Method for controlling a multi-engine rotary-wing aircraft with reduced ground consumption

Description

[0001] The present invention relates to a method for piloting a multi-engine rotary wing aircraft with reduced fuel consumption on the ground, and an aircraft implementing this method.

[0002] A rotary wing aircraft may include several engines operating with fuel to drive a rotary wing and accessories. A rotorcraft may thus include several free turbine engines to drive a power transmission chain, this power transmission chain in particular driving at least one rotary wing into rotation.

[0003] A free turbine engine comprises a gas generator equipped with a compressor, a combustion chamber and a high-pressure expansion assembly connected to the compressor. The compressor may be equipped with one or more compression stages. Similarly, the expansion assembly may comprise one or more expansion turbines. In addition, the free turbine engine comprises at least one low-pressure working turbine known as "free", i.e. independent in rotation of the compressor of the high-pressure expansion assembly.

[0004] The operation of the turbine engine is controlled by a control system. For example, a control system is known by the acronym FADEC, which stands for "Full Authority Digital Engine Control." A control system usually includes a computer connected to various sensors and a fuel metering unit. The fuel metering unit then allows the control system to control the fuel flow transmitted to the turbine engine.

[0005] The control system typically includes a selector, called a "control selector" for convenience. For example, the control selector has three positions.

[0006] When the control selector is in a first position, for example called the “STOP position”, the turbo engine is switched off.

[0007] When the control selector is in a second position, for example called the "FLIGHT position", the turboshaft engine is in nominal operation. The turboshaft engine can then operate using a variety of normal flight regimes.

[0008] Typically, flight regimes include a takeoff regime during which an engine can develop maximum takeoff power PMD for a limited duration of use, and a maximum continuous regime during which an engine can develop maximum continuous power PMC without duration limitation.Twin-engine aircraft may include emergency regimes usable in the event of an engine failure, such as: (i) a first emergency regime allowing, for example, the development of a super emergency power OEI30' of approximately 112% to 120% of the PMD, usable possibly for a maximum of thirty consecutive seconds, and this three times during a flight, (ii) a second emergency regime OEI2" allowing, for example, the development of a maximum emergency power of approximately 105% to 110% of the PMD, possibly for two consecutive minutes, (iii) a third emergency regime OEICont allowing, for example, the development of an intermediate emergency power equal to or greater than the PMD continuously for the remainder of the flight after the failure of the turbine engine.

[0009] Finally, the control selector includes an intermediate position called, for example, the "IDLE position." When the control selector is positioned in this IDLE position, the turbine engine operates at an idle speed. When the idle speed is applied, an engine develops a non-zero idle power lower than the powers developed when the flight speeds are applied.

[0010] When starting a rotary-wing aircraft with multiple engines, the start-up procedure requires the pilot to start both engines sequentially. Then, to carry out the various operations required on the ground, and in particular to move the aircraft from its parking position to a take-off area during a phase of movement of the aircraft on the ground, usually called "taxiing" in English, the selectors must be placed in the FLIGHT position.

[0011] Similarly, the engines are stopped at the end of a flight when the aircraft is stationary, or after a phase of movement on the ground.

[0012] The use of a twin-engine powerplant is advantageous. However, the aircraft's fuel consumption is impacted on the ground by the operation of several engines. However, a rotary-wing aircraft has specific characteristics compared to an airplane, being likely to land during a mission, without the possibility of refueling. Fuel consumption on the ground is therefore a parameter that should not be overlooked.

[0013] In addition, a rotary-wing aircraft is likely to land in an area where noise and / or fine particle emissions are sensitive. However, the operation of several engines can have an impact on noise and / or fine particle emissions.

[0014] In this context, patent FR2967132 B1 describes a method for optimizing the specific consumption of a helicopter having two turboshaft engines. According to this method, the two turboshaft engines provide significantly different powers. In stabilized flight, one of the turboshaft engines can operate in continuous mode by developing a power close to its maximum takeoff power, but less than or equal to its maximum continuous power, while the other turboshaft engine is put on standby at zero power and the combustion chamber is switched off. If a conventional restart fails, the restart can be achieved by emergency assistance through additional firing of the combustion chamber.

[0015] Patent FR2967133 B1 describes a method for optimizing the specific consumption of a helicopter having two turboshaft engines. According to this method, one of the turboshaft engines can operate, in flight, in continuous mode while the other turboshaft engine operates at a super-idle speed at zero power. In the event of failure of a conventional restart, a restart of the turboshaft engine at super-idle speed can be achieved by emergency assistance produced by autonomous energy and dedicated to this restart.

