FR3133371A1 - Foldable multi-rotor electric aeronautical propulsion with regulated thrust - Google Patents

Abstract

This invention relates to a new type of aerodynamic propulsion intended for light leisure, professional or military flying devices and in particular of the ULM type (Ultra Light Motorized in French legislation). The invention particularly concerns paramotor type ULMs. A paramotor is a leisure ULM. A paramotor, shown schematically in Figure 1, is a motorized paraglider which can take off in the plain, maintain itself and evolve in the air thanks to engine thrust, with or without the help of meteorological updrafts. When the engine thrust is greater than the drag, the force which opposes the advancement of any object in the air, the device goes up, when it is smaller it goes down. When drag and thrust are equal, the aircraft flies at constant altitude. Figure for abstract: Fig 1

Description

Foldable multi-rotor electric aeronautical propulsion with regulated thrust

This invention relates to a new type of aerodynamic propulsion intended for light leisure, professional or military flying devices and in particular of the ULM type (Ultra Light Motorized in French legislation). The invention particularly concerns paramotor type ULMs.

A paramotor is a leisure ULM. A paramotor, represented schematically on the , is a motorized paraglider which can take off in the plain, maintain itself and evolve in the air thanks to engine thrust, with or without the help of meteorological updrafts. When the engine thrust is greater than the drag, the force which opposes the advancement of any object in the air, the device goes up, when it is smaller it goes down. When drag and thrust are equal, the aircraft flies at constant altitude.

There represents a top view of a paramotor in flight. A paramotor consists of a motor frame (2) and a paraglider wing (8). More precisely, a paramotor comprises a propulsion group formed by a motor (4) and a propeller (6), a pilot harness (3), it is the pilot's cockpit (1), a chassis (2) and a flexible paraglider-type wing (8) which creates lift from a certain forward speed in the air. The role of the chassis (2) is to mechanically connect the soleplate (3), the propulsion unit (4 and 6) and the supporting wing (8). The chassis also has the role of protecting the rotating propeller with a circular protective cage (5). A paramotor is the combination of a flexible paraglider-type wing (8), a propulsion unit (4 and 6) and at least one harness (3) and a chassis (2 and 5) which assemble them mechanically and protects the propulsion propeller (6).

The wing is connected to the chassis by two risers (9) and hangers (10) shown on the . The final connection with the chassis is made by two carabiners (11) which allow the wing to be easily removed from the paramotor chassis to facilitate its transport. Control is done using 2 brake handles (12) connected to the left and right of the trailing edge of the paraglider wing (8). Tension on the brakes will deform the trailing edge of the wing and slow it down. This increases the drag of the wing (8) asymmetrically. This causes a degradation of lift asymmetrically and creates a yaw movement followed quickly by a roll movement. A paramotor is said to have 2 axes because roll and yaw are linked and cannot be controlled independently. This is called yaw-induced roll.

The engine thrust, i.e. the power of the engine, is controlled by a gas handle, generally wired, which activates the butterfly of the carburetor or the injection system of the thermal engine (4). The pilot can hold the throttle grip in either the right or left hand.

There are currently 4 different types of chassis configurations for paramotors: single-seater foot take-off (the landing gear are the pilot's legs) presented on the And , single-seater trolley (generally tricycle type), two-seater foot take-off and two-seater trolley. This invention concerns these 4 types of paramotors but particularly focuses on the most widespread type which is the single-seater foot take-off.

The propulsion of ULM type aircraft has historically been achieved using a single engine (4) and a single propeller (6) of the tractive or propulsive type for reasons of mass limitation, simplicity of design and costs. A propeller located at the rear of the machine is a propulsion configuration. It creates thrust thanks to a motorized propulsion unit located at the rear of the machine as illustrated on the . This concerns ULMs of the tilting, paramotor or autogyro type. A propeller located at the front of the machine is a traction configuration. It creates a traction type thrust. This configuration is generally used in 3-axis type ULMs, which resemble light single-engine aircraft. However, there are also propulsion configurations on 3-axis ULMs.

Propulsive thrust with a propeller plane close to the pilot's cell presents significant aerodynamic disadvantages which therefore limit the performance of ULM machines, especially paramotor and pendulum types. The position of the propeller in the flow of the pilot harness, in the case of a paramotor, or of the pilot pod, in the case of a pendulum type ULM. This position limits the propulsive efficiency and propulsive efficiency of the propeller.

