to be driven by an output from the core shaft.

The gas turbine engine may be a gas turbine engine of an auxiliary power unit (APU) of the aircraft.

• eine Hilfsturbine („Auxiliary Power Unit“ - APU) mit einem Gasturbinentriebwerk, das so angeordnet ist, dass es einen Kraftstoff verbrennt, um das Luftfahrzeug mit Energie zu versorgen; und
• einen oder mehrere Kraftstofftanks, die so angeordnet sind, dass sie nur einen Kraftstoff enthalten, der ein nachhaltiger Flugkraftstoff ist;
• und bei dem der gesamte von der APU verwendete Kraftstoff der nachhaltige Flugkraftstoff ist.

According to a fifteenth aspect, there is provided a propulsion system for an aircraft, comprising:

• an auxiliary power unit (APU) having a gas turbine engine arranged to combust a fuel to power the aircraft; and
• one or more fuel tanks arranged to contain only one fuel that is a sustainable aviation fuel;
• and where all fuel used by the APU is the sustainable aviation fuel.

• ein Gasturbinentriebwerk, das so angeordnet ist, dass es einen Kraftstoff verbrennt, um das Luftfahrzeug mit Energie zu versorgen;
• einen oder mehrere erste Kraftstofftanks, die für den Betrieb des Luftfahrzeugs am Boden verwendet werden können;
• einen oder mehrere sekundäre Kraftstofftanks, die jeweils so angeordnet sind, dass sie einen Kraftstoff enthalten, der für den Antrieb des Luftfahrzeugs während des Flugs verwendet wird; und
• einen Kraftstoffmanager, der die Kraftstoffzufuhr so steuert, dass Kraftstoff nur aus dem einen oder den mehreren ersten Kraftstofftanks entnommen wird, um zumindest den Großteil der bodengestützten Operationen zu betreiben.

According to a sixteenth aspect, there is provided a propulsion system for an aircraft, comprising:

• a gas turbine engine arranged to combust a fuel to power the aircraft;
• one or more primary fuel tanks that can be used for operations of the aircraft on the ground;
• one or more secondary fuel tanks each arranged to contain a fuel used to propel the aircraft in flight; and
• a fuel manager that controls fuel delivery to draw fuel from only the first one or more fuel tanks to power at least the majority of ground-based operations.

Therefore, it may be advantageous to fill the first fuel tank(s) with a fuel optimized for use in ground-based operations, e.g. B. for more efficient operation of the engine and / or for lower emissions. Having one or more primary fuel tanks arranged and optionally provided for this purpose may facilitate refueling and operation.

In some examples, only fuel from the first fuel tank(s) may be used for aircraft operations on the ground such that all ground-based operations are fueled by the first fuel tank(s).

In other examples, most but not all of the fuel for ground operations is taken from the first fuel tank, while only small amounts are used from other sources (e.g. less than 10% or less than 5% of the fuel consumption and/or the operating time of the ground operation).

In many examples, a single first fuel tank is provided. However, it is clear that the disclosure is not limited to a single first fuel tank, even if the following explanations often relate to a single first fuel tank.

In some examples, particularly when fuel in the first fuel tank has a higher viscosity than fuel in another fuel tank at a particular temperature, fuel from another fuel tank may be used to start the engine and the fuel source may then be switched to the first fuel tank as soon as the engine is running, e.g. B. when a certain temperature is reached. In such examples, fuel from the first fuel tank may be used for all ground operations other than engine starting.

The fuel manager may also be configured to only draw fuel from the one or more secondary fuel tanks for at least the majority of other operations (e.g., climb and cruise). It goes without saying that any remaining fuel in the first fuel tank may be used up during flight (alone or as part of a mixture), either in the early stages after ground operations or thereafter.

The fuel manager may be configured to draw fuel from the one or more secondary fuel tanks for at least the majority of the other operations.

The fuel manager can be set up to only use the first fuel tank for all ground based operations.

A gas turbine engine of the one or more gas turbine engines may be an auxiliary power unit (APU) gas turbine engine. The auxiliary power unit may be designed to be active only during ground operations.

The first fuel tank may be arranged to supply fuel to the APU during operation on the ground and to serve as a trim tank during flight.

The APU shall not provide propulsion power to the aircraft.

• einen Triebwerkskern mit einer Turbine, einem Verdichter und einer Kernwelle, die die Turbine mit dem Verdichter verbindet; und
• einen Fan, der stromaufwärts des Triebwerkkerns angeordnet ist, wobei der Fan eine Vielzahl von Fanschaufeln umfasst und so angeordnet ist, dass er durch einen Abtrieb von der Kernwelle angetrieben wird.

A gas turbine engine of the one or more gas turbine engines may be a gas turbine engine arranged to provide motive power to the aircraft. The gas turbine engine may include:

• an engine core having a turbine, a compressor, and a core shaft connecting the turbine to the compressor; and
• a fan positioned upstream of the engine core, the fan including a plurality of fan blades and arranged to be driven by an output from the core shaft.

The fuel manager may be configured to only fuel the gas turbine engine in flight from the one or more secondary fuel tanks such that the primary fuel tank is not used to fuel an engine in flight.

• ein Gasturbinentriebwerk, wobei das Gasturbinentriebwerk optional umfasst:
  • einen Triebwerkskern mit einer Turbine, einem Verdichter und einer Kernwelle, die die Turbine mit dem Verdichter verbindet; und
  • einen Fan, der stromaufwärts des Triebwerkkerns angeordnet ist, wobei der Fan eine Vielzahl von Fanschaufeln umfasst und so angeordnet ist, dass er durch einen Abtrieb von der Kernwelle angetrieben wird;
• einen oder mehrere erste Kraftstofftanks, die für den Betrieb des Luftfahrzeugs am Boden verwendet werden können;
• einen oder mehrere sekundäre Kraftstofftanks, die jeweils so angeordnet sind, dass sie einen Kraftstoff enthalten, der zum Antrieb des Gasturbinentriebwerks während des Flugs verwendet wird; und
• einen Kraftstoffmanager, der so angeordnet ist, dass er die Kraftstoffzufuhr zum Gasturbinentriebwerk so steuert, dass nur aus dem einen oder den mehreren ersten Kraftstofftanks Kraftstoff entnommen wird, um zumindest den Großteil der bodengestützten Operationen anzutreiben.

According to a seventeenth aspect, there is provided a propulsion system for an aircraft, comprising:

• a gas turbine engine, the gas turbine engine optionally comprising:
  • an engine core having a turbine, a compressor, and a core shaft connecting the turbine to the compressor; and
  • a fan positioned upstream of the engine core, the fan including a plurality of fan blades and arranged to be driven by an output from the core shaft;
• one or more primary fuel tanks that can be used for operations of the aircraft on the ground;
• one or more secondary fuel tanks each arranged to contain a fuel used to power the gas turbine engine in flight; and
• a fuel manager arranged to control fueling of the gas turbine engine to only draw fuel from the one or more first fuel tanks to power at least the majority of ground-based operations.

The fuel manager may be further configured to only draw fuel from the one or more secondary fuel tanks for at least a majority of the other modes of operation (e.g., climb and cruise).

The first fuel tank may be configured to contain only fuel that is sustainable aviation fuel.

In examples with only a first fuel tank, the first fuel tank may be smaller than the one or more secondary fuel tanks. In examples with multiple first fuel tanks, the total volume of the first fuel tanks may be less than the total volume of the secondary fuel tanks, and optionally less than the volume of each individual secondary fuel tank.

The propulsion system may include a plurality of secondary fuel tanks. The fuel manager may be configured to be able to mix fuels from the secondary fuel tanks to power the gas turbine engine during flight, but may not be able to mix fuel from the primary fuel tank with fuel from the secondary fuel tanks to mix.

Fuel in the first fuel tank may have a lower heating value and/or produce lower nvPM emissions than fuel in one or more secondary fuel tanks.

• ein Gasturbinentriebwerk, das so angeordnet ist, dass es einen Kraftstoff verbrennt, um das Luftfahrzeug mit Energie zu versorgen;
• einen oder mehrere erste Treibstofftanks, die so angeordnet sind, dass sie für den bodengestützten Betrieb des Luftfahrzeugs verwendet werden können; und
• einen oder mehrere sekundäre Kraftstofftanks, die jeweils einen Kraftstoff enthalten, der für den Antrieb des Luftfahrzeugs während des Flugs verwendet wird,

das Verfahren umfasst:

• Steuerung der Kraftstoffzufuhr, so dass nur aus dem einen oder den mehreren ersten Kraftstofftanks Kraftstoff entnommen wird, wenn das Luftfahrzeug zumindest den größten Teil der bodengestützten Operationen durchführen muss.

According to an eighteenth aspect, there is provided a method of operating an aircraft, comprising:

• a gas turbine engine arranged to combust a fuel to power the aircraft;
• one or more first propellant tanks arranged to support the ground-based ten operation of the aircraft can be used; and
• one or more secondary fuel tanks, each containing a fuel used to propel the aircraft in flight;

the procedure includes:

• Controlling fuel delivery so that fuel is only drawn from the first one or more fuel tanks when the aircraft is required to perform at least the majority of ground-based operations.

The method may further include withdrawing fuel from only the one or more secondary fuel tanks for at least the majority of the other operations.

In some examples, only fuel from one or more secondary fuel tanks may be used for other operations such that the primary fuel tank is used exclusively for ground-based operations.

• einen Triebwerkskern mit einer Turbine, einem Verdichter und einer Kernwelle, die die Turbine mit dem Verdichter verbindet; und
• einen Fan, der stromaufwärts des Triebwerkkerns angeordnet ist, wobei der Fan eine Vielzahl von Fanschaufeln umfasst und so angeordnet ist, dass er durch einen Abtrieb von der Kernwelle angetrieben wird.

The gas turbine engine may be arranged to provide motive power to the aircraft and may include:

• an engine core having a turbine, a compressor, and a core shaft connecting the turbine to the compressor; and
• a fan positioned upstream of the engine core, the fan including a plurality of fan blades and arranged to be driven by an output from the core shaft.

The gas turbine engine may be a gas turbine engine of an auxiliary power unit (APU) of the aircraft.

The first fuel tank may be a trim tank of the aircraft. The fuel in the first fuel tank, which may be sustainable aviation fuel, can be arranged to be consumed in carrying out the work on the ground, such that the first fuel tank is eventually essentially empty and ready to receive fuel is available, which is pumped in during the flight.

• Bereitstellung eines oder mehrerer erster Kraftstofftanks, die von anderen (sekundären) Kraftstofftanks der Vielzahl von Kraftstofftanks strömungstechnisch getrennt sind; und
• Bereitstellung eines Kraftstoffmanagers, der so angeordnet ist, dass er die Kraftstoffzufuhr zu dem einen oder den mehreren Gasturbinentriebwerken so steuert, dass Kraftstoff nur aus dem einen oder den mehreren ersten Kraftstofftanks entnommen wird, um zumindest den Großteil der bodengestützten Operationen anzutreiben.

According to a nineteenth aspect there is provided a method of modifying an aircraft comprising one or more gas turbine engines and a plurality of fuel tanks, the method comprising:

• providing one or more first fuel tanks fluidly isolated from other (secondary) fuel tanks of the plurality of fuel tanks; and
• providing a fuel manager arranged to control fueling of the one or more gas turbine engines to draw fuel from only the one or more primary fuel tanks to power at least the majority of ground based operations.

The fuel manager may also be configured to only draw fuel from the one or more secondary fuel tanks for at least most other operations.

The first fuel tank(s) may be permanently fluidly isolated from the other fuel tanks, or it(they) may be reversibly isolated from the other fuel tanks, e.g. B. with the help of one or more pumps and / or valves.

In some examples, only fuel from one or more secondary fuel tanks may be used for other operations such that the primary fuel tank is used exclusively for ground-based operations.

• eine Hilfsturbine („Auxiliary Power Unit“ - APU) mit einem Gasturbinentriebwerk, das so angeordnet ist, dass es einen Kraftstoff verbrennt, um das Luftfahrzeug mit Energie zu versorgen; und
• einen oder mehrere erste Kraftstofftanks, die von allen anderen Kraftstofftanks des Antriebssystems strömungstechnisch getrennt sind;
• und wobei der eine oder die mehreren ersten Kraftstofftanks für die Hilfsturbine bestimmt sind, so dass der gesamte von der Hilfsturbine verbrauchte Kraftstoff aus dem einen oder den mehreren ersten Kraftstofftanks entnommen wird (im Normalbetrieb).

According to a twentieth aspect, there is provided a power system for an aircraft, comprising:

• an auxiliary power unit (APU) having a gas turbine engine arranged to combust a fuel to power the aircraft; and
• one or more first fuel tanks fluidly isolated from all other fuel tanks of the power system;
• and wherein the one or more first fuel tanks are dedicated to the APU such that all fuel consumed by the APU is drawn from the one or more first fuel tanks (in normal operation).

An aircraft is generally set up in such a way that the APU can also be supplied with fuel from one or more other tanks, e.g. B. in the event that the APU needs to start and work in an in-flight emergency, e.g. for non-propulsive purposes such as powering aircraft flight control surfaces after a main engine flameout and/or providing power to restart the main engines.

• ein Gasturbinentriebwerk, das so angeordnet ist, dass es einen Kraftstoff in einer Brennkammer verbrennt, um das Luftfahrzeug mit Energie zu versorgen;
• eine Mehrzahl von Kraftstofftanks, die so angeordnet sind, dass sie einen unterschiedlichen Kraftstoff enthalten, der verwendet wird, um das Luftfahrzeug mit Energie zu versorgen, wobei ein erster Kraftstofftank der Mehrzahl von Kraftstofftanks so angeordnet ist, dass er einen ersten Kraftstoff enthält, und ein zweiter Tank der Mehrzahl von Kraftstofftanks so angeordnet ist, dass er einen zweiten Kraftstoff mit einer vom ersten Kraftstoff unterschiedlichen Zusammensetzung enthält; und
• einen Kraftstoffmanager, der so beschaffen ist, dass er Informationen über den in jedem Kraftstofftank enthaltenen Kraftstoff speichert und die Kraftstoffzufuhr so steuert, dass beim Anlassen des Motors Kraftstoff aus dem zweiten Tank entnommen wird, bevor auf den ersten Kraftstofftank umgeschaltet wird.

According to a twenty-first aspect, there is provided a power system for an aircraft, comprising:

• a gas turbine engine arranged to combust a fuel in a combustor to power the aircraft;
• a plurality of fuel tanks arranged to contain a different fuel used to power the aircraft, a first fuel tank of the plurality of fuel tanks arranged to contain a first fuel, and a a second tank of the plurality of fuel tanks is arranged to contain a second fuel having a different composition from the first fuel; and
• a fuel manager arranged to store information about the fuel contained in each fuel tank and to control the fuel supply so that when the engine is started, fuel is taken from the second tank before switching to the first fuel tank.

The second fuel can be selected for its improved starting properties, e.g. B. because it has a lower viscosity than the fuel in the first fuel tank at a certain temperature to facilitate cold starting of an engine.

The fuel selected for its better starting properties may have a lower viscosity at a certain temperature than the fuel in the first tank.

The second fuel can consist of fossil raw materials / petroleum.

• (i) Der Kraftstoff erreicht am Eintritt in die Brennkammer eine Temperatur von 60°C;
• (ii) Das Gasturbinentriebwerk war für einen Zeitraum von 30 Sekunden in Betrieb; und
• (iii) Das Gasturbinentriebwerk hat den Leerlauf erreicht.

The fuel manager may be arranged to control fuel delivery to switch from drawing fuel from the second tank to drawing fuel from the first tank when at least one of the following conditions is met:

• (i) The fuel reaches a temperature of 60°C at the entrance to the combustion chamber;
• (ii) the gas turbine engine has been operating for a period of 30 seconds; and
• (iii) The gas turbine engine has reached idle.

The first tank can be set up to contain sustainable aviation fuel.

The second tank can be set up to hold a fossil hydrocarbon fuel.

The gas turbine engine may be an auxiliary power unit (APU) gas turbine engine. The auxiliary turbine can be designed in such a way that it is only active during ground operation, at least in normal operation.

The first fuel tank may be dedicated to the APU such that fuel from the first fuel tank cannot be supplied to any other aircraft gas turbine engine.

The first fuel tank may be arranged to supply fuel to the APU during operation on the ground and to serve as a trim tank during flight.

The APU can be arranged not to provide propulsion power to the aircraft.

Alternatively, the gas turbine engine may be arranged to provide motive power to the aircraft.

The gas turbine engine may include an engine core having a turbine, a compressor, and a core shaft connecting the turbine to the compressor, and a fan disposed upstream of the engine core, the fan having a plurality of fan blades and disposed to extend from an exit of the core shaft is driven.

The first fuel in the first fuel tank can be selected such that the gas turbine engine can be operated solely on this fuel. The second fuel in the second fuel tank can be selected such that the gas turbine engine can be operated solely on this fuel both in flight and during start-up.

Each fuel tank may be arranged to contain fuel with a different type or proportion of Sustainable Aviation Fuel (SAF).

The fuel manager may be arranged to control in-flight fuel delivery to the gas turbine engine by selecting a particular fuel or fuel combination from one or more of the plurality of fuel tanks.

The primary fuel may be SAF or a high percentage SAF blend and the fuel manager may be set up to control fuel delivery such that fuel is drawn from the primary fuel tank for the majority of ground based operations - take off may be the only exception .

• Anordnen von mindestens zwei der Kraftstofftanks, um einen unterschiedlichen Kraftstoff zu speichern, wobei ein erster Kraftstofftank der mehreren Kraftstofftanks so angeordnet ist, dass er einen ersten Kraftstoff enthält, und ein zweiter Tank der mehreren Kraftstofftanks so angeordnet ist, dass er einen zweiten Kraftstoff mit einer anderen Zusammensetzung als der erste Kraftstoff enthält; und
• Steuern der Kraftstoffzufuhr derart, dass zum Anlassen des Motors Kraftstoff aus dem zweiten Tank entnommen wird, bevor auf den ersten Kraftstofftank umgeschaltet wird.

According to a twenty-second aspect, there is provided a method of operating an aircraft including a gas turbine engine and a plurality of fuel tanks arranged to store fuel for powering the gas turbine engine, the method comprising:

• arranging at least two of the fuel tanks to store a different fuel, wherein a first fuel tank of the plurality of fuel tanks is arranged to contain a first fuel and a second tank of the plurality of fuel tanks is arranged to contain a second fuel having a contains a different composition than the first fuel; and
• Controlling fuel delivery such that fuel is taken from the second tank to start the engine before switching to the first fuel tank.

The method may further include storing information about the fuel contained in each fuel tank. The control can be carried out on the basis of the stored information.

The gas turbine engine may be arranged to provide motive power to the aircraft. The gas turbine engine may include an engine core having a turbine, a compressor, and a core shaft connecting the turbine to the compressor, and a fan disposed upstream of the engine core, the fan including a plurality of fan blades and disposed to be driven by an output from the Core shaft is driven.

The first fuel tank may be a trim tank of the aircraft. The first fuel may be Sustainable Aviation Fuel (SAF) or a high-percentage SAF blend, and the fuel in the first fuel tank may be arranged to be consumed in conducting operations on the ground (after takeoff), so that the first Fuel tank at the end of climb, if not at takeoff, essentially empty and available to receive fuel pumped into it during flight.

• Anordnen eines ersten Kraftstofftanks der Vielzahl von Kraftstofftanks, um einen ersten Kraftstoff zu enthalten, und eines zweiten Tanks der Vielzahl von Kraftstofftanks, um einen zweiten Kraftstoff mit einer vom ersten Kraftstoff verschiedenen Zusammensetzung zu enthalten; und
• Bereitstellen eines Kraftstoffmanagers, der die Kraftstoffzufuhr so steuert, dass er beim Anlassen des Motors Kraftstoff aus dem zweiten Tank entnimmt, bevor er auf den ersten Kraftstofftank umschaltet.

According to a twenty-third aspect, there is provided a method of modifying an aircraft that includes a gas turbine engine and a plurality of fuel tanks arranged to store fuel for powering the gas turbine engine, the method comprising:

• arranging a first fuel tank of the plurality of fuel tanks to contain a first fuel and a second tank of the plurality of fuel tanks to contain a second fuel having a different composition than the first fuel; and
• providing a fuel manager that controls fuel delivery such that upon engine cranking, it takes fuel from the second tank before switching to the first fuel tank.

The fuel manager can additionally be set up to store information about the fuel contained in each fuel tank. The control can be carried out on the basis of the stored information.

The gas turbine engine may be arranged to provide motive power to the aircraft and may include an engine core having a turbine, a compressor, and a core shaft connecting the turbine to the compressor, and a fan located upstream of the engine core, the fan including a A plurality of fan blades and arranged to be driven by an output from the core shaft.

The gas turbine engine can be a gas turbine engine of an auxiliary power unit (APU) of the aircraft.

• Erhalten eines Flugprofils für einen Flug des Luftfahrzeugs; und
• Bestimmen eines Betankungsplans für den Flug auf der Grundlage des Flugprofils und der Kraftstoffmerkmale, wobei der Betankungsplan die zeitliche Veränderung der Kraftstoffentnahme aus den einzelnen Tanks regelt/diktiert.

According to a twenty fourth aspect there is provided a method of operating an aircraft comprising a gas turbine engine and a plurality of fuel tanks arranged to supply fuel to the gas turbine engine, at least two of the fuel tanks containing fuels having different fuel properties, the method is performed by a processing circuit and comprises:

• obtaining a flight profile for a flight of the aircraft; and
• determining a refueling plan for the flight based on the flight profile and the fuel characteristics, the refueling plan including the regulates/dictates the change in fuel extraction over time from the individual tanks.

The fueling schedule lists how much fuel is to be taken from each tank and is intended to direct a fueling manager to fuel the gas turbine engine accordingly. The refueling plan can therefore be described as a regulation, dictate or instruction for the fuel consumption for the flight (either only for the aircraft in flight or also for operations on the ground).

The procedure can be carried out on the wing (“on-wing”), e.g. by a module for determining the aircraft refueling schedule, which may be part of an aircraft electronic engine control unit (EEC). Alternatively, the procedure can also be carried out outside the wing (“off-wing”) and the refueling plan can be provided to the aircraft for implementation.

1. i. Anteil von nachhaltigem Flugbenzin im Kraftstoff;
2. ii. Gehalt an aromatischen Kohlenwasserstoffen im Kraftstoff;
3. iii. Gehalt an multiaromatischen Kohlenwasserstoffen im Kraftstoff;
4. iv. Prozentsatz der stickstoffhaltigen Spezies im Kraftstoff;
5. v. Vorhandensein oder Prozentsatz einer Tracer-Spezies oder eines Spurenelements im Kraftstoff;
6. vi. Wasserstoff-Kohlenstoff-Verhältnis des Kraftstoffs;
7. vii. Kohlenwasserstoffverteilung des Kraftstoffs;
8. viii. Niveau der nichtflüchtigen Partikelemissionen bei der Verbrennung;
9. ix. Naphthalin-Gehalt des Kraftstoffs;
10. x. Schwefelgehalt des Kraftstoffs;
11. xi. Cycloparaffingehalt des Kraftstoffs;
12. xii. Sauerstoffgehalt des Kraftstoffs;
13. xiii. thermische Stabilität des Kraftstoffs;
14. xiv. Grad der Verkokung des Kraftstoffs;
15. xv. die Angabe, dass es sich bei dem Kraftstoff um einen fossilen Brennstoff handelt; und
16. xvi. mindestens eines der Kriterien Dichte, Viskosität, Heizwert und Wärmekapazität.

The fuel characteristics of the fuel include at least one of the following characteristics:

1. i. Percentage of sustainable aviation fuel in the fuel;
2. ii. content of aromatic hydrocarbons in the fuel;
3. iii. content of multiaromatic hydrocarbons in the fuel;
4. IV. percentage of nitrogenous species in the fuel;
5. v. Presence or percentage of a tracer species or trace element in the fuel;
6. vi. hydrogen to carbon ratio of the fuel;
7. vii. hydrocarbon distribution of the fuel;
8. viii. level of non-volatile particulate emissions from combustion;
9. ix. naphthalene content of the fuel;
10. x. fuel sulfur content;
11. xi. cycloparaffin content of the fuel;
12. xiii. fuel oxygen content;
13. xiii. fuel thermal stability;
14. xiv. degree of fuel coking;
15. xv. the statement that the fuel is a fossil fuel; and
16. xv. at least one of the criteria density, viscosity, calorific value and heat capacity.

• (i) vorgesehene Flughöhe; und
• (ii) geplante Route.

The refueling schedule may be determined using information from the flight profile that includes at least one of the following:

• (i) intended flight altitude; and
• (ii) planned route.

The method may further include receiving predicted weather conditions for a planned route of the aircraft defined in the flight profile, and the received predicted weather conditions may be used to influence the refueling plan.

When determining the fueling plan, it may be determined how much Sustainable Aviation Fuel (SAF) is available to the aircraft and/or which tanks contain SAF or a high percentage SAF blend, and will preferably favor the use of SAF (alone or as part of a blend ) planned for the operation of the aircraft on the ground.

Determining the fueling schedule may include determining the calorific value of each fuel on board the aircraft and preferring to use a fuel with a lower calorific value during periods of reduced thrust demand.

The method may further include controlling fuel delivery to the gas turbine engine during operation according to the fueling schedule.

The determining and determining steps can be performed outside the wing. The method may further include providing the aircraft with the refueling plan prior to the controlling step.

• ein Gasturbinentriebwerk, wobei das Gasturbinentriebwerk optional umfasst:
  • einen Triebwerkskern mit einer Turbine, einem Verdichter und einer Kernwelle, die die Turbine mit dem Verdichter verbindet; und
  • einen Fan, der stromaufwärts des Triebwerkkerns angeordnet ist, wobei der Fan eine Vielzahl von Fanschaufeln umfasst und so angeordnet ist, dass er durch einen Abtrieb von der Kernwelle angetrieben wird;
• eine Vielzahl von Kraftstofftanks, die so angeordnet sind, dass sie Kraftstoff zum Antrieb des Gasturbinentriebwerks enthalten, wobei mindestens zwei der Kraftstofftanks Kraftstoffe mit unterschiedlichen Kraftstoffeigenschaften enthalten; und
• ein Modul zur Bestimmung eines Betankungsplans, das dafür eingerichtet ist:
  • ein Flugprofil für einen Flug des Luftfahrzeugs zu erhalten; und
  • einen Betankungsplans für den Flug auf der Grundlage des Flugprofils und der Kraftstoffstoffmerkmalen zu bestimmen, wobei der Betankungsplan die zeitliche Veränderung der Kraftstoffentnahme aus jedem Tank während des Fluges regelt.

According to a twenty-fifth aspect, there is provided a propulsion system for an aircraft, comprising:

• a gas turbine engine, the gas turbine engine optionally comprising:
  • an engine core having a turbine, a compressor, and a core shaft connecting the turbine to the compressor; and
  • a fan positioned upstream of the engine core, the fan including a plurality of fan blades and arranged to be driven by an output from the core shaft;
• a plurality of fuel tanks arranged to contain fuel for powering the gas turbine engine, at least two of the fuel tanks containing fuels having different fuel properties; and
• a module for determining a refueling schedule that is set up to:
  • obtain a flight profile for a flight of the aircraft; and
  • determine a refueling schedule for the flight based on the flight profile and the fuel characteristics, the refueling schedule governing the timing of fuel withdrawal from each tank during the flight.

The fuel properties of the fuel may include one or more of the fuel properties listed above in the twenty-fourth aspect.

• (i) vorgesehene Flughöhe; und
• (ii) geplante Route.

The refueling plan determination module may be configured to determine the refueling plan using information from the flight profile that includes at least one of the following:

• (i) intended flight altitude; and
• (ii) planned route.

The propulsion system may further include a receiver arranged to receive data on forecast weather conditions for a planned route of the aircraft, the route being specified in the flight profile. The received predicted weather conditions can be used to influence the fueling plan.

The refueling plan determination module may be configured to determine the refueling plan based on the determination of the amount of sustainable aviation fuel (SAF) available for the aircraft and to schedule the use of SAF preferably for ground-based aircraft operations.

The fueling schedule determination module may be arranged to determine the fueling schedule based on the determination of the calorific value of each fuel on board the aircraft and to schedule the use of a lower calorific value fuel preferentially for periods of lower thrust demand.

The fuel consumption schedule determination module may be configured to control fuel delivery to the gas turbine during operation according to the fuel consumption schedule.

• Bestimmen eines Betankungsplans für einen Flug eines Luftfahrzeugs, wobei das Luftfahrzeug ein Gasturbinentriebwerk und mehrere Kraftstofftanks umfasst, die so angeordnet sind, dass sie das Gasturbinentriebwerk mit Kraftstoff versorgen, wobei mindestens zwei der Kraftstofftanks Kraftstoffe mit unterschiedlichen Kraftstoffeigenschaften enthalten. Der Betankungsplan wird auf der Grundlage eines Flugprofils für den Flug des Luftfahrzeugs und der Kraftstoffmerkmale der für das Luftfahrzeug verfügbaren Kraftstoffe bestimmt. Der Betankungsplan gibt an, wie viel Kraftstoff im Laufe des Fluges aus den einzelnen Tanks entnommen wird und wie sich dies zeitlich verändert.