[0016] Document FR3011587 A1 describes a method for optimizing the specific consumption of a helicopter having two turboshaft engines. According to this method, each turboshaft engine can operate alone in continuous flight mode, the other turboshaft engine then being in so-called super-idle mode at zero power. The super-idle mode is obtained with the combustion chamber of the gas generator ignited and assistance by the mechanical rotational drive of a shaft of the gas generator.

[0017] Document FR3001525 A1 describes a reduced power super-idle regime, implemented by supplying fuel to starter injectors and interrupting the supply to main injectors.

[0018] Document FR2871138 describes a transmission mechanism between at least one accessory and drive motor members of a rotorcraft rotor, selectively, separately or jointly.

[0019] Documents EP2735512 A1 and US2018 / 0187604 A1 are also known.

[0020] The present invention therefore aims to propose a method for an innovative multi-engine rotary wing aircraft, in particular to reduce its fuel consumption.

[0021] The invention thus aims at a method for piloting a rotary wing aircraft, said aircraft having a power plant comprising at least two engines burning fuel and a transmission chain connected to the rotary wing, each engine having a power shaft connected to the transmission chain.

[0022] This method comprises on the ground an energy-saving phase applicable on the ground and comprising at least one economic period. This economic period comprises regulation at an active speed, with a regulation system, of an active engine among the at least two engines to ensure the rotation of the rotary wing, the active engine developing during the active speed and with its power shaft a non-zero active driving power. The economic period comprises, together with the regulation of the active engine at the active speed, a stop with the regulation system or regulation with the regulation system at a rest speed of each non-active engine among the at least two engines which is not the active engine, the non-active engine at the rest speed developing with its power shaft a non-zero power lower than the active driving power or a zero power with possibly a gas generator in motion.

[0023] The term "on the ground" refers to an aircraft resting on a surface, for example on earth or other ground, a building, a ship, a platform, etc.

[0024] The expression "active engine" designates one of the engines developing motive power during an economic period, this active engine being able, for example, to develop an active motive power greater than or equal to an idling power.

[0025] In particular, each engine may, for example, operate in particular at an idle speed, enabling non-zero idle power to be developed with its power shaft, and at least one flight speed enabling flight power to be developed with its power shaft. The flight power is then greater than the idle power. Therefore, the active speed may be the idle speed, or even the flight speed. Using a flight speed as the active speed optimizes the stability of the aircraft, while using the idle speed as the active speed reduces fuel consumption more significantly.

[0026] Conversely, the expression "inactive engine" refers to the engine(s) switched off or put to rest, in particular to reduce fuel consumption.

[0027] In particular, an engine is said to be "stopped" or "off" when the engine has no moving parts.

[0028] The engines of a state-of-the-art twin-engine rotary-wing aircraft are all operating on the ground, i.e., implementing a flight regime. A phase of movement of the aircraft on the ground is thus achieved by setting the rotary wing in motion using all the engines that are permanently applying a flight regime. On the other hand, a significant portion of the engine operating time corresponds to operation on the ground.

[0029] In this context, when the energy-saving phase according to the invention is engaged, then the engines operate asymmetrically, the non-active engine(s) being either stopped or operating according to a rest regime. Thus, only one engine is, for example, started on the ground in order to carry out all the planned operations, the other engine(s) only being made active during the take-off phase as such.

[0030] The term "take-off phase" means the phase during which the aircraft is on its take-off area and rises from the ground. The energy-saving phase is undertaken before this take-off phase, for example when moving the aircraft on the ground from a parking area to the take-off area.

[0031] Consequently, putting at least one engine on the ground to rest or keeping it stopped can reduce fuel consumption on the ground and limit the emission of fine particles and / or noise. Such a reduction in fuel consumption can increase the duration of the mission or the range of the aircraft, or can simply allow financial savings to be made. In areas with strong environmental constraints, for example near a hospital, the economic period can limit the emission of fine particles and / or noise pollution.

[0032] Furthermore, this process can be compatible with the requirements of certification regulations. Indeed, it is not imperative to guarantee a rapid start of the non-active engine(s). A failure preventing the active engine(s) from starting is not a catastrophic event since the aircraft is on the ground and therefore not at risk of crashing. This process therefore does not necessarily have to be associated with an expensive and / or cumbersome restart system.

[0033] The method may further comprise one or more of the following features, taken alone or in combination.

[0034] According to one example, the method may comprise activating the energy-saving phase using a human-machine interface for selecting the control system.

[0035] The selection human-machine interface can then be operated by a human pilot so that the energy-saving phase is engaged. For example, the selection human-machine interface transmits a control signal to engine computers or to a management computer controlling the engine computers so that the engine computers apply the required speed(s) to the ground according to the method of the invention.