Indeed ; the air flow which feeds the plane of the propeller is downwind of obstacles (nacelle, pilot, harness, chassis and engine group, etc.). It is then subjected to aerodynamic disturbances such as vortices or rollers. As a result, part of the air arrives at the propeller in a disturbed and disordered manner and forms a zone of turbulence (7). This increases phenomena such as boundary layer separation and reduces the propulsive performance of the propeller. These disturbances increase with air speed and therefore with the speed of movement in the air of the aircraft.

There shows that overall 40 to 50% of the surface swept by the propulsive propeller of a paramotor can be located in the disturbed air flow of the harness and the pilot. As a result, the efficiency of a propulsion propeller located downstream of the obstacle constituted by the cockpit is degraded by aerological disturbances. These disturbances are all the greater when the propeller plane is close to the obstacle and the air speed is high.

The propulsive efficiencies and propulsive yields of a propeller located downstream of the harness or piloting nacelle are therefore not optimal.

Another significant disadvantage of a single propeller configuration is that of engine counter torque, called engine torque below. The engine torque is felt permanently when the propeller rotates and increases with the propeller rotation speed. It is felt more or less significantly depending on the phases of flight and the need for thrust. The greater the thrust, the greater the propeller rotation speed and the greater the torque. This torque is present in all phases of flight except in the descent phase for paramotors (engine off or at idle). The engine torque is particularly present at takeoff, the phase where the need for thrust is maximum. It is also the most dangerous flight since there is only a very low safety height from the ground. Accidents linked to too much engine torque are unfortunately not rare in paramotors, particularly when changing machines (engine or wing).

During flight, this engine torque creates an asymmetrical tension at the level of the 2 risers (9) and the lines (10). The tension is not the same on the left side of the air or the right. As a result, the engine torque requires permanent aerodynamic corrections by the pilot or by a balancing system or “trim” which adjusts the trajectory of the aircraft. In both cases, this degrades the overall finesse of the aircraft, that is to say its ability to glide and its ability to fly with reduced power.

Another consequence of the engine torque is that a 2-axis ULM, particularly of the paramotor type, has asymmetrical maneuverability. It turns in flight more easily to the left if its propulsive propeller turns clockwise (which creates a trigonometric torque in the aircraft) and, conversely, it turns better to the right if its propulsive propeller turns counterclockwise. The motor torque creates an asymmetry in the roll and yaw of a 2-axis machine since the two are linked. The motor torque creates a significant asymmetry in the maneuverability of a 2-axis machine.

Indeed ; engine torque is particularly sensitive on 2-axis flight devices where roll and yaw are inseparable. This is, for example, the case for paramotors and commuters. In addition, paramotors use a foldable and flexible paraglider wing. This flexibility has advantages in terms of space on the ground (easy transport and storage) but presents a risk of deformation of the wing in flight. This risk of deformation is mainly linked to meteorological and aerological conditions, for example, zones of rising air shear, vortices or weather rollers. This risk of deformation is accentuated by the effect of engine torque on a paramotor due to asymmetrical tensions on the risers (9) and consequently on the two left and right halves of the wing. A deformation of the wing creates an imbalance of aerodynamic forces. The more deformed the wing, the greater the imbalance. This deformation will degrade the lift, generally asymmetrically, and therefore the trajectory of the aircraft. This can lead to the paramotor crashing during the take-off phase if the pilot does not control or does not know his machine well or if the weather conditions are bad. A crash which can have significant human and material consequences, up to the death of the pilot.

Generally speaking, the engine torque on a single-propeller aircraft is restrictive or even dangerous above a certain thrust requirement. Engine torque was the cause of numerous air crashes in military aviation during the Second World War. Some single-engine fighter models of the time had such high engine torque that pilots in training or beginners crashed on takeoff due to the machine turning over when applying full throttle too suddenly and not sufficiently corrected.

A single-helix configuration also forms a gyroscope. The gyroscopic effect and gyroscopic precession will also degrade maneuverability in flight. The effects of torque and gyroscopic cumulate in flight, the effect of gyroscopic precession is less important and less sensitive than that of engine torque. However, these gyroscopic phenomena exist and degrade the aeronautical maneuverability of single-propeller aircraft.

Another disadvantage linked to the use of a single propeller is the very limited possibility of adjusting the thrust vector both on the point of application and on the direction on the chassis. These 2 parameters are fixed during the design of the machine.