According to a twenty-sixth aspect, there is provided a non-transitory computer-readable medium storing instructions which, when executed by a processor, cause the processor to:

• determining a refueling schedule for a flight of an aircraft, the aircraft including a gas turbine engine and a plurality of fuel tanks arranged to fuel the gas turbine engine, at least two of the fuel tanks containing fuels having different fuel properties. The refueling schedule is determined based on a flight profile for the flight of the aircraft and the fuel characteristics of the fuels available for the aircraft. The refueling plan indicates how much fuel is taken from the individual tanks during the flight and how this changes over time.

The instructions may also be arranged to cause the processor to control fuel delivery to the gas turbine engine during operation in accordance with the fueling schedule. The processor may include or consist of an onboard module for determining the fuel economy schedule and may form part of or consist of an electronic engine controller.

The instructions may also be arranged to cause the processor to provide the refueling plan to the aircraft for execution. The processor may include or consist of an off-wing refueling schedule determination module.

• ein oder mehrere Gasturbinentriebwerke, die so angeordnet sind, dass sie einen Kraftstoff verbrennen, um das Luftfahrzeug mit Energie zu versorgen;
• eine Vielzahl von Kraftstofftanks, die jeweils so angeordnet sind, dass sie einen Kraftstoff enthalten, der verwendet wird, um das Luftfahrzeug mit Energie zu versorgen, wobei mindestens zwei Tanks der Vielzahl von Kraftstofftanks unterschiedliche Kraftstoffe enthalten, wobei die unterschiedlichen Kraftstoffe jeweils einen unterschiedlichen Anteil eines nachhaltigen Flugkraftstoffs aufweisen; und
• ein Kraftstoffmanager, der dazu eingerichtet ist:
  • Informationen über den in jedem Kraftstofftank enthaltenen Kraftstoff zu speichern;
  • Festzustellen, welcher Tank den Kraftstoff mit dem höchsten Anteil an nachhaltigem Flugkraftstoff enthält; und
  • die Kraftstoffzufuhr so zu steuern, dass nur Kraftstoff aus dem Tank entnommen wird, der den höchsten Anteil an nachhaltigem Flugbenzin enthält, um zumindest den Großteil des Betriebs am Boden zu gewährleisten.

According to a twenty-seventh aspect, there is provided a propulsion system for an aircraft, comprising:

• one or more gas turbine engines arranged to combust a fuel to power the aircraft;
• a plurality of fuel tanks each arranged to contain a fuel used to power the aircraft, at least two tanks of the plurality of fuel tanks containing different fuels, the different fuels each containing a different proportion of a have sustainable aviation fuel; and
• a fuel manager set up to:
  • store information about the fuel contained in each fuel tank;
  • Determine which tank contains the fuel with the highest proportion of sustainable aviation fuel; and
  • to control the fuel supply so that only fuel is drawn from the tank containing the highest proportion of sustainable aviation fuel, in order to ensure at least the majority of operations on the ground.

The different proportion of a sustainable aviation fuel (SAF) can be between 0% SAF and 100% SAF. The fuel with the highest proportion of sustainable aviation fuel can be more than 50% SAF.

A gas turbine engine of the one or more gas turbine engines may be an auxiliary power unit (APU) gas turbine engine.

A first fuel tank of the plurality of fuel tanks may be arranged to contain the fuel with the highest percentage of sustainable aviation fuel, and optionally the fuel may be a sustainable aviation fuel (i.e., a fuel where the percentage of SAF is 100%). The first fuel tank may be dedicated to the APU such that fuel from the first fuel tank cannot be supplied to any other aircraft gas turbine engine.

• (i) die Höhe der Emissionen nichtflüchtiger Partikel bei der Verbrennung der Kraftstoffe; und
• (ii) Wasserstoff-Kohlenstoff-Verhältnis der Kraftstoffe.

Where multiple fuel tanks contain a fuel with the same highest percentage of sustainable aviation fuel, the tank to be used may be selected based on a comparison of at least one of the following criteria:

• (i) the level of emissions of non-volatile particles from the combustion of the fuels; and
• (ii) Hydrogen to carbon ratio of fuels.

One or more other parameters related to air quality may also be compared to select the fuel that is likely to produce the best air quality results. Environmental factors (such as flight altitude and humidity) may also be considered in this assessment.

The propulsion system may be an aircraft propulsion system and the gas turbine engine (at least one gas turbine engine of the one or more gas turbine engines) may be arranged to provide motive power to the aircraft.

The fuel with the highest proportion of sustainable aviation fuel can be chosen so that the propulsion system can be operated with this fuel alone.

The fuel with the highest proportion of sustainable aviation fuel - SAF - can contain more than 50% SAF and optionally at least 55% SAF.

The fuel manager may be arranged to control in-flight fuel delivery to the gas turbine engine by selecting a particular fuel or fuel combination from one or more of the plurality of fuel tanks.

A first fuel tank of the plurality of fuel tanks may be arranged to contain the fuel having the highest percentage of sustainable aviation fuel and may be smaller than the other fuel tanks. The first fuel tank can be arranged such that it is used exclusively for ground-based operation of the aircraft.

The fuel with the highest proportion of sustainable ground-use aviation fuel may have a lower calorific value than fuel stored in another fuel tank of the plurality of fuel tanks.

The fuel with the highest proportion of sustainable aviation fuel can be used for all aircraft ground operations.

A first fuel tank of the plurality of fuel tanks may be arranged to contain the fuel having the highest proportion of sustainable aviation fuel and may be arranged to supply fuel to the gas turbine engine when operating on the ground and that it serves as a trim tank in flight.

The fuel with the highest proportion of sustainable aviation fuel - SAF - can consist of 100% SAF.

• ein Gasturbinentriebwerk, das so angeordnet ist, dass es einen Kraftstoff verbrennt, um das Luftfahrzeug mit Energie zu versorgen;
• eine Vielzahl von Kraftstofftanks, die jeweils so angeordnet sind, dass sie einen Kraftstoff enthalten, der zur Energieversorgung des Luftfahrzeugs verwendet werden soll, wobei mindestens zwei Tanks der Vielzahl von Kraftstofftanks unterschiedliche Kraftstoffe enthalten, wobei ein erster Tank einen Kraftstoff enthält, der zu mehr als 50 % aus nachhaltigem Flugkraftstoff besteht, und ein zweiter Tank einen Kraftstoff enthält, der zu weniger als 50 % aus nachhaltigem Flugkraftstoff besteht; und
• ein Kraftstoffmanager, der dazu eingerichtet ist:
  • Informationen über den in jedem Kraftstofftank enthaltenen Kraftstoff zu speichern; und
  • die Kraftstoffversorgung so zu steuern, dass nur Kraftstoff verwendet wird, der zu mehr als 50 % aus nachhaltigem Flugbenzin besteht, um zumindest den Großteil des Betriebs am Boden zu gewährleisten.

According to a twenty-eighth aspect, there is provided a power system for an aircraft, comprising:

• a gas turbine engine arranged to combust a fuel to power the aircraft;
• a plurality of fuel tanks each arranged to contain a fuel to be used to power the aircraft, at least two tanks of the plurality of fuel tanks containing different fuels, a first tank containing a fuel intended for more than Consists of 50% sustainable aviation fuel and a second tank contains a fuel that consists of less than 50% sustainable aviation fuel; and
• a fuel manager set up to:
  • store information about the fuel contained in each fuel tank; and
  • To manage the fuel supply to only use fuel that consists of more than 50% sustainable aviation fuel in order to ensure at least the majority of operations on the ground.

The first tank may contain a fuel that is a sustainable aviation fuel (i.e. 100% SAF).

• Anordnen von zwei oder mehr Kraftstofftanks aus der Vielzahl von Kraftstofftanks, um verschiedene Kraftstoffe zu speichern, wobei die verschiedenen Kraftstoffe jeweils einen unterschiedlichen Anteil eines nachhaltigen Flugkraftstoffs aufweisen;
• Feststellen, welcher Tank den Kraftstoff mit dem höchsten Anteil eines nachhaltigen Flugkraftstoffs enthält; und
• Steuerung der Kraftstoffzufuhr derart, dass nur aus dem Tank mit dem höchsten Anteil an nachhaltigem Flugkraftstoff Kraftstoff entnommen wird, wenn das Luftfahrzeug zumindest den größten Teil des Betriebs am Boden durchführt.

According to a twenty-ninth aspect, there is provided a method of operating an aircraft including a gas turbine engine and a plurality of fuel tanks arranged to store fuel for powering the gas turbine engine, the method comprising:

• arranging two or more fuel tanks of the plurality of fuel tanks to store different fuels, the different fuels each having a different proportion of a sustainable aviation fuel;
• Determine which tank contains the fuel with the highest proportion of sustainable aviation fuel; and
• Control fueling such that fuel is only drawn from the tank with the highest proportion of sustainable aviation fuel when the aircraft is conducting at least the majority of its operations on the ground.

The method may further include storing information about the fuel contained in each fuel tank. The control can be carried out on the basis of the stored information.

The gas turbine engine may be arranged to provide motive power to the aircraft.

The gas turbine engine may be a gas turbine engine of an auxiliary power unit (APU) of the aircraft.

A first fuel tank of the one or more tanks may be arranged to contain the fuel having the highest percentage of sustainable aviation fuel. This first fuel tank may be arranged to act as the aircraft's trim tank - the fuel in the first fuel tank may therefore be arranged to be used up (at least substantially) in performing the operations on the ground, so that the first fuel tank eventually is essentially empty and available to receive fuel that will be pumped in during flight.

• Anordnen von zwei oder mehr Kraftstofftanks aus der Vielzahl von Kraftstofftanks, um verschiedene Kraftstoffe zu speichern, wobei die verschiedenen Kraftstoffe jeweils einen unterschiedlichen Anteil eines nachhaltigen Flugkraftstoffs aufweisen; und
• Bereitstellung eines Kraftstoffmanagers, der dazu eingerichtet ist:
  • festzustellen, welcher Tank den Kraftstoff mit dem höchsten Anteil an nachhaltigem Flugkraftstoff enthält; und
  • die Kraftstoffzufuhr so zu steuern, dass nur aus dem Tank mit dem höchsten Anteil an nachhaltigem Flugkraftstoff Kraftstoff entnommen wird, wenn das Luftfahrzeug zumindest den überwiegenden Teil des Betriebs am Boden durchführt.

According to a thirtieth aspect, there is provided a method of modifying an aircraft that includes a gas turbine engine and a plurality of fuel tanks arranged to store fuel for powering the gas turbine engine, the method comprising:

• arranging two or more fuel tanks of the plurality of fuel tanks to store different fuels, the different fuels each having a different proportion of a sustainable aviation fuel; and
• Provision of a fuel manager set up to:
  • determine which tank contains the fuel with the highest proportion of sustainable aviation fuel; and
  • to control the fuel supply so that fuel is taken only from the tank with the highest proportion of sustainable aviation fuel when the aircraft is conducting at least the majority of its operations on the ground.

The fuel manager may be configured to store information about the fuel contained in each fuel tank. The fuel manager may be configured to perform tank identification and fuel delivery control based on the stored information.

As noted elsewhere, the present disclosure may relate to a gas turbine engine. Such a gas turbine engine may include an engine core having a turbine, a combustor, a compressor, and a core shaft connecting the turbine to the compressor. Such a gas turbine engine may include a fan (having fan blades) located upstream of the engine core. Alternatively, in some examples, the gas turbine engine may also include a fan located downstream of the engine core. Thus, the gas turbine engine may be an open rotor or a turboprop engine.

If the gas turbine engine is an open rotor or turboprop engine, the gas turbine engine may comprise two counter-rotating propeller stages which are attached to and driven by a free power turbine via a shaft. The propellers can rotate in opposite directions, so one rotates clockwise and the other counter-clockwise around the engine's axis of rotation. Alternatively, the gas turbine engine may include a propeller stage and a vane stage downstream of the propeller stage. The vane stage may have a variable pitch. Accordingly, high-pressure, medium-pressure and free power turbines can drive high- and medium-pressure compressors or propellers via suitable connecting shafts. This allows the propellers to provide most of the propulsion thrust.

Where the gas turbine engine is an open rotor or turboprop engine, one or more propeller stages may be driven by a gearbox of the type described.

The arrangement of the present disclosure may be particularly, although not exclusively, advantageous for gear driven fans. Accordingly, the gas turbine engine may include a gearbox that receives input from the core shaft and outputs output to the fan to drive the fan at a lower speed than the core shaft. Input to the gearbox may be direct from the core shaft or indirectly from the core shaft, for example via a spur shaft and/or gearbox. The core shaft can rigidly connect the turbine and compressor so that the turbine and compressor rotate at the same speed (with the fan rotating at a lower speed).

The gas turbine engine as described and/or claimed herein may have any suitable general architecture. For example, the gas turbine engine may have any number of spools connecting the turbine and compressor, such as one, two, or three spools. For example only, the turbine connected to the core shaft may be a first turbine, the compressor connected to the core shaft may be a first compressor, and the core shaft may be a first core shaft. The engine core may further include a second turbine, a second compressor, and a second core shaft connecting the second turbine to the second compressor. The second turbine, the second compressor, and the second core shaft may be arranged to rotate at a higher speed than the first core shaft.

In such an arrangement, the second compressor may be positioned axially downstream of the first compressor. The second compressor may be arranged to receive flow from the first compressor (e.g. receive directly, e.g. via a generally annular duct).

The gearbox may be arranged to be driven from the core shaft configured to rotate (e.g. in use) at the lowest speed (e.g. the first core shaft in the example above). For example, the gearbox can be arranged to be driven only by the core shaft that is configured to rotate (e.g., in use) at the lowest speed (e.g., only by the first core shaft and not by the second core shaft in the example above ). Alternatively, the gearbox may be arranged to be driven by one or more shafts, for example the first and/or second shaft in the example above.

The gearbox may be a reduction gearbox (in that the output to the fan is at a lower speed than the input from the core shaft). Any type of gear can be used. For example, the gearing may be a "planetary gear" or a "star gear" as described elsewhere herein. The transmission may have any desired reduction ratio (defined as input shaft speed divided by output shaft speed), for example greater than 2.5, for example in the range 3 to 4.2 or 3.2 to 3.8, for example in the order of or at least 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1 or 4, 2. The

For example, transmission ratio can be between any two of the values mentioned in the previous sentence. By way of example only, the gear may be a "star gear" with a ratio in the range of 3.1 or 3.2 to 3.8. In some arrangements, the transmission ratio may be outside of these ranges.

In any gas turbine engine as described and/or claimed herein, a combustor may be provided axially downstream of the fan and compressor(s). For example, the combustor may be located directly downstream of the second compressor (e.g., at its exit) where a second compressor is provided. As another example, the flow at the exit to the combustor may be delivered to the inlet of the second turbine where a second turbine is provided. The combustor may be provided upstream of the turbine(s).

The or each compressor (e.g. the first compressor and the second compressor, as above described) may include any number of stages, for example multiple stages. Each stage may include a row of rotor blades and a row of stator vanes, which may be variable stator vanes (in that their angle of incidence may be variable). The row of rotor blades and the row of stator vanes may be axially offset from one another.

The or each turbine (such as the first turbine and the second turbine as described above) may include any number of stages, such as multiple stages. Each stage may include a row of rotor blades and a row of stator vanes. The row of rotor blades and the row of stator vanes may be axially offset from one another.

Each fan blade may be defined as having a radial span extending from a root (or hub) at a radially inner gas bath or 0% span position to a tip at a 100% span position. The ratio of the radius of the fan blade at the hub to the radius of the fan blade at the tip may be less than (or of the order of): 0.4, 0.39, 0.38, 0.37, 0.36, 0 .35, 0.34, 0.33, 0.32, 0.31, 0.3, 0.29, 0.28, 0.27, 0.26 or 0.25. The ratio of the radius of the fan blade at the hub to the radius of the fan blade at the tip may be in an inclusive range bounded by two of the values in the preceding sentence (i.e. the values may form upper or lower limits), for example in the range from 0.28 to 0.32. These ratios can be referred to generically as the hub to tip ratio. The radius at the hub and the radius at the tip can both be measured at the leading edge (or axially foremost part) of the blade. The hub-to-tip ratio is of course related to the gas-swept portion of the fan blade, i. H. to the portion radially outside of any platform.

The radius of the fan can be measured between the centerline of the engine and the tip of a fan blade at its leading edge. The fan diameter (which may be simply twice the fan radius) may be greater than (or of the order of): 220 cm, 230 cm, 240 cm, 250 cm (about 100 in), 260 cm, 270 cm (about 105 in in), 280 cm (about 110 in), 290 cm (about 115 in), 300 cm (about 120 in), 310 cm, 320 cm (about 125 in), 330 cm (about 130 in), 340 cm (about 135 in), 350 cm, 360 cm (about 140 in), 370 cm (about 145 in), 380 cm (about 150 in), 390 cm (about 155 in), 400 cm, 410 cm (about 160 in) or 420 cm (about 165 in). The fan diameter can be in an inclusive range bounded by any two of the values in the preceding sentence (i.e. the values can form upper or lower limits), for example in the range of 240 cm to 280 cm or 330 cm to 380 cm .

Fan speed may vary with use. In general, larger diameter fans will have lower RPMs. By way of example and not by way of limitation, the rotational speed of the fan may be less than 2500 rpm, for example less than 2300 rpm, in cruise conditions. By way of further non-limiting example only, for an engine having a fan diameter in the range of 220 cm to 300 cm (e.g. 240 cm to 280 cm or 250 cm to 270 cm), the fan speed at cruise conditions may be in the range of 1700 rpm to 2500 rpm, for example in the range from 1800 rpm to 2300 rpm, for example in the range from 1900 rpm to 2100 rpm. By way of further non-limiting example, for an engine with a fan diameter in the range of 330 cm to 380 cm, the speed of the fan at cruise conditions may be in the range of 1200 rpm to 2000 rpm, for example in the range of 1300 rpm to 1800 rpm, for example in the range from 1400 rpm to 1800 rpm.

In use of the gas turbine engine, the fan (with associated fan blades) rotates about an axis of rotation. This rotation causes the tip of the fan blade to move at a speed U _tip . The work done by the fan blades 13 on the stream results in an increase in enthalpy dH of the stream. A fan tip loading can be defined as dH/U _peak ² , where dH is the enthalpy rise (e.g. mean 1-D enthalpy rise) across the fan and U _peak is the (translational) velocity of the fan tip, e.g. at the tip leading edge ( which can be defined as the fan tip radius at the leading edge multiplied by the angular velocity). Fan peak loading at cruise conditions may be greater than (or on the order of): 0.28, 0.29, 0.30, 0.31, 0.32, 0.33, 0.34, 0.35, 0, 36, 0.37, 0.38, 0.39 or 0.4. The fan tip loading may be in an inclusive range bounded by two of the values in the previous sentence (ie the values may form upper or lower bounds), for example in the range of 0.28 to 0.31 or 0.29 up to 0.3.

Gas turbine engines according to the present disclosure may have any bypass ratio, where bypass ratio is defined as the ratio of the mass flow rate of flow through the bypass duct to the mass flow rate of flow through the core at cruise conditions. In some arrangements it can Bypass ratio must be greater than (or close to) any of the following: 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5 , 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, or 20. The bypass ratio may be in an inclusive range bounded by two of the values in the previous sentence (i.e. the values can form upper or lower limits), for example in the range from 12 to 16 or 13 to 15 or 13 to 14. The bypass channel can be essentially ring-shaped. The bypass duct can be located radially outside of the core engine. The radially outer surface of the bypass duct can be defined by a nacelle and/or a fan casing.

The overall pressure ratio of a gas turbine engine, as described and/or claimed herein, may be defined as the ratio of the ram pressure upstream of the fan to the ram pressure at the highest pressure compressor exit (before entering the combustor). As a non-limiting example, the overall pressure ratio of a gas turbine engine as described and/or claimed herein at cruise conditions may be greater than (or on the order of) any of the following: 35, 40, 45, 50, 55, 60, 65, 70, 75. The overall pressure ratio may be in an inclusive range bounded by any two of the values in the preceding sentence (i.e. the values may form upper or lower limits), for example in the range 50 to 70.

The specific thrust of an engine can be defined as the net thrust of the engine divided by the total mass flow through the engine. At cruise conditions, the specific thrust of an engine described and/or claimed herein may be less than (or on the order of) any of the following: 110 Nkg ^-1 s, 105 Nkg ^-1 s, 100 Nkg ^-1 s, 95 Nkg ^-1 s, 90 Nkg ^-1 s, 85 Nkg ^-1 s or 80 Nkg ^-1 s. The specific thrust may be in an inclusive range bounded by any two of the values in the preceding sentence (i.e. the values may have upper or lower limits form), for example in the range of 80 Nkg ^-1 s to 100 Nkg ^-1 s or 85 Nkg ^-1 s to 95 Nkg ^-1 s. Such engines can be particularly efficient compared to conventional gas turbine engines.

A gas turbine engine as described and/or claimed herein can have any desired maximum thrust. As a non-limiting example, a gas turbine as described and/or claimed herein may be capable of producing a maximum thrust of at least one of (or on the order of): 160 kN, 170 kN, 180 kN, 190 kN , 200 kN, 250 kN, 300 kN, 350 kN, 400 kN, 450 kN, 500 kN or 550 kN. The maximum thrust can be in an inclusive range bounded by any two of the values from the previous sentence (i.e. the values can form upper or lower limits). For example, a gas turbine as described and/or claimed herein may be capable of producing a maximum thrust in the range of 330 kN to 420 kN, for example 350 kN to 400 kN. The above thrust may be the maximum net thrust under normal atmospheric conditions at sea level plus 15 degrees C (ambient pressure 101.3 kPa, temperature 30 degrees C) with the engine static.

In use, the temperature of the stream entering the high-pressure turbine can be particularly high. This temperature, which may be referred to as TET, may be measured at the exit of the combustor, for example immediately upstream of the first turbine blade, which may itself be referred to as the nozzle guide vane. In flight, the TET may be at least (or on the order of) one of the following: 1400K, 1450K, 1500K, 1550K, 1600K, or 1650K. The TET in flight may be in an inclusive range divided by two any of the values in the previous sentence is bounded (i.e. the values can form upper or lower bounds). For example, the maximum TET in use of the engine may be at least (or on the order of) one of the following: 1700K, 1750K, 1800K, 1850K, 1900K, 1950K, or 2000K. The maximum TET may be in an inclusive range bounded by any two of the values in the previous sentence (i.e. the values may form upper or lower bounds), for example in the range 1800K to 1950K. The maximum TET may e.g. B. at a high thrust condition, z. B. at a maximum take-off (engl .: Maximum take-off - MTO) occur.

A fan blade (blower blade) and/or an airfoil of a fan blade as described and/or claimed herein may be made from any suitable material or combination of materials. For example, at least a portion of the fan blade and/or airfoil may be formed at least in part from a composite material, such as a metal matrix composite material and/or an organic matrix composite material, such as e.g. B. carbon fiber, are produced. As another example, at least a portion of the fan blade and/or airfoil may be at least partially fabricated from a metal, such as a titanium-based metal, or an aluminum-based material (such as an aluminum-lithium alloy), or a steel-based material. The fan blade can consist of at least two areas that are different materials are made. For example, the fan blade may have a protective leading edge made of a material that resists impact (e.g., from birds, ice, or other material) better than the rest of the blade. Such a leading edge can, for. Example, be made of titanium or a titanium alloy. For example, the fan blade may have a carbon fiber or aluminum (such as an aluminum-lithium alloy) body with a titanium leading edge.

A fan as described and/or claimed herein may include a central portion from which the fan blades may extend, for example in a radial direction. The fan blades can be attached to the central section in any desired manner. For example, each fan blade may have a fastener that engages a corresponding slot in the hub (or disc). By way of example only, such an attachment may be in the form of a dovetail which inserts and/or snaps into a corresponding slot in the hub/disk to secure the fan blade to the hub/disc. As another example, the fan blades may be integral with a central portion. Such an arrangement can be referred to as a vane disk or vane ring. Any suitable method can be used to manufacture such a bladed disc or ring. For example, at least a portion of the fan blades may be machined from one block and/or at least a portion of the fan blades may be attached to the hub/disk by welding, such as linear friction welding.

The gas turbine engines described and/or claimed herein may or may not be equipped with a variable area nozzle (VAN). With such a nozzle with a variable cross section, the exit area of the bypass channel can be varied during operation. The general principles of the present disclosure may apply to engines with or without a VAN.

The gas turbine fan as described and/or claimed herein may have any number of fan blades, for example 14, 16, 18, 20, 22, 24 or 26 fan blades.

As used herein, the terms coast, taxi, takeoff, climb, cruise, descent, approach, and landing have their usual meanings and are readily understood by those skilled in the art. Thus, given a particular aircraft gas turbine engine, those skilled in the art would readily recognize that each term refers to a phase of operation of the engine within a particular aircraft operation for which the gas turbine engine is intended.

In this context, the term "idle" may refer to a phase of engine operation when the aircraft is stationary and in contact with the ground, but the engine must be running. During idle, the engine can produce between 3% and 9% of the engine's available thrust. In other examples, the engine may produce between 5% and 8% of the available thrust. In other examples, the engine may produce between 6 and 7% of the available thrust. Taxiing may refer to a phase of engine operation during which the aircraft is propelled over the ground by the thrust produced by the engine. While taxiing, the engine can generate between 5% and 15% of the available thrust. In other examples, the engine may produce between 6% and 12% of the available thrust. In other examples, the engine may produce between 7% and 10% of the available thrust. The term "take-off" may refer to a phase of engine operation during which the aircraft is propelled by the thrust produced by the engine. In a first phase of the take-off phase, the aircraft can be propelled while touching the ground. At a later stage of the take-off phase, the aircraft can be powered while off the ground. During takeoff, the engine can generate between 90% and 100% of the available thrust. In other examples, the engine may produce between 95% and 100% of the available thrust. In other examples, the engine may produce 100% of the available thrust.

Climb may refer to a phase of engine operation during which the aircraft is propelled by the thrust produced by the engine. During climb, the engine can generate between 75% and 100% of the available thrust. In other examples, the engine may produce between 80% and 95% of the available thrust. In other examples, the engine may produce between 85% and 90% of the available thrust. In this context, the term climb may refer to an operational phase within an aircraft flight cycle between takeoff and reaching cruise conditions. Additionally or alternatively, the term climb may refer to a nominal point in an aircraft flight cycle between takeoff and landing where a relative gain in altitude is required, which may require additional engine thrust demand.

As used herein, the term "cruise conditions" has the usual meaning and is for the readily understandable to those skilled in the art. Thus, for a given gas turbine engine for an aircraft, one skilled in the art would immediately recognize that the cruise conditions mean the operating point of the engine at mid-cruise of a particular mission (which may be termed "economic mission" in the industry) of an aircraft at which the Gas turbine engine to be installed. In this context, mid-cruise is the point in an aircraft's flight cycle when 50% of all fuel burned between the highest point of climb and the start of descent has been burned (which is represented by the mid-point - in terms of time and/or distance - between the top of the climb and the beginning of the descent can be approximated). The cruise conditions thus define an operating point of the gas turbine engine that delivers a thrust that ensures steady-state operation (i.e. maintaining a constant altitude and a constant Mach number) in the middle of the cruise flight of an aircraft for which it is designed, where the number of engines for this aircraft is considered. For example, if an engine is designed for installation on an aircraft with two engines of the same type, the engine will deliver half the total thrust at cruise that would be required for stationary operation of the aircraft at mid-cruise.

In other words, for a given gas turbine engine for an aircraft, the cruising conditions are defined as the operating point of the engine which produces a given thrust (which - in combination with other engines in the aircraft - is necessary for steady-state operation of the aircraft for which it is designed at a certain Mach number is required at mid-cruise) at the atmospheric conditions at mid-cruise (defined by the international standard atmosphere according to ISO 2533 at cruise altitude). For any aircraft gas turbine engine, the mid-cruise thrust, atmospheric conditions and Mach number are known so that the operating point of the engine at cruise conditions is well defined.

By way of example only, the cruise forward speed may be any point in the range of Mach 0.7 to 0.9, e.g. 0.75 to 0.85, e.g. 0.76 to 0.84, e.g. 0.77 to 0.83, e.g. 0.78 to 0.82, e.g. 0.79 to 0.81, e.g. B. on the order of Mach 0.8, on the order of Mach 0.85 or in the range of 0.8 to 0.85. Any single speed within these ranges can be part of the cruise conditions. Some aircraft may have cruising conditions outside of these ranges, e.g. B. below Mach 0.7 or above Mach 0.9.

By way of example only, cruise conditions may correspond to standard atmospheric conditions (according to International Standard Atmosphere, ISA) at an altitude ranging from 10000m to 15000m, for example from 10000m to 12000m, for example from 10400m to 11600m (about 38000 ft ) is, e.g. in the range of 10500m to 11500m, e.g. in the range of 10600m to 11400m, e.g. in the range of 10700m (about 35000 ft) to 11300m, e.g. in the range of 10800m to 11200m, e.g. in the range of 10900m to 11100m, e.g. in of the order of 11000m. Cruise conditions may correspond to standard atmospheric conditions at any altitude in these ranges.