[0036] The term "signal" refers throughout the text to an analog or digital signal, electrical or optical for example.

[0037] The active engine may be chosen by a crew, cyclically, randomly, or according to a predetermined logic. For example, a particular engine may always act as the active engine. In another example, the control system may apply other logic to designate the active engine, such as alternating logic, logic based on engine health or maintenance information, logic based on events or conditions outside the engine perimeter such as wind direction, preferred passenger boarding side, etc.

[0038] According to a possibility compatible with the previous ones, the regulation system being able to comprise for each engine a man-machine start interface specific to this engine configured to require at the choice of a pilot the stopping of the engine and an application of an idle speed and an application of at least one flight speed to be developed in flight, the method can comprise prior to the energy saving phase: a regulation of the active engine, with the regulation system, at the idle speed controlled with the man-machine start interface of this active engine or a regulation of the engines at the idle speed, with the regulation system, controlled with the respective man-machine start interfaces.

[0039] Thus, at least one engine is started in the usual manner by being placed at idle speed, or then at a flight speed, with its starting human-machine interface. A pilot can then request the aforementioned selection human-machine interface to apply the energy-saving phase, each engine then possibly changing operating speed.

[0040] The flight regime(s) may be selected from a list including the takeoff regime, the maximum continuous regime, the first emergency regime OEI30', the second emergency regime OEI2" and the third emergency regime OEICont described previously.

[0041] Optionally, said selection human-machine interface may be separate from the start human-machine interfaces. The start human-machine interfaces may take the form of a conventional three-position stop / idle / flight selector.

[0042] According to a possibility compatible with the previous ones, the economic period may include at least one of the following stages: control of the rotary wing to taxi the aircraft on the ground, opening of a door to embark or disembark at least one passenger or goods on the ground, waiting stage during which no aircraft control interface is requested by a crew.

[0043] The economic period not only allows the active engine to be started, but can also allow for routine ground operations, including the ability to rotate the rotary wing to roll the aircraft on the ground.

[0044] The energy-saving phase comprises at least two alternating operating phases, the alternating operating phases comprising an economic period and a co-operating period, said co-operating period comprising regulation with the engine regulation system at the active speed

[0045] According to a variant which does not fall within the scope of claim 1, the energy-saving phase comprises a single phase of alternating operation. The aircraft is piloted so as to carry out all ground operations during the economy period. When a takeoff is possible, a pilot or a controller commands the regulation system to apply the co-operation period in order to reactivate the inactive engines.

[0046] This solution can, for example, make it possible to carry out a check of the proper functioning of all the motors during the joint operation period of the first alternating operation phase, then to return to an economic period during the second alternating operation phase.

[0047] Eventually, the inactive motor(s) can develop with their power shafts different powers between the two economic periods of the two alternating operating phases.

[0048] For example, when starting the aircraft, said energy-saving phase may comprise a first alternating operation phase and one or more second alternating operation phases, the non-active engine being switched off by the regulation system during the first alternating operation phase and at rest speed during the second alternating operation phase(s).

[0049] This feature helps to optimize the lifespan of the engines.

[0050] According to one possibility, each of said economic period and joint operation period can be applied for a predetermined duration.

[0051] According to a possibility compatible with the previous ones, the energy-saving phase can be a pre-takeoff phase at the start of the mission, or an intermediate phase on the ground during the mission or an end-of-mission phase.

[0052] In other words, each part of a mission taking place on the ground can be subject to the implementation of an energy-saving phase to optimize fuel consumption and / or noise emissions and / or fine particle emissions.

[0053] According to a possibility compatible with the previous ones, the energy-saving phase can be a pre-takeoff phase at the start of the mission comprising several alternating operating phases, each comprising an economic period followed by a period of joint operation.

[0054] According to a possibility compatible with the previous ones, the energy-saving phase can be an end-of-mission phase comprising several alternating operating phases, each comprising a period of joint operation followed by an economic period.

[0055] According to a possibility compatible with the previous ones, the energy-saving phase can be an intermediate phase on the ground during the mission comprising a period of joint operation after landing followed by several phases of alternating operation comprising a period of joint operation followed by an economic period.

[0056] According to a possibility compatible with the previous ones, the method can include a take-off phase comprising regulation with the regulation system of each engine at a flight speed, each engine developing with its power shaft a driving power greater than the idle power.

[0057] During an initial start-up of the aircraft or during an intermediate phase of a mission carried out between two parts of the flight mission, the method can implement the energy-saving phase to optimize fuel consumption and / or noise emission and / or fine particle emission, then a take-off phase as such jointly requesting all the engines to develop sufficient engine power for take-off.