A propulsion configuration based on 2 propellers offset laterally on the chassis and rotating in opposite directions, in a so-called counter-rotating manner, largely reduces aerodynamic disturbances on the plane of the propellers and completely cancels the effect of engine torque and gyroscopic effects. This solution is presented on the And

A multi-rotor configuration comprising at least 2 offset propellers also allows asymmetric thrust if the rotation speed of the 2 propellers are different. The left propeller can create more thrust than the right propeller and vice versa. A yaw torque is then created which will improve maneuverability in turns or, on the contrary, stabilize the aircraft in a straight trajectory when the weather conditions are choppy by electronic regulation and controlled asymmetric thrust. Thus a multi-rotor configuration makes it possible to create assistance in the trajectories of an aircraft, in particular 2 axes. The most advanced stage of this assistance is the possibility of autopiloting the trajectory. The trajectory of the machine would no longer be controlled by action on the controls which degrade the finesse of the machine but by asymmetry of thrust. In the case of paramotors, we would end up with an autopilot aerodynamically similar to harness piloting. Piloting in the harness is done without any action on the control surfaces and only by shifting the pilot's weight to the left or right side of the wing. This causes a turn on the side of the wing most loaded by offset from the center of gravity. This is the only way to turn tilting ULMs and hang gliders which have no rudders.

A twin-engine configuration based on 2 thermal engines was difficult to implement on ULMs for reasons of on-board mass and regulation. It is now entirely possible with an electric motor for limited weight and performance comparable to thermal models. This is possible thanks to recent advances, both technical and economic, in materials, on-board electronic regulation, electric motors and batteries.

Another important aeronautical physical quantity in aeronautical performance is finesse. Glide is the ability of an aircraft to glide. The greater the glide ratio, the smaller the fall slope of the aircraft and the further the aircraft can fly before hitting the ground from a given height. In fact, finesse defines the thrust necessary to maintain an aircraft in level flight. The higher the aeronautical glide ratio, the lower the thrust required to fly an aircraft. The glide ratio required to maintain the altitude of any lifting wing aircraft is given by the formula

The PTV (Total Flying Weight) is given in N or kg, the glide ratio is dimensionless and the thrust or drag are in N or kgF (kilogram Force). So to keep a paramotor of, for example, 6 glide ratio and 120 kg total flying weight in level flight, it must be provided with a thrust of 20 kgF. Another 8 finesse paramotor will need a thrust of 15 kgF for the same GVW of 120 kg. Therefore, to gain in aeronautical performance, optimal finesse must be obtained.

In non-level flight, the tangent of the aircraft's attitude angle, i.e. the angle of the aircraft's trajectory relative to the horizontal, is given by the formula

α is the trim angle. Effective thrust is the force actually applied to the aircraft, i.e. engine thrust subtracted from aeronautical drag. Thrust, drag and PTV are expressed in N or in kg and kgF. Calculating the angle α makes it possible, for a given ground speed, to determine the vertical ground speed Vz, i.e. the ascent speed. It is generally given m/min or in m/s. Ascent rate defines the ability to gain altitude. Climbing speed is a fundamental criterion for characterizing any aircraft.

There shows the evolution of the theoretical climbing speed according to the effective thrust and the PTV according to the equation [Math 2]. The comfort and safety zone for using a paramotor is between 2 and 3 m/s ascent speed. It is necessary, in order of magnitude, 25 to 30 kgF of effective thrust to obtain such a speed between 90 and 130 kg of PTV.

If we assume that aeronautical drag is constant in level or ascension trajectory, which is substantially true for aircraft with a low angle of attack such as paramotors, then the formula [Math 2] can be written in an approximate and increased manner as follows :

In the case of a paramotor with 50 kgF maximum thrust, PTV of 120 kg and finesse of 6, we obtain a maximum angle α of 14°. If this paramotor flies at 40 km/h air speed, or 11 m/s, then it will have a maximum ascent speed of 2.67 m/s/ If the glide ratio increases to 8 then the maximum ascent speed, still at 40 km/ h air and 120 kg of PTV, will be 3.08 m/s. These are increased values because the real finesse is degraded during the ascent phase.