By way of example only, cruise conditions may correspond to an engine operating point having a known required thrust level (e.g. a value in the range 30kN to 35kN) at a forward Mach number of 0.8 and standard atmospheric conditions (according to the International Standard Atmosphere) in a Altitude of 11582m (38000 ft) delivers. As another example, the cruise conditions may correspond to an engine operating point having a known required thrust (eg, a value in the range of 50kN to 65kN) at a forward Mach number of 0.85 and standard atmospheric conditions (according to the International Standard Atmosphere) in a Altitude of 10668m (35000ft) delivers.

In operation, a gas turbine engine described and/or claimed herein may operate at cruise conditions as defined elsewhere herein. These cruise conditions may be determined by the cruise conditions (e.g. mid-cruise conditions) of an aircraft which may have at least one gas turbine engine (e.g. 2 or 4) fitted to provide propulsion.

Additionally, those skilled in the art would readily recognize that descent or approach to landing refers to an operational phase within an aircraft's flight cycle between cruise and landing of the aircraft. During descent or approach, the engine can generate between 20% and 50% of the available thrust. In other examples, the engine may produce between 25% and 40% of the available thrust. In other examples, the engine may produce between 30% and 35% of the available thrust. Additionally or alternatively, the term "descent" may refer to a nominal point in an aircraft's flight cycle between takeoff and Lan where relative altitude drop is required and which may require less engine thrust demand.

According to one aspect, there is provided an aircraft having a gas turbine engine as described and/or claimed herein. The aircraft in this aspect is the aircraft for which the gas turbine engine is designed to be fitted. Accordingly, cruise conditions in accordance with this aspect correspond to the aircraft's mean cruise flight as defined elsewhere herein.

In one aspect, there is provided a method of operating a gas turbine engine as described and/or claimed herein. Operation may be at cruise conditions as defined elsewhere herein (e.g., related to thrust, atmospheric conditions, and Mach number).

According to one aspect, there is provided a method of operating an aircraft having a gas turbine engine as described and/or claimed herein. Operation in accordance with this aspect may include (or may be) operation at mid-cruise of the aircraft as defined elsewhere herein.

Those skilled in the art will understand that a feature or parameter described in relation to any of the above aspects may also be applied to any other aspect, provided they are not mutually exclusive. In addition, any feature or parameter described herein may be applied to any aspect and/or combined with any other feature or parameter described herein, provided they are not mutually exclusive.

• 1 ist eine Seitenschnittansicht eines Gasturbinentriebwerks;
• 2 ist eine Seitenschnittgroßansicht eines stromaufwärtigen Abschnitts eines Gasturbinentriebwerks;
• 3 ist eine zum Teil weggeschnitte Ansicht eines Getriebes für ein Gasturbinentriebwerk;
• 4 ist eine schematische Ansicht eines Luftfahrzeugs mit einem Kraftstoffzusammensetzungs-Tracker;
• 5 ist eine schematische Darstellung eines Verfahrens zur Kraftstoffidentifizierung;
• 6 ist eine schematische Ansicht eines Systems zur Verfolgung der Kraftstoffzusammensetzung eines Luftfahrzeugs in Verbindung mit einer Kraftstoffzufuhrleitung und einem Bordtank, was die optionale Verwendung als Modul zur Bestimmung der Kraftstoffzusammensetzung anzeigt;
• 7 ist eine schematische Ansicht eines Luftfahrzeugs mit einem Modul zur Bestimmung der Kraftstoffzusammensetzung;
• 8 ist eine schematische Darstellung eines Luftfahrzeugbetriebsverfahrens;
• 9 ist eine schematische Darstellung eines anderen Luftfahrzeugbetriebsverfahrens;
• 10 ist eine schematische Ansicht eines Luftfahrzeugs mit einem Kraftstoffmanager;
• 11 ist eine schematische Darstellung eines anderen Luftfahrzeugbetriebsverfahrens;
• 12 ist eine schematische Ansicht eines Luftfahrzeugkraftstoffzufuhrsystems in Verbindung mit einem Kraftstofftank und einem Gasturbinentriebwerk;
• 13 ist eine schematische Darstellung eines Luftfahrzeugmodifikationsverfahrens; und
• 14 ist eine schematische Ansicht eines Luftfahrzeugs mit einer anderen Tankanordnung als der in 4, 7 oder 10 gezeigten, einschließlich eines Kraftstoffmanagers und eines Trimmtanks;
• 15 ist eine schematische Darstellung eines anderen Luftfahrzeugbetriebsverfahrens;
• 16 ist eine schematische Ansicht eines Luftfahrzeugkraftstoffzufuhrsystems in Verbindung mit einem Kraftstofftank, einer Hilfsturbine und einem Gasturbinentriebwerk;
• 17 ist eine schematische Darstellung eines anderen Luftfahrzeugmodifikationsverfahrens; und
• 18 ist eine schematische Ansicht eines Luftfahrzeugs mit einer anderen Tankanordnung als der in 14 gezeigten;
• 19 ist eine schematische Ansicht eines Luftfahrzeugs mit einem Kraftstoffmanager und einer anderen Tankanordnung als in 14 dargestellt;
• 20 ist eine schematische Darstellung eines Luftfahrzeugbetriebsverfahrens;
• 21 ist eine schematische Ansicht eines Luftfahrzeugkraftstoffzufuhrsystems im Zusammenhang mit Kraftstofftanks und einem Gasturbinentriebwerk;
• 22 ist eine schematische Darstellung eines Luftfahrzeugmodifikationsverfahrens;
• 23 ist eine schematische Darstellung eines Luftfahrzeugbetriebsverfahrens;
• 24 ist eine schematische Darstellung eines Luftfahrzeugmodifikationsverfahrens; und
• 25 ist eine schematische Darstellung eines Luftfahrzeugbetriebsverfahrens.

The embodiments will now be described, by way of example only, with reference to the figures, in which:

• 1 Figure 12 is a side sectional view of a gas turbine engine;
• 2 Figure 12 is a close-up side sectional view of an upstream portion of a gas turbine engine;
• 3 Figure 12 is a partially cut-away view of a transmission for a gas turbine engine;
• 4 Figure 12 is a schematic view of an aircraft with a fuel composition tracker;
• 5 Fig. 12 is a schematic representation of a fuel identification method;
• 6 Figure 12 is a schematic view of an aircraft fuel composition tracking system in connection with a fuel supply line and an onboard tank, indicating optional use as a fuel composition determination module;
• 7 Figure 12 is a schematic view of an aircraft having a fuel composition determination module;
• 8th Figure 12 is a schematic representation of an aircraft operating procedure;
• 9 Figure 12 is a schematic representation of another aircraft operating procedure;
• 10 Figure 12 is a schematic view of an aircraft with a fuel manager;
• 11 Figure 12 is a schematic representation of another aircraft operating procedure;
• 12 Figure 12 is a schematic view of an aircraft fuel delivery system in connection with a fuel tank and a gas turbine engine;
• 13 Figure 12 is a schematic representation of an aircraft modification process; and
• 14 Fig. 12 is a schematic view of an aircraft having a different tank arrangement than that shown in Fig 4 , 7 or 10 shown, including a fuel manager and trim tank;
• 15 Figure 12 is a schematic representation of another aircraft operating procedure;
• 16 Figure 12 is a schematic view of an aircraft fuel delivery system in connection with a fuel tank, an APU and a gas turbine engine;
• 17 Figure 12 is a schematic representation of another aircraft modification process; and
• 18 Fig. 12 is a schematic view of an aircraft having a different tank arrangement than that shown in Fig 14 shown;
• 19 FIG. 12 is a schematic view of an aircraft with a fuel manager and a different tank arrangement than FIG 14 shown;
• 20 Figure 12 is a schematic representation of an aircraft operating procedure;
• 21 Figure 12 is a schematic view of an aircraft fuel delivery system associated with fuel tanks and a gas turbine engine;
• 22 Figure 12 is a schematic representation of an aircraft modification process;
• 23 Figure 12 is a schematic representation of an aircraft operating procedure;
• 24 Figure 12 is a schematic representation of an aircraft modification process; and
• 25 Figure 12 is a schematic representation of an aircraft operating procedure.

1 Figure 1 shows a gas turbine engine 10 having a main axis of rotation 9. The engine 10 includes an air intake 12 and a thrust fan 23 that produces two airflows: a core airflow A and a bypass airflow B. The gas turbine engine 10 includes a core 11 that receives the core airflow A. The engine core 11 includes, in axial flow order, a low pressure compressor 14, a high pressure compressor 15, a combustor 16, a high pressure turbine 17, a low pressure turbine 19 and a core exhaust nozzle 20. An engine nacelle 21 surrounds the gas turbine engine 10 and defines a bypass duct 22 and a bypass exhaust nozzle 18. The bypass airflow B flows through the bypass duct 22. The blower (fan) 23 is attached via a shaft 26 and an epicycloidal gear 30 to the low-pressure turbine 19 and is driven thereby.

In use, the core airflow A is accelerated and compressed by the low pressure compressor 14 and passed into the high pressure compressor 15 where further compression occurs. The compressed air discharged from the high pressure compressor 15 is directed into the combustor 16 where it is mixed with fuel and the mixture is burned. The resultant hot products of combustion then propagate through and thereby drive the high and low pressure turbines 17, 19 before being expelled through the nozzle 20 to provide some thrust. The high pressure turbine 17 drives the high pressure compressor 15 through a suitable connecting shaft 27 . The fan 23 generally provides the majority of the thrust. The epicycloidal gear 30 is a reduction gear.

An example arrangement for a geared fan gas turbine engine 10 is shown in 2 shown. The low-pressure turbine 19 (see 1 ) drives the shaft 26 which is coupled to a sun gear 28 of the epicycloidal gear assembly 30 . A plurality of planetary gears 32, which are coupled to one another by a planetary carrier 34, are located radially outward of the sun gear 28 and mesh therewith. The planetary carrier 34 constrains the planetary gears 32 to orbit synchronously about the sun gear 28 while allowing each planetary gear 32 to rotate about its own axis. Planet carrier 34 is coupled to fan 23 via linkage 36 to drive its rotation about engine axis 9 . An outer gear or ring gear 38, which is coupled to a stationary support structure 24 via linkage 40, is radially outward of the planetary gears 32 and meshes therewith.

It is noted that the terms "low pressure turbine" and "low pressure compressor" as used herein may be construed to mean the lowest pressure turbine stage and the lowest pressure compressor stage, respectively (i.e. not including the fan 23) and/or mean the turbine and compressor stages interconnected by the lowest speed connecting shaft 26 in the engine (i.e. not including the transmission output shaft driving the fan 23). In some writings, the "low-pressure turbine" and "low-pressure compressor" referred to herein may alternatively be known as the "intermediate-pressure turbine" and "intermediate-pressure compressor." Using such alternative nomenclature, fan 23 may be referred to as a first stage or lowest pressure stage.

The epicycloidal gear 30 is in 3 shown in more detail as an example. The sun gear 28, planet gears 32 and ring gear 38 each include teeth around their periphery for meshing with the other gears. However, for the sake of clarity, only exemplary sections of the teeth are shown in 3 shown. Although four planetary gears 32 are illustrated, those skilled in the art will recognize that more or fewer planetary gears 32 may be provided within the scope of the claimed invention. Practical applications of an epicycloidal gear 30 generally include at least three planetary gears 32.

This in 2 and 3 The epicycloidal gear 30 illustrated by way of example is a planetary gear in which the planet carrier 34 is coupled to an output shaft via linkage 36, with the ring gear 38 being fixed. However, any other suitable type of epicycloidal gear 30 may be used. As another example, the epicycloidal gear 30 may be a star arrangement in which the planetary carrier 34 is held fixed while allowing the ring gear (or ring gear) 38 to rotate. With such an arrangement, the fan 23 is driven by the ring gear 38 . As another alternative example, the transmission 30 may be a differential where both the ring gear 38 and the planetary carrier 34 are allowed to rotate.

It is understood that the in 2 and 3 The arrangement shown is exemplary only and various alternatives are within the scope of the present disclosure. Any suitable arrangement for positioning the gearbox 30 within the engine 10 and/or connecting the gearbox 30 to the engine 10 may be used, for example only. As another example, the connections (e.g., linkages 36, 40 in the example of FIG 2 ) between the transmission 30 and other parts of the engine 10 (such as the input shaft 26, the output shaft, and the fixed structure 24) can have some degree of rigidity or flexibility. As another example, any suitable arrangement of bearings between rotating and stationary parts of the engine (e.g., between the input and output shafts of the transmission and fixed structures such as the transmission case) may be used and the disclosure is not on the exemplary arrangement of 2 limited. For example, those skilled in the art will readily appreciate that the output and support linkage arrangements and bearing locations for a star configuration (described above) of the transmission 30 will typically differ from those exemplified in FIG 2 are shown would differ.

Accordingly, the present disclosure extends to a gas turbine engine having any arrangement of gear types (e.g., star or planetary), support structures, input and output shaft arrangement, and bearing locations.

Optionally, the transmission can drive secondary and/or alternative components (e.g., the intermediate pressure compressor and/or a booster).

Other gas turbine engines to which the present disclosure may have application may have alternative configurations. For example, such engines may have an alternative number of compressors and/or turbines and/or an alternative number of connecting shafts. As a further example, this points to 1 The gas turbine engine shown has a split flow nozzle 18, 20, which means that the flow through the bypass duct 22 has its own nozzle which is separate from the engine core nozzle 20 and radially outward therefrom. However, this is not limiting and any aspect of the present disclosure may also apply to engines where flow through bypass duct 22 and flow through core 11 are upstream of (or upstream of) a single nozzle, which may be referred to as a mixed flow nozzle. be mixed or combined. One or both nozzles (whether mixed or split flow) may have a fixed or variable area.

While the example described relates to a turbofan engine, the disclosure may apply to any type of gas turbine engine, e.g. for an open rotor (where the fan stage is not surrounded by a nacelle) or turboprop engine. In some arrangements, the gas turbine engine 10 may not include a gearbox 30 .

The geometry of the gas turbine engine 10 and its components is defined by a conventional axis system having an axial direction (which is aligned with the axis of rotation 9), a radial direction (in 1 from bottom to top) and a circumferential direction (perpendicular to the page in the view of 1 ) includes. The axial, radial and circumferential directions are perpendicular to each other.

The fuel F supplied to the combustor 16 may be a fossil hydrocarbon fuel such as kerosene. Thus, the fuel F can include molecules from one or more of the chemical families of n-alkanes, iso-alkanes, cycloalkanes and aromatics. Additionally or alternatively, the fuel F may consist of renewable hydrocarbons produced from biological or non-biological resources, also known as Sustainable Aviation Fuel (SAF). In each of the examples given, the fuel F may contain one or more trace elements, e.g. As sulfur, nitrogen, oxygen, inorganic substances and metals.

The functional performance of a particular composition or fuel blend for a particular service may be defined, at least in part, by the fuel's ability to service the Brayton cycle of the gas turbine engine 10 . Examples of parameters that define functional performance include specific energy, energy density, thermal stability, and emissions, including particulate emissions. Relatively higher specific energy (ie, energy per unit mass), expressed as MJ/kg, may at least partially reduce takeoff weight and thereby potentially provide a relative improvement in fuel economy. A relatively higher energy density (ie, energy per unit volume), expressed as MJ/L, may at least partially reduce takeoff fuel volume, which may be particularly important for volume-constrained missions or military operations involving refueling. Relatively higher thermal stability (i.e. preventing fuel from degrading or coking under thermal stress) may allow the fuel to withstand higher temperatures in the engine and in the injectors, which can lead to a relative improvement in combustion efficiency. Lower emissions, including particulate matter, can reduce contrail formation while reducing the environmental impact of a given mission. Other properties of the fuel can also be decisive for its functionality. A relatively low freezing point (°C) for long-distance missions can enable the flight profile to be optimized; a minimum concentration of aromatics (%) can ensure sufficient swelling of certain materials used in the manufacture of O-rings and seals that have previously been exposed to fuels with high aromatic content; and a maximum surface tension (mN/m) can ensure sufficient spray atomization and atomization of the fuel.

The ratio between the number of hydrogen atoms and the number of carbon atoms in a molecule can affect the specific energy of a particular composition or blend of fuels. Fuels with a higher ratio of hydrogen atoms to carbon atoms can have higher specific energies in the absence of bond strain. For example, fossil-based hydrocarbon fuels may consist of molecules having from about 7 to 18 carbon atoms, with a significant proportion of a given composition being made up of molecules having from 9 to 15 carbon atoms, with an average of 12 carbon atoms.

ASTM International (ASTM) D7566, Standard Specification for Aviation Turbine Fuels Containing Synthesized Hydrocarbons (ASTM 2019c) approves a range of sustainable aviation fuel blends containing between 10% and 50% sustainable aviation fuel (the remainder being one or more fossil hydrocarbon fuels such as kerosene) , with other compositions awaiting approval. However, the aviation industry believes that sustainable aviation fuel blends containing up to 100% Sustainable Aviation Fuel (SAF) will eventually be approved for use.

Sustainable aviation fuels can contain one or more of the following elements: n-alkanes, iso-alkanes, cyclo-alkanes and aromatics. For example, they can be made from one or more of the following elements: synthesis gas (syngas), lipids (e.g. fats, oils and fats), sugars and alcohols. Sustainable aviation fuels can therefore have lower levels of aromatics and sulfur, or both, compared to fossil hydrocarbon fuels. Additionally or alternatively, sustainable aviation fuels can have a higher content of iso-alkanes and cyclo-alkanes compared to fossil hydrocarbon fuels. For example, in some examples, sustainable aviation fuels may have a density between 90% and 98% of the density of kerosene and a calorific value between 101% and 105% of the density of kerosene.

Due at least in part to the molecular structure of sustainable aviation fuels, they may offer the following advantages compared to fossil hydrocarbon fuels (e.g. when burned in the incinerator 16): higher energy density, higher specific energy, higher specific heat capacity, higher thermal stability, higher lubricity, lower viscosity, lower surface tension, lower freezing point, lower soot emissions and lower CO ₂ emissions. Accordingly, sustainable aviation fuels may result in a relative decrease in specific fuel consumption or a relative decrease in maintenance costs compared to fossil hydrocarbon fuels such as kerosene.

As in the 4 and 7 As shown, an aircraft 1 may include a plurality of fuel tanks 50, 53, for example a larger main fuel tank 50 in the fuselage of the aircraft and a smaller fuel tank 53a, 53b in each wing. In other examples, an aircraft 1 may have only a single fuel tank 50, and/or the wing fuel tanks 53 may be larger than the center fuel tank 50, or there may be no center fuel tank (with all fuel instead being stored in the wings of the aircraft ) - it is clear that many different tank configurations are conceivable and that the examples shown are for ease of description and are not intended to be limiting.

4 and 7 show an aircraft 1 with a propulsion system 2, which comprises two gas turbine engines 10. The gas turbine engines 10 are supplied with fuel from a fuel supply system on board the aircraft 1 . The fuel supply system of the illustrated examples includes a single fuel source.

For purposes of this application, the term “fuel source” means either 1) a single fuel tank or 2) a plurality of fuel tanks that are fluidly connected to one another. Each fuel source is arranged to provide a separate fuel source, ie a first fuel source may contain a first fuel having a different property or properties than a second fuel substance contained in a second source of fuel. The first and second fuel sources are therefore not fluidly connected to separate the different fuels (at least under normal operating conditions).

In the present examples, the first (and in these examples only) fuel source consists of a center fuel tank 50, which is mainly located in the fuselage of the aircraft 1, and several wing fuel tanks 53a, 53b, with at least one wing fuel tank in the port wing and at least one wing fuel tank located in the starboard wing for balance. All tanks 50, 53 are connected to each other in the example shown and thus form a single fuel source. Each of the middle fuel tanks 50 and the wing fuel tanks 53 may consist of a plurality of fuel tanks connected to each other.

In another example, the wing fuel tanks 53a, 53b may not be connected to the center tank 50, thus forming a separate secondary fuel source. One or more fuel tanks in the port wing may be connected to one or more fuel tanks in the starboard wing for balancing purposes. This can be done either via a center fuel tank (if not part of the other fuel source), or bypassing the center fuel tank(s), or both (for maximum flexibility and safety).

In another example, the first fuel source includes wing fuel tanks 53 and a center fuel tank 50, while a second fuel source includes another separate center fuel tank. A fluid connection between the wing fuel tanks and the center fuel tank of the first fuel source may be provided to balance the aircraft 1.

In some examples, the distribution of the fuel tanks 50, 53 available in the aircraft 1 may be determined such that the first fuel source and the second fuel source are each substantially symmetrical about the centerline of the aircraft. In cases where an asymmetrical distribution of fuel tanks is permitted, an appropriate means of fuel transfer between the fuel tanks of the first fuel source and/or between the fuel tanks of the second fuel source is generally provided such that the position of the center of gravity of the aircraft is maintained throughout flight can be kept within acceptable lateral limits.

An aircraft 1 can be refueled by connecting a fuel storage tank 60, such as that provided by an airport fuel truck, or a permanent pipeline via a fuel line 61 to a port 62 of the aircraft. A desired quantity of fuel can be transferred from the fuel tank 60 into one or more tanks 50, 53 of the aircraft 1. Particularly in examples with more than one fuel source, where different tanks 50, 53 are to be filled with different fuels, instead of one connection, multiple fuel line connections 62 can be provided and/or valves can be used to route the fuel accordingly.

Aircraft typically refuel at several different airports, e.g. B. at the beginning and end of a long-haul flight. As mentioned above, while there are standards that all aviation fuels must meet, different aviation fuels have different compositions, e.g. B. depending on their source (e.g. various petroleum sources, biofuels or other synthetic aviation fuels (often referred to as sustainable aviation fuels - SAF -) and/or mixtures of petroleum-based fuels and other fuels) as well as on the additives contained (e.g. antioxidants and metal deactivators, biocides, antistatic agents, anti-icing agents, corrosion inhibitors) and contaminants. The composition of available aviation fuel can vary not only from airport to airport and from fuel supplier to fuel supplier, but also from batch to batch, even at a particular airport or fuel supplier. In addition, the fuel tanks 50, 53 of the aircraft 1 are not usually emptied before they are refilled for the next flight, which means that there are mixtures of different fuels in the tanks - and from the mixture actually one fuel with one different composition arises.

The inventors have recognized that knowledge of the fuels available to an aircraft 1 enables more efficient, tailored control of the aircraft 1 and in particular of the aircraft's propulsion system 2 (i.e. the one or more gas turbine engines 10 of the aircraft 1 and associated controls and components). possible, as different fuels can have different properties without violating the standards. Knowledge of fuel can therefore be used as a tool to improve aircraft performance, so monitoring fuel composition can bring benefits.

In various examples, an active, infinite summation approach can be chosen to account for the time-varying fuel composition to track the composition of a fuel in a fuel tank 50, 53 after several refuelings. This approach assumes that all aviation fuels are fully miscible and that, at least during aircraft operation, a homogeneous mixture forms in a fuel tank 50, 53 (a fuel split in the tank due to density differences can be observed in static tanks when a less dense fuel is topped up to a denser fuel, but such a split is unlikely to persist in flight as tank movement and system vibration cause mixing). In examples where the aircraft 1 has multiple fuel tanks 50, 53, a record may be kept for each fuel tank.

One such approach involves determining one or more fuel characteristics of the fuel already in the fuel tank 50, 53 prior to refueling.

1. i. den prozentualen Anteil an nachhaltigem Flugbenzin (SAF) im Kraftstoff oder die Angabe, dass es sich um einen fossilen Kraftstoff handelt, z. B. fossiles Kerosin, oder dass der Kraftstoff ein reiner SAF-Kraftstoff ist;
2. ii. Parameter einer Kohlenwasserstoffverteilung des Kraftstoffs, wie z. B.:
   • • den Gehalt an aromatischen Kohlenwasserstoffen des Kraftstoffs und gegebenenfalls auch / alternativ den Gehalt an multiaromatischen Kohlenwasserstoffen des Kraftstoffs;
   • • das Wasserstoff-Kohlenstoff-Verhältnis (H/C) des Kraftstoffs;
   • • Angaben zur prozentualen Zusammensetzung für einige oder alle vorhandenen Kohlenwasserstoffe;
3. iii. das Vorhandensein oder der prozentuale Anteil eines bestimmten Elements oder einer bestimmten Art, wie z. B.:
   • • der prozentuale Anteil der stickstoffhaltigen Spezies im Kraftstoff;
   • • das Vorhandensein oder der Prozentsatz einer Tracer-Spezies oder eines Spurenelements im Kraftstoff;
   • • Naphthalin-Gehalt des Kraftstoffs;
   • • Schwefelgehalt des Kraftstoffs;
   • • Cycloparaffingehalt des Kraftstoffs;
   • • Sauerstoffgehalt des Kraftstoffs;
4. iv. eine oder mehrere Eigenschaften des Kraftstoffs bei der Verwendung in einem Gasturbinentriebwerk 10, wie z. B.:
   • • Niveau der Emissionen nichtflüchtiger Partikel (nvPM) oder CO₂ bei der Verbrennung;
   • • Grad der Verkokung des Kraftstoffs;
5. v. eine oder mehrere Eigenschaften des Kraftstoffs selbst, unabhängig von der Verwendung in einem Motor 10 oder der Verbrennung, wie z. B.:
   • • thermische Stabilität des Kraftstoffs (z. B. thermische Durchbruchstemperatur); und
   • • eine oder mehrere physikalische Eigenschaften wie Dichte, Viskosität, Heizwert, Gefriertemperatur und/oder Wärmekapazität.

As used herein, the term “fuel characteristics” refers to intrinsic or inherent fuel properties, such as fuel composition, and not to variable properties such as volume or temperature. Examples of fuel characteristics include one or more of the following characteristics:

1. i. the percentage of sustainable aviation fuel (SAF) in the fuel or an indication that it is a fossil fuel, e.g. B. fossil kerosene, or that the fuel is a pure SAF fuel;
2. ii. Parameters of a hydrocarbon distribution of the fuel, such as. e.g.:
   • • the content of aromatic hydrocarbons in the fuel and possibly also/alternatively the content of multiaromatic hydrocarbons in the fuel;
   • • the hydrogen to carbon ratio (H/C) of the fuel;
   • • percentage composition information for some or all hydrocarbons present;
3. iii. the presence or percentage of a particular element or species, such as e.g.:
   • • the percentage of nitrogenous species in the fuel;
   • • the presence or percentage of a tracer species or trace element in the fuel;
   • • naphthalene content of the fuel;
   • • fuel sulfur content;
   • • cycloparaffin content of the fuel;
   • • fuel oxygen content;
4. IV. one or more properties of the fuel when used in a gas turbine engine 10, such as. e.g.:
   • • Level of emissions of non-volatile particles (nvPM) or CO ₂ during combustion;
   • • Degree of fuel coking;
5. v. one or more properties of the fuel itself, regardless of use in an engine 10 or combustion, such as. e.g.:
   • • thermal stability of the fuel (e.g. thermal breakdown temperature); and
   • • one or more physical properties such as density, viscosity, calorific value, freezing temperature and/or heat capacity.

The fuel characteristics to be tracked may be selected based on which properties of the fuel are most important to the changes to be made to the propulsion system 2 .

• (i) physikalischer und/oder chemischer Nachweis eines oder mehrerer Merkmale oder Parameter der Zusammensetzung des bereits im Kraftstofftank 50, 53 vorhandenen Kraftstoffs (dies kann den direkten Nachweis der Kraftstoffmerkmale ermöglichen und/oder die Bestimmung der Kraftstoffmerkmale unter Verwendung der Nachweisergebnisse gestatten) und/oder Nachweis eines oder mehrerer Tracer-Elemente oder -Verbindungen, die dem Kraftstoff zugesetzt werden, um seine Identifizierung zu erleichtern (z. B. ein Farbstoff);
• (ii) Erhalten des Ergebnisses einer früheren Bestimmung, die unter Verwendung eines aktiven unendlichen Summierungsansatzes, wie hier beschrieben, durchgeführt wurde, beispielsweise durch Abrufen eines oder mehrerer Kraftstoffmerkmale aus einem lokalen Datenspeicher an Bord des Luftfahrzeugs 1;
• (iii) Empfang von Daten, z. B. von einer Eingabe an einer Benutzerschnittstelle, oder von Daten, die an das Luftfahrzeug 1 übertragen werden.

Obtaining the fuel characteristics of a fuel already present in the fuel tank 50, 53 before refueling can include one or more of the following features:

• (i) physical and/or chemical detection of one or more compositional characteristics or parameters of the fuel already present in the fuel tank 50, 53 (this may allow direct detection of the fuel characteristics and/or allow determination of the fuel characteristics using the detection results) and/ or detection of one or more tracer elements or compounds added to the fuel to facilitate its identification (e.g. a dye);
• (ii) obtaining the result of a previous determination made using an active infinite summation approach as described herein, for example by retrieving one or more fuel characteristics from a local data store on board aircraft 1;
• (iii) receiving data, e.g. B. from an input at a user interface, or from data that are transmitted to the aircraft 1.

In some examples, several different methods of determining the fuel characteristics can be performed - for example, can different methods can be used for different characteristics and/or different methods can be used for the same characteristic for verification. In some examples, determining the one or more fuel characteristics of a fuel already present in the fuel tank 50, 53 prior to refueling, determining stored fuel characteristics and chemically or physically sensing one or more parameters of a fuel already present in the fuel tank 50, 53 prior to refueling and include checking these parameters against the stored fuel characteristics. The input to the calculation step described below may therefore be validated based on the one or more sensed parameters. A warning message can be issued in the event of a mismatch between the stored fuel attribute and the corresponding sensed parameter.

