GB2424712A

GB2424712A - Aircraft fuel gauging system with sensor back-up

Info

Publication number: GB2424712A
Application number: GB0606353A
Authority: GB
Inventors: Andrew Ceri Davis
Original assignee: Smiths Group PLC
Current assignee: Smiths Group PLC
Priority date: 2005-03-31
Filing date: 2006-03-29
Publication date: 2006-10-04
Anticipated expiration: 2026-03-29
Also published as: GB2424712B; US20060220890A1; GB0506466D0; US7843355B2; GB0606353D0

Abstract

A system to measure the quantity of fuel in an aircraft fuel tank, comprises a plurality of liquid level measuring sensors 11-18, 21-28, 31-34 in each fuel tank 1, 2, 3. The sensors are divided into two subgroups of odd sensors 11, 13, 15, 17, 31, 33, 27, 25, 23, 21 and even sensors 12, 14, 16, 18, 32, 34, 28, 26, 24, 22. Each group is connected with a respective processor 7 and 8. The two processors 7 and 8 provide separate indications of fuel quantity (each using measurements from the respective sensor set) on a display on a refuel panel 42 on the exterior of the airplane, or a combined indication (using measurements from all the sensors) on a display 41 in the cockpit. In the event of a failure of the system, the system can provide a reduced accuracy fuel indication using only one of the sensors sets and processors. Thus the system provides a back-up fuel measurement system without the need for additional sensors. The separate indications on the refuel panel 42 may be compared with a flow meter in a fuel dispenser to confirm that the correct amount of fuel has been dispensed.

Description

I

FLUID-GAUGING SYSTEMS

This invention relates to fluid-gauging systems and methods.

The invention is more particularly, but not exclusively, concerned with aircraft fuel- gauging Systems.

Aircraft include fuel-gauging systems to measure the quantity of fuel present in the fuel tanks. There are usually several fuel tanks, often located in the wings, each tank usually having several sensors or probes to measure the height of fuel present. With knowledge of the shape of the tank and the height of fuel at several different locations, the system can compute the volume of fuel in each tank. The number of probes needed depends on the pitch and roll angles likely to be experienced by the aircraft during flight. The gauging probes may be of the capacitive kind, where the capacitance of the probe varies with height of fuel. Alternatively, the probes may be of the ultrasonic kind, where the height is calculated from time for a pulse of acoustic energy to travel from an acoustic transducer at the bottom of the probe to the fuel surface and back to the transducer after reflection from the fuel surface. These systems can provide a highly accurate indication of fuel quantity over a wide range of aircraft attitudes during flight. The fuel-gauging system is also used on the ground during refuelling in order to check on the quantity of fuel dispensed to the aircraft. Aircraft often also include a secondary, back-up fuel-gauging system of a simpler, less accurate, mechanical kind. This is used to provide additional evidence of fuel quantity if there is disagreement between the primary fuel- gauging system and the flow meter in a fuel tanker dispensing fuel to the aircraft on the ground.

It is undesirable to have to provide a secondary gauging system because of the additional cost and weight of such systems, and the difficulty of fitting such a system to modem composite wings. It is possible to provide a secondary electronic gauging system but the cost of the additional sensors makes this prohibitive in most cases. The additional weight is also a severe disadvantage.

It is an object of the present invention to provide an alternative fluidgauging system.

According to one aspect of the present invention there is provided a fluid-gauging system including a plurality of gauging sensors operable to provide an indication of the height of fluid at the location of the sensor, the system including processing means operable to provide a first indication of fluid quantity from a first group of sensors, and a second indication of fluid quantity from a second group of sensors different from said first group.

The system preferably includes a plurality of fluid tanks, each tank including a plurality of gauging sensors. The processing means preferably includes two processors separate from one another, one processor being arranged to provide the first indication of fluid quantity and the other processor being arranged to provide the second indication of fluid quantity. The two processors are preferably interconnected with one another in such a way that each can provide an indication separately or can provide a combined indication derived from substantially all the sensors. The system may be operable in two different modes in one of which the system provides an indication of fluid quantity from a reduced number of sensors and in the other of which it provides an indication from substantially all the sensors.

The sensors may be capacitive or acoustic sensors. The system is preferably an aircraft fuel- gauging system in which the first and second indications of fuel quantity are provided to a display of fuel quantity visible on the exterior of the aircraft. The display of fuel quantity is preferably provided adjacent a refuelling port of the aircraft.

According to another aspect of the present invention there is provided a method of gauging the quantity of fluid in a tank comprising the steps of: computing the quantity of fluid from outputs of a first group of a plurality of gauging sensors, computing the quantity of fluid from outputs of a second group of gauging sensors different from the first group, and displaying two separate indications of fluid quantity derived from the different groups of sensors such that the two indications can be compared with one another.

According to a further aspect of the present invention there is provided a method of confirming delivery of the correct quantity of fuel to an aircraft comprising the steps of: computing the quantity of fuel from outputs of a first group of a plurality of fuel-gauging sensors, computing the quantity of fuel from outputs of a second group of fuel- gauging sensors different from the first group, and displaying for viewing externally of the aircraft two separate indications of fuel quantity derived from the different groups of sensors such that the two indications can be compared with one another to confirm delivery of the correct fuel quantity.

According to a fourth aspect of the present invention there is provided a system for use in performing a method according to the above other or further aspect of the present invention.

An aircraft fuel-gauging system according to the present invention will now be described, by way of example, with reference to the accompanying drawing, which shows the system schematically.