There shows the evolution of the theoretical climbing speed according to the glide ratio and the PTV for an engine thrust of 50 kgF according to equation [Math 3]. From a certain PTV and for certain finesse, the climbing speed is well below 2 m/s: the engine thrust is insufficient. The rate of climb even becomes negative above a certain weight: the aircraft cannot take off. A finesse of at least 5 is necessary to safely operate a PTV paramotor of between 90 and 130 kg PTV with an engine thrust of 50 kgF.

In paramotor as in paragliding, finesse is defined on the one hand by the finesse of the wing used and on the other hand by the finesse of the harness and the chassis which carries the pilot and the engine. The actual finesse of a paramotor is always lower than that of the wing used in paragliding mode. This is a degraded finesse due to the presence of the paramotor chassis which increases aerodynamic drag. Thus the real effective glide ratio in a conventional paramotor is of the order of 50% of the maximum glide ratio of the wing. A loss of 50% of glide ratio is a very significant degradation for the performance of the aircraft. There allows you to make some quick comparisons of thrust requirements depending on PTV and finesse.

On the other hand, the glide ratio depends on the air speed and is maximum for a given air speed, and it depends on the aerodynamic characteristics of the aircraft.

There shows, as an example, the evolution of finesse depending on speed and for 4 configurations of paragliding harnesses. We see on the one hand the significant influence on the finesse depending on the type of harness and that there is a potential gain of 27% between the lowest and the best finesse. We also see that the speeds of maximum finesse, and therefore maximum performance, of a paraglider are between 38 and 43 km/h. These are the speeds where an optimized electric paramotor must evolve to obtain the best performance in terms of thrust and therefore autonomy.

The configuration of offset propellers makes it possible to improve the finesse of the chassis behind the pilot and therefore to reduce the engine thrust requirements and improve autonomy.

Another advantage of the offset propeller configuration, apart from considerations of drag, torque or aerodynamic disturbance, is to increase the surface swept by the propellers for the same ground clearance during takeoff. Science and the state of the art of aeronautical propellers show that for the same thrust, a doubled propeller sweeping surface increases the propulsive efficiency by around 20 to 40%. Two propellers consume less power, and therefore energy, than a single propeller to provide the same thrust. Practically, 2 “propeller motor” configurations (i.e. 2 propellers and 2 identical motors) which would consume 500W each, or 1000W in total, will provide 20 to 40% additional thrust than a single identical “propeller motor” configuration which would consume 1000W. There gives the propulsive efficiency in N/kW, according to comparative experimental measurements, between single or twin propeller configurations, all other quantities constant.

THE And detail this twin-engine configuration and its aerodynamic advantages. The pilot (1) is installed in a harness (3) mounted on a chassis (2). The turbulence zone (7) is reduced by the presence of an aerodynamic fairing (8) made of a lightweight, flexible or rigid material. This aerodynamic fairing (8) will have a spindle shape in order to improve airflow and reduce aerodynamic drag. This fairing can for example be made from a light, airtight and watertight technical fabric based on elastane. The second function of this fairing is to protect the batteries and on-board electronics. This fairing also improves the general visual appearance of the machine. The turbulence zone (7) is on the one hand reduced by improving the air flow thanks to the fairing (8) and disturbs less the plane of the propellers (10 and 12) due to the lateral offset of the latter.

The propellers (10 and 12) are driven directly by 2 identical electric motors (9 and 11) but rotating in opposite directions to cancel the torque and reduce gyroscopic effects. These 2 motors are held to the chassis (2) by a central connection (17) and 2 folding arms (13 and 14) mounted on 2 symmetrical lockable pivots (15 and 16). The foldable arms (13 and 14) have an aerodynamic spindle or cylindrical shape which promotes air flow so as not to degrade finesse.

Force arms (18 and 19) can be used optionally depending on the mechanical resistance of the folding arms (13 and 14) and the thrust requirement. The sizing is done while respecting the ULM safety coefficients. These force arms (18 and 19) can be quickly disassembled at at least one of their ends when folding the machine. If only one end can be quickly disassembled, they are mounted on a ball joint or pivot on the other end. Dismantling of one or both ends is done using a tool-free quick disassembly system, pin type or other tool-free rapid assembly means.