As previously mentioned, this approach generally assumes that the fuels are perfectly miscible and form a homogeneous mixture in the tanks 50,53. However, if there is a possibility of imperfect mixing of the fuels within the tank 50, 53 (e.g. after a long period of time in which a fuel mixture known to contain fuels of different densities has not moved), the fuel composition obtained from the Fuel tank 50, 53 leaking on the way to the engine 10, 44 are examined. If the measured, calculated or otherwise determined fuel characteristics of the fuel exiting the tank 50, 53 differ from those of the homogeneous mixture believed to be in the tank 50, 53, a potential problem with an imperfect mixing (e.g. when there is a significant density difference between the fuel already in the tank and the newly added fuel which could result in stratification) instead of or in addition to an indication of possible errors in understanding the full tank contents.

• • Der Aromaten- oder Cycloparaffingehalt des Kraftstoffs kann anhand von Messungen der Quellung einer Sensorkomponente aus einem Dichtungsmaterial wie z. B. einem Nitrildichtungsmaterial bestimmt werden.
• • Anhand von Spurenstoffen oder -arten, die entweder von Natur aus im Kraftstoff vorhanden sind oder als Tracer zugesetzt werden, lassen sich Kraftstoffmerkmale wie der prozentuale Anteil an nachhaltigem Flugbenzin im Kraftstoff oder der Kerosinanteil bestimmen.
• • Messungen der Schwingungsmode eines piezoelektrischen Kristalls, der dem Kraftstoff ausgesetzt ist, können als Grundlage für die Bestimmung verschiedener Kraftstoffmerkmale verwendet werden, einschließlich des Aromatengehalts des Kraftstoffs, des Sauerstoffgehalts des Kraftstoffs und der thermischen Stabilität oder des Verkokungsgrads des Kraftstoffs - zum Beispiel durch Messung des Aufbaus von Oberflächenablagerungen auf dem piezoelektrischen Kristall, die zu einer Veränderung der Schwingungsmode führen.
• • Verschiedene Kraftstoffmerkmale können durch Erfassung von Leistungsparametern des Gasturbinentriebwerks 10 während einer ersten Betriebsperiode (z. B. während des Starts) und optional auch während einer zweiten Betriebsperiode (z. B. während des Reiseflugs) ermittelt werden, wobei diese erfassten Parameter mit den erwarteten Werten bei Verwendung von Kraftstoff mit bekannten Eigenschaften verglichen werden.
• • Verschiedene Kraftstoffmerkmale, einschließlich des Gehalts an aromatischen Kohlenwasserstoffen, können auf der Grundlage von Sensormessungen des Vorhandenseins, des Nichtvorhandenseins oder des Grades der Bildung eines Kondensstreifens durch die Gasturbine 10 während ihres Betriebs bestimmt werden.
• • Die Eigenschaften des Kraftstoffs, einschließlich des Gehalts an aromatischen Kohlenwasserstoffen, können anhand einer UV-Vis-Spektroskopie-Messung des Kraftstoffs bestimmt werden.
• • Verschiedene Kraftstoffmerkmale wie der Schwefelgehalt, der Naphthalin-Gehalt, der Gehalt an aromatischem Wasserstoff und das Wasserstoff-Kohlenstoff-Verhältnis können durch Messung der in den Abgasen des Gasturbinentriebwerks 10 enthaltenen Stoffe bestimmt werden.
• • Der Heizwert des Kraftstoffs kann während des Betriebs des Luftfahrzeugs 1 anhand von Messungen ermittelt werden, die während der Verbrennung des Kraftstoffs durchgeführt werden, z. B. anhand des Kraftstoffdurchsatzes und der Wellendrehzahl oder der Änderung der Temperatur in der Brennkammer 16.
• • Verschiedene Kraftstoffmerkmale können bestimmt werden, indem eine Betriebsänderung vorgenommen wird, die den Betrieb des Gasturbinentriebwerks 10 beeinflusst, eine Reaktion auf die Betriebsänderung erfasst wird und die ein oder mehreren Kraftstoffmerkmale des Kraftstoffs auf der Grundlage der Reaktion auf die Betriebsänderung bestimmt werden.
• • Verschiedene Kraftstoffcharakteristiken können in Bezug auf die Kraftstoffcharakteristiken eines ersten Kraftstoffs bestimmt werden, indem ein dem Gasturbinentriebwerk 10 zugeführter Kraftstoff von dem ersten Kraftstoff auf einen zweiten Kraftstoff umgestellt wird und die eine oder mehrere Kraftstoffcharakteristiken des zweiten Kraftstoffs auf der Grundlage einer Änderung des Verhältnisses zwischen T30 und einem von T40 und T41 bestimmt werden (wobei das Verhältnis den Temperaturanstieg in der Brennkammer 16 anzeigt). Die Merkmale können als relative Werte im Vergleich zum ersten Kraftstoff oder als absolute Werte bestimmt werden, z. B. durch Bezugnahme auf bekannte Werte für den ersten Kraftstoff.

Fuel characteristics can be determined in a variety of ways, both directly (e.g., from sensor data corresponding to the fuel characteristic of interest) and indirectly (e.g., by inference or calculations from other characteristics or measurements, or by reference to data for a particular identified one tracers in the fuel). The characteristics can be determined as relative values compared to another fuel or as absolute values. For example, one or more of the following detection methods can be used:

• • The aromatics or cycloparaffin content of the fuel can be determined from measurements of the swelling of a sensor component made of a sealing material such as e.g. B. a nitrile sealing material can be determined.
• • Trace substances or species, either naturally present in the fuel or added as tracers, can be used to determine fuel characteristics such as the percentage of sustainable aviation fuel in the fuel or the percentage of kerosene.
• • Measurements of the vibration mode of a piezoelectric crystal exposed to the fuel can be used as a basis for determining various fuel characteristics, including the aromatic content of the fuel, the oxygen content of the fuel and the thermal stability or degree of coking of the fuel - for example by measuring the Build-up of surface deposits on the piezoelectric crystal, leading to a change in the vibration mode.
• • Various fuel characteristics may be determined by sensing performance parameters of the gas turbine engine 10 during a first period of operation (e.g., during takeoff) and optionally also during a second period of operation (e.g., during cruise), comparing these sensed parameters with the expected Values are compared when using fuel with known properties.
• Various fuel attributes, including aromatic hydrocarbon content, may be determined based on sensor measurements of the presence, absence, or degree of contrail formation by the gas turbine engine 10 during its operation.
• • Fuel properties, including aromatic hydrocarbon content, can be determined by UV-Vis spectroscopy measurement of the fuel.
• Various fuel properties such as sulfur content, naphthalene content, aromatic hydrogen content and hydrogen to carbon ratio can be determined by measuring the species contained in the gas turbine engine 10 exhaust gases.
• • The calorific value of the fuel can be determined during the operation of the aircraft 1 based on measurements that are carried out during the combustion of the fuel, e.g. B. based on the fuel flow rate and the shaft speed or the change in temperature in the combustion chamber 16.
• • Various fuel characteristics may be determined by making an operational change that affects operation of the gas turbine engine 10, detecting a response to the operational change, and determining the one or more fuel characteristics of the fuel based on the response to the operational change.
• • Various fuel characteristics may be determined with respect to the fuel characteristics of a first fuel by switching a fuel supplied to the gas turbine engine 10 from the first fuel to a second fuel and the one or more fuel characteristics of the second fuel based on a change in the ratio between T30 and one of T40 and T41 (where the ratio indicates the temperature rise in the combustion chamber 16). The characteristics can be determined as relative values compared to the first fuel or as absolute values, e.g. B. by reference to known values for the first fuel.

• • T30 = Hochdruckkompressor (HPC) Auslass-Gesamttemperatur;
• • T40 = Gesamttemperatur am Verbrennungsausgang;
• • T41 = Gesamttemperatur am Rotoreintritt der Hochdruckturbine (HPT).

(Herein T30, T40 and T41 and all other numbered pressures and temperatures are defined using the station numbering listed in the SAE AS755 standard, specifically:

• • T30 = High Pressure Compressor (HPC) Total Outlet Temperature;
• • T40 = total temperature at the combustion outlet;
• • T41 = total temperature at the rotor inlet of the high-pressure turbine (HPT).

In the examples currently described, the amount of fuel (e.g. mass, volume and/or % full) present in the tank 50, 53 before refueling is also noted, which is automatically recognized, for example, and recorded in a computer-controlled memory on board the aircraft 1 becomes.

In addition to determining one or more fuel characteristics of a fuel that is already present in the fuel tank 50, 53 before refueling, one or more fuel characteristics of a fuel that is to be supplied to the fuel tank 50, 53 during refueling are also determined.

• (i) Physikalischer und/oder chemischer Nachweis eines oder mehrerer Merkmale der Kraftstoffzusammensetzung (z. B. in einer Prüfeinheit außerhalb des Flügels oder während des Transports des Kraftstoffs zu einem Kraftstofftank im Flügel oder bei der Verwendung im Gasturbinentriebwerk 10), so dass ein direkter Nachweis der Kraftstoffmerkmale möglich ist oder Daten bereitgestellt werden, aus denen sie, wie oben erwähnt, bestimmt werden können, und/oder Nachweis eines oder mehrerer Tracer-Elemente oder -Verbindungen, die dem Kraftstoff zugesetzt werden, um seine Identifizierung zu erleichtern (z. B. ein Farbstoff);
• (iii) Empfang von Daten, z. B. von einer Eingabe an einer Benutzerschnittstelle oder von Daten, die an das Luftfahrzeug übermittelt werden, z. B. durch Scannen eines mit der Kraftstofflieferung verbundenen Strichcodes.

The fuel characteristics of the fuel to be filled into the fuel tank 50, 53 during refueling may include one or more of the following:

• (i) Physical and/or chemical detection of one or more characteristics of the fuel composition (e.g. in an off-wing testing unit or during transport of the fuel to an on-wing fuel tank or when used in the gas turbine engine 10) so that a direct detection of the fuel characteristics is possible or data are provided from which they can be determined as mentioned above and/or detection of one or more tracer elements or compounds added to the fuel to facilitate its identification (e.g. B. a dye);
• (iii) receiving data, e.g. B. from an input at a user interface or from data transmitted to the aircraft, z. B. by scanning a bar code associated with the fuel delivery.

With regard to determining the fuel characteristics of the fuel already in the tank 50, 53, in some examples several different methods may be performed to determine the fuel characteristics of the resulting fuel mixture - for example, different methods may and/or may be used for different characteristics different methods for the same characteristic can be used for verification. Any suitable detection method as mentioned above can be used. Assuming that the assumption of uniform mixing is correct, the fuel characteristics of the fuel leaving the tank 50, 53 and entering the engine 10 can be determined as a means of validating the result of the mixture 2006 fuel characteristics calculation.

In the examples currently described, the amount of fuel poured into the tank 50, 53 during refueling (e.g. explicitly by the mass or volume filled in and/or implicitly by the change in mass, volume or degree of filling) is also recorded ( eg by automatic detection or provision by a fuel supplier and recording in computational memory on board the aircraft 1).

One or more fuel characteristics of the fuel in the fuel tank 50, 53 after refueling is then calculated from the data about the fuel originally in the tank and the data about the fuel added to the tank. Such calculations may be performed separately for each fuel source - for example, a first fuel source may be empty prior to refueling and therefore contain only the new fuel, and a second fuel source may not be empty prior to refueling and contain a mixture of the old and new fuel after refueling. In such cases, the combustion of fuel from the first fuel source in the gas turbine engine 10 may enable the fuel characteristics of the new fuel to be determined, and the fuel characteristics of the mixture in the second fuel source may then be determined from the determined new fuel characteristics, mixture fraction and data be calculated using the older fuel.

Current fuel characteristics for the fuel in the tank can be stored, with the recorded fuel characteristics of the fuel present in the fuel tank 50, 53 being updated after each refueling of the aircraft 1. Optionally, a continuous record of fuel compositions used over time may be kept; alternatively, only a current fuel composition can be stored.

A fuel composition tracker 202 may be used to record and store fuel composition data and optionally also to receive the fuel characteristics of the fuel to be added during refueling and calculate updated fuel composition data. The fuel composition tracker 202 can be used as a separate fuel composition monitoring unit 202 as shown in FIGS 4 and 6 shown, or as a module built into the propulsion system 2 and/or as software and/or hardware integrated into the already existing aircraft control systems, e.g. as part of an electronic engine control (EEC) 42.

In the example shown, two sensors 204a, 204b are provided, each arranged in such a way that they physically and/or chemically detect one or more characteristics of the composition of the fuel that is supplied to the fuel tank 50, 53 during refueling. Sensors 204 and fuel composition tracker 202 may collectively be referred to as fuel composition tracking system 203, as in FIG 6 shown.

In alternative examples, no such sensors 204 may be provided (e.g., a barcode associated with fuel storage container 60 may be read and the appropriate data about the fuel transmitted to fuel composition tracker 202), or more or fewer sensors may be provided .

In some examples, the resulting fuel in the fuel tank 50, 53 after refueling may be chemically or physically analyzed for one or more parameters. The detected parameters can then be compared to one or more of the calculated fuel characteristics to verify the result. A warning can be issued in the event of a mismatch between the calculated fuel characteristics and the corresponding sensed parameter.

An active infinite summation approach as described here could be used continuously throughout the life of an aircraft 1 (or between maintenance operations where a fuel tank 50, 53 may be drained). However, it may be beneficial to periodically re-evaluate fuel composition data.

Rebasing may involve chemically and/or physically determining one or more parameters of the fuel in the fuel tank 50, 53 and using the determined values to substitute the stored fuel characteristics for the fuel in the fuel tank.

In some examples, the chemical and/or physical determination of one or more parameters of the fuel in the fuel tank 50, 53 for baselining may be accomplished by taking a fuel sample from the fuel tank for off-wing testing; it can be sent to a laboratory for analysis, for example, or made available to a ground-based testing station at an airport. In other examples, on-wing and optionally in-situ testing methods may be used.

The re-determination (i.e., chemically and/or physically determining one or more parameters of the fuel in the fuel tank 50, 53 and using the determined values to replace the stored fuel characteristics for the fuel in the fuel tank) may be performed in response to a triggering event. A triggering event may be a threshold time elapsed since a previous (chemical and/or physical) determination of the one or more parameters of the fuel in the fuel tank, or a threshold number of refueling events and/or flights elapsed since a previous (chemical and/or or physical) determination of the one or more parameters of the fuel in the fuel tank has been achieved.

Additionally or alternatively, a trigger event can be the determination of a discrepancy between one or more of the calculated features and an observed parameter - for example, when a calculated value differs from an observed value by an amount that exceeds a threshold or tolerance value. In some examples, if such a deviation is detected, a warning is issued (e.g. an audible and/or visual alarm and/or a message to the pilot or other party) - a decision can then be made as to whether to establish a new baseline immediately or whether it is accepted that the uncertainty in fuel composition means that operations will not be optimal for the next flight(s) until a new baseline opportunity is available. The intelligent control of the propulsion system 2 based on the fuel characteristics can be deactivated until the next recalculation.

Once the one or more fuel characteristics of the resulting fuel in the fuel tank 50, 53 after refueling have been determined, the propulsion system 2 can be controlled based on the calculated fuel characteristics.

• • Ein Betriebsparameter eines Wärmemanagementsystems des Luftfahrzeugs (z. B. eines Kraftstoff-Öl-Wärmetauschers) kann geändert werden, oder die Temperatur des der Brennkammer 16 des Triebwerks 10 zugeführten Kraftstoffs kann geändert werden.
• • Wenn an Bord eines Luftfahrzeugs 1 mehr als ein Kraftstoff gelagert wird, kann die Auswahl des zu verwendenden Kraftstoffs für bestimmte Einsätze (z. B. für bodengestützte Einsätze im Gegensatz zu Flügen, für Starts bei niedrigen Temperaturen oder für Einsätze mit unterschiedlichen Schubanforderungen) auf der Grundlage von Kraftstoffmerkmalen wie %SAF, nvPM-Erzeugungspotenzial, Viskosität und Heizwert getroffen werden. Ein Kraftstoffzufuhrsystem kann daher auf der Grundlage der Kraftstoffmerkmale entsprechend gesteuert werden.
• • Eine oder mehrere Flugsteuerungsflächen des Luftfahrzeugs 1 können so eingestellt werden, dass die Flugroute und/oder die Flughöhe auf der Grundlage der Kenntnis des Kraftstoffs geändert wird.
• • Der Überlaufprozentsatz einer Kraftstoffpumpe (d. h. der Anteil des gepumpten Kraftstoffs, der zurückgeführt wird, anstatt der Verbrennungsanlage zugeführt zu werden) kann geändert werden, z. B. auf der Grundlage des %SAF des Kraftstoffs. Die Pumpe und/oder ein oder mehrere Ventile können daher auf der Grundlage der Kraftstoffmerkmale entsprechend gesteuert werden.
• • Die Planung der Leitschaufeln mit variablem Einlass (VIGVs) kann auf der Grundlage der Kraftstoffmerkmale geändert werden. Die VIGVs können daher auf der Grundlage der Kraftstoffeigenschaften verschoben werden oder eine Bewegung der VIGVs kann aufgehoben werden.

For example:

• An operational parameter of an aircraft thermal management system (e.g., a fuel-to-oil heat exchanger) may be changed, or the temperature of the fuel supplied to the combustor 16 of the engine 10 may be changed.
• • When more than one fuel is stored on board an aircraft 1, the choice of fuel to use for specific missions (e.g. for ground versus flight missions, for low temperature takeoffs, or for missions with different thrust requirements) may vary based on fuel characteristics such as %SAF, nvPM generation potential, viscosity and calorific value. A fuel delivery system can therefore be appropriately controlled based on the fuel characteristics.
• One or more aircraft 1 flight control surfaces can be adjusted to change flight path and/or altitude based on knowledge of fuel.
• • A fuel pump's spill percentage (ie the proportion of pumped fuel that is returned instead of going to the incinerator) can be changed, e.g. B. based on the %SAF of the fuel. The pump and/or one or more valves can therefore be controlled accordingly based on the fuel characteristics.
• • The scheduling of variable inlet guide vanes (VIGVs) can be changed based on fuel characteristics. The VIGVs may therefore be moved or the VIGVs may be unmoved based on the fuel properties.

• Speichern 2002 aktueller Kraftstoffmerkmale, wobei die Kraftstoffmerkmale eine oder mehrere Kraftstoffmerkmale des im Kraftstofftank 50, 53 vorhandenen Kraftstoffs umfassen;
• Erhalten 2004 einer oder mehrerer Kraftstoffmerkmale eines Kraftstoffs, der dem Kraftstofftank 50, 53 beim Tanken zugeführt wird; und
• Berechnen 2006 der aktualisierten Werte für das eine oder mehrere Kraftstoffmerkmale des Kraftstoffs im Kraftstofftank 50, 53 nach dem Betanken. Das Erhalten 2004 der ein oder mehreren Kraftstoffmerkmale eines Kraftstoffs, der dem Kraftstofftank 50, 53 beim Tanken zugeführt wird, kann vor, während oder nach dem Tanken selbst erfolgen, z. B. unter Verwendung einer Prüfeinheit außerhalb des Flügels, von Sensoren in der Kraftstoffleitung bzw. von Leistungssensoren des Gasturbinentriebwerks oder auch durch den elektronischen Empfang von Daten von Dritten.

A propulsion system 2 for an aircraft can therefore comprise a fuel composition tracking system (203):

• Storage 2002 of current fuel characteristics, the fuel characteristics comprising one or more fuel characteristics of the fuel present in the fuel tank 50, 53;
• obtaining 2004 one or more fuel characteristics of a fuel supplied to the fuel tank 50, 53 during refueling; and
• Calculating 2006 the updated values for the one or more fuel characteristics of the fuel in the fuel tank 50, 53 after refueling. Obtaining 2004 the one or more fuel characteristics of a fuel that is supplied to the fuel tank 50, 53 during refueling can take place before, during or after the refueling itself, e.g. B. using a test unit outside the wing, sensors in the fuel line or performance sensors of the gas turbine engine or by the electronic receipt of data from third parties.

6 FIG. 2 shows an example of a system for tracking the fuel composition 203 in connection with a refueling operation in which a fuel F is filled into a fuel tank 50, 53. Arrows with dashed lines inside 6 indicate fuel flow, while solid lines indicate electronic communications.

The fuel composition tracking system 203 includes a fuel composition tracker 202 . The fuel composition tracker 202 of the example described comprises a memory 202a (which may also be referred to as arithmetic memory) arranged to store the current fuel characteristics and a processing circuit 202c arranged to store updated values for the one or more fuel characteristics of the fuel in the fuel tank 50, 53 are calculated after refueling. The calculated values may then replace the fuel characteristics previously stored in memory and/or may be time and/or date stamped and added to memory. In this way, a history of fuel characteristics can be established over time.

The fuel composition tracker 202 of the example shown also includes a receiver 202b arranged to receive fuel composition data and/or requests for fuel composition information. The fuel composition tracker 202 of the example shown is part of or communicates with an electronic engine control unit (EEC) 42 . The EEC 42 may be configured to issue propulsion system control commands based on the calculated fuel characteristics. It will be appreciated that an EEC 42 may be provided for each gas turbine engine 10 of the aircraft 1 and that the role that the EEC plays in or for the fuel composition tracker 202 may be only a small part of the functionality of the EEC. Indeed, the fuel composition tracker 202 may be provided by the EEC or, in various embodiments, may comprise an EEC module separate from the engine's EEC 42 . In alternative examples, fuel composition tracker 202 may not include engine control functionality and instead simply provide fuel composition data on demand that may be used by another system. Optionally, the fuel composition tracker 202 may provide a proposed change to engine control functionality for pilot approval; the pilot can then implement the proposed change directly or approve or reject the automatic implementation of the proposed change.

The procedure carried out in 2000 is in 5 shown. In step 2002 current fuel characteristics, comprising one or more fuel characteristics of the fuel present in the fuel tank 50, 53, are stored, optionally in the memory of a fuel composition tracker 202. This data may be provided for storage in any suitable manner, e.g. B. by manual input, z. B. via a graphical user interface that communicates with the fuel composition tracker 202, by electronic transmission to the fuel composition tracker 202, z. B. by wired or wireless communication from a barcode scanner after reading a barcode (or equivalently any other type of optically or otherwise readable code, such as a QR code), and/or by determination from sensor data. If the tank 50, 53 is currently empty, zero values or the like can of course also be stored.

In step 2004, the characteristics of a fuel that is supplied to the fuel tank 50, 53 during refueling are determined. The determination may be performed by the fuel composition tracker 202 itself, e.g. B. by evaluating sensor data, or otherwise determined fuel characteristics can be made available to the fuel composition tracker 202 .

In step 2006, updated values for the one or more fuel attributes of the fuel in the fuel tank 50, 53 after refueling are calculated, optionally by the fuel composition tracker 202, using the stored fuel attribute data (if any/if not zero) and the obtained fuel attributes .

The method 2000 may then be repeated at or after each fueling event, returning to step 2002 with the updated values replacing the stored values (or being included in memory as part of a log) and proceeding accordingly.

The method 2000 may further include controlling 2008 a propulsion system 2 of an aircraft 1 based on the calculated one or more fuel characteristics of the resulting fuel in the fuel tank 50, 53 after refueling. Updated values can be used to affect this control after each refueling event. Control 2008 may be performed automatically in response to the determination of fuel characteristics or upon approval by a pilot after being notified of a proposed change. In some examples, the same method 2000 may include making some changes automatically and requesting others depending on the type of change. In particular, changes that are "transparent" to the pilot - such as internal changes within the engine flows that do not affect engine performance and would not be noticed by a pilot - can be made automatically, while any changes that the pilot would notice would be made to the pilot communicated (i.e. a message will appear that the change will be made unless otherwise instructed by the pilot) or suggested to the pilot (i.e. the change will not be made without positive input from the pilot). In implementations where a notification or suggestion is made to the pilot, it may be on an aircraft cockpit display and/or as an audible alarm and/or sent to a separate device such as a portable tablet or other computing device.

In examples where an aircraft 1 has multiple fuel tanks 50, 53, all fluidly connected so that the fuels in all tanks 50, 53 are the same, a single set of fuel composition data may be stored and updated. In examples where an aircraft 1 has multiple fuel tanks 50, 53 that are not fluidly connected so that there may be differences between the fuels in the different tanks 50, 53, a separate set of fuel composition data can be stored for each tank and be updated. In such cases, what fuel will be supplied to the gas turbine engine 10 can be determined before any changes are made or proposed to the control of the power system.

The inventors have also recognized that knowledge of the fuels available to an aircraft 1 can allow for more efficient, tailored flight profile control, as different fuels can have different properties without violating standards. For example, a fuel with a higher hydrogen-to-carbon ratio may allow contrail formation at higher threshold temperatures/lower altitudes, and a decision may be made to fly at a slightly higher altitude (e.g. 100m to 200m higher) or transition to a nearby, discrete altitude (typically 2000 feet vertically, according to current guidelines) to compensate for otherwise increased contrail formation. Additionally or alternatively, a different flight route can be chosen that leads through slightly warmer or less humid air in order to reduce the formation of contrails. Knowledge of the fuel can therefore be used as a tool to improve aircraft performance, e.g. B. by reducing the formation of contrails. The formation of contrails is described here only as an example and is not intended as a limitation. The prior knowledge of the fuel for a flight of an aircraft 1 can therefore be used for the preplanning and adjustment of details of the flight profile in order to improve the environmental results and/or the performance of the aircraft.

Thus, one or more fuel characteristics of a fuel to be supplied to an aircraft gas turbine engine 10 may be determined. The fuel attributes may include one or more of the fuel attributes listed above.

• • ein Strichcode eines Kraftstoffs, der in einen Kraftstofftank 50, 53 des Luftfahrzeugs 1 eingefüllt werden soll, kann gescannt werden, um die Daten des Kraftstoffs zu lesen, oder eine Tracer-Substanz (z. B. ein Farbstoff) wird identifiziert und die Kraftstoffeigenschaften werden anhand dieses Tracers ermittelt;
• • die Daten können manuell eingegeben oder an das Luftfahrzeug 1 übermittelt werden;
• • es kann vor dem Start eine Kraftstoffprobe für eine bodenseitige Analyse entnommen werden;
• • die Kraftstoffmerkmale können aus Messungen der Aktivität des Antriebssystems während eines oder mehrerer Betriebszeiträume des Luftfahrzeugs abgeleitet werden, z. B. Aufwärmen des Triebwerks (einschließlich der Verwendung des Triebwerks vor der Bewegung des Luftfahrzeugs 1), Taxi, Start, Steigflug und/oder Reiseflug; und/oder
• • eine oder mehrere Kraftstoffeigenschaften können während des Fluges ermittelt werden, z. B. mit Inline-Sensoren und/oder anderen Messungen.

The determination can be performed in many different ways. For example:

• • A barcode of a fuel to be filled in a fuel tank 50, 53 of the aircraft 1 can be scanned to read the data of the fuel, or a tracer substance (e.g. a dye) is identified and the fuel properties are determined using this tracer;
• • the data can be entered manually or transmitted to the aircraft 1;
• • a fuel sample can be taken for ground analysis before take-off;
• • the fuel characteristics may be derived from measurements of propulsion system activity during one or more periods of aircraft operation, e.g. B. Engine warm-up (including engine use prior to aircraft 1 movement), taxi, takeoff, climb and/or cruise; and or
• • one or more fuel properties can be determined during flight, e.g. B. with inline sensors and/or other measurements.

The fuel characteristics may therefore be chemically and/or physically sensed, determined from other sensed data, or determined in some other way.

In some examples, combinations of these techniques can be used to determine and/or verify one or more fuel characteristics, e.g. B. using one or more of the example detection techniques described above.

In some examples, such as those in the 4 and 7 described above, the aircraft 1 may have only a single fuel tank 50 (which may be embodied in the form of a pair of interconnected wing tanks rather than a central tank) and/or multiple fuel tanks 50, 53 each containing the same fuel and/or fluidly interconnected or are fluidly connected to the gas turbine engine 10 so that only a single type of fuel is supplied to the gas turbine engine 10 between refueling events - ie the fuel characteristics can remain constant during a flight.

In other examples, the aircraft 1 may have multiple fuel tanks 50, 53 containing fuels of different compositions, and the propulsion system 2 may include an adjustable fuel delivery system that allows selection of the tank(s) to be used, and hence the fuel/fuel mixture. in sole For example, fuel characteristics may vary over the course of a flight, and a particular fuel or fuel blend may be selected to improve operation at particular phases of flight or under particular environmental conditions.

Once one or more fuel characteristics have been determined, a flight profile can be selected, changed, or adjusted based on those fuel characteristics. In many examples, external data - e.g. B. weather data such as humidity and temperature and time data such as day and night - in combination with the determined fuel characteristics to select or adjust the flight profile.

The implemented method can include, for example, receiving weather forecasts for a planned route of the aircraft 1 . These received weather forecasts can be used to make or affect changes to the planned route and/or altitude, or to control the planning of the route and/or altitude.

The term "flight profile" as used herein refers to the operational characteristics (e.g. altitude, power setting, flight path angle, airspeed, etc.) of an aircraft 1 while flying along a flight path, and also to the flight path/path (route) itself. Changes of the flight route are therefore included in the term “flight profile” used here.