[0058] According to a possibility compatible with the previous ones, the method can include human activation of the take-off phase with a human-machine interface for starting the regulation system to regulate the engines according to a flight regime.

[0059] In addition to a method, the invention relates to a rotary wing aircraft, said aircraft having a power plant comprising at least two engines burning fuel and a transmission chain connected to the rotary wing, each engine having a power shaft connected to the transmission chain. This aircraft comprises a regulation system configured to apply the piloting method according to the invention.

[0060] The invention and its advantages will appear in more detail in the context of the description which follows with examples given for illustrative purposes with reference to the appended figures which represent: there figure 1 , a view of an aircraft according to the invention, the figure 2 , a diagram illustrating the process applied, the figure 3 , a diagram illustrating an example of a process applied to the start-up of the aircraft, the figure 4 , a diagram illustrating an example of a process applied to the start-up of the aircraft, the figure 5 , a diagram illustrating an example of a process applied during an aircraft mission, the figure 6 , a diagram illustrating an example of a process applied at the end of the aircraft mission, and the figure 7 , a diagram illustrating an example of a process applied at the end of the aircraft mission.

[0061] There figure 1 presents an example of an aircraft 1 according to the invention. This aircraft 1 comprises a rotary wing 5. The rotary wing 5 comprises a plurality of blades 6 movable in rotation around an axis of rotation ROT of the rotary wing 5, the blades 6 being for example carried by a hub 7 or equivalent.

[0062] The pitch of the blades 6 can be controlled by a conventional flight control device 90. For example, such a flight control device 90 can comprise a cyclic pitch lever 91 and a collective pitch lever 94 connected by a linkage system 93 to several servocontrols 92. Each servocontrol 92 can be articulated to a swashplate system 95 connected by pitch rods 96 to the respective blades 6.

[0063] According to another aspect, the aircraft 1 may comprise at least one door 100 to allow the boarding and disembarkation of people and / or freight.

[0064] The aircraft 1 comprises a power plant 2 for rotating the rotary wing 5 in order to provide lift, or even advancement, for the aircraft 1. This power plant 2 is provided with at least two engines 10. The reference 10 designates any engine, the references 11, 12 designating particular engines if necessary to identify a specific engine 10.

[0065] According to one example, at least one engine 10 may be a turbine engine. Such a turbine engine 10 comprises a gas generator 15 which is provided with at least one compression turbine 16, a combustion chamber 17 into which the fuel is injected and at least one expansion turbine 18 linked in rotation to the compression turbine(s) 16. In addition, the turbine engine 10 may comprise at least one free turbine 19 which directly or indirectly sets in motion a power shaft 20 of the engine.

[0066] Regardless of the type of engines, each engine 10 therefore comprises a power shaft 20 connected to a power transmission chain 25. The power transmission chain 25 is then connected in the usual manner to the rotary wing 5. The reference 20 designates any power shaft, the references 21, 22 designating particular power shafts respectively of the two engines 11, 12.

[0067] By way of illustration, the power transmission chain 25 may be provided with a power transmission box 26 which is mechanically interposed between the motors 20 and the rotary wing 5. For example, the power transmission box 26 comprises a rotor mast 35, provided with one or more collinear shafts 36, 37 connected to the rotary wing 5, and according to the example to the hub 7. The power transmission box 26 may be provided with an input shaft 30 per motor 20 and various gears arranged between the input shafts 30 and the rotor mast 35. According to an example given by way of illustration, each input shaft 30 is engaged on a large wheel 40. This large wheel 40 is then mechanically connected by an internal shaft 41 to a planetary pinion 46 of a power reduction stage 45. Planetary pinions 47 are then engaged on the one hand on the planetary pinion 46 and on a toothed crown 48 stationary in the reference frame of the aircraft.In addition, the planet gears 47 are carried by a planet carrier 49 integral in rotation with the rotor mast 35. Therefore, each input shaft 30 is driven in rotation by an output shaft 20 of a motor 10 directly or via a respective mechanical input chain.

[0068] The power transmission chain 25, and according to the example illustrated a mechanical input chain, may comprise at least one freewheel 51, and / or at least one connecting shaft 52, and / or at least one connector allowing misalignments...

[0069] The literature describes various types of power transmission boxes and various drive trains, the example described being given for illustrative purposes only.

[0070] Furthermore, the engines 10 are thermal engines operating with fuel. Therefore, the aircraft 1 includes a regulation system 55 to control the power delivered by each engine 10 with its power shaft 20.