The span in unfolded mode between the ends of the 2 propellers can exceed 250 cm depending on the size of the propellers. The arms (13 and 14) are folding to facilitate transport and storage of the machine. To further limit the bulk during storage and transport, the propellers (10 and 12) are also foldable along their axis of rotation as shown in the . The foldable propellers occupy in folded mode the length of a single blade and the width of 2 blades

The paramotor in folded mode is shown on the . When not locked, the lockable pivots (15 and 16) form an angle with the plane of the thrust vector, such that the 2 arms (13 and 14) bend on a negative and positive vertical component. As a result, in folded mode, the folded half propellers (10 and 12) are found above and below the plane of the thrust vector when the pivots (15 and 16) are unlocked. The 2 arms (13 and 14), the propellers (10 and 12) and the motors (9 and 11) are found above and below the plane of the thrust vector. The flexible fairing (8) can be easily deformed by the presence of these folded half propellers. The overall width of the paramotor in folded mode is of the order of magnitude of the width of the chassis (2) and the pilot harness (3). For example, the paramotor with his arms folded can pass through a standard width door of 80 cm when he is on his back. This is completely impossible with a single-propeller paramotor. You have to go sideways for most existing thermal models, not all of them allow it depending on the build of the pilot or the dimensions of the paramotor.

Folding allows for easier storage and transport: the machine can fit into most station wagon trunks and can be stored lying down or on its side without any particular restrictions. The machine can fit into certain “sedan” type car trunks. Sufficient trunk volume even allows you to transport several machines. This is very difficult, if not impossible, with a thermal paramotor unless you completely drain the tank and the fuel circuits and dismantle the protective cage (5) when it is removable, this is not the case for all models. Indeed, like any engine using liquid fuel, it risks leaking from a certain angle of inclination. Without complete draining, a thermal paramotor must be transported and stored in vertical mode close to the inclination of use. This limits transport possibilities.

Obviously the use of electricity as energy eliminates all odors and risks of leaks during storage, transport and use in the field, whether at the level of the machine or the transport of fuel in jerry cans. . The risk of soil pollution by petroleum-based fuel is eliminated. Pollution and odor in flight or on the ground, with the engine running, linked to the use of internal combustion engines, essentially 2-stroke engines burning oil, are eliminated. The CO2 balance in use is entirely to the advantage of electricity. [Table 1] of the carried out a comparative analysis between a thermal paramotor, a single-rotor electric paramotor and a multi-rotor paramotor.

The protective cage (5) of the paramotors prevents the lines and brake controls from being in the path of the propeller, especially during the ground inflation and take-off phases when the wing is not not yet powered on. Any contact between a rotating propeller and the lines destroys the latter and breaks the profile of the wing. The cage avoids contact during the inflation phase, particularly during so-called “back sail” inflation used by the majority of paramotor pilots. The wing is lowered to the ground behind the pilot and the engine and it is inflated by the pilot who pulls on certain lines with or without movement of the pilot depending on the wind speed. These lines under mechanical tension will rub and run along the circular cage during this inflation phase. Once the wing is above the pilot, the pilot begins the takeoff run by running and applying the throttle to obtain maximum propulsive thrust. The takeoff distance depends on the engine thrust, the PTV and the wing used but also strongly on the weather conditions. With a laminar headwind of at least 25 km/h, a paramotor can take off in just a few steps. In the absence of wind, on the other hand, you sometimes have to run more than 100 m to obtain sufficient lift for takeoff. During this take-off run, in the event of unstable weather conditions, for example a lateral gust, the wing may deform and the lines may move behind the machine. There is also a risk of collision with the rotating propeller. The protective cage (5) helps prevent significant damage, including the destruction of the wing, the propeller, or even the engine.

The 2nd technique for inflating the wing is called "face sail" and eliminates the risk of collision with the propeller lines during the inflation phase since the wing is inflated facing the pilot who must turn around when the wing is inflated to begin its race. flight. The risk of collision persists during this takeoff phase. In addition, the friction of the lines on the cage during the “back canopy” inflation phase of a paramotor causes premature wear of the latter.

In flight, during significant weather disturbances, the wing can deform significantly until it completely closes, the lines and elevators and controls are no longer under tension. The wing profile no longer exists, there is no more lift and the machine begins to fall more or less quickly. In most cases, the wing eventually re-inflates itself and returns to a normal flight envelope. If this is not the case, the only solution is to throw the emergency parachute. But before re-inflating and re-energizing the lines and risers, there is a risk of collision between the propeller and these vital parts of the machine. A collision in flight with the lines or the control lines with a rotating propeller results in the latter being cut or rolled up on the propeller. In both cases it is synonymous with total destruction, or in the best case partial, of the wing profile. This even if the engine power is zero or reduced since the propeller turns on its own with the relative wind or the idling speed of the thermal engine if there is no automatic clutch. The risk of the lines breaking is then limited because the rotation speed of the propeller is reduced but they can become entangled in the propeller or parts of the engine which would prevent the wing from reopening and returning to the area. normal flight.