In examples where some or all fuel characteristics are derived from measurements of propulsion system activity during the early stages of aircraft operation, e.g. during engine start/warm-up, taxiing, takeoff and climb, or otherwise measured on the wing, the flight profile can be adjusted during cruise even if knowledge of the fuel characteristics is not available in time to convert the flight profile into the to control earlier operating phases.

In examples where some or all of the fuel characteristics are determined prior to takeoff (e.g., during refueling or by analyzing the propulsion system 2 while taxiing), the flight profile for takeoff and/or climb may also be adjusted; e.g. B. start time, direction and / or steepness of the ascent can be chosen so that regions or periods of high humidity are avoided.

In both cases the future course and/or the operational characteristics of the aircraft 1 can be adjusted on the basis of the determined fuel characteristics - thus it can be planned in advance how the aircraft 1 should be controlled on the basis of the available fuel, and in particular a certain Trajectory (particularly route and altitude) can be determined.

A propulsion system 2 for an aircraft 1 may therefore comprise: a fuel composition determination module 210 arranged to determine 2052 one or more fuel characteristics of the fuel to be supplied to the gas turbine engine 10; and a flight profile adjuster 212 arranged to propose or initiate a change in the planned flight profile based on the one or more fuel characteristics of the fuel.

In some examples, fuel characteristics may be determined some time prior to the start of a flight, and planned flight profile changes may then be proposed to a pilot and/or air traffic controller or other authority (optionally via an automated system) for approval of the changes before the to get started. In other examples, the changes made may be so minor that they do not require air traffic controller or pilot approval, and may be performed automatically. Automatic notification or a proposal for the change may be sent to air traffic control and/or the pilot, as appropriate. The notification or the suggestion can be displayed on a cockpit display of the aircraft 1 and/or sent to a separate device, such as e.g. a portable tablet or other computing device.

If the fuel composition is known long enough before the flight, one or more competent authorities with which a flight plan has been filed can also be informed of a flight plan change, or a new flight plan can be filed. Examples of cases where the fuel composition is known with certainty well before a flight is e.g. B. Cases where an aircraft 1 carries sufficient fuel for the current flight from a first airport to a second and for the next scheduled onward flight (or return flight to the first airport) from the second airport. The decision to carry excess fuel instead of refueling at the second airport may be made to allow for quick turnaround at the second airport, or to avoid high fuel prices at the second airport, or also when a fuel composition available at the second airport is not desirable . so can After refueling at the first airport, any changes that need to be made for the second flight from the second airport can be identified before or during the first flight and a flight plan submitted for the second flight can be replaced or adjusted accordingly.

Different locations and types of fuel determination modules 210 may be used depending on when, where, and how the fuel composition is to be determined. For example, the fuel composition can be determined for the fuel when it first enters the aircraft 1 via a fuel line connection opening 62, with a module 210a for determining the fuel composition optionally being located along a fuel supply line in the aircraft 1, which runs from the fuel line connection opening 62 to a Tank 50, 53 leads. If fuel composition data is provided manually or electronically to the aircraft 1 during refueling, no measurement of the incoming fuel is required and the fuel composition determination module 210a can be placed anywhere and arranged to receive this data can. Alternatively (or additionally), the fuel composition for fuel in a tank 50, 53 can be determined, with a module 210b for determining the fuel composition being optionally located in or next to a tank 50, 53 in the aircraft 1. Alternatively (or in addition), fuel composition may be determined for fuel approaching a combustor 16 of gas turbine engine 10, with a fuel composition determination module 210c optionally located near a fuel supply line from fuel tank 50, 53 to combustor 16, or using a different approach described above. In some examples, one or more fuel characteristic sensors may be provided integrally with the processing circuitry and/or memory of the fuel composition determination module 210 . In alternative examples, one or more fuel attribute sensors may be remotely located from and in communication with the processing circuitry and/or memory of the fuel composition determination module 210 . In alternative or additional examples, one or more fuel characteristics may be communicated to the fuel composition determination module 210, which in such cases may not include one or more sensors. The arrangement of the processing circuitry and/or memory of the fuel composition determination module 210 may vary accordingly. In 7 Although three modules for determining the fuel composition (210a, b, c) are shown, these only serve to illustrate possible positions - in other examples only a single module for determining the fuel composition (210) can be provided. A second fuel composition determination module 210 may be provided in some examples to perform a redundant check and/or determine the fuel composition of another fuel source when an aircraft 1 includes one or more fuel tanks 50, 53 that are not fluidly connected.

In some examples, fuel composition may be sensed as aircraft 1 is being refueled. The fuel composition determination module 210a may be or include a fuel composition tracker 202 in such examples.

In such examples, a fuel composition tracker 202, as described in 6 illustrated, may be used to record and store fuel composition data and optionally also to receive the fuel characteristics of the fuel to be added at refueling and calculate updated fuel composition data as described above. Arrows with dashed lines inside 6 indicate fuel flow, while solid lines indicate electronic communications.

The active infinite summation approach described above can therefore be used in conjunction with the flight profile adaptation approach currently described, or both approaches can be used in isolation. In the 6 The flight profile adjuster 212 shown may not be present in examples where the presently described flight profile adjustment approach is not implemented.

As already mentioned in the previous examples, the fuel composition tracker 202 can be used as a separate unit 202, as in 6 shown, or as a module built into the propulsion system 2 and/or as software and/or hardware that can be integrated into the already existing aircraft control systems, e.g. the EEC 42, can be provided.

In the example shown, two sensors 204a, 204b are provided, which are each arranged in such a way that they physically and/or chemically detect one or more characteristics of the fuel that is filled into the fuel tank 50, 53 during refueling. Sensors 204 and fuel composition tracker 202 may work together referred to as fuel composition measurement system 203, as in 6 shown.

The fuel composition tracking system 203 includes a fuel composition tracker 202 . The fuel composition tracker 202 of the example described comprises a memory 202a arranged to store the current fuel characteristics and a processing circuit 202c arranged to store updated values for the one or more fuel characteristics of the fuel in the fuel tank 50 , 53 calculated after refueling. The calculated values may then replace the previously stored fuel attributes in memory and/or may be time and/or date stamped and added to memory. In this way, a history of fuel characteristics can be established over time.

The fuel composition tracker 202 of the example shown also comprises a receiver 202b arranged to receive fuel composition data and/or requests for fuel composition information. The fuel composition determination module 210 may therefore include a receiver 202b arranged to receive fuel composition data from which one or more fuel characteristics may be determined (either directly by extraction or by calculation, optionally in conjunction with data from another source).

The fuel composition determination module 210 may therefore include one or more sensors 204 arranged to provide data relating to, or have access to the output of, one or more fuel characteristics. The sensor data may provide one or more fuel characteristics directly or allow one or more fuel characteristics to be obtained through computation, possibly in conjunction with data from another source. In alternative examples, no such sensors 204 may be provided (e.g., a barcode associated with fuel storage tank 60 may be read and the appropriate data about the fuel transmitted to fuel composition tracker 202), or more or fewer sensors may be provided .

The fuel composition tracker 202 data may be used to alter the planned flight profile based on one or more fuel characteristics. A flight profile adjuster 212 may be used to change the planned flight profile based on the one or more fuel characteristics of the fuel based on data provided by the fuel composition tracker 202 and optionally other data as well. The flight profile setting device 212 can be implemented as a separate flight profile setting device 212 built into the propulsion system 2 and/or as software and/or hardware that can be integrated into the already existing aircraft control systems, such as e.g. B. the EEC 42, can be provided. Fuel composition tracking capability (e.g., tracker 202) may be provided as part of the same unit or package.

The performed flight profile control procedure 2050 is in 8th shown. In step 2052, one or more fuel characteristics of the fuel to be supplied to the gas turbine engine 10 are determined, optionally using any of the methods described above.

At step 2054, the flight profile of the aircraft 1 is modified based on the one or more fuel characteristics. The change in flight profile may be or include a change in flight path, flight path, angle of attack or flight altitude.

A flight profile adjuster 212 may be used to initiate and/or effect the change in flight profile. In some examples, the flight profile adjuster 212 can change the flight profile itself, and in some implementations it can additionally control the implementation of this change, for example by recording a planned change and then sending a command to one or more flight control surfaces of the aircraft 1 to implement the to change altitude at the appropriate time. In other examples, the flight profile adjuster 212 may seek approval for the planned change and/or may not send instructions to change the flight profile itself. The flight profile adjuster 212 may therefore present a notification or proposal for a planned flight profile change to the pilot and/or other authority for approval. A notification or suggestion may be presented to the pilot on an aircraft cockpit display and/or sent to a separate device such as a a portable tablet or other computing device. In some examples, the same flight profile adjuster 212 may automatically make some changes and require approval for others, depending on the type of change (e.g., whether the proposed change is significant enough to require approval from air traffic control or another agency or not). The flight profile setting device 212 can therefore change 2054 a flight profile of the aircraft 1 on the Propose and/or initiate based on the at least one fuel characteristic.

The inventors have also recognized that knowledge of one or more fuel characteristics, selected and determined in any of the ways described above, can be used to suggest, guide or make in-flight adjustments to the propulsion system 2 to improve performance of the aircraft. For example, a fuel with a higher heat capacity can be used for more engine cooling than a fuel with a lower heat capacity, and a fuel with a higher heating value can allow a lower fuel flow rate to be delivered to the combustion chamber for the same power. Knowledge of the fuel can therefore be used as a tool to improve aircraft performance in flight. Compared to the forward planning and flight profile changes described above, decisions may be made and implemented in real time or near real time, and these decisions may affect only the internal functioning of the engine 10 and not a change in flight route and/or flight altitude, e.g Example.

In some examples, the aircraft 1 may have only a single fuel tank 50 and/or multiple fuel tanks 50, 53, each containing the same fuel and/or fluidly connected to the gas turbine engine 10 such that the gas turbine engine 10 only consumes a single type of fuel between refueling is supplied - i.e. the fuel characteristics can remain constant during a flight. In such examples, fuel characteristics do not change during a flight, but external conditions (e.g. weather, altitude) and internal conditions (e.g. thrust demand) do, and the changes may be (i) initially made when the fuel characteristics are being determined or processed for the first time, and/or (ii) on the basis of what is appropriate for that fuel given the changed conditions.

In other examples, the aircraft 1 may have multiple fuel tanks 50, 53 containing fuels of different compositions, and the propulsion system 2 may include an adjustable fuel delivery system allowing to select which tank(s) 50, 53 and hence which fuel or which fuel mixture is to be used. In such examples, fuel characteristics may vary over the course of a flight, and a particular fuel or fuel blend may be selected to improve operation at particular phases of flight or under particular environmental conditions. In such examples, changes can also be made to the control of the propulsion system when the fuel changes, e.g. B. when it is determined that a fuel is almost running out, or when a different fuel or fuel mixture is selected. (It will be appreciated that a fuel system can generally be set up so that a tank 50, 53 never becomes completely empty as this could result in engine 10 flaring - however a tank can be completely drained if its fuel is part of a mixture; for one or more other fuels of the mixture, the flow rate may be increased to ensure that the engine 10 is never starved of fuel). A fuel switch may therefore be in response to a power-system control change and may trigger one or more other power-system control changes.

In examples in which one or more fuel characteristics are directly detected or in which the fuel characteristics are calculated from the detected parameters, the detection can take place in the individual tank or tanks 50, 53 (and the fuel characteristics for a resulting fuel mixture from different tanks can then may be calculated) and/or when approaching the engine 10, e.g. B. in a line containing a mixture of several tanks. In some examples, the identification of the fuel may be done just prior to entering the engine 10, more specifically the combustion chamber 16, to ensure that the correct fuel/fuel mixture is identified and that the data is as current as possible (nearly). Real time).

Once one or more fuel characteristics have been determined for the fuel currently being supplied to gas turbine engine 10, control of power system 2 may be adjusted based on the determined fuel characteristics.

Additional data may be used in conjunction with the determined fuel characteristics to adjust powertrain 2 control. For example, data on the current conditions around the aircraft 1 may be received (either from a provider, e.g. an external weather monitoring company, or from onboard detectors). This received data (e.g. weather data, temperature, humidity, presence of a contrail, etc.) can be used to make or influence changes in the control of the propulsion system. Instead of Weather forecast data for the aircraft's flight path may also be used from or in addition to "live" or "near-live" weather data to estimate current conditions.

Examples of propulsion system changes that may be made based on fuel characteristics include some or all of the control examples described above, e.g. B. the adjustment of the VIGV planning.

A propulsion system 2 for an aircraft 1 may therefore comprise a fuel composition determination module 210 arranged to determine 2052 one or more fuel characteristics of the fuel to be supplied to the gas turbine engine 10; and an engine electronic controller 42 arranged to issue propulsion system control commands based on the determined fuel characteristics. The fuel composition tracker 202 of the example shown may be part of, or have access to, an electronic engine controller (EEC) 42 arranged to issue propulsion system control commands based on fuel characteristics. In some cases, the EEC may make recommendations for pilot (or other authority) approval and then issue a propulsion system control command dependent on that approval. It will be appreciated that an EEC 42 may be provided for each gas turbine engine 10 of the aircraft 1 and that the role that the EEC plays for the fuel composition tracker 202 may be only a small part of the functionality of the EEC. Indeed, the fuel composition tracker 202 may be provided by the EEC or, in various embodiments, may comprise an EEC module separate from the engine's EEC 42 . In alternative examples, fuel composition tracker 202 may not include engine control functionality, and instead simply provide fuel composition data on demand that may be used by another system.

Various locations and types of fuel composition determination module 210 and associated fuel characteristic sensors may be used depending on when, where, and how fuel composition is to be determined. For example, as above in relation to the in 8th flight profile control method 2050 shown is described.

In some examples, fuel composition may be sensed as aircraft 1 is refueled. The fuel composition determination module 210a may be or may include a fuel composition tracker 202 in such examples.

The active infinite summation approach described above may therefore be used in conjunction with the flight profile adaptation approach described above and/or with the in-flight adaptation approach currently described, or each of the three approaches may be used in isolation. As already mentioned, the in 6 flight profile adjuster 212 shown may not be present in examples where the flight profile adjustment approach described above is not implemented.

The fuel composition tracker 202 and fuel composition measurement system 203 may be as described above.

The fuel composition tracker 202 data may be used to alter the planned flight profile and/or to control or adjust the propulsion system 2 during flight based on the one or more fuel characteristics.

A propulsion system 2 for an aircraft 1 may therefore comprise a fuel composition tracker 202 or other fuel composition determination module (210) arranged to record and store data on the fuel composition and optionally also the fuel characteristics of the fuel to be added during refuelling fuel and calculates updated fuel composition data. The fuel composition determination module 210 may be provided as a separate fuel composition monitoring unit built into the propulsion system and/or as software and/or hardware integrated into the existing aircraft control systems.

The data from the fuel composition determination module 210 may be used to adjust control of the powertrain 2 based on the one or more fuel characteristics.

A power-system controller 42, also referred to as an electronic engine controller 42, may be used to adjust control of the power-system 2 based on the one or more fuel characteristics of the fuel, using data provided by the fuel composition determination module 210, and optionally other data can be used. It becomes clear that the propulsion control controls 42 elements of the propulsion system which may or may not be considered components of the engine 10 itself, such as one or more flight control surfaces. The term "engine electronic control unit" (EEC) 42, used interchangeably herein, is not intended to be limited in this sense. Propulsion control 42 may be provided as a separate propulsion control unit 42 built into propulsion system 2, as part of fuel composition determination module 210, and/or as software and/or hardware integrated into existing aircraft control systems. Fuel composition tracking capabilities may be provided as part of the same unit or package.

The propulsion system controller 42 may make changes to the propulsion system 2 directly or provide the pilot (or other authority) with a notification or suggestion regarding the change for approval. A notification or suggestion may be presented to the pilot on an aircraft cockpit display and/or sent to a separate device such as a portable tablet or other computing device. In some examples, the same power system 42 controller may automatically make some changes and request others depending on the type of change. In particular, as mentioned above, changes that are "transparent" to the pilot - such as e.g. B. Internal changes within engine currents that do not affect engine performance and would not be noticed by a pilot - can be made automatically, while any changes that the pilot would notice can be communicated to the pilot (i.e. a message appears that the change is made unless otherwise instructed by the pilot) or can be suggested to the pilot (i.e. the change will not be made without positive input from the pilot).

The performed procedure 2051 is in 9 shown. At step 2052, one or more fuel characteristics of the fuel to be delivered to the gas turbine engine 10 are determined. The fuel characteristics may be or include any of the characteristics listed above and may be selected based on those characteristics that have the greatest impact on optimal powertrain control. In step 2056, the propulsion system 2 of the aircraft 1 is controlled based on the one or more fuel characteristics. The control actions taken may be or include any of the actions listed above.

A propulsion controller 42 may therefore be used to initiate and/or perform control of the propulsion system 2 . In some examples, the propulsion system 42 controller may make a change automatically, for example by commanding the position of one or more variable inlet guide vanes of the aircraft propulsion system 2 in response to an assessment of fuel characteristics (and optionally other conditions). In other examples, power-system controller 42 may not automatically send instructions to control power-system 2, but instead may submit a proposed power-system controller change for approval based on one or more fuel characteristics.

The inventors have also recognized that knowledge of the fuels available to an aircraft 1 can enable more efficient, tailored control of the propulsion system 2, as different fuels can have different properties without violating standards. So e.g. For example, switching to a fuel with a higher calorific value allows for a constant fuel supply to the combustor 16 while at the same time achieving a higher power output. The selection of a specific fuel based on intended or current flight operations can therefore be used as a tool to improve aircraft performance. In particular, the calorific value of a fuel can be taken into account.

This approach is described below for two different fuel supply systems for aircraft, which differ from the 4 shown arrangement differ. It will be appreciated that any of the approaches described herein can be used with any suitable fuel delivery system and that the examples illustrated and detailed are not intended to be limiting.

In particular, an aircraft 1, as in 10 and 14 shown, comprise a plurality of fuel tanks 50, 52, 53, e.g. B. a first fuel tank 52 and a second, larger fuel tank 50, each located in the aircraft fuselage, and a smaller fuel tank 53a, 53b located in each wing. In other examples only two fuel tanks 50, 52 or more fuel tanks can be provided. Size, shape and location of fuel tanks may vary; for example, all of the fuel in the tanks 53 can be stored in the wings.

10 1 shows an aircraft 1 with a propulsion system 2 which comprises two gas turbine engines 10 . The gas turbine engines 10 are supplied with fuel from a fuel supply system on board the aircraft 1 . The fuel supply system of the illustrated example includes two sources of fuel. Each of the fuel sources is arranged to provide a separate fuel source, ie, they are fluidly isolated, and the first fuel source may contain a first fuel having a different property or properties than a second fuel contained in the second fuel source . For example, the fuels may have different compositions and/or different origins, e.g. B. a fossil-derived fuel such as Jet-A, a paraffinic SAF, a non-paraffinic SAF, a paraffinic SAF with a different composition or a mixture. The first and second fuel sources are therefore not fluidly connected such that the different fuels are separated (at least under normal operating conditions). A fuel source may be a single tank or multiple fluidly connected tanks and may be referred to as a fuel tank when in fact it is multiple connected tanks.

In this example, the first fuel source is the first fuel tank 52. In other examples, the first fuel source may be multiple tanks connected together.

In the present example, the second fuel source comprises a center fuel tank 50 located primarily in the fuselage of the aircraft and a plurality of wing fuel tanks 53a, 53b, with at least one wing fuel tank located in the port wing and at least one wing fuel tank located in the starboard wing to balance. in the in 10 shown example, all tanks 50, 53 with the exception of the first fuel tank 52 are connected to each other and thus form a single second fuel source. The center fuel tank and the wing fuel tanks may each consist of multiple fuel tanks connected to each other.

In another example, the wing fuel tanks 53a, 53b may not be connected to the center tank 50, thus forming a separate, third source of fuel. For balancing purposes, one or more fuel tanks in the port wing may be fluidly connected to one or more fuel tanks in the starboard wing, as described above. In the example of 10 however, fluid communication is provided between the wing fuel tanks 53 and center fuel tank 50 of the second fuel source for balancing the aircraft 1.

This in 14 The example shown is generally similar to that in 10 shown, but the differences are described below.

in the in 14 In the example shown, the first fuel tank 52 is smaller than the second fuel tank 50. The first fuel tank 52 is located further back in the fuselage in this embodiment. The first fuel tank 52 can therefore be used as a trim tank 52 during flight - it is known that a trim tank 52 can be used to control the center of gravity in the longitudinal axis of the aircraft 1; the aircraft is "trimmed" by pumping fuel into (or withdrawing from) a trim tank. One or more pumps, valves, sensors, controllers and the like can be provided to control the trimming process. In other implementations, the first fuel tank 52 may not be a trim tank; its connections to other fuel tanks 50, 53 may be different or absent in such other embodiments. A trim tank 52 is therefore fluidically connected to at least one other fuel tank 50, 53 of an aircraft 1 so that trimming can be carried out in flight. It is a controllable fluid connection so that the first tank 52 can be isolated from the other tanks 50, 53 and used as a separate fuel source if required.

In addition to the in 10 The drive system 2 described includes a drive system 4 of the 14 shown embodiment, an auxiliary power unit (APU) 44. The APU 44 is a gas turbine engine which is smaller than the engines 10 on the wings of the aircraft 1 and which is arranged in such a way that it is systems of the aircraft 1 supplied with electrical energy, e.g. B. lighting, heating, air conditioning and / or the like. The APU 44 may be, for example, a Honeywell 331 series APU, such as the HGT1700 Auxiliary Power Unit (APU). In some cases, the APU 44 may be certified for in-flight use, in other cases it may be certified for ground use only. An aircraft APU 44 is typically designed to be started using one or more aircraft batteries to provide electrical power and optionally bleed air for air conditioning and engine starting. The APU 44 of the embodiment shown is located in the rear part of the fuselage and is not intended to supply the aircraft 1 with propulsion energy. In alternative designs, the APU may be arranged differently (e.g. in a Gondola 21 of the aircraft 1) and / or provide a certain propulsion power.

in the in 14 For example, as illustrated, the first fuel tank 52 is arranged to supply fuel to the APU 44 . In this example, the first fuel tank 52 is also arranged to supply fuel directly to the main gas turbine engines 10, although in some embodiments these connections may not be present, or alternatively the first fuel tank 52 may be arranged to supply the main gas turbine engines 10 and does not directly fuel the APU 44 in some implementations.

In alternative implementations, the first fuel tank 52 may be a dedicated APU fuel tank and may not be fluidly connected to either the main gas turbine engines 10 or any other fuel tank. In some such examples, a fuel manager 214 may not be used for APU fueling, as described below.

In various embodiments, a plurality of fuel line fittings 62 may be provided to facilitate the supply of different fuels to different tanks/fuel sources 50, 52, 53. Alternatively or additionally, a fuel supply management system may route incoming fuel from the same port 62 to different tanks, as appropriate. In particular, in the examples described, the first tank 52 can be fed directly from a fuel supply instead of being filled from another fuel tank 50, 53 of the aircraft 1 by decanting. In 14 the internal fuel lines from the ports 62 to the tanks are not shown for the sake of clarity. In 10 an internal fuel line (to the larger tank 50) is shown; it will be appreciated that at least a second fuel line to the first fuel tank 52 would generally also be provided, but is not shown for the sake of clarity.

In exemplary embodiments of the present invention, the aircraft 1 has a plurality of fuel tanks 50, 52, 53, in particular at least two different fuel sources and optionally more. At least two of the fuel tanks are arranged to contain different fuels - i.e. fuels with at least one difference in fuel properties - and in particular fuels with different calorific values.

One or more fuel characteristics can be determined for each fuel stored on board the aircraft 1 . The determined fuel characteristics may include one or more of the example fuel characteristics listed above.

• • ein Barcode eines Kraftstoffs, der in einen Kraftstofftank 50, 52, 53 des Luftfahrzeugs 1 eingefüllt werden soll, kann gescannt werden, um die Daten des Kraftstoffs zu lesen, oder eine Tracer-Substanz (z. B. ein Farbstoff) kann identifiziert und die Kraftstoffeigenschaften auf der Grundlage dieses Tracers ermittelt werden;
• • die Daten können manuell eingegeben oder an das Luftfahrzeug 1 übermittelt werden;
• • es kann vor dem Start eine Kraftstoffprobe für eine bodenseitige Analyse entnommen werden;
• • die Kraftstoffmerkmale können aus Messungen der Aktivität des Antriebssystems während einer oder mehrerer Betriebsperioden des Luftfahrzeugs abgeleitet werden, z. B. beim Warmlaufen des Motors, beim Rollen, beim Start, im Steigflug und/oder im Reiseflug; und/oder
• • eine oder mehrere Kraftstoffeigenschaften können während des Fluges ermittelt werden, beispielsweise mit Hilfe von Inline-Sensoren und/oder anderen Messungen sowie mit jedem der oben beschriebenen Erfassungsmethoden.

The determination can be performed in many different ways. For example:

• • A barcode of a fuel to be filled in a fuel tank 50, 52, 53 of the aircraft 1 can be scanned to read the data of the fuel, or a tracer substance (e.g. a dye) can be identified and the fuel properties are determined on the basis of this tracer;
• • the data can be entered manually or transmitted to the aircraft 1;
• • a fuel sample can be taken for ground analysis before take-off;
• • the fuel characteristics may be derived from measurements of propulsion system activity during one or more periods of aircraft operation, e.g. B. during engine warm-up, taxiing, take-off, climbing and/or cruising; and or
• • one or more fuel properties can be determined in-flight, for example using in-line sensors and/or other measurements, and using any of the detection methods described above.

The fuel characteristics can therefore be chemically and/or physically detected or otherwise determined by any suitable means described herein. In some examples, combinations of these techniques can be used to determine and/or verify one or more fuel characteristics.

The calorific values (also referred to as calorific values) of the fuels can be determined directly - e.g. by measuring or deriving the energy released upon combustion of a given volume or mass of fuel in the gas turbine 10 - or calculated from other fuel parameters, e.g. B. by looking at the hydrocarbon distribution of the fuel and the calorific value of each hydrocarbon type. Alternatively or additionally, the calorific value can be determined for verification using external data, e.g. B. from a look-up table for a tracer substance in the fuel or from data encoded in a bar code associated with the fuel.

In some examples, each fuel tank 50, 52, 53 of the aircraft 1 may be arranged to contain a fuel of a different calorific value, e.g. H. each fuel tank can be a separate fuel source.

Unless otherwise specified, the term "heating value" as used herein means the net calorific value (also referred to as net calorific value) of the fuel. The net calorific value is defined as the amount of heat released on combustion of a given quantity of the fuel, generally in J/kg, assuming that the latent heat of vaporization of the water in the reaction products is not recovered (i.e. that the generated water remains as water vapor after combustion).

In some examples, two or more aircraft tanks 50, 52 may be arranged to contain fuels of a different type or proportion of sustainable aviation fuel, with the fuels having different calorific values.

The propulsion system 2 includes an adjustable fuel delivery system 220 which allows selection of which source(s)/tank(s) 50, 52, 53 and hence which fuel or fuel mixture is to be used. In such examples, fuel characteristics may vary over the course of a flight, and a particular fuel or fuel blend may be selected to improve operation at particular phases of flight or under particular environmental conditions.

A first fuel tank 52 of the plurality of fuel tanks 50, 52, 53 may have a higher Sustainable Aviation Fuel (SAF) fraction than a second fuel tank 50 of the plurality of fuel tanks and may have a higher calorific value than a fossil fuel or SAF-fossil blend in one other, second fuel tank. More fuel may be used from the second tank 50 during cruise, while more fuel may be used from the first tank 52 at higher power operating points (e.g., takeoff and climb).

In other examples, the first fuel tank 52 may contain fuel with a lower calorific value than the fuel in the other tank 50. More fuel may be used from the first tank 52 during cruise flight, while during higher power operating points (e.g., takeoff and during climb) more fuel from the second tank 50 can be used.

One fuel tank 52 of the plurality of fuel tanks may be arranged to contain only one fuel that is Sustainable Aviation Fuel (SAF) - this tank may contain 100% pure SAF or SAF with one or more additives, but no fossil-based fuel Base. (As used herein, "SAF" means a pure sustainable aviation fuel that contains no fuel of fossil/petroleum origin (but optionally one or more additives, e.g. an anti-icing agent); the term "SAF blend" or "blended fuel" may be used for a mixture containing both SAF and petroleum-based origin fuel.) The SAF in this tank 52 can be chosen such that the propulsion system 2 can be operated solely on this fuel (e.g. for ground operation or at an in-flight emergency or if fuel regulations change so that flight on SAF fuel alone is generally permitted).

In such examples, the fuel tank 52 containing only the sustainable aviation fuel may be used to power the aircraft 1 when the aircraft is operating on the ground. Optionally, all or at least most of the fuel used for ground operations may be taken from the fuel tank 52 containing the sustainable aviation fuel, for example to meet airport emissions requirements and/or use of SAF. In other cases, a SAF blend fuel with a high SAF content can be used instead of SAF.