[0071] Thus, the regulation system 55 comprises a fuel metering device 69 per engine 10. Each engine 10 is then connected via its own fuel metering device 69 to at least one fuel tank 70. The reference 69 designates any fuel metering device, the references 71, 72 designating particular fuel metering devices respectively of the two engines 11, 12.

[0072] The regulation system 55 may comprise an engine computer 60 per engine 10. Each engine computer 60 may comprise, for example, at least one processor 64 and at least one memory 65, at least one integrated circuit, at least one programmable system, at least one logic circuit, these examples not limiting the scope given to the expression “engine computer”. The engine computers may communicate with each other via wired or wireless links.

[0073] According to the example described, the power plant 2 comprises two engine computers 61, 62 respectively controlling two engines 11, 12. Each engine computer is configured to control the associated engine and operate it according to the required speed, for example so that the controlled engine develops a power tending towards a limit power of this speed. Each engine computer 61, 62 can in particular control the fuel metering device 71, 72 of this engine 11, 12.Each engine computer 61, 62 can be connected to multiple regulation sensors to control the associated engine 11, 12, such as for example a temperature sensor 930 measuring the gas temperature for example at the inlet of a free turbine, a speed sensor measuring for example the rotational speed of a gas generator of the turbine engine, a torque meter 910, 920 measuring an engine torque on a rotating member, a speed sensor 940, 950 measuring for example the rotational speed of this rotating member. Such a rotating member can be a power shaft 20 of an engine 10. In addition, the power plant 2 can also comprise regulation sensors comprising a torque meter measuring a torque exerted on the rotor mast 35, a speed sensor measuring for example the rotational speed of this rotor mast 35, a sensor measuring the external pressure, a sensor measuring the external temperature.

[0074] The engine computers 60 can form a controller 75 applying the method of the invention, or a management computer 78 of the regulation system 55 can act as a controller 75 controlling the engine computers 60. The management computer 78 can comprise for example at least one processor 76 and at least one memory 77, at least one integrated circuit, at least one programmable system, at least one logic circuit, these examples not limiting the scope given to the expression “management computer”. The management computer 78 can communicate by wired or wireless links with each engine computer 60, or can even be merged with at least one engine computer 60. The management computer 78 can communicate with each of the aforementioned measurement systems.

[0075] Regardless of its composition, the controller 75 can communicate via a wired or wireless connection with at least one alerter 80 to provide information to a pilot. Such an alerter 80 can, for example, comprise a display capable of displaying a message, a light-emitting diode which lights up on command from the controller 75, a loudspeaker, etc.

[0076] Further, the controller 75 may communicate with a stop human-machine interface 82 and / or a selection human-machine interface 81.

[0077] Furthermore, the controller 75 can communicate with a starting human-machine interface 85 per engine, namely two interfaces 86, 87 according to the example given. Each starting human-machine interface 85 can for example emit a signal carrying a stop command, an idle speed command or a flight speed command of the engine concerned. figure 1 illustrates three-position interfaces stop POS1 / idle POS2 / flight POS3 for this purpose.

[0078] Each human-machine interface 81, 82, 85 may include a device operable by a pilot, such as a button or a lever for example, a touch screen, a voice command, etc.

[0079] According to the example illustrated, the human-machine interfaces 81, 82, 85 and the alerter 80 communicate with the management computer 78. Alternatively or additionally, the human-machine interfaces 81, 82, 85 and the alerter 80 communicate with one or even each engine computer 60.

[0080] There figure 2 illustrates the piloting method according to the invention, this method being able to be implemented by a rotary wing aircraft 1 of the type of the figure 1 . The process is illustrated with the use of the regulation system 55 of the figure 1 . However, this method is applicable with a regulation system without a management computer 78, the engine computers 60 being able to be easily configured to apply it.

[0081] This piloting method involves the implementation on the ground, namely when a landing gear of the aircraft 1 is resting on the ground, of a MODECENER energy-saving phase.

[0082] Prior to the MODECENER energy-saving phase, the method may comprise an STP0 regulation of one or more engines 11, 12 at idle speed. For example, at least one starting human-machine interface 85 is positioned in the idle position, the engine computer(s) 60 regulating the respective engine(s) 10 at idle speed on the order of the management computer 78.

[0083] The MODECENER energy-saving phase can be triggered subsequently, for example manually by requesting the selection human-machine interface 81.

[0084] A pilot operates the selection human-machine interface 81 which transmits a control signal to the controller 75. The controller 75 can be configured to check that one or more required conditions are met, and if necessary triggers the energy-saving phase MODECENER.

