Method for monitoring an energy level of an electrical energy source of a hybrid aircraft power plant

Abstract

The present invention relates to a method for monitoring an energy level of an electrical energy source capable of delivering a reference electrical power PRef during a reference duration DTRef for a reference load level NRef. Said source comprises at least one electrical energy storage device and several sensors. Said method comprises an acquisition of parameters of said electrical energy source (10) via said sensors, then a calculation of a main consumption duration DTprin during which said source is capable of providing an electric current carrying said reference electrical power PRef, as a function of said parameters of said source. Then, a main display of main symbols (31) indicating said main consumption duration DTprin is carried out in order to indicate to an operator for how long the source can provide said reference electrical power PRef.Abbreviated figure: figure 6.

Description

Title of the invention: Method for monitoring an energy level of an electrical energy source of a hybrid power plant for an aircraft

[0001] The present invention lies in the technical field of hybrid power plants for aircraft, and more particularly relates to the management of the electrical energy sources of these hybrid power plants.

[0002] The invention relates to a method for monitoring an energy level of an electrical energy source of a hybrid power plant as well as an electrical energy source and an aircraft implementing this method.

[0003] An aircraft, and in particular a rotorcraft, may comprise one or more rotors capable of generating thrust and driven in rotation by a hybrid power plant. A rotorcraft may, for example, comprise a lift rotor participating in the lift, or even in the movement of the rotorcraft. A rotorcraft may also comprise an auxiliary rotor, for example a tail rotor, in particular to oppose the yaw torque exerted by the lift rotor on the fuselage of the rotorcraft and to control the yaw movements of the rotorcraft. A rotorcraft may also comprise one or more propellers.

[0004] The hybrid power plant of such an aircraft comprises one or more thermal engines as well as at least one mechanical transmission chain arranged between, on the one hand, the rotor(s) and, on the other hand, the thermal engine(s).

[0005] A hybrid power plant further comprises one or more electrical machines for driving the rotor(s), via said at least one mechanical transmission chain.

[0006] A hybrid power plant also comprises an electrical energy source, provided with one or more storage devices, such as a battery or a supercapacitor for example. The electrical energy source supplies electrical energy to each electrical machine, via an electrical transmission chain. Some electrical energy sources may comprise rechargeable electrical energy storage devices.

[0007] It should be noted that the expression "thermal engine" designates for convenience throughout the text any thermal engine that can be used in such a rotorcraft power plant, for example turboshaft engines or piston engines. The expression "thermal engine" is to be contrasted with the expressions "electric motor" or "electric machine" qualifying engines powered by electrical energy.

[0008] Depending on the operation of the hybrid power plant, the thermal engines and the electric machines can be used independently or in combination, simultaneously or sequentially.

[0009] However, the use of an electric machine for driving a rotor is subject to certain constraints, in particular related to the source of electrical energy. Indeed, the charge level of the source of electrical energy, corresponding to the quantity of electrical energy that it contains and capable of being supplied to the electric machine in flight, is limited. This charge level of an electrical energy source therefore allows the supply of electrical power for a limited duration.

[0010] An electrical energy source with a maximum energy level is then sized to provide a predefined electrical reference power during a predefined nominal consumption duration.

[0011] However, the electric machine can generate an electric power different from this reference electric power, this electric power being variable depending on the flight phase and the load on the electric machine. Thus, in the case of using an electric power lower than the reference electric power, the duration of supply of such electric power is greater than the nominal consumption duration.

[0012] Furthermore, parameters of the electrical energy source, in particular its temperature and its aging, can influence the value of this charge level and / or the electric current that the source is capable of supplying. Furthermore, an electrical energy source can be rechargeable and can therefore be recharged, at least partially, in flight, its charge level then increasing.

[0013] As a result, it may then