It is becoming clear that the use of SAF (either alone or in a fuel blend) can result in a significant reduction in non-volatile particulate emissions (nvPM) at idle - the percentage reduction can be more than 90% in some cases. The percentage reduction in nvPM emissions when using SAF at idle is expected to be greater than at high power requirements, since soot formation (nvPM) is more closely related to fuel aromatic content at these low power conditions than at higher ones Performance requirements where other mechanisms of soot formation come into play - SAFs are generally lower in aromatic content than petroleum-based aviation fuels. If the total amount of SAF is limited, using SAF for ground-based/airport-environment operations instead of another part of the flight cycle may provide greater benefit in reducing nvPM production. In addition, the air quality at the airport can be improved. Also during flight, greater benefit can be derived from the use of SAF if the SAF is used for lower performance parts of the flight envelope.

For the same reasons, SAF can also be selected for use in an auxiliary power unit (APU) of the aircraft 1 at an airport gate.

However, SAF often have a higher calorific value than conventional jet fuels - in such cases, therefore, the control of fueling the gas turbine engine 10 for operation on the ground (where reducing nvPM may be a priority) may be different than in flight (where adjusting calorific value to may prioritize thrust) when only a limited amount of SAF is available. In scenarios where fuels with similar nvPM properties but different calorific values are available on board an aircraft 1, the same control can be used throughout the operation; for operation on the ground as well as in flight.

In examples with a pure SAF tank 52, this fuel tank 52 can be smaller than the other fuel tanks 50, 53. The first fuel tank 52 can, for example, make up 3% to 20% and optionally 5% to 10% of the total available tank volume of the aircraft 1. This tank 52 can optionally be arranged in such a way that it is used exclusively for the ground-based operation of the aircraft 1. A selection between the other tanks 50, 53 based on calorific value can then be made in flight based on engine thrust.

For versions like the one in 14 shown, in which a trim tank 52 is present on the aircraft 1 and is used as the first fuel tank 52, would during operation on the ground, z. B. at a standstill, during the warm-up phase and optionally during taxiing or take-off, fuel is taken from the trim tank 52, the mass of which therefore decreases due to the loss of fuel. In particular, when the trim tank 52 is filled with SAF (or a high percentage SAF fuel mixture), the air quality benefits resulting from the use of this SAF from the trim tank 52 for the APU 44 during stationary operation can be used, and this SAF can additionally be used for the main gas turbine engines 10 may be used during warm-up, taxi, takeoff and possibly part of the climb (optionally as a mixture with another fuel) until the trim tank 52 is empty. In some cases, the amount of fuel in the trim tank 52 can be selected in such a way that the trim tank 52 is at least essentially empty on takeoff, so that it can be (partially) refilled during the climb so that it can also be used during the climb to trim the aircraft 1 can be used. In other examples, it can only be used to trim the aircraft 1 later in the flight. Thereafter, fuel from another fuel source 50, 53 can be used. Such implementations may be particularly useful when the aircraft 1 is conducting missions at the limit of its payload range; thus, all fuel tanks can be initially filled to full capacity while the capacity of the trim tank is available immediately after launch/before the trim tank 52 is normally used.

When the aircraft 1 is airborne, the first fuel tank 52 would be relatively light, if not completely empty, and would not significantly affect the center of mass. The first fuel tank 52 is therefore available for normal use as a trim tank 52 for at least the cruise portion of the flight - fuel from one or more of the other fuel sources 50, 53 can be pumped into it when ready to reduce drag during cruise and optionally also during the climb (after the first fuel tank 52 has been at least largely emptied no later than halfway through the climb).

The initial amount of fuel in the trim tank 52 can be chosen so that this fuel is completely consumed before the aircraft 1 reaches its cruising altitude. In particular, the amount of fuel that is supplied to the first fuel tank 52 during filling can be calculated in such a way that it is at least substantially consumed by the time the aircraft 1 takes off, optionally by the time the aircraft rotates (rotation is what is against End of takeoff roll occurs when the nose wheel of aircraft 1 leaves the ground but the main gear is still on the ground (in the moments after the turn, aircraft 1 picks up speed and then the main gear leaves the ground as well). The fuel in the first fuel tank 52 in such examples may be selected based on its air quality and air pollution impact, and may or may not have a lower calorific value than the fuel(s) in the other tanks 50,53.

In examples where the first fuel tank 52 is used as a trim tank 52, an onboard fuel manager 214 may be configured to detect the fuel level in the first fuel tank 52 and automatically switch supply to another tank (regardless of how much additional NvPM caused) when it detects that this tank 52 is on the verge of running dry to avoid cutting off the fuel supply to the engine 10,44. It should be understood that a relatively small amount of fuel remaining in the trim tank 52 does not prevent it from being used as such and/or that the fuel manager 214 can be set up to transfer fuel from the trim tank 52 and into a other tank pumps before the takeoff run begins, possibly after a negative result of a check that the trim tank 52 is sufficiently empty to keep the longitudinal center of gravity within acceptable limits.

In some embodiments, the fuel manager 214 may be set up to automatically switch from the first fuel tank 52 to another, optionally larger, tank 50, 53 prior to the start of the takeoff roll to eliminate the possibility that the first tank 52 could become empty during the takeoff roll and/or of the climb runs empty.

In some embodiments, the fuel manager 214 may be set up to request or enforce a longer engine idle time prior to the start of a takeoff run to ensure that the trim tank 52 is sufficiently empty if it is expected that the aircraft 1 is required and/or when there is no spare capacity available for pumping fuel from the trim tank 52.

In examples where the detection is used to determine one or more fuel characteristics, the detection can be performed in each tank 50, 52, 53 (or in a tank of each fuel source) and the fuel characteristics for a resulting fuel mixture from different tanks can then be determined where appropriate calculated on the basis of mixing ratios. Alternatively or additionally, the detection can take place when approaching the engine 10, e.g. B. in a pipeline/fuel line, which may contain a mixture from several tanks.

When collecting data for a fuel mixture, e.g. e.g. on approach to the engine 10, the data can be recorded as the mixture is changed (by taking more or less fuel from a particular tank 50, 52) to change the composition of the fuel in each individual tank 50, 52, 53 to determine. This determination may allow in-flight fuel selection or blending to be adjusted, e.g. by using different fuels for different parts of the flight envelope, even if the fuel composition at take-off is not known. Additionally, in some implementations, such a determination may be made during engine warm-up and/or in the early stages of coasting, so that fuel selection for the remainder of the coasting may be adjusted accordingly, e.g. B. by selecting a fuel or fuel blend with maximum nvPM benefits while still at the airport.

In some examples, the identification of the fuel may occur just before it enters the engine 10 or combustion chamber 16 to ensure that the correct fuel or fuel mixture is identified (e.g., as a check of the intended composition if it is already known) and that the fuel burned data is as up-to-date as possible (near real-time).

Once the calorific value of each fuel available to power the gas turbine engine 10 has been determined, a single fuel (from a single tank) or a fuel mixture (from multiple tanks) can be selected based on the thrust requirements of the gas turbine engine 10 using any suitable method and the gas turbine engine 10 be supplied. In particular, a fuel (single fuel or mixture) with a lower calorific value can be supplied to the gas turbine engine 10 when the need for thrust is lower. Accordingly, a fuel (single fuel or mixture) with a higher calorific value can be supplied to the gas turbine engine 10 when there is a higher demand for thrust. Fuel control based on calorific value can only be done in flight in some scenarios, allowing fueling for operations on the ground to be controlled differently (e.g. by prioritizing reduction of nvPM generation over adapting calorific value to power demand). is granted).

It will be appreciated that the thrust demand may be determined using one or more approaches known in the art, for example based on fuel flow and/or cockpit throttle angle or one or more other pilot settings and optionally taking into account outside air density or a proxy therefor, such as altitude, ambient temperature and/or pressure. Using fuel flow rate alone may be insufficient due to the different fuel flow ranges at altitude compared to ground.

Varying the heating value of the fuel according to thrust demand may facilitate maintaining a more constant fuel flow and/or smoother operation of the fuel pump and spill in flight. In general, the fuel mass flow varies greatly between the different flight segments of an aircraft 1, so that the differences in the calorific value of the fuel are not large enough to compensate for the differences in the energy demand of the fuel between climb and initial cruise. However, during a cruising flight segment in which the aircraft 1 burns fuel at a constant altitude, the thrust requirement can exceed one decrease slowly over a period of time, so adjusting the fuel flow calorific value may allow a nearly constant flow to be maintained. Therefore, a substantially constant fuel flow rate can be maintained during certain portions of aircraft operation if the approach described herein is implemented. Additionally, fuel flow maxima may be reduced and/or fuel flow minima increased by selecting a fuel with an appropriate calorific value at the appropriate points in aircraft operation. The “more constant fuel flow rate” can therefore refer to a reduction in the maximum spread of fuel flow rates over the entire engine operating range/flight range.

It will be appreciated that in some aircraft 1 the pump speed is generally coupled to the shaft speed, with the spill ratio adjusted as needed for a given speed such that the fuel flow rate to the combustion chamber 16 is controlled by a fuel delivery system 220 (e.g. having a hydro-mechanical unit, HMU), which includes several components, and not only by a fuel pump. This smoother operation can be beneficial to ensure adequate fuel flow through the system even at very low power demands, e.g. B. for lubrication, fuel hydraulics and heat transfer. The use of a lower calorific value fuel in the engine 10 when the power requirement is lower may aid in thermal management since the higher fuel flow through the engine provides a larger heat transfer medium. Also, large engines 10 can be difficult to run smoothly at low idle thrust on standard fuels - therefore, the ability to switch to a fuel with a lower calorific value could improve low idle thrust performance.

A method 2060 for operating an aircraft 1 having a gas turbine engine 10 and a plurality of fuel tanks 50, 52, 53 arranged to store fuel for driving the gas turbine engine 10 is in 11 shown.

The method 2060 includes arranging 2062 each fuel source/tank 50, 52 of the plurality of fuel tanks to contain a different fuel to be used to power the gas turbine engine 10, the fuels having different heating values. In some examples, one or more of the fuel tanks 50, 52 may be part of a separate set of interconnected fuel tanks. In other examples, each fuel tank 50, 52 may be a self-contained single tank fuel source.

The method 2060 further includes storing 2064 information about the fuel contained in each fuel tank 50, 52, optionally in memory of an on-board fuel manager 214.

The method 2060 further includes controlling 2066 the fueling of the gas turbine engine 10 by selecting a particular fuel or fuel combination from one or more of the plurality of fuel tanks 50, 52. The control 2066 may be performed only during flight or throughout aircraft operation. The selection is made based on the thrust demand of the gas turbine engine 10 so that the gas turbine engine 10 can use a fuel with a lower calorific value for lower thrust demands (e.g., ground operations (if used on the ground), descent, cruise) and for higher thrust demands ( E.g. climb) a fuel with a higher calorific value is supplied.

Even in an example with only two separate fuel sources 50, 52, a range of different fuel heating values can be provided by dynamically mixing the two fuels to different values depending on the thrust demand. In some arrangements, method 2060 includes switching between two, three, four, or five fuels and/or preset blends with specific heating values depending on thrust demand. In other arrangements, the mixture may be changed as a function of thrust demand, optionally continuously (within the accuracy limits of the fuel pump and/or other flow controller).

Additional data may be used in conjunction with the determined fuel characteristics to adjust powertrain 2 control. For example, the method may include receiving data about the current conditions around the aircraft 1 (either from a provider, e.g. an external weather monitoring company, or from on-board detectors). This received data (e.g., weather data, temperature, humidity, presence of a contrail, etc.) may be used to make or affect changes to the composition of the fuel supplied to the gas turbine engine 10 . Instead of or in addition to the use of "live" or "near-live" weather data, weather forecast data for the flight route of the aircraft can be used to estimate current conditions.

A propulsion system 2 for an aircraft 1 may therefore comprise a fuel manager 214 arranged to store information about the fuel contained in each fuel tank 50, 52 and the fuel supply to the main gas turbine engine(s) 10 and optionally also to a APU 44 controls in operation. The fuel manager 214 may be provided as part of a fuel delivery system 220 that allows for control and adjustment of the fuel delivered to the gas turbine engine 10 .

This in 12 Fuel delivery system 220 shown may include one or more flow regulators 216, such as , valves and pumps, arranged to be controlled by the fuel manager 214 to control fuel delivery to the main gas turbine engine(s) 10 and optionally also to an APU 44 . For example, a flow regulator 216a, 216b may be provided between each fuel source and each engine 10. Such arrangements may allow different engines 10 of the same aircraft propulsion system 2 to be supplied with different fuels.

Optionally, the fuel manager 214 may additionally receive other data (in addition to the fuel characteristics) and use that other data and the fuel characteristics to determine a desired fuel or fuel blend for the gas turbine engine 10 . The fuel manager 214 may be provided as a separate fuel management unit 214 built into the propulsion system 2 and/or as software and/or hardware integrated into the existing aircraft control systems (e.g., the EEC 42). In some examples, the fuel composition data may be stored separately from the circuitry that performs fuel supply management and retrieved when needed - wherever the data is stored, that memory may be considered part of the fuel manager 214, regardless of whether it is integrated into it or in some way physically connected to it.

The more comprehensive term “drive system” 4 can be used for the drive system 2 to ensure that versions are also included in which the fuel is additionally or alternatively supplied to an auxiliary turbine 44, since the drive power is not always provided by such drive systems 4, e.g . when performing passenger operations while the aircraft 1 is stationary (it will also be appreciated that in many configurations the main gas turbine engines 10 can also be used to provide non-motive power).

The fuel manager 214 may be configured to select a particular fuel or fuel combination from one or more of the plurality of fuel tanks 50, 52, 53 based on the thrust demand of the gas turbine engine 10. In particular, a fuel with a lower calorific value is supplied to the gas turbine engine 10 when there is a lower demand for thrust, and vice versa. A fuel with a higher calorific value can therefore be used in high-performance flight phases, e.g. e.g. during take-off. The fuel's heating value can be adjusted linearly with a percentage increase or decrease in the demand for thrust in some scenarios within an available range.

The fuel manager 214 may be configured to provide the gas turbine engine 10 with fuel having a lower calorific value during cruise than during climb. Optionally, a fuel having an even lower calorific value may be supplied to the gas turbine engine 10 at base idle or low idle--this fuel may also be supplied to the APU 44 in some embodiments.

It will be understood that the term "low idle" is a generic term for the idle setting on the ground or in flight when the engine is operated to one of its minimum limits (e.g. minimum speed, pressure and/or temperature), set in the EEC 42 with the throttle lever in the idle detent position.

In-flight idle performance may vary significantly depending on factors such as altitude, power derating, customer tapping and anti-icing requirements; the term “low idle” therefore encompasses a range of power/thrust requirements.

The idling operation of the aircraft 1 on the ground is referred to as "ground idle" and the idling operation of the aircraft 1 in flight is referred to as "flight idle".

High idle is a more specific term that refers to conditions where the aircraft 1 is in an approach configuration and the idle is raised above low flight idle to achieve adequate thrust response if required for a go-around. While the throttle remains in the idle detent, there is increased boost and the high idle can only be done during of flight (not for operation on the ground). In some embodiments, gas turbine engine 10 may be supplied with fuel having a higher calorific value at high idle than at low idle, and fuel with an even higher calorific value may be supplied if the thrust demand increases above the level required for high idle.

The fuel manager 214 may make changes to the fueling system directly or provide the pilot with a proposal or notification of the change for approval (e.g., as described above for the control of the propulsion system 42, noting that the fuel manager 214 is part of the Control of the drive system 42 can be or be in connection with this). In some examples, the same fuel manager 214 can automatically make some changes and request others depending on the type of change.

In some examples, an aircraft 1 may be modified to perform the method 2060 described above, optionally by installing an adjustable fueling system 220.

A method 2070 for modifying an aircraft 1 in this way is in 13 shown. The original aircraft 1 comprises a gas turbine engine 10, which in the example described comprises an engine core 11 with a turbine 19, a compressor 14 and a core shaft 26 connecting the turbine to the compressor. The aircraft 1 also includes a plurality of fuel tanks 50, 52 and a fan 23, located upstream of the engine core, which includes a plurality of fan blades and is arranged to be driven from an output of the core shaft. The aircraft 1 can also include an auxiliary power unit 44 .

Method 2070 includes arranging 2072 each fuel tank 50, 52, 53 (or at least two fuel tanks of a plurality of fuel tanks) to contain a different fuel to be used to power the gas turbine engine(s) 10, 44, wherein the Fuels have different calorific values.

In some cases, the aircraft 1 may already have a plurality of fuel tanks 50, 52, 53 arranged to store fuel for powering the gas turbine engine 10; in such examples, the step 2072 of arranging the fuel tanks may simply be to selectively fill the tanks with different fuels. In cases where the aircraft 1 previously had only a single fuel tank 50, a new fuel tank 52 can be added to provide a plurality of fuel tanks. In cases where the aircraft 1 previously had only a single source of fuel, albeit consisting of multiple tanks, a new fuel tank 52 can be added and/or the fuel lines can be adjusted so that the original tanks 50, 53 are no longer all are interconnected so that at least two separate sources of fuel are present. The assembly step 2072 may therefore vary depending on the original aircraft configuration.

The method 2070 further includes providing 2074 a fuel manager 214 arranged to store information about the fuel contained in each fuel tank 50, 52, 53 and to control fuel delivery to the gas turbine engine 10. The fuel manager 214 can only operate during flight. In examples where it operates both in flight and during ground operations, the control strategy it uses may differ between flight and ground operations in some examples. In other examples, e.g. e.g. if all available fuels have acceptably low nvPM emissions, fuel control based on thrust and calorific value can additionally be done during ground operation.

The storage and control functions can be performed by separate entities or by the same entity; it will be appreciated that the fuel manager 214 can therefore be a distributed system or a single unit or module. The step of deploying 2074 the fuel manager 214 may, in some examples, include or consist of installing software into existing memory to be run with existing systems. In other examples, a new physical unit or module may be added to powertrain 2, optionally with one or more flow regulators 216 and/or replacement fuel line sections, to achieve the desired fuel flow and mixture control.

The fuel manager 214 is arranged to control fuel delivery to the gas turbine engine 10 by selecting a particular fuel or fuel combination from one or more of the plurality of fuel tanks 50, 52, 53 based on the thrust demand of the gas turbine engine 10 such that the gas turbine engine 10 with a lower demand for thrust, a fuel with a lower calorific value is supplied and vice versa. This control can be used throughout the operation of the aircraft vehicle or only in certain phases (e.g. only in flight or only in cruise flight).

It was also clear to the inventors that the current standards mean that (pure) SAF cannot be used in commercial aviation, but SAF could be used for ground operations, for example to reduce emissions from airports. Likewise, there may be advantages to using such a sustainable aviation fuel for ground-based operations, even if it can also be used in flight, for example to maximize environmental benefits from a limited amount of SAF available. If aircraft 1 has fuels available that are not pure SAF but have a SAF fraction, using the fuel(s) with the highest SAF fraction for ground operations can result in a corresponding reduction in airport emissions and thus leading to an improvement in air quality. A redesign of the aircraft fuel system can therefore provide the technical and environmental benefits of SAF, whether the SAF is provided as part of a blend or not.

When an aircraft 1 has only a relatively small amount of pure SAF or a high strength SAF blend available (the remainder of the fuel is either petroleum based fuel or a lower percentage SAF blend), the greatest benefit from that SAF (or the high strength SAF SAF blend) can be achieved by using this fuel in and around the airport where the power demand is relatively low (see above for nvPM generation).

For the same reasons, this SAF or high percentage SAF mixture, which can be stored in a first fuel tank 52 as described above, can be used in the auxiliary power unit (APU) 44 of the aircraft 1, e.g. B. at the gate of an airport.

While a synthetic fuel can be manufactured to closely mimic a conventional kerosene fuel, one or more fuel properties of SAF stored on board aircraft 1 may differ from the fuel properties of one or more other fuels stored on board the Aircraft 1 are stored in other tanks.

The fuel characteristics may include one or more of the fuel characteristics described above and may be determined using any of the approaches described above, including the example detection methods listed.

If two or more different SAFs or two or more different SAF blends with the same %SAF are available to aircraft 1, one or more other fuel characteristics - such as the hydrogen-to-carbon (H/C) ratio of the fuel or the level of non-volatile Combustion Particulate Matter (nvPM) - used to choose between the two or more fuels with the same %SAF. One or more other parameters that may affect the air quality in the vicinity of the aircraft 1 exhaust may also be compared to select the fuel that provides the best air quality results. Environmental factors (e.g. airport altitude and humidity) may also be considered in this assessment.

In the present examples, in the 14 and 18 described, the first fuel source is the first fuel tank 52. In other examples, the first fuel source may be multiple tanks connected together.

In the example described, the first fuel tank 52 is arranged to contain only one fuel which is clean Sustainable Aviation Fuel (SAF), i. H. 100% from sustainable sources and not from kerosene or fossil origin. In other examples, multiple fuel tanks of a plurality of fuel tanks may all contain SAF - each of the subset of fuel tanks containing SAF can therefore be used to provide SAF; it will be appreciated that the example of only one fuel tank 52 containing SAF is described herein by way of non-limiting example only.

In other examples, the first fuel tank 52 is arranged to contain a fuel that is a SAF blend having a higher %SAF than any other fuel tank 50, 53. In other examples, multiple fuel tanks may be a Plurality of fuel tanks all contain a SAF blend with the same %SAF so that there are multiple first fuel tanks 52 - each of the first fuel tanks can therefore be used to supply fuel for at least the majority of ground based operations; it will be appreciated that the example of a single first fuel tank 52 is described herein by way of non-limiting example only. One or more second fuel tanks 50, 53 contain one or more fuels with a lower %SAF (optionally 0%SAF) and are used for other operations.

This in 18 The example shown is generally similar to that in 14 shown, but the differences are described below. (In 18 an internal fuel line to the larger tank 50 is shown; it becomes clear that at least one second fuel line to the first fuel tank 52 is generally also provided, which, however, is not shown for reasons of clarity—also shown in FIG 14 For reasons of clarity, no such fuel lines are shown, but they would generally be present).

In the examples described here, the aircraft 1 has a plurality of fuel tanks 50, 52, 53, in particular at least two fuel sources or separate tanks 50, 52 and optionally more. Each fuel tank 50,52 is arranged to store fuel used to power one or more gas turbine engines 10,44 of the aircraft. One of the fuel tanks 52 - referred to as the first fuel tank 52 - is arranged to contain only a fuel that is Sustainable Aviation Fuel (SAF) or to contain a fuel blend with a high SAF content. In some embodiments, such as B. the in 18 1, this first fuel tank 52 is arranged to always contain only the SAF or high percentage SAF blend and may be isolated from the other fuel source(s) 50,53 at all times. In other versions, such as that in 14 1, this first fuel tank 52 is arranged to initially contain the SAF or high percentage SAF mixture and is fluidically isolated from the other fuel source(s) 50, 53 while that fuel is being used (e.g. for ground operation), but can then be connected to one or more other fuel sources 50, 53 during flight (e.g. by opening one or more valves) and another fuel from another fuel source 50, 53 can be pumped in (eg, to serve as trim tank 52).

The first fuel tank 52 of such examples is therefore arranged to contain only fuel that is Sustainable Aviation Fuel (SAF) or a high percentage SAF blend, at least during ground operations. In an embodiment where the fuel consists of 100% SAF, the SAF in this tank 52 can be selected so that the propulsion system 2 can only be operated with this fuel (e.g. for operation on the ground, in a in-flight emergency, or if fuel regulations change such that flight at 100% SAF is generally permitted), or it may be tailored for use in an APU 44 only and is not suitable for combustion in a main gas turbine engine 10. The fuel tank 52, containing only the sustainable aviation fuel, can therefore be arranged to be used to propel the aircraft 1 when the aircraft is operating on the ground. Optionally, the first fuel tank 52 may be used to supply SAF to the gas turbine engine 10, but only during ground operations. Alternatively, the first fuel tank 52 may be used to supply the gas turbine engine 10 with SAF as part of an in-flight mixture, or it may be arranged to supply SAF to the APU 44 only.

For configurations where the fuel in the first fuel tank(s) 52 is not pure SAF, that fuel may also be used more flexibly during flight under the regulations in force at the time of writing.

In some embodiments, the first fuel tank 52 may be used to fuel both the main gas turbine engine 10 and the APU 44 .

In some of the examples described, all fuel used for ground operations is sustainable aviation fuel or the highest possible %SAF blend, and all fuel used for ground operations is therefore taken from the first fuel tank 52 (in examples with multiple first tanks, one or more of these tanks are used). In other examples, most of the fuel used for ground operations is SAF or the highest possible %SAF blend, with only small amounts used from other sources (e.g. less than 10% or less than 5% of fuel consumption and/or operating time or using fuel from another source only for the first engine start).

When a first fuel tank 52 is empty, a second fuel tank 50, 53 with the highest %SAF blend among the second fuel tanks can be designated as the first fuel tank and used for continued ground operations.

• • Anlassen des Motors selbst;
• • Heizung, Beleuchtung, Klimatisierung und/oder andere nicht-antriebsbedingte Anforderungen, während das Luftfahrzeug 1 steht (z. B. an einem Flugsteig) oder sich bewegt;
• • das Rollen des Luftfahrzeugs 1; und
• • Einleitung des Startrollens, gegebenenfalls einschließlich des Anhebens des Bugrads, falls erforderlich.

A fuel manager 214 may be arranged to control fuel delivery to the gas turbine engine(s) 10, 44 such that fuel is only drawn from the one or more first fuel tanks 52 when the aircraft 1 is conducting at least most of its operation performed on the ground. As used herein, "operations on the ground" generally refers to pre-launch operations and may include one or more of the following:

• • starting the engine itself;
• • heating, lighting, air conditioning and/or other non-power requirements while the aircraft 1 is stationary (e.g. at a gate) or moving;
• • aircraft 1 taxiing; and
• • Initiation of take-off roll, including nose wheel raise, if necessary.

The first fuel tank 52 (or one or more other fuel tanks containing SAF or the high percentage SAF blend, in other examples) may therefore be used to provide some or all of the fuel required by the aircraft's propulsion system 4 when stationary (e.g., at rest). e.g. at a gate) and consumed during warm-up, taxiing and take-off.

In this way, the airport's requirements regarding emissions and/or the use of SAF can be met.

Upon completion of ground operations, if fuel remains in one or more of the first fuel tanks 52, it may optionally be reserved for use at the destination airport for further ground operations upon landing, including approach and taxiing.

Leftover fuel in one or more first fuel tanks 52 may additionally or alternatively be used for the early part of the climb (on takeoff) and/or the latter part of the approach (on landing) - i.e. H. for one or more non-ground parts of the flight that are nevertheless close to the ground and therefore relevant to local air quality and human health. The use of SAF when approaching a destination airport (as opposed to takeoff) can be of particular benefit for nvPM, since the power requirement is lower and the reduction in nvPM that can be achieved by using SAF is therefore higher.

The selection can be made based on the amount of SAF available, the types of SAF blend available and an order of priority for the use of SAF in the different areas of aircraft operations.

The fuel manager 214 may be arranged to control fuel delivery to the gas turbine engine(s) 10 during flight by selecting a particular fuel or fuel combination from one or more of the plurality of fuel tanks 50,52.

The first fuel tank 52 of the multiple fuel tanks 50, 52, which is arranged to contain only the fuel with the highest %SAF (which may be SAF), may be smaller than one or the other fuel tanks 50, 53. For example, may the first fuel tank 52 accounts for 3% to 20% and optionally 5% to 10% of the total available tank volume of the aircraft 1. This tank 52 can optionally be arranged in such a way that it is used exclusively for the ground-based operation of the aircraft 1.

Each fuel tank 50, 52, 53 on board the aircraft 1 may be arranged to contain a different type of fuel (e.g. petroleum or SAF fuel or different types of SAF) and some tanks may contain mixed fuels, where a proportion of a sustainable aviation fuel is blended with a conventional jet fuel or other fuel derived from petroleum. In some examples, two or more tanks 50, 52 may contain the same fuel provided that at least two different fuels are available from the aircraft 1 fuel tanks in total. In some examples, at least one tank contains 52 SAF, i. H. a purely sustainable aviation fuel, not a mixture.

For versions like the one in 14 As shown, where a trim tank 52 is present on the aircraft 1 and used as the first fuel tank 52, the approaches and advantages described above in relation to SAF use can also be achieved.

The drive system 2 of the examples described in turn comprises an adjustable fuel supply system 220 with which it is possible to select which tank(s) 50, 52 and thus which fuel or which fuel mixture is to be used. In such examples, fuel characteristics may vary over the course of a voyage (including flight and ground operations at the beginning and/or end of a voyage) - a particular fuel or fuel blend may be selected to support operations at particular phases of flight or under particular external conditions to improve conditions.

In examples where one or more fuel characteristics are detected (either by direct detection or by inference from detected parameters), e.g. B. to determine or verify which tank contains the highest %SAF fuel, any of the detection approaches described above may be implemented. In other examples, a detection can be dispensed with and the supplied data on the fuel composition can be used instead - this data can simply be SAF shares, e.g. '100% SAF' versus 'Other', or by %SAF for each tank, or they may contain more detailed information about the fuel characteristics. In other examples, no fuel data may be provided at all - instead, each tank 50, 52, 53 may be designated as a "SAF Only" tank, or as a "Non-SAF Only" tank, or as a "Highest %SAF" tank, or "Other ' tank can be identified and the method can be relied upon to fill the tanks 50, 52, 53 correctly accordingly.