The system includes two wing tanks 1 and 2 and a centre tank 3. The wing tanks 1 and 2 each include eight fuel height gauging probes or sensors 11 to 18 and 21 to 28 respectively, each of a conventional kind. The centre tank 3 has four sensors 31 to 34. A first group of odd-numbered sensors 11, 13, 15, 17, 21, 23, 25, 27, 31 and 33 are connected by wiring 5 to a first fuel- gauging computer or processor 7. A second group of even-numbered sensors 12, 14, 16, 18, 22, 24, 26, 28, 32 and 34 are connected by wiring 6 to a second fuel-gauging computer or processor 8, independent from the first processor 7. The processors 7 and 8 are each programmed to provide an output indication indicative of fuel quantity from a suitable fuel- gauging algorithm, pre-programmed with information about the shape of the tanks 1, 2 and 3 and from the height information from the sensors 11 to 18, 21 to 28 and 31 to 34 connected with the processors. The quantity information may be in the form of fuel volume or mass, which may require an input from a densitometer (not shown) or from two densitometers divided between the two different groups of height sensors. Other sensors, such as temperature sensors, may need to be divided between the two different groups.

The two processors 7 and 8 are interconnected with one another via a digital databus 40, which also connects with a cockpit display 41. The processors 7 and 8 are also connected to a refuel panel 42 mounted externally on the aircraft, typically adjacent a refuelling port 43 so as to be visible on the exterior of the aircraft to anyone refuelling the aircraft.

The system may operate in various different ways.

In one arrangement, the information from the two processors 7 and 8 is shared via the databus 40 during flight to provide the best possible indication of fuel quantity making use of information from all the sensors immersed in fuel. This information is displayed on the cockpit display 41. When the aircraft is on the ground and being refuelled, the two processors 7 and 8 provide two separate, nominally-identical display indications of fuel quantity to the refuel panel 42, derived from the two separate groups of sensors. These indications are not as accurate as those provided when the two processors 7 and 8 are interconnected, because of the reduced number of sensors used in each fuel quantity calculation. However, because the aircraft is static, on the ground, the attitude of the aircraft is such that a reduced number of sensors is sufficient for reasonable accuracy.

During the refuelling procedure it would be possible for the combined indication of fuel quantity derived from all the sensors to be supplied to the refuel panel 42 via a connection 44 s that three separate indications of fuel quantity are provided for comparison one against the other and against the flowmeter associated with the fuel dispenser.

In the event of a failure of the fuel-gauging system during flight, the system could be arranged to provide a reduced integrity fuel-quantity indication from either one of the gauging computers 7 or 8.

It can be seen that this arrangement provides a back-up fluid-quantity indication to be provided without the need for additional sensors. This enables the cost and weight of the fuel- gauging system to be kept to a minimum. The extra weight contributed by the additional processor is minimal. It may be necessary to position the sensors in the tanks such as to optimise the performance of each group of sensors. It will be appreciated that it is not essential to divide the sensors into just two groups since three or more groups, each with separate processors could be provided. The invention could be used in other fluid-gauging applications and is not confined to aircraft fuel- gauging systems.

Claims

1. A fluid-gauging system including a plurality of gauging sensors operable to provide an indication of the height of fluid at the location of the sensor, wherein the system includes processing means operable to provide a first indication of fluid quantity from a first group of sensors, and a second indication of fluid quantity from a second group of sensors different from said first group.

2. A fluid-gauging system according to Claim I including a plurality of fluid tanks, wherein each tank includes a plurality of gauging sensors.

3. A fluid-gauging system according to Claim I or 2, wherein the processing means includes two processors separate from one another, wherein one processor is arranged to provide the first indication of fluid quantity and the other processor is arranged to provide the second indication of fluid quantity.

4. A fluid-gauging system according to Claim 3, wherein the two processors are interconnected with one another in such a way that each can provide an indication separately or can provide a combined indication derived from substantially all the sensors.

5. A fluid-gauging system according to any one of the preceding claims, wherein the system is operable in two different modes in one of which the system provides an indication of fluid quantity from a reduced number of sensors and in the other of which it provides an indication from substantially all the sensors.

6. A fluid-gauging system according to any one of the preceding claims, wherein the sensors are capacitive or acoustic sensors.

7. An aircraft fuel-gauging system according to any one of the preceding claims, wherein the first and second indications of fuel quantity are provided to a display of fuel quantity visible on the exterior of the aircraft.

8. An aircraft fuel-gauging system according to Claim 7, wherein the display of fuel quantity is provided adjacent a refuelling port of the aircraft.

9. An aircraft fuel-gauging system substantially as hereinbefore described with reference to the accompanying drawing.

10. A method of gauging the quantity of fluid in a tank comprising the steps of: computing the quantity of fluid from outputs of a first group of a plurality of gauging sensors, computing the quantity of fluid from outputs of a second group of gauging sensors different from the first group, and displaying two separate indications of fluid quantity derived from the different groups of sensors such that the two indications can be compared with one another.

11. A method of confirming delivery of the correct quantity of fuel to an aircraft comprising the steps of: computing the quantity of fuel from outputs of a first group of a plurality of fuel-gauging sensors, computing the quantity of fuel from outputs of a second group of fuel- gauging sensors different from the first group, and displaying for viewing externally of the aircraft two separate indications of fuel quantity derived from the different groups of sensors such that the two indications can be compared with one another to confirm delivery of the correct fuel quantity.

12. A method of fuel gauging substantially as hereinbefore described with reference to the accompanying drawing.

13. A system for use in performing a method according to any one of Claims 10 to 12.

14. Any novel and inventive feature or combination of features as hereinbefore described.