[0085] Regardless of the method used to trigger the energy-saving phase MODECENER, this energy-saving phase MODECENER comprises one or more economic periods STPASY. This economic period STPASY comprises the regulation, with the regulation system 55, of a motor 10 called the “active motor” at an active speed, and jointly the stopping or regulation at a rest speed of the other motor(s) called the “non-active motors”.

[0086] The active engine 10 at active speed is controlled by its engine computer 60 to develop a non-zero active engine power PWACT with its power shaft 20. This active engine power PWACT can be sufficient on its own to rotate the rotary wing 5, and allow the aircraft 1 to move on the ground with only the active engine 10.

[0087] According to the illustrated examples, the active regime may be the idle regime. In this case, this active engine power PWACT is the idle power PWRAL lower than an in-flight engine power PWVOL used during at least one usable flight regime during a takeoff phase, in flight and during a landing phase. Optionally, the idle engine power is lower than the maximum continuous power.

[0088] According to another example, the active regime may be a flight regime. In this case, the active engine power PWACT is greater than the idle power PWRAL, and equal to an in-flight engine power PWVOL or possibly to the maximum continuous power. Conversely, an engine 10 not active at idle regime does not generate any engine power via its power shaft 20, with a gas generator possibly set in motion via an external starter, or produces a non-zero super idle power PWSR possibly with the combustion chamber ignited. The super idle power PWSR is less than the active engine power PWACT, or even the idle power PWRAL.

[0089] For example, the management computer 78 transmits a regulation signal to each engine computer 60 to apply the required speed to each engine 10. According to another example, each engine computer 60 receives the control signal and is configured to apply the required speed accordingly.

[0090] From then on, each engine computer 60 controls in particular the associated fuel metering device 69 according to the signals emitted by the regulation sensor(s) so that the controlled engine 10 develops the required driving power with its power shaft 20.

[0091] The MODECENER energy-saving phase also comprises at least two alternating operating phases, the alternating operating phases comprising a joint operating period STPAEO and an economic period STPASY. Depending on the cases described below, the joint operating period STPAEO may be carried out before the economic period STPASY as illustrated by dotted lines or after the economic period STPASY as illustrated by solid lines.

[0092] The STPAEO joint operating period includes the regulation, with the regulation system 55, of all the engines 10 at active speed. Each engine 10 at active speed then develops, with its power shaft 20, the active engine power PWACT, and possibly the idle power PWRAL.

[0093] The transition from the joint operation period STPAEO to the economic period STPASY, or vice versa, may be required by the controller 75. For example, the controller 75 may be configured to change period at the end of a predetermined duration, and / or following the operation of an interface and for example the stopping human-machine interface 82.

[0094] During the economic period, at least one of the following steps can be carried out: STP1 control of the rotary wing 5 with the flight control device 90 to taxi the aircraft 1 on the ground, STP2 opening of a door 100 to embark or disembark at least one passenger or goods on the ground, STP3 waiting step during which no aircraft control interface is requested by a crew.

[0095] The energy-saving phase MODECENER can finally be interrupted, for example manually using the start-up human-machine interfaces 85. These start-up human-machine interfaces 85 can transmit stop signals to the controller 75 to either stop STPEXT all the engines 10 still in operation by positioning them in the aforementioned position POS1, or on the contrary require the application of a flight regime with each engine 10 in order to initiate a takeoff phase PHASDEC by positioning them in the aforementioned position POS3.

[0096] Indeed, the energy-saving phase can be a pre-takeoff phase at the start of the mission followed by a takeoff phase, or an intermediate phase on the ground during the mission preceded by a landing phase and followed by a takeoff phase, or an end-of-mission phase followed by the shutdown of the engines 10.

[0097] THE figures 3 à 7 illustrate various configurations through diagrams showing a driving power developed by each engine 10 on the ordinate and the time on the abscissa. These examples illustrate in solid lines the power developed by a first engine 11 of a twin-engine aircraft 1 and in broken lines the power developed by a second engine 12 of the aircraft 1. These examples illustrate an active regime of the idle regime type allowing the active engine to develop with its working shaft an active driving power PWACT equal to the idle power PWRAL. Alternatively, the active regime can be a regime allowing the active engine to develop with its working shaft an active driving power PWACT greater than the idle power PWRAL, and possibly equal to a flight power.