In some examples, the calorific values for each available fuel can be calculated or provided, and a fuel or fuel mixture can be supplied based on the thrust requirements described above (optionally also taking into account the flight altitude) - a portion of the fuel from the first tank 52 can used alone and/or in one or more mixtures in such examples. In examples with only a first tank 52, control based on calorific value may only occur in flight. In examples having more than one first tank 52, the selection between the first tanks may also be made during ground operations based on calorific value for different thrust requirements.

A method 2061 for operating an aircraft 1 with a gas turbine engine 10, 44 and a plurality of fuel tanks 50, 52 arranged to store fuel for driving the gas turbine engine 10, 44 is in 15 shown.

The method 2061 includes arranging 2063 at least two fuel tanks 50, 52 from the plurality of fuel tanks to each store a different fuel, in particular fuels with different proportions of SAF. A first fuel tank 52 contains a fuel with a higher proportion of SAF than a second fuel tank 50, 53. A first fuel tank 52 of the plurality of fuel tanks can be arranged to contain only one fuel that is a sustainable aviation fuel.

This arranging step 2063 may include fluidly isolating one or more tanks from one another, if required, so that different fuels can be stored in different tanks (e.g., by closing valves). This arrangement step 2063 can include filling the tanks 50, 52, 53 accordingly.

In some examples, one or more of the fuel tanks 50, 52 may be part of a separate set of interconnected fuel tanks. In other examples, each fuel tank 50, 52 may be a self-contained single tank fuel source.

In some examples, the fuel in the first fuel tank 52 has a %SAF greater than 50%, e.g. B. greater than or equal to 55%, 60% or 70%, and can optionally be 100% SAF.

The method 2061 of some examples includes identifying 2067 which tank 52 contains the fuel with the highest percentage of sustainable aviation fuel. If multiple tanks 50, 52 each contain fuel with the same, highest %SAF, the multiple tanks can all be identified as first fuel tanks 52. Optionally, one or more other attributes (e.g., heating value, nvPM emissions) may be used to select which first fuel tank 52 to use in such scenarios. Identification 2067 may be by detection or determination based on engine operating parameters, e.g. e.g., using any of the approaches described herein, or using provided data (e.g., data transmitted to or otherwise received from or accessible to the fuel manager 214).

The method 2061 further includes controlling 2065 the fueling of the gas turbine engine 10 so that only fuel from the tank 52 containing the fuel with the highest proportion of sustainable aviation fuel (or in some cases any fuel with more than 50% SAF) is used , when the aircraft 1 performs at least most of the operations on the ground. This fuel can have a SAF content of more than 50% SAF and optionally at least 55% SAF. The use of that fuel for “at least the majority” of operations may mean that at least 90% or 95% of the fuel used for ground operations is that fuel and/or at least 90% or 95% of the ground operations time is operated on this fuel and/or that the fuel with the highest SAF fraction is used for all ground operations with the exception of engine launch (for which a specific fuel may be used, as described below).

The method 2061 also optionally includes storing 2064 information about the fuel contained in each fuel tank 50, 52, optionally in the memory of an onboard fuel manager 214. The information stored may simply be an identifier indicating whether a particular tank 50, 52 the fuel with the highest %SAF or a fuel containing over 50% SAF or not. In other examples, additional information may be stored. This stored information can be used for the control step 2065, in particular to identify the first fuel tank 52 (and/or correspondingly one or more other tanks if several tanks contain SAF or the fuel with the highest %SAF) if this is not fixed in the Drive system 2 is programmed/wired. Instead, a look-up table of the characteristics of the tanks can be used to identify the first fuel tank(s) 52 if the tanks are always arranged to hold specific fuels.

A propulsion system 4 for an aircraft 1 can therefore comprise a fuel manager 214 which is arranged to store information about each fuel tank 50, 52 or about the fuel contained in each fuel tank 50, 52 and to control the fuel supply to the gas turbine engine 10 during operation . The information stored may simply include an indicator of whether or not each tank is the tank with the highest %SAF, or it may include more detailed information such as B. a %SAF content for each tank and/or one or more other fuel characteristics of the fuel currently in each tank 50, 52 (the %SAF value can be defined by volume and/or mass, it being noted is that the densities can vary within accepted limits). In such examples, the first tank 52 of the plurality of fuel tanks 50, 52, 53 may vary over the lifetime of the power system 4, e.g. B. depending on which tank is filled with which fuel. In other examples, this can be in 16 The fuel delivery system 220 shown can be arranged such that a particular tank 52 is always the tank with the highest %SAF, and no such fuel information needs to be stored.

The fuel manager 214 may also be configured to identify which tank 52 contains the fuel with the highest proportion of sustainable aviation fuel and/or to identify all tanks containing fuels with greater than 50% SAF.

In cases where the highest percentage of the SAF or SAF mixture is fed to a gas turbine main engine 10 of the aircraft 1, which provides propulsion power to the aircraft 1, the propulsion system 4 may more accurately be referred to as propulsion system 2. The broader term “drive system” 4 is used here to ensure that versions are also covered in which the fuel is additionally or alternatively supplied to an auxiliary power unit 44, since the drive power may not be provided by such drive systems 4.

The fuel manager 214 may be provided as part of a fuel delivery system 220 that allows for control and adjustment of the fuel delivered to the gas turbine engine 10, 44 and may be as described above for the earlier examples.

The fuel manager 214 is generally as described above. In examples including APUs 44, the fuel manager 214 may additionally be configured to control the fuel or fuel mixture supplied to the APU 44.

In some of the examples described, the fuel manager 214 is set up in such a way that, for ground-based operation of the energy system 4, it only takes fuel from the first fuel tank 52, i. H. the fuel tank 52 containing the fuel with the highest SAF fraction.

As described above for other examples, the fuel manager 214 may additionally receive other data (in addition to information indicating which tank(s) contain(s) SAF), provide a %SAF for each tank, and/or other fuel characteristics provide), and use this other data and the fuel characteristics to determine a desired fuel or fuel blend for the gas turbine engine 10, 44 in flight.

The fuel manager 214 may be arranged to control fuel delivery to the gas turbine engine 10, 44 such that fuel is drawn primarily or exclusively from a first fuel tank 52 when the aircraft 1 is operating on the ground.

In some examples, an aircraft 1 may be modified to perform the method 2061 described above by optionally installing an adjustable fuel delivery system 220 .

A method 2071 for modifying an aircraft 1 in this way is in 17 shown. The original aircraft 1 includes a gas turbine engine 10, the gas turbine engine 10 in this example including an engine core 11 with a turbine 19, a compressor 14 and a core shaft 26 connecting the turbine to the compressor. The aircraft 1 also includes a fan 23 placed upstream of the engine core, the fan having a includes a plurality of fan blades and is arranged to be driven by an output of the core shaft. The original aircraft 1 may further include an APU 44, which APU itself is or includes a gas turbine engine 44.

The method 2071 includes arranging 2073 at least two separate fuel tanks 50, 52 to store a different fuel such that one fuel has a higher proportion of SAF than the other. One or more fuel tanks may be arranged to contain only one fuel that is a sustainable aviation fuel (in one example described, the first fuel tank 52 of the plurality of fuel tanks 50, 52 is the only tank containing pure SAF).

In some cases, the aircraft 1 may already have a plurality of fuel tanks 50, 52 arranged to store fuel for powering the gas turbine engines 10, 44; in such examples, the step 2073 of arranging the fuel tanks may simply be to selectively fill the tanks with different fuels. In cases where the aircraft 1 previously had only a single fuel tank 50, a new fuel tank 52 can be added to provide a plurality of fuel tanks. In cases where the aircraft 1 previously had only a single source of fuel, albeit consisting of multiple tanks, a new fuel tank 52 can be added and/or the fuel lines can be adjusted so that the original tanks 50, 53 are no longer all connected are connected so that at least two separate sources of fuel are present. The arrangement step 2073 may therefore vary depending on the original aircraft configuration.

The method 2071 further includes providing 2075 a fuel manager 214 arranged to control fuel delivery to the gas turbine engine(s) 10, 44 such that only or primarily SAF is used when the aircraft 1 is operating on the ground becomes.

The fuel manager 214 may also be arranged to determine which tank 52 contains the fuel with the highest percentage of sustainable aviation fuel - this tank 52 may be referred to as the first fuel tank 52 . In cases where two or more tanks contain a fuel with the same, highest %SAF, a plurality of tanks can be identified as first fuel tanks. Choosing between these tanks can be done using one or more of the approaches described above.

The fuel manager 214 may use fuel from the first fuel tank 52 (e.g., SAF in a particular example described, or more generally the highest %SAF fuel available, or optionally any fuel with more than 50% SAF) for some, but not all, ground-based operations. For example, the fuel manager 214 may use a different fuel for launch before switching to the first tank 52, may switch to a different fuel if the first fuel tank 52 runs out of fuel before ground operations are complete, and /or the fuel manager 214 may supply the fuel from the first fuel tank 52 to the APU 44 but a different fuel to the other gas turbine engine(s) 10.

In some examples, e.g. B. if the tank or tanks 52 in which the fuel with the highest %SAF is stored may vary during the life of the propulsion system 2, the fuel manager 214 can store additional information about the fuel contained in each fuel tank 50, 52 so that the first tank 52 or equivalent tanks can be identified.

The storage and control functions can be performed by separate entities or by the same entity; it will be appreciated that the fuel manager 214 can therefore be a distributed system or a single unit or module. The step of deploying 2075 the fuel manager 214 may, in some examples, include or consist of installing software into existing memory to be run with existing systems. In other examples, a new physical unit or module may be added to powertrain 2, optionally with one or more flow regulators 216 and/or replacement fuel line sections, to achieve the desired fuel flow and mixture control.

In some examples, the fuel manager 214 may additionally be configured to perform other functions, such as controlling fuel delivery to the gas turbine engine 10 by selecting a particular fuel or fuel combination from one or more of the plurality of fuel tanks 50, 52 based on thrust demand of the gas turbine engine 10, so that the gas turbine engine 10 is supplied with a fuel having a lower calorific value when there is less demand for thrust, and vice versa. It will be appreciated that the thrust demand can be determined using one or more approaches known in the art, for example as mentioned above.

The inventors have also recognized that fuel differentials can allow redesign of the aircraft fuel system to achieve technical and environmental advantages for operating an aircraft on the ground. In the present examples, with reference to the 14 and 19 are described, the usage of the first fuel tank 52 is adjusted accordingly.

19 shows an aircraft 1 with a propulsion system 2, which essentially corresponds to that in 14 shown, but with three separate fuel sources 50, 52, 53 instead of two. The first, second and third fuel sources are therefore not fluidly connected to separate the different fuels (at least under normal operating conditions). In other examples, like the one in 14 shown, only two separate fuel sources can be provided.

In this example, the first fuel source is the first fuel tank 52. In other examples, the first fuel source may be multiple tanks connected together. The first fuel tank 52 is arranged to be used at least primarily (and in some cases exclusively) for ground based operations. The fuel from the first fuel tank 52 is arranged to be used for at least the majority of ground based operations, similar to the use of SAF or the high percentage SAF blend described in the previous examples.

in the in 19 In the example shown, the second fuel source includes a center fuel tank 50 located primarily in the fuselage of the aircraft, and the third fuel source includes multiple wing fuel tanks 53a, 53b, with at least one wing fuel tank located in the port wing and at least one wing fuel tank located in the starboard wing to balance. In the example shown, the tanks 53a and 53b are fluidically connected to one another and thus form a single, third fuel source. A fluid connection between the wing fuel tanks 53 of the third fuel source may be provided to balance the aircraft 1 as previously described.

The center fuel tank 50 and the wing fuel tanks 53 may each consist of a plurality of fuel tanks which are fluidly connected to one another.

In another example, the wing fuel tanks 53a, 53b may be fluidly connected to the center tank 50 to form a single, secondary fuel source. To compensate, one or more fuel tanks in the port wing may be fluidly connected to one or more fuel tanks in the starboard wing. This can be done either via the center fuel tank 50 (if not part of a separate fuel source), or bypassing the center fuel tank(s), or both (for maximum flexibility and safety).

In some examples, the distribution of fuel tanks 50, 52, 53 available in the aircraft 1 may be determined such that each fuel source is substantially symmetrical about the centerline of the aircraft. In cases where an asymmetrical distribution of fuel tanks is permissible, an appropriate means of fuel transfer between the fuel tanks of the primary fuel source and/or between the fuel tanks of the secondary fuel source may be provided such that the position of the aircraft's center of mass is within acceptable lateral limits can be maintained. However, in examples where the first fuel tank 52 is much smaller than the other fuel tanks 50, 53, its mass change when using fuel from that tank may be less significant, so symmetry may not be an issue.

At the in the 14 and 19 illustrated examples, the first fuel tank 52 is again smaller than the second fuel tank 50. In the example of 14 it is further back in the fuselage. The first fuel tank 52 of this embodiment can therefore be more easily used as the trim tank 52 in flight; the trimming procedure described above can therefore also be used in connection with the initial dedication of a tank 52 for ground use. If the first tank 52 is to be used as an in-flight trim tank, the fuel in that tank 52 will either be consumed during the initial phase of ground operations and takeoff, if any, or the remainder will be mixed with other fuel used in that tank for in-flight trim is pumped. In contrast, in implementations where the first tank 52 is not used as a trim tank, the remaining SAF could be stored in the first tank 52 until aircraft 1 lands and then to power final ground operations (e.g., landing and/or taxiing ) can be used to provide further air quality benefits at the destination airport, rather than being consumed or diluted in flight.

In various examples, an APU 44 as described above may be used to provide some or all of the power for operation on the ground, and the first fuel tank 52 may be used to supply the APU 44 with fuel.

In alternative embodiments, the first fuel tank 52 may be a dedicated APU fuel tank and not associated with either the main gas turbine engines 10 (as in 14 ) still be fluidically connected to another fuel tank. In some of these examples, a fuel manager as described elsewhere herein may not be present or used.

An aircraft 1 can be refueled by connecting a fuel storage tank 60, such as is provided by an airport fuel truck, or a pipeline via a fuel line 61 to a connection opening 62 of the aircraft 1, as described above. In particular, in the examples described, the first tank 52 can be fed directly from a fuel supply and does not have to be filled by decanting from another fuel tank 50, 53 of the aircraft 1. In 14 the internal fuel lines from the ports 62 to the tanks are not shown for the sake of clarity. In 19 an internal fuel line (to the larger tank 50) is shown; it is clear that at least one second fuel line to the first fuel tank 52 can also be provided—instead of filling the first tank 52 from another tank—which, however, is not shown for reasons of clarity.

In embodiments of the present invention, the aircraft 1 has a plurality of fuel tanks 50, 52, 53, in particular a first fuel tank 52 arranged to be used for part or all of the ground operations of the aircraft 1, and one or more secondary fuel tanks 50, 53 each arranged to contain a fuel used to power the gas turbine engine 10 in flight. One or more gas turbine engines 10, 44 may be involved in ground operations of the aircraft 1 - the gas turbine engine 44 of the APU 44 may be used for some ground operations and one or more of the main gas turbine engines 10 may be used for other ground operations.

Each of the fuel tanks 50, 52, 53 is arranged to store fuel used to power one or more gas turbine engines 10, 44 of the aircraft 1. One of the fuel tanks - referred to as the first fuel tank 52 - is arranged to be used for some or all of the aircraft 1's ground-based operations.

in the in 21 In the example shown, the first fuel tank 52 is dedicated solely to ground operations and the fuel from this tank 52 is not used in flight. The fuel manager 214 of this example (which may be generally as described above) is arranged to control the fuel supply to the gas turbine engines 10, 44 such that fuel is only drawn from the first fuel tank 52 when the aircraft 1 is performing ground-based operations , and for other operations fuel is drawn from only the one or more secondary fuel tanks 50,53. The flow regulator 216c may prevent fuel from being drawn from the first fuel tank 52 during flight. In other examples, some fuel from the first tank 52 may also be used in flight and/or some fuel from other tanks may be used for ground operations.

In some examples, the first fuel tank 52 is arranged to contain a fuel that is Sustainable Aviation Fuel (SAF), at least during ground operations. H. tank 52 may contain 100% pure SAF. The fuel in the first tank 52 can be selected in such a way that the propulsion system 2 can be operated exclusively with this fuel for operation on the ground, regardless of whether this fuel is approved for use in flight or not. Alternatively, the fuel in the first tank 52 may not be suitable for use in the main gas turbine engines 10 and may be used solely for the APU 44 .

In the examples described here, the first fuel tank 52 is therefore arranged to be used for the operation of the aircraft 1 on the ground, regardless of whether this fuel tank 52 contains SAF or not.

In some embodiments, such as B. the in 19 shown, this first fuel tank 52 is arranged so that it is always used only for operations on the ground (optionally a small remainder can be consumed after rotation of the aircraft 1 during climb as previously described) and it can always be used by isolated from the other fuel source(s) 50,53. In other embodiments, such as B. the in 14 1, this first fuel tank 52 is arranged to be used initially for ground operations and is fluidically isolated from the other fuel source(s) 50, 53 while it is used for ground operations, but then in Flight with one or more other forces fuel sources 50, 53 and can be used as a trim tank 52 and/or to fuel an engine 10, 44 in flight. A different fuel from a different fuel source 50, 53 can be pumped into the first fuel tank 52 in flight than the fuel with which it was originally filled for operation on the ground.

In some embodiments, the first fuel tank 52 is configured to fuel one or more gas turbine engines 10, 44 only during ground operations, i. H. this tank is arranged so that it is used exclusively for ground operations of the aircraft 1. In some embodiments, a fuel suitable only for use in an APU 44 and not suitable for combustion in a main gas turbine engine 10 may be provided in the first tank 52 . However, the fuel manager 214 of some examples may be configured to provide fuel from the first fuel tank 52 to the main gas turbine engine 10, e.g. alone in emergency situations, or as part of a mixture in normal flight, or the first fuel tank 52 may have a different role in flight - e.g. B. that of the trim tank. In other examples, an interlock may be provided (e.g., by a flow regulator 216c) to prevent fuel from entering the gas turbine engine 10 from the first tank 52 during flight.

In some of the examples described, all of the fuel used for ground operations is drawn from the first fuel tank 52 . The fuel manager 214 may be arranged to control the fueling of the gas turbine engines 10, 44 such that only fuel is drawn from the first fuel tank 52 when the aircraft 1 is performing all operations on the ground.

In other examples, the fuel drawn from the first fuel tank 52 may be used for a subset of the ground-based operations, using fuel from other tanks 50, 53 as appropriate. For example, the first fuel tank 52 may fuel the APU 44 for its operations on the ground (e.g., lighting, air conditioning, main engine start) while another fuel tank 50, 53 fuels the main gas turbine engine(s) 10 for operation fueled on the ground (e.g. taxiing) or a different fuel may be used for initial engine warm up/start and the supply may then be switched to the first fuel tank 52 (e.g. once a threshold temperature is reached). In the following, the term "operation on the ground" is defined as above.

The first fuel tank 52 can therefore be used to provide some or all of the fuel consumed by the aircraft's propulsion system 4 when stationary (e.g. at a gate) and during warm-up, taxiing and take-off.

This has the advantage of being able to store and use a fuel tailored to the relatively low power requirements of ground operations and/or to more easily meet airport emissions and/or SAF use requirements, and /or that the performance of the engine 10 at low thrusts can be improved.

The first fuel tank 52 of the plurality of fuel tanks can be arranged to contain only one fuel, which is a sustainable aviation fuel, or to contain a high percentage SAF blend; thereby achieving some or all of the nvPM and air quality benefits described above. For the same reasons, 100% or high percentage SAF/fuel from the first fuel tank 52 may be selected for use in an auxiliary power unit (APU) 44 of the aircraft 1 at an airport gate.

The first fuel tank 52 of the plurality of fuel tanks may be smaller than the other fuel tanks. For example, the first fuel tank 52 can make up 3% to 20% and optionally 5% to 10% of the total available tank volume of the aircraft 1 .

For versions like the one in 14 As shown, where the first fuel tank 52 can be operated as a trim tank 52, the method described above can be used whether or not the fuel in the first fuel tank 52 is SAF or a high percentage SAF blend.

Each fuel tank 50, 52, 53 on board the aircraft may be arranged to contain fuel of a different type or grade of sustainable aviation fuel. While a synthetic fuel could be manufactured to closely mimic a conventional kerosene fuel, one or more fuel properties of the SAF fuel stored on board aircraft 1, either as pure SAF fuel or as part of a blend, may differ from the fuel properties one or more other fuels (SAF blends or others) distinguish, which are stored on board the aircraft 1 in other tanks.

The fuel characteristics may include one or more of the properties listed above and may be determined using any of the techniques listed above, alone or in combination as appropriate, including the various detection methods exemplified.

Other examples may omit detection and instead rely on the supplied fuel composition data - this data may simply be "ground use fuel" versus "flight use fuel" or contain more detailed information about the fuel characteristics. In other examples, no fuel data may be provided at all - instead each tank 50, 52, 53 may be identified as a ground use tank 52 or as a standard use tank 50, 53, and such examples may rely on the tanks 50, 52, 53 being properly filled accordingly become.

The drive system 4 comprises an adjustable fuel supply system 220, with which it is possible to select which tank(s) 50, 52, 53 and thus which fuel or which fuel mixture is to be used. A fuel manager 214 as described above can control this system 220. In examples where the fuel blend or fuel can be changed mid-flight (rather than having a flight and ground setting), the fuel characteristics can vary over the course of a flight - a particular fuel or fuel blend can be chosen to match the to improve operation in certain phases of flight or under certain external conditions. In some examples, heating values may be calculated or provided for each available fuel and in-flight fueling may be controlled accordingly.

In embodiments where the fuel from the first fuel tank 52 is supplied to a main gas turbine engine 10 of the aircraft 1 which provides motive power to the aircraft 1 , the propulsion system 4 may be more specifically referred to as propulsion system 2 . The broader term “drive system” 4 is used to ensure that designs are also covered in which the fuel is additionally or alternatively supplied to an auxiliary power unit 44, since such drive systems 4, as explained above, may not provide any driving force.

A method 2080 for operating an aircraft 1 with one or more gas turbine engines 10, 44 and a plurality of fuel tanks 50, 52, 53 arranged to store fuel for driving the gas turbine engines 10, 44 is in 20 shown.

The method 2080 includes providing 2082 at least two fluidly separate fuel tanks 50, 52, 53, i.e. at least two fuel sources.

The method 2080 further includes 2086 controlling the fueling of the gas turbine engine(s) 10, 44 so that only fuel from the first fuel tank 52 is used when the aircraft 1 is conducting at least the majority of its operations on the ground. Here, using fuel from the first tank 52 for “at least the majority” of operations may mean that at least 90% or 95% of the fuel used for ground operations is from the first tank 52 and/or at least 90% or 95% % of operational time for ground operations is fueled from the first tank 52 and/or that fuel from the first tank 52 is used for all ground operations except for the first engine start. The fuel manager 214 may therefore use fuel from the first fuel tank 52 for some, but not all, ground based operations. For example, the fuel manager 214 may switch to a different fuel if fuel from the first fuel tank 52 is depleted before ground operations are complete, and/or the fuel manager 214 may route fuel from the first fuel tank 52 to the APU 44, but supply a different fuel to the other gas turbine engine(s) 10. Optionally, only fuel from this tank 52 can be used for the entire operation on the ground.

Optionally, method 2080 may include withdrawing fuel from only the one or more secondary fuel tanks 50, 53 for other operations. In other examples, fuel from the first fuel tank 52 may be provided during flight as part of a mixture, but optionally not alone (except in emergency situations).

In some examples, one or more of the fuel tanks 50, 52 may be part of a separate set of interconnected fuel tanks. In other examples, each fuel tank 50, 52 may be a self-contained single tank fuel source.

The method 2080 of some examples further includes storing 2084 information information about the fuel contained in each fuel tank 50, 52, 53 and/or the identification of each fuel tank 50, 52, 53, optionally in the memory of an onboard fuel manager 214. The information stored may simply be an identifier indicating whether or not a particular tank 50, 52 is the first tank 52 or is intended for use on the ground. In other examples, additional information may be stored. Control step 2086 may be performed based on this stored information.

A propulsion system 2 or another propulsion system 4 for an aircraft 1 can therefore comprise a fuel manager 214 arranged to control the fuel supply to the gas turbine engine(s) 10, 44 so that it draws fuel from the first fuel tank 52 takes fuel when the aircraft 1 is performing ground-based operations and takes fuel from the one or more secondary fuel tanks 50, 53 for other operations. In some embodiments, the fuel manager 214 may be configured to control fuel delivery to the gas turbine engine(s) 10, 44 such that it only draws fuel from the first fuel tank 52 when the aircraft 1 is performing ground-based operations, and draws fuel from only the one or more secondary fuel tanks 50, 53 for other operations.

In some examples, the fuel manager 214 may be configured to store information about each tank or the fuel contained in each fuel tank 50, 52, 53 and to control fueling of the gas turbine engine(s) 10, 44 during operation accordingly . The information about the fuel contained in each fuel tank 50, 52, 53 may simply include an indication of whether or not each tank is the ground use tank. In such examples, which of the plurality of fuel tanks 50, 52, 53 is the first tank 52 may change over the life of the powertrain 2, e.g. B. depending on which tank is filled with which fuel. In other examples, the fuel delivery system 220 may be set so that a particular tank 52 is always the tank used on the ground, and this information need not be stored. In examples in which fuel information is stored, the information about the fuel contained in the individual fuel tanks 50, 52, 53 can additionally include other information, e.g. B. a %SAF content for each tank and/or one or more other fuel characteristics of the fuel currently in each tank 50,52,53.

The fuel manager 214 may be provided as part of a fuel delivery system 220 that allows for control and adjustment of the fuel delivered to the gas turbine engine 10, 44 and may be as described above.

in the in 21 In the example shown, the fuel management system 220 is set up so that fuels from the second and third fuel sources 50, 53 can be mixed to form a mixture for the supply of the engine 10, but not that fuel from the first, ground-mounted tank 52 can be mixed with the other fuels. In other examples, other approaches can be used.

In the examples described here, the fuel manager 214 is arranged in such a way that it only draws fuel from the first fuel tank 52 for the operation of the drive system 4 on the ground. It can be seen that while the aircraft 1 is technically still grounded with one or more wheels, takeoff is a relatively high power activity and is generally classified as part of the flight envelope and not as ground operations.

Optionally, the fuel manager 214 may additionally receive other data (in addition to information indicating which tank 50, 52, 53 is the first tank 52 and other optional fuel attributes) and use that other data and the fuel attributes to determine a desired fuel composition for the Gas turbine engine 10, 44 to determine in flight.

As mentioned above, the fuel manager 214 may be provided as a separate fuel management unit 214 built into the propulsion system 2 and/or as software and/or hardware integrated into the existing aircraft control systems. In some examples, the fuel composition and/or tank identification data may be stored separately from the circuitry that performs fuel supply management and retrieved when needed - wherever the data is stored, that storage may be considered part of the fuel manager 214 , whether or not it is integrated or physically connected in any way.

The fuel manager 214 of the examples described herein is arranged to control the fueling of the gas turbine engine 10, 44 such that fuel is drawn from the first fuel tank 52 to power at least the majority of ground operations.

In some examples, the fuel manager 214 may be configured to be able to mix fuels from the secondary fuel tanks 50, 53 that are arranged to power the gas turbine engine 10 in flight, but not able to To mix fuel from the first fuel tank 52 with fuel from the secondary fuel tanks 50,53.

In some examples, the fuel manager 214 may be configured to select a particular fuel or fuel combination from one or more of the plurality of fuel tanks based on the thrust demand of the gas turbine engine in flight. In particular, a fuel with a lower calorific value can be supplied to the gas turbine engine 10 when there is a lower demand for thrust, and vice versa. A fuel with a higher calorific value can therefore be used in phases with high power requirements, e.g. e.g. during take-off. The fuel manager 214 may be configured to provide the gas turbine engine 10 with fuel having a lower calorific value during cruise than during climb. A fuel with an even lower calorific value can optionally be supplied to the gas turbine engine 10 in the basic idle state (low idle).

The fuel manager 214 can make changes to the fueling directly or provide the pilot with a notification or suggestion regarding the change for approval, as described in more detail above. In some examples, the same fuel manager 214 can automatically make some changes and request others depending on the type of change.

In some examples, an aircraft 1 may be modified to perform the method 2080 described above, optionally by installing an adjustable fueling system 220.

A method 2081 for modifying an aircraft 1 in this way is in 22 shown. The original aircraft 1 includes a gas turbine engine 10, and in this example the gas turbine engine 10 includes an engine core 11 with a turbine 19, a compressor 14 and a core shaft 26 connecting the turbine to the compressor. The aircraft 1 also includes a fan 23 located upstream of the engine core, the fan including a plurality of fan blades and arranged to be driven from an output of the core shaft. The original aircraft 1 may further include an APU 44, which APU itself is or includes a gas turbine engine 44.

The method 2081 includes the provision 2083 of at least two separate fuel tanks 50, 52, 53 (not fluidly connected or at least fluidically isolable from one another), which are arranged in such a way that they can supply the engine 10 with fuel. A first fuel tank 52 of the plurality of fuel tanks 50, 52, 53 is arranged to provide fuel for at least the majority of ground based operations. One or more other fuel tanks 50, 53 are arranged to supply fuel for all operations not covered by the first fuel tank 52.