These flight conditions are extreme and fortunately rare but they are possible: it is therefore necessary to protect the vital organs of the wing from a collision with a propeller. A protective device is therefore essential to protect the wing during all phases of flight: inflation, take-off and the flight phase, but also landing to a lesser extent.

On single-rotor paramotors, thermal or electric, this cage is annular and encompasses the entire propeller. This is mandatory to allow “back sail” inflation. This cage creates additional mass and above all drag.

In the case of multi-rotor propulsion, the cage does not need to completely cover the propellers because the risk of collision with the propellers is geometrically very greatly reduced as can be seen in [Fig 11 A]. In case of multi-rotor design, only the upper and central part of the propellers must be protected. Partial protection of each propeller at an angle of approximately 120° is sufficient to ensure sufficient protection during all phases of flight (takeoff, flight in normal conditions and landing). During flight incidents, i.e. total or partial closure of the wing, the risk of collision with the propellers is limited by 2 geometric aspects. First, the propeller plane of a multi-rotor aircraft is further from the risers and lines by design: the propellers are further back from the wing attachment point. Secondly, the surface swept by the propellers is offset on either side of the chassis, this greatly reduces the risk of collision between the lines and the propellers. A partial cage is detailed in [Fig 11 A] where the position of a riser (9) and a suspension cone (10) are indicated in dotted lines during a flight in normal conditions. The 2nd cage is symmetrically identical and therefore not shown.

A cage is made up of 2 long, flat and thin elements named profiles below (20 and 21). These profiles are light and flexible in aeronautical quality material, for example metallic aluminum, magnesium, stainless steel, titanium, polymer type or composite material type, for example glass fiber or carbon fiber. The section of the profiles (20 and 21) is of the flat profile type. The section is thin to have sufficient flexion according to its greatest length and to limit drag. The section is wide to have sufficient mechanical inertia to counter the force of the lines during a flight incident or takeoff. [Fig 11 C] shows an example of a usable profile. The profiles (20 and 21) are held together by an intermediate piece (23) comprising 2 slots identical to their profile [Fig 11 C] with a functional clearance in which the dishes are inserted. The connecting part (23) forms an angle of around 60° between its 2 slots. It is glued to one of the 2 profiles (21). To facilitate transport and storage, the connecting part (23) is fixed with a quick disassembly means, such as a pin (22) on the other profile (20). The partial and total disassembly are shown in [Fig 11 B].

Two slotted parts for attachment to the frame (24 and 25) hold the cage in position during use. These parts are made up of slots at approximately 60° to the horizontal into which the profiles enter with sufficient depth to be self-maintained by internal friction. The tension linked to the deformation by bending of the longest plate and the friction between the cage and the fixing parts allow mechanical balance of the cage. These cages can be assembled and dismantled by pinning without tools using pins (22). The assembled structure is self-supporting even without pinning. The pinning only has a safety role linked to accelerations and vibrations during use. When dismantled, the cage occupies the place of the 2 flat profiles (20 and 21): the elements of the cage return to a rectilinear shape which greatly facilitates their transport and storage [Fig 11 B].

The pins (22) as well as the attachment parts (24 and 25) as well as the intermediate part (23) are sized and manufactured according to current aeronautical standards and in aeronautical quality materials. They can be made of UV-resistant plastic or an aircraft-grade metal, ferrous or non-ferrous, for example 7075 aluminum.

The 2-rotor configuration presented above does not directly allow for “sail back” inflation with the lines placed on the ground and the sail lowered behind the machine. Indeed ; the lines would get stuck either in the propellers (10 and 12), or under the arms (13 and 14) or in the engines (9 and 11) or in certain elements of the cage (21, 23 and 24).