[0098] There figure 3 illustrates a first example of application of a method which does not fall within the scope of claim 1 to the start of an aircraft 1. At the initialization of the energy-saving phase MODECENER, the first engine 11 is started using its starting human-machine interface 85 positioned in the “idle” position POS2. If necessary, the selection human-machine interface 81 is maneuvered. The economic period STPASY then begins. The first engine 11 provides active motive power, equal to the idle power PWRAL according to the example, sufficient to set the rotary wing 5 in motion. The second engine 12 is in the given example stopped but could operate at rest speed, having been previously started by positioning its starting human-machine interface 85 in the “idle” position POS2.Under predetermined conditions, for example following the operation of the stopping human-machine interface 82 or at the end of a predetermined duration, the joint operation period STPAEO is initiated. The first engine 11 and the second engine 12 are controlled to develop the active engine power PWACT, equal to the idle power PWRAL according to the example. The takeoff phase PHASDEC is then initiated by positioning the starting human-machine interfaces 85 in the flight position POS3.

[0099] During the takeoff phase PHASDEC, the first engine 11 and the second engine 12 are driven to each develop a flight operating power PWVOL, for example the maximum takeoff power PMD. The aircraft 1 takes off and then a flight phase PHASVOL is initiated. The first engine 11 and the second engine 12 are driven to develop a flight operating power PWVOL, for example the maximum continuous power PMC.

[0100] There figure 4 illustrates an example of application of the invention to the start-up of an aircraft 1. According to this example, the energy-saving phase MODECENER comprises several alternating operating phases PHASALT, each alternating operating phase PHASALT comprising an economical period STPASY followed by a joint operating period STPAEO. The transition from one alternating operating phase to another can be obtained at the end of a duration or using the stopping human-machine interface 82 for example. For example, the non-active engine 12 is switched off, by the regulation system 55, during the first alternating operating phase P1, and at rest speed to develop a non-zero power PWSR during the second alternating operating phase(s) P2.

[0101] There figure 5 illustrates an example that does not fall within the scope of claim 1 during a mission. During a landing phase, each engine 10 operates according to a flight regime, for example by developing the maximum continuous power PMC. Once the aircraft 1 has landed on the ground, the starting human-machine interfaces 85 are positioned in the “idle” position. A joint operation period STPAEO is thus implemented. The energy-saving phase MODECENER is then triggered, for example by maneuvering the selection human-machine interface 81. The first engine 11 is controlled by its engine computer 61 to become the active engine 10 requested during the economic period STPASY. The first engine 11 provides the active engine power PWACT, equal to the idle power PWRAL according to the example. The second engine 12 is stopped in the given example but could operate at rest regime while being regulated by its engine computer 62.Under predetermined conditions, the joint operating period STPAEO is initiated, for example by operating the shutdown human-machine interface 82. The first engine 11 and the second engine 12 are controlled by the engine computers 61, 62 to develop the active engine power PWACT, equal to the idle power PWRAL according to the example. On command from the start human-machine interfaces 85 positioned in the flight positions for example, the takeoff phase PHASDEC is then initiated. The first engine 11 and the second engine 12 are controlled to develop an in-flight operating power PWVOL, for example the maximum takeoff power PMD.

[0102] There figure 6 illustrates a first example of application which does not fall within the scope of claim 1 at the end of the mission. During a landing phase, each engine 10 operates according to a flight regime, for example by developing the maximum continuous power PMC. Once the aircraft 1 has landed on the ground, the starting human-machine interfaces 85 are positioned in the “idle” position. The energy-saving phase MODECENER is then engaged, for example by maneuvering the selection human-machine interface 81. The first engine 11 is piloted to become the active engine 10 requested during the economic period STPASY. The first engine 11 provides the active engine power PWACT, equal to the idle power PWRAL according to the example. The second engine 12 is stopped in the given example but could operate at rest regime.Under predetermined conditions, the stopping of all the motors 10 is triggered, for example by maneuvering the starting human-machine interfaces 85 to position them in the stop position POS1.

[0103] There figure 7 illustrates an example of application of the invention at the end of the mission. According to this example, the energy-saving phase MODECENER comprises several phases of alternating operation PHASALT, each phase of alternating operation PHASALT comprising a period of joint operation STPAEO followed by an economic period STPASY.

[0104] Naturally, the present invention is subject to numerous variations in its implementation. Although several embodiments have been described, it is conceivable to replace a described means with an equivalent means without departing from the scope of the present invention and the claims.