In some cases, the aircraft 1 may already have a plurality of fuel tanks 50, 52, 53 arranged to store fuel for powering one or more gas turbine engines 10, 44; in such examples, the fuel tank arrangement step 2083 may simply be to ensure that one of the tanks 52 is arranged for ground operations and at least one other tank 50, 53 is arranged for flight operations.

In cases where the aircraft 1 previously had only a single fuel tank 50, a new fuel tank 52 can be added so that there are multiple fuel tanks. In cases where the aircraft 1 previously had only a single source of fuel, albeit consisting of multiple tanks, a new fuel tank 52 can be added and/or the fuel lines can be adjusted so that the original tanks 50, 53 are no longer all connected are connected so that at least two separate sources of fuel are present. The arrangement of the fuel tanks or the provision of a separate first fuel tank 52 in step 2083 can therefore vary depending on the original aircraft configuration.

The method 2081 further includes providing 2085 a fuel manager 214 arranged to control fuel delivery to the gas turbine engine(s) 10, 44 such that only fuel from the first fuel tank 52 is used, at least for the majority of aircraft operations on the ground. The fuel manager 214 may also be arranged to store information about the fuel contained in each fuel tank 50, 52, 53 and/or an identifier for each tank to indicate its intended use.

The storage and control functions can be performed by separate entities or by the same entity; it will be appreciated that the fuel manager 214 can therefore be a distributed system or a single unit or module, such as described above. The step of providing 2085 the fuel manager 214 may, in some examples, include or consist of installing software into existing memory to be executed with existing systems. In other examples, a new physical unit or module may be assembled to powertrain 2 (or other powertrain 4), optionally with one or more flow regulators 216 and/or replacement fuel line sections to achieve the desired fuel flow and mixture control .

In some examples, fuel manager 214 may be additionally configured to perform other functions, for example fuel manager 214 may additionally be configured to manage fuel delivery to gas turbine engine 10 during flight by selecting a particular fuel or fuel combination from a or one or more of the plurality of fuel tanks 50, 53 based on the thrust demand of the gas turbine engine 10 so that the gas turbine engine 10 is supplied with a lower heating value fuel when the thrust demand is lower, and vice versa. It will be appreciated that the thrust demand may be determined using one or more approaches known in the art, for example based on fuel flow rate and/or cockpit throttle angle or one or more other pilot settings, and optionally taking into account outside air density or one proxy for it, such as altitude, ambient temperature, and/or pressure. The examples now described can therefore be used in conjunction with the examples described above.

The inventors also recognized that while the use of SAF can provide benefits in many areas of the flight envelope, engine starting (i.e., from the time the engine is "cold" or not operating while the aircraft 1 is parked) due to certain characteristics of some SAF types, e.g. B. the potentially higher viscosity and/or lower lubricity of SAF compared to conventional fossil-derived fuels. By changing the control of the aircraft's fuel system, the technical and ecological advantages of SAF can therefore be used without impairing the take-off process. In particular, the use of a short "burst" of a fossil hydrocarbon fuel such as Jet A, Jet A-1, or another fuel optimized for use under cold start/acceleration conditions (SAF or otherwise) can be used for starting before switching to a SAF fuel (or any other SAF fuel) allows for a smoother starting process while still reaping the benefits of SAF afterwards. In general, regardless of the fuel to be used later in operation, a fuel optimized for starting can be used first - such a fuel can have a lower freezing temperature and/or a lower viscosity at a certain temperature than other fuel on board the aircraft 1.

While a synthetic fuel can be manufactured to closely mimic a conventional kerosene fuel, one or more fuel properties of SAF stored on board the aircraft may differ from the fuel properties of one or more other fossil-derived fuels that are stored in other tanks on board the aircraft. In particular, the viscosity of SAF can be higher than that of a conventional fossil-based fuel at a given temperature and decrease with increasing temperature. Once the engine has warmed up, such fuel has a better viscosity for use due to the higher temperature.

Therefore, a fuel optimized for starting can be selected, e.g. having higher lubricity and/or lower heat capacity at a certain temperature, which can be of particular advantage for cold starting, regardless of whether one or all fuels are carried SAF included or not. The cranking optimized fuel may or may not be approved for use in flight - it can be used specifically for starting.

Thus, first and second fuel sources that provide different first and second fuels can be used. The second fuel can be selected to have better launch characteristics. In some cases, the first fuel may be a sustainable aviation fuel and the second fuel may be a fossil fuel; however, this option is not intended to be limiting.

In the present examples, in the 14 and 18 described, the first fuel source is the first fuel tank 52. In other examples, the first fuel source may be multiple tanks connected together. In some examples, the first fuel tank 52 is arranged to contain only one fuel that is pure Sustainable Aviation Fuel (SAF), ie, 100% sustainably sourced and not derived from kerosene or fossil fuels. In other examples, multiple fuel tanks of a plurality of fuel tanks may all contain SAF - each of the subset of fuel tanks containing SAF may therefore be used to supply SAF, or the first fuel tank 52 may contain a SAF blend or fossil-derived fuel; it will be appreciated that the example of a single fuel tank 52 containing SAF is described herein by way of non-limiting example only. In the present examples, with reference to the 14 and 18 , the second source of fuel is or includes the second fuel tank 50. The second fuel tank 50 is arranged to contain only a fuel selected for improved launch characteristics, which may be fossil-based or petroleum-based. Again, it is clear that these arrangements are described by way of example only and are not intended to be limiting.

In some embodiments, the first fuel tank 52 and the second fuel tank 50 may be used to fuel both the main gas turbine engine(s) 10 and the APU 44 . In other embodiments, either or both of the tanks 50, 52 may be used to supply fuel to either the main gas turbine engine(s) 10 or the APU 44, but not both - in such embodiments other fuel tanks may be provided to supply the to fuel the other gas turbine engine(s) 10,44.

In some of the examples described, all fuel used for ground operations, with the exception of initial start-up fuel, is a sustainable aviation fuel or high percentage SAF blend, and all other fuel used for ground operations is therefore taken from the first fuel tank 52. containing the sustainable aviation fuel or high percentage SAF blend (in examples with multiple tanks containing SAF, one or more of these tanks may be used as needed). The fuel used for launch may be SAF or a SAF blend in some cases.

A fuel manager 214, as described above, may be arranged to control fuel delivery to the gas turbine engines 10, 44 such that fuel is withdrawn from the second fuel tank 50 and then switched to another fuel tank 52 during launch.

SAF or a high percentage SAF blend can therefore be used when the aircraft performs at least most of its operations on the ground (as defined above), optionally providing one or more of the benefits described above (e.g. lower nvPM ) can be achieved regardless of whether the fuel used for the first engine start is SAF or not. In some embodiments, SAF or SAF blends can be used for most or all aircraft operations, both on the ground and in flight.

Although in the 14 and 18 the second fuel tank 50 is shown relatively large, in some embodiments the second fuel tank 50 may be smaller than the other fuel tank(s) 52, 53. For example, the first fuel tank 50 may contain 1% or 2% to 15% and optionally 3% to 5 % of the total available tank volume of aircraft 1. Optionally, this tank 50 can be arranged so that it is used exclusively for starting the engine. A fuel that is optimized for the starting process can therefore be selected as the second fuel, even if this is at the expense of performance in normal operation.

Each fuel tank 50, 52 on board the aircraft 1 may be arranged to contain a different type of fuel (e.g. petroleum or SAF fuel or different types of SAF) and some tanks may contain mixed fuels in which A proportion of sustainable aviation fuel is blended with conventional jet fuel or another petroleum derived fuel. At least one tank 52 may contain SAF - i. H. in some examples a pure sustainable aviation fuel, not a mixture. At least one tank 50 contains a start-up fuel, which may or may not be a fossil-based fuel.

The drive system 2 of the examples described in turn comprises an adjustable fuel supply system 220 with which it is possible to select which tank(s) 50, 52, 53 and thus which fuel or which fuel mixture is to be used. In such examples, fuel characteristics may vary over the course of a trip - a particular fuel or fuel blend may be selected to improve operation at particular flight phases or under particular external conditions, for example as described above in relation to other aspects.

In examples where one or more fuel characteristics are detected (either by direct detection or by inference from the detected parameters), e.g. B. to determine or check which tank contains the fuel to be used when starting, any of the above described detection approaches are used. In other examples, a detection can be dispensed with and instead the supplied data on the fuel composition can be used - this data can e.g. E.g. simply read "Starting fuel" or "Other" or contain more detailed information about the fuel characteristics. In other examples no fuel data can be provided at all - instead each tank 50, 52, 53 can e.g. B. be identified as a "start-up" tank or as a "normal use" tank, and the example can rely on the fact that the tanks 50, 52, 53 are filled correctly accordingly.

In some examples, the calorific values for each available fuel can be calculated or provided, and a fuel or fuel mixture can be provided based on the thrust requirement described above (optionally also taking into account altitude) - a portion of the fuel from the first tank 52 (e.g., SAF) and/or the fuel from the second tank 50 (e.g., a fossil fuel) may be used alone and/or in one or more mixtures in such examples.

A method 2021 for operating an aircraft 1 with a gas turbine engine 10, 44 and a plurality of fuel tanks 50, 52 arranged to store fuel for driving the gas turbine engine 10, 44 is in 23 shown.

The method 2021 includes arranging 2023 two fuel tanks 50, 52 of the plurality of fuel tanks to each store a different fuel. In particular, a first fuel tank 52 of the plurality of fuel tanks is arranged to contain only one fuel, which in this example is a sustainable aviation fuel, and a second fuel tank 50 of the plurality of fuel tanks is arranged to contain a fuel designed for improved launch characteristics has been selected and may be or comprise a fossil-based hydrocarbon fuel. This locating step 2023 may include fluidly isolating one or more tanks from one another so that different fuels can be stored in different tanks (e.g., by closing valves). This arrangement step 2023 can include filling the tanks accordingly.

In some examples, one or more of the fuel tanks 50, 52 may be part of a separate set of interconnected fuel tanks. In other examples, each fuel tank 50, 52 may be a self-contained single tank fuel source.

The method 2021 further includes controlling 2025 fueling of the gas turbine engine 10 such that fuel is withdrawn from the second tank 50 prior to switching to the first fuel tank 52 to start the engine. The first fuel tank 52 may contain SAF and may be the only source of fuel used for ground operations after start-up such that SAF is used when the aircraft 1 is conducting at least the majority of ground operations.

• (i) der Kraftstoff am Einlass der Brennkammer 16 eine Temperatur von mindestens 60°C und wahlweise von 80°C, 85°C, 90°C, 95°C oder 100°C erreicht; oder
• (ii) nachdem das Gasturbinentriebwerk 10, 44 mindestens dreißig Sekunden, mindestens eine Minute, mindestens drei Minuten oder mindestens fünf Minuten lang gelaufen ist. Bei einigen Triebwerken 10 kann ein Zeitraum von mindestens 10 Minuten oder 15 Minuten gewählt werden.

Fuel control 2025, which is optionally managed by a fuel manager 214, may include switching from drawing fuel from the second tank 50 to drawing fuel from the first fuel tank 52 when a selected parameter, such as fuel consumption. B. the fuel temperature, the turbine gas temperature, the oil temperature, the shaft speed or the time since the engine was switched on, reaches a certain threshold. The fuel can be changed, for example, if:

• (i) the fuel at the inlet of the combustion chamber 16 reaches a temperature of at least 60°C and optionally 80°C, 85°C, 90°C, 95°C or 100°C; or
• (ii) after the gas turbine engine 10, 44 has been running for at least thirty seconds, at least one minute, at least three minutes, or at least five minutes. For some engines 10, a period of at least 10 minutes or 15 minutes may be selected.

It becomes clear that the appropriate period of time depends on the environmental conditions (e.g. a lower air temperature and a correspondingly lower initial fuel temperature can lead to a longer take-off time) and on the characteristics of the aircraft 1 and the fuel supply system and for a given aircraft 1 and a specific environment can be adjusted accordingly.

In some embodiments, switching from drawing fuel from the second tank 50 to drawing fuel from the first fuel tank 52 may occur when the engine 10 reaches idle, and optionally a short time (e.g., thirty seconds) after Reaching idle to ensure idle operation has stabilized. In some cases, the engine 10 may be allowed to idle for at least two minutes or at least five minutes. In some embodiments, the amount of time may be determined based on how long the engine 10 has been off since it was last used, e.g. B. to two minutes, if the engine 10 has been off for less than 90 minutes and to five minutes if the engine has been off for more than 90 minutes.

The point in time at which idle mode is reached can e.g. B. can be determined based on a temperature or a shaft speed, which may be specific to the engine 10 in question and / or the aircraft 1 in question.

In some embodiments, the transition from drawing fuel from the second tank 50 to drawing fuel from the first fuel tank 52 may occur when the engine 10 reaches an engine manual limit that prevents starting until certain criteria are met . It will be appreciated that specific parameters and values can be looked up in the engine operating instructions for a particular engine 10 . When the engine 10 reaches a condition where it would be ready for start, this means that the start phase is complete (although the fuel switch may occur earlier in some implementations).

The method 2021 also optionally includes storing 2027 information about the fuel contained in each fuel tank 50, 52, optionally in the memory of an onboard fuel manager 214. The stored information may simply be an identifier indicating whether a particular tank 50, 52 contains a fuel selected for its launch properties (which may be fossil-based) or not. A label identifying one or more tanks as 100% SAF or a high percentage SAF blend may also be provided. In other examples, additional information may be stored. This stored information can be used for the control step 2025, in particular to identify the first fuel tank 52 (and/or one or more tanks containing fuel for general use or for purposes other than starting if there are several such tanks). and the second fuel tank 50 (and/or one or more other tanks if multiple tanks contain fuels suitable for starting) if not hard-wired into the powertrain system 2 .

An engine system 4 for an aircraft 1 may therefore comprise a fuel manager 214 arranged to store information about each fuel tank 50, 52, 53 / about the fuel contained in each fuel tank 50, 52, 53 and the fuel supply to the gas turbine engine 10 , 44 controls during operation. The information stored may simply include an indication of whether each tank is the launch tank or not, or it may include more detailed information such as B. a %SAF content for each tank and/or one or more other fuel characteristics of the fuel currently in each tank 50,52. In such examples, the indication of which of the plurality of fuel tanks 50, 52, 53 is the first tank 52 and which is the second fuel tank 50 may vary over the life of the powertrain 4, e.g. B. depending on which tank is filled with which fuel. In other examples, this can be in 16 The fuel delivery system 220 shown can be set so that a particular tank 50 is always the starting tank and this information need not be stored. Optionally, a particular tank 52 may always be a SAF tank or a high %SAF tank.

In embodiments in which the starting fuel and the other, first fuel are supplied to a main gas turbine engine 10 of the aircraft 1 which provides the propulsion power of the aircraft 1 , the propulsion system 4 can be more precisely referred to as propulsion system 2 . The broader term “propulsion system” 4 is used here to ensure that configurations in which the fuels are additionally or alternatively supplied to an auxiliary power unit (APU) 44 are covered, since the propulsion power may not be provided by such propulsion systems 4 .

As described above for other examples, the fuel manager 214 may be provided as part of a fuel delivery system 220 that allows for control and adjustment of the fuel delivered to the gas turbine engine 10, 44; all of the features described above can be applied mutatis mutandis to the examples currently described. In examples including APUs 44, the fuel manager 214 may be configured to control the fuel or fuel mixture supplied to the APU 44 as well as the main propulsion engine(s) 10.

The APU 44 may be required in flight under certain circumstances, and its availability may be time-sensitive in such circumstances - for example, to restart the main engines 10 following a main engine flameout. When started in flight, the APU 44 may be cold (after being idle for up to several hours); the fuel manager 214 may therefore (alternatively or additionally) be configured to provide the second fuel to perform the in-flight launch of the APU 44 quickly and reliably. To avoid wasting time accidentally trying to start the APU 44 with a bad starting fuel characteristics, the APU 44 could be automatically switched to draw fuel from the second tank (e.g., with a lower viscosity fuel at a certain temperature) whenever aircraft 1 is airborne ( e.g., referencing the "weight-on-wheels" gauge), but uses any fuel when on the ground (when takeoff time is likely to be less important).

In some embodiments, the first tank 52 may be empty for at least a portion of the flight portion of the trip, or even filled with a different fuel if the tank 52 is used as a trim tank. The fuel manager 214 may therefore be arranged to take appropriate action based on the current contents and/or usage of the first fuel tank 52 when considering whether to withdraw fuel from the first fuel tank for starting the engine 10, 44 during flight should or not.

As described above for other examples, the fuel manager 214 may additionally receive other data (in addition to information indicating which tank(s) contain(s) contain(s) a fuel selected for launch) and other optional fuel features such as the SAF -grade), and use this other data and the fuel characteristics to determine a desired fuel composition for the gas turbine engine 10, 44 in flight.

In some examples, an aircraft 1 may be modified to perform the method 2021 described above by optionally installing an adjustable fuel delivery system 220 .

A method 2031 for modifying an aircraft 1 in this way is in 24 shown. The original aircraft 1 includes a gas turbine engine 10, the gas turbine engine 10 optionally including an engine core 11 with a turbine 19, a compressor 14 and a core shaft 26 connecting the turbine to the compressor. The aircraft 1 also includes a fan 23 located upstream of the engine core, the fan including a plurality of fan blades and arranged to be driven from an output of the core shaft. The original aircraft 1 may further include an APU 44, which APU itself is or includes a gas turbine engine 44.

The method 2031 includes arranging 2033 two fuel tanks 50, 52 of the plurality of fuel tanks to each store a different fuel. In particular, a first fuel tank 52 of the plurality of fuel tanks is arranged to contain a first fuel that may be a sustainable aviation fuel, and a second fuel tank 50 of the plurality of fuel tanks is arranged to contain a fuel that is due to selected for its improved launch characteristics compared to the first fuel and which may be a fossil-based hydrocarbon fuel.

In some cases, the aircraft 1 may already have a plurality of fuel tanks 50, 52 arranged so that they Fuel to power gas turbine engines 10, 44 save on computer; in such examples, the step 2033 of arranging the fuel tanks may simply be to selectively fill the tanks with different fuels. In cases where the aircraft 1 previously had only a single fuel tank 50, one or more new fuel tanks 52, 53 can be added so that a plurality of fuel tanks is available. In cases where the aircraft 1 previously had only a single source of fuel, albeit consisting of multiple tanks, a new fuel tank 52 can be added and/or the fuel lines can be adjusted so that the original tanks 50, 53 are no longer all connected are connected so that at least two separate sources of fuel are present. The assembly step 2033 may therefore vary depending on the original aircraft configuration.

The method 2031 further includes providing 2035 a fuel manager 214 arranged to control fuel delivery such that it draws fuel from the second fuel tank 50 before switching to the first fuel tank 52 during engine cranking. The fuel manager 214 may use fuel from the first fuel tank 52 (which is SAF in a particular example described, but may be a SAF blend or pure fossil-based fuel in other examples) for all post-launch ground-based operations.

In some examples, such as B. in arrangements in which the tank or tanks in which the fuel selected for commissioning may vary during the life of the propulsion system 2, the fuel manager 214 can additionally be set up to receive information about the fuel stored in each fuel tank 50 , 52 stores fuel contained so that the first tank 52 and the second tank 50 or equivalent tanks can be identified.

The storage and control functions can be performed by separate entities or by the same entity; it will be appreciated that the fuel manager 214 can therefore be a distributed system or a single unit or module. The step of providing 2035 the fuel manager 214 may, in some examples, include or consist of installing software into existing memory to be executed using existing systems. In other examples, a new physical unit or module may be added to powertrain 2, optionally with one or more flow regulators 216 and/or replacement fuel line sections, to achieve the desired fuel flow and mixture control.

In some examples, the fuel manager 214 may additionally be configured to perform other functions, such as controlling fuel delivery to the gas turbine engine 10 by selecting a particular fuel or fuel combination from one or more of the plurality of fuel tanks 50, 52, 53 on the basis of the thrust requirement of the gas turbine engine 10, so that the gas turbine engine 10 is supplied with a fuel having a lower calorific value when the thrust requirement is lower, and vice versa. It will be appreciated that the thrust demand can be determined using one or more approaches known in the art, for example as mentioned above.

The inventors have also recognized that since different fuels can have different properties and still comply with the standards, knowledge of the flight profile can enable selection of which of the fuels available to an aircraft 1 for which part(s) of the flight profile used (when multiple fuels are available) - this may result in improved aircraft performance. For example, a fuel with better emission values can be selected for operation at or near an airport, and a fuel with a higher calorific value can be used for higher thrust operation. A refueling plan specifying what fuel or fuel blend to use for each leg of the flight profile can therefore be established based on knowledge of the flight profile and available fuels.

Such a procedure 3020 is in 25 shown. It becomes clear that an aircraft 1 for which the method 3020 is implemented must comprise at least two fuel sources 50, 53, so that at least two different fuels (ie fuels with at least one difference in fuel properties) are available for use. It is becoming clear that the use of fuel blends with different mixing ratios can allow for many more than two fueling options, even if only two different fuels are stored on board.

The method 3020 can be performed in the aircraft, e.g. B. by a module 250 for determining the refueling plan of the aircraft 1, as in 21 shown. Such a fuel plan determination module 250 may be part of an engine electronic control unit (EEC) 42 of the aircraft 1, optionally installed as software on an existing EEC 42 or added as a module, or it may be provided by a separate module. Alternatively, the method 3020 may be performed off-aircraft and the refueling plan may be provided to the aircraft 1 for implementation. It will be appreciated that any suitable processing device may be used to perform the role of the fueling plan determination module 250 and that computer readable instructions may be provided to cause the processing device to perform the described method 3020 .

The method 3020 can therefore be performed by the processing circuitry of the aircraft 1 or by separate off-wing processing circuitry. Method 3020 may be performed by processing circuitry of a portable computing device, e.g. a pilot's personal computing device.

A fuel manager 214, as described above, may be used to implement the fueling plan. The fueling plan determination module 250 or other processing circuitry may forward the fueling plan to the fuel manager 214 for implementation.

The method 3020 includes the creation of a flight profile for a flight of the aircraft 1. The flight profile can be supplied to a refueling plan determination module 250 of the aircraft 1 or to an outer wing refueling plan determination module. The flight profile can be obtained in any suitable way, e.g. B. sent electronically, entered manually via a user interface or retrieved from memory.

The method 3020 further includes determining 3024 a refueling plan for the flight of the aircraft 1 based on the flight profile and the fuel characteristics of the available fuels. The fueling plan determination 3024 also takes into account the amount of any fuel available on board the aircraft 1 . The altitude and route of the aircraft 1 for the planned flight are defined in the flight profile. Expected thrust requirements may be included in the flight profile or may be determined or derived based on the flight profile and may guide fuel selection. In addition, data on the forecast weather conditions along the planned flight route of the aircraft 1, as defined in the flight profile, can be provided with the flight profile or requested based on the flight profile. The weather data may be used to influence fuel planning determination 3024 .

The refueling plan determined specifies a desired time profile for fuel removal from the individual tanks 50, 53, i. H. it lists which fuel or fuel mixture is to be used for each flight phase defined in the flight profile, and thus determines when and what type of refueling change should be made.

The fuel characteristics contemplated include one or more of the fuel characteristics defined elsewhere herein.

For example, the amount of sustainable aviation fuel—SAF—that is available to the aircraft 1 can be determined, optionally both as pure SAF and in mixtures. As described above, the use of SAF or high percentage SAF blends for ground operations can result in reduced nvPM emissions and hence improved airport air quality, and the fueling plan can include the use of SAF or a high SAF fuel for prioritize the ground operation of the aircraft 1.

Similarly, as described above, the heating value of each fuel on board aircraft 1 can be a fuel attribute of interest, and the fueling plan can include the use of higher heating value fuels for higher thrust aircraft 1 operation and lower heating value fuels for prioritize aircraft 1 operation at lower thrust.

The fueling plan can be determined on board the aircraft 1, e.g. B. in an electronic engine controller 42 or other processing circuitry of the aircraft 1 or in a device belonging to the pilot. Alternatively, the refueling plan can also be determined outside of the aircraft, e.g. B. in a ground based server or other computer system. The determined refueling plan can therefore be made available 3025 to the aircraft 1 before or at the start of the flight for which the refueling plan applies. Various steps of the method 3020 can therefore in some cases be carried out by completely separate units or in other cases all within the aircraft 1 or be carried out by them.

In some embodiments, the method 3020 further includes controlling 3026 fuel delivery to the gas turbine engine 10 during operation according to the fueling schedule. Specifically, as described above, a fuel manager 214 may receive the fueling plan and control fuel delivery accordingly, for example by opening or closing one or more valves or activating or deactivating one or more pumps to deliver the desired fuel or fuel mixture at each stage of the flight.

A drive system 2 for an aircraft 1 can be set up in such a way that the method 3020 described above can be carried out. The propulsion system 2 comprises a gas turbine engine having at least two separate fuel sources 50, 53 such that at least two different fuels (i.e. fuels with different fuel properties) are stored on board the aircraft 1.

The propulsion system 2 of such examples comprises a refueling plan determination module 250 arranged to obtain 3022 a flight profile for a flight of the aircraft 1; and determine 3024 a refueling schedule for the flight based on the flight profile and fuel characteristics.

The fueling plan determination module 250 may perform the fueling control 3026 to the gas turbine engine 10 itself or forward the fueling plan to a fuel manager 214 for performance.

The propulsion system 2 of some examples additionally comprises a receiver 251 arranged to receive the forecast weather conditions for the planned route of the aircraft 1 defined in the flight profile. As mentioned above, the received forecast weather conditions can be used to influence the refueling plan.

It is understood that the invention is not limited to the embodiments described above is limited and various changes and improvements can be made without departing from the concepts described herein. Except where the features are mutually exclusive, each of the features may be used separately or in combination with other features, and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Non-patent Literature Cited

• Fuel for powering gas turbine engines 10, 44 [0571]

Claims (13)

A method (2050) of operating an aircraft (1) having a gas turbine engine (10) and a fuel tank (50, 53) arranged to supply fuel to the gas turbine engine (10), the method comprising: determining (2052) at least one fuel attribute of the fuel to be supplied to the gas turbine engine (10); and Proposing or initiating a change (2054) to a flight profile of the aircraft (1) based on the at least one fuel attribute. Method (2050) according to claim 1 , wherein the at least one fuel characteristic of the fuel comprises at least one of the following characteristics: i. Percentage of sustainable aviation fuel in the fuel; ii. content of aromatic hydrocarbons in the fuel; iii. content of multiaromatic hydrocarbons in the fuel; IV. percentage of nitrogenous species in the fuel; v. Presence or percentage of a tracer species or trace element in the fuel; vi. hydrogen to carbon ratio of the fuel; vii. hydrocarbon distribution of the fuel; viii. level of non-volatile particulate emissions from combustion; ix. naphthalene content of the fuel; x. fuel sulfur content; xi. cycloparaffin content of the fuel; xiii. fuel oxygen content; xiii. fuel thermal stability; xiv. degree of fuel coking; xv. the statement that the fuel is a fossil fuel; and xvi. at least one of the criteria density, viscosity, calorific value and heat capacity. Method (2050) according to claim 1 wherein the change in flight profile based on the fuel characteristics comprises at least one of the following: (i) a change in intended flight altitude; and (ii) a change in planned route. Method (2050) according to claim 1 , wherein the determination of at least one fuel characteristic of the fuel comprises: determining at least one fuel characteristic of the fuel already present in the fuel tank (50, 53) before refueling; determining at least one fuel attribute of a fuel supplied to the fuel tank (50, 53) during refueling; and calculating at least one fuel attribute of the resulting fuel in the fuel tank after refueling. Method (2050) according to claim 3 , further comprising receiving weather forecast conditions for a planned route of the aircraft, and wherein the received weather forecast conditions are used to affect the planned route and/or altitude changes. Method (2050) according to claim 1 , wherein the determining of the at least one fuel characteristic is performed based on the detection of at least one fuel property. Method (2050) according to claim 6 , where the detection is performed on the wing. Method (2050) according to claim 1 , wherein determining the at least one fuel attribute is performed based on received fuel composition data. Method (2050) according to claim 8 , the fuel composition data being made available to the aircraft during refueling. Method (2050) according to claim 1 , wherein the at least one fuel characteristic for fuel in one or more fuel tanks (50, 53) of the aircraft (1) is determined. Method (2050) according to claim 1 wherein at least one fuel attribute is derived from the performance of the gas turbine engine (10) during taxi and/or takeoff and/or climb of the aircraft, and wherein the planned flight profile is modified during cruise based on the at least one derived fuel attribute. A propulsion system (2) for an aircraft (1), comprising: a gas turbine engine (10); a fuel tank (50,53) arranged to contain fuel for powering the gas turbine engine (10); and a fuel composition determination module (210) designed to: determining at least one fuel attribute of the fuel to be supplied to the gas turbine engine (10); and a flight profile adjuster (212) arranged to: to propose or initiate a change in the flight profile of the aircraft (1) based on the at least one fuel characteristic of the fuel. Drive system (2) after claim 12 wherein the flight profile adjuster (212) is arranged to initiate or suggest at least one of the following actions based on the fuel characteristics: (i) a change in the intended flight altitude; and (ii) a change in planned route.

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