To allow take-off using the so-called “back sail” technique compared to a single-rotor paramotor with an annular cage, it is necessary to maintain the lines during “back sail” inflation. This support must be done at a height close to that of the risers and with an optimum spacing. This spacing is optimal when it deforms the suspension cone of the wing as little as possible when it is placed on the ground behind the pilot. A “hanger holder” part (26) has been designed to allow “sail back” inflation. It is a V-shaped part which maintains all of the lines during the ground preparation phase and the take-off phase. There is one on the left cage and one on the right cage. The 2 “hanger holders” (26) are adjustable on the ground in spacing and can slide on the profile (20) of the cage to adapt as closely as possible to the configuration of the wing. A radial set screw maintains their position when the correct setting is found. A change of wing requires a new adjustment. [Fig 11 A] shows 2 possible positions of the “hanger holder” (26). This part is designed not to significantly degrade the finesse of the machine: it is thin and elongated and made or not in the same material as the other parts of the cage (23, 24 and 25).

The use of these “hanging doors” (26) allows easier inflation than with a central cage of a single-rotor paramotor. Indeed ; the lines are already located at the same height as the risers and the lines will be less deformed during the inflation phase. The deformation of the line cones during inflation is less significant than with an annular central cage. In addition, they no longer rub on the annular cage (5) when they are mechanically tensioned. Inflation becomes easier and the lines wear less with each takeoff since they do not rub on anything. We find a sensation close to “back sail” inflation of a paraglider.

If the user wishes to take off using the “face sail” technique then he can dismantle the “hanging doors” by sliding them along the profile (20) after having loosened the pressure screw. The “hanging doors” have no use outside of the “back sail” inflation phase.

The cage is not necessary on fixed-wing pendulum-type aircraft.

Concerning the energy chain and on-board electronics: the battery and electronic regulations will be protected from dust and water splashes by the flexible fairing (8) which is dust and watertight. The internal air volume of this fairing and the absence of thermal insulation allow the calories to be dissipated to prevent any overheating of both the electronics and the batteries.

The machine includes an electronic flight controller which will regulate the power setpoint of each motor independently for the same thrust setpoint by the pilot. This differential regulation is done according to the flight conditions and in particular the altitude and the angles of evolution of the aircraft: yaw, roll and pitch.

• Maintenir l’asymétrie de la poussée dans les phases de vol sans changement de direction
• Créer une poussée asymétrique facilitant le virage lors des changements de direction
• Maintenir l’altitude sur demande du pilote
• Limiter l’angle de tangage
• Procurer une sécurité passive de surveillance de défaillance d’un des 2 moteurs

The flight controller has 4 essential regulation functions:

• Maintain thrust asymmetry in flight phases without change of direction
• Create an asymmetrical thrust making it easier to turn when changing direction
• Maintain altitude at the pilot's request
• Limit pitch angle
• Provide passive security for monitoring failure of one of the 2 motors

The first function of the flight controller is to maintain symmetrical thrust of the two engines during the take-off, altitude gain and flight at constant altitude phases. This regulation is done by analyzing the roll and yaw angle which must be constant during these phases. If a roll angle greater than a certain angle, the neutral zone, is observed then the lowest motor increases its power to reduce the roll angle. The neutral zone can be configured around the horizontal to avoid too frequent corrections which would increase energy consumption and could even lead to resonance. For example between -20° and +20° there is no roll correction. The neutral zone setting is factory setting with the possibility of adjustment by the user on the ground.

From a certain configurable safety height, for example, 150 m which is the minimum flight height of an ULM, the symmetrical thrust control is deactivated automatically following a setting of this minimum height on the ground or can be deactivated manually by the pilot in flight. The regulation then switches to a regulated asymmetric thrust mode. Deactivation is not systematic, it is the pilot who chooses to use it or not depending on the piloting mode he desires. If the asymmetric thrust mode is engaged, from a certain roll angle the thrust becomes asymmetric. A certain roll angle signifies a pilot's willingness to turn. Engine power on the inside of the turn will be reduced to create yaw torque on the aircraft. Under these conditions, the maneuverability of a 2-axis aircraft is considerably increased and allows energy to be saved and the autonomy of the machine to be improved. The aircraft will turn better with less action on the controls (12) and therefore less degradation of finesse when turning. The overall finesse of the aircraft is less degraded. There is an energy saving and a gain in autonomy. There indicates as an example a possible adjustment curve for the engine power inside the bend according to the roll angle. For example, a roll angle of 30° will give a setpoint of 70% to the internal motor at the turn, i.e. a reduction of 30% compared to the power of the external motor at the turn. On a paramotor type ULM, you must not create too much asymmetrical thrust as there is a risk of causing a “twist” of the risers, i.e. a winding of the risers depending on the yaw angle. On a rigid wing aircraft, for example, a pendulum, there is no limitation on thrust asymmetry. The left motor can have 100% thrust when the right motor is at 0%.