Claims

1. Method for controlling an aircraft (1) with a rotary wing (5), said aircraft (1) having a power plant (2) comprising at least two engines (10) burning fuel and a transmission chain (25) connected to the rotary wing (5), each engine (10) having a power shaft (20) connected to the transmission chain (25), the method comprising an energy-saving phase (MODECENER) applicable on the ground and comprising at least one energy-saving period (STPASY), this energy-saving period (STPASY) comprising controlling, at an active rating, with a control system (55), one active engine from the at least two engines (10), in order to ensure rotation of the rotary wing (5), the active engine producing, at the active rating and with its power shaft (20), a non-zero active driving power, the energy-saving period (STPASY) comprising, together with the control of the active engine at the active rating, use of the control system (55) to stop or use of the control system (55) to control, at an inactive rating, each inactive engine from the at least two engines (10) that is not the active engine, the inactive engine at the inactive rating producing, with its power shaft (20), a non-zero power that is less than the active driving power or zero power, characterized in that during which said energy-saving phase (MODECENER) comprises at least two alternating operating phases (PHASALT), each alternating operating phase (PHASALT) comprising an energy-saving period (STPASY) and a joint operation period (STPAEO), said joint operation period (STPAEO) comprising controlling the engines (10) at the active rating with the control system (55).

2. Method according to Claim 1, characterized in that the method comprises activating the energy-saving phase by means of a human-machine selection interface (81) of the control system (55).

3. Method according to any one of Claims 1 to 2, characterized in that control system (55) comprising, for each engine, a human-machine starting interface (85) specific to this engine configured to prompt, at the choice of a pilot, the stopping of the engine and the application of an idle rating and the application of at least one flight rating to be reached during flight, the method comprises, prior to the energy-saving phase (MODECENER): controlling the active engine, with the control system (55), at the idle rating set with the human-machine starting interface (85) of this active engine or controlling the engines, with the control system (55), at the idle rating set with the respective human-machine starting interfaces (85).

4. Method according to Claims 2 and 3, characterized in that said human-machine selection interface (81) is separate from the human-machine starting interface (85).

5. Method according to any one of Claims 1 to 4, characterized in that each engine being able to operate at an idle rating, enabling a non-zero idle power to be produced with its power shaft and at least one flight rating enabling a flight power greater than the idle power to be produced with its power shaft, the active rating is the idle rating.

6. Method according to any one of Claims 1 to 5, characterized in that said energy-saving period comprises at least one of the following steps: controlling (STP1) the rotary wing (5) in order to taxi the aircraft (1) on the ground, opening (STP2) a door (100) to embark or disembark at least one passenger or goods on the ground, a waiting step (STP3) during which no control interface of the aircraft is operated by a crew.

7. Method according to any one of Claims 1 to 6, characterized in that each of said energy-saving period (STPASY) and said joint operation period (STPAEO) is applied for a predetermined time period.

8. Method according to any one of Claims 1 to 7, characterized in that the inactive engine produces different powers with its power shaft (20) in the two energy-saving periods of the two alternating operating phases (PHASALT).

9. Method according to Claim 8, characterized in that when the aircraft (1) is started up, said energy-saving phase (MODECENER) comprises a first alternating operating phase (P1) and one or more second alternating operating phases (P2), the inactive engine being switched off by the control system (55) during the first alternating operating phase (P1) and switched to the inactive rating during the second alternating operating phase or phases (P2).

10. Method according to any one of Claims 1 to 9 characterized in that the energy-saving phase (MODECENER) is a pre-take-off phase at the start of a mission, or an intermediate phase on the ground during a mission or an end-of-mission phase.

11. Method according to any one of Claims 1 to 9, characterized in that the energy-saving phase (MODECENER) is a pre-take-off phase at the start of a mission comprising multiple alternating operating phases (PHASALT) each comprising an energy-saving period (STPASY) followed by a joint operation period (STPAEO).

12. Method according to any one of Claims 1 to 9, characterized in that energy-saving phase (MODECENER) is an end-of-mission phase comprising multiple alternating operating phases (PHASALT) each comprising a joint operation period (STPAEO) followed by an energy-saving period (STPASY).

13. Method according to any one of Claims 1 to 9, characterized in that the energy-saving phase (MODECENER) is an intermediate phase on the ground during a mission comprising a joint operation period (STPAEO) after landing followed by at least two alternating operating phases comprising a joint operation period (STPAEO) followed by an energy-saving period (STPASY).

14. Method according to any one of Claims 1 to 13, characterized in that l the method comprises a take-off phase comprising controlling each engine (10) at a flight rating with the control system (55), each engine (10) producing, with its power shaft (20), a driving power greater than an idle power.

15. Method la according to Claim 14, characterized in that the method comprises activation by a human of the take-off phase with a human-machine starting interface (85) of the control system (55), in order to control the engines according to a flight rating.

16. Aircraft (1) with a rotary wing (5), said aircraft (1) having a power plant (2) comprising at least two engines (10) burning fuel and a transmission chain (25) connected to the rotary wing (5), each engine having a power shaft (20) connected to the transmission chain (25), characterized in that said aircraft (1) comprises a control system (55) configured to apply the method according to any one of Claims 1 to 15.