The flight controller also provides constant altitude regulation. It is a barometric or GPS altitude hold that can be activated on instructions from the pilot. Altitude regulation can only be activated from a certain minimum flight height and maintains the desired altitude by regulating the overall thrust. This is the “Altitude Hold” operating mode of autopilots widely used in civil, recreational or military aviation. The minimum activation height can be configured by factory setting or by the pilot on the ground. Altitude regulation is deactivated as soon as there is a new power setting on the throttle grip. A considerable advantage of maintaining altitude on a paramotor is being able to automatically benefit from the thermal rises of the air, therefore providing free energy and improving autonomy. When altitude hold is activated, the thrust is automatically regulated to maintain the current altitude of the aircraft. There is also a maintenance of the rectilinear direction of flight by asymmetric correction on the yaw. As soon as the roll angle leaves the neutral zone, altitude hold is deactivated.

On a paramotor, taking too large a pitch angle is useless: it is a waste of power and energy. If the thrust at the pilot level is too great, the pilot will move forward in a rocking motion in front of the wing. The wing will pitch up and increase its drag without increasing the rate of climb. There is absolutely no aeronautical benefit for a paramotor to exceed a certain pitch angle. The electronic regulation maintains an optimum pitch angle and will limit the engine thrust so as not to exceed too large an angle. This angle strongly depends on the characteristics of the wing and is defined by a software learning program. This software learning is done during the first flights of a new machine and monitors the pitch angle from which the ascending speed begins to no longer increase. This is the optimum pitch angle. This setting can be reset by the user in the event of a wing change.

In the event of an unplanned shutdown of one of the 2 motors, a safety function of the flight controller is to immediately stop the other motor to avoid the “Twist” of the elevators. This is done by analyzing the evolution of the yaw angle or by comparing the power of each of the engines or by comparing the RPM of each of the engines. If the change in the yaw angle is too rapid, for example 180° in less than 1 second, or if the difference in power or RPM is too great when the machine is not rotating, then the yaw is locked out. other engine. That is to say a shutdown of the 2nd motor because the probability of a failure of the ^1st motor is high. The 2 motors cut off to avoid the “Twist”.

Sampling of all flight controller functions is at least 10 Hz, or 10 scans and 10 corrections per second.

If the flight controller is coupled to a GPS and due to the yaw control possible by thrust asymmetry, automatic piloting is possible. The aircraft can change trajectory simply by adjusting the asymmetry of the thrust without the pilot needing to control the controls. It is an autopilot mode of a 2-axis device without degradation of finesse and lift. This autopilot mode can follow a route predefined by the pilot before the flight but also provide safety with a return to the takeoff field as quickly as possible, for example in the event of a sudden loss of meteorological visibility or a low battery indication.

The throttle handle is electronic, it sends a single thrust instruction via a flight controller which will distribute this instruction to the 2 engines following the flight phases as defined previously. The handle can be wireless with setpoint transmission by wave or wire. Wireless mode increases in-flight comfort with the absence of a wire which can be restrictive but reduces safety, for example in the event of a throttle battery failure or loss of signal for any reason. It is therefore preferable to make the throttle handle in a wired version, especially since paramotor pilots are used to having a wired handle.

The lower noise level of electric propulsion is also advantageous. If the noise is not completely reduced in flight due to the shearing noise of a propeller, the absence of exhaust noise from the heat engine allows a reduction in the sound level of around 10 dB at maximum speed. For the same maximum thrust, the sound level 3m behind at 45° of the machine goes from 112 dB with a thermal paramotor to 102 dB with an electric configuration. The noise is completely eliminated when the power setpoint is zero in electric mode while a thermal engine continues to make noise, and consume energy, when slowing down. In stabilized flight mode, at mid-range, noise is also reduced, as a result of which the pilot no longer needs to wear a noise-cancelling device. Simple hearing protection such as a motorcycle or paragliding helmet covering the ears is sufficient.

The noise level on the ground is also greatly reduced, which is an advantage for people on the ground. The latter will be less bothered by the noise level, particularly during events which concentrate many pilots at the same takeoff and landing location.

Local wildlife will also be less disturbed by noise levels and air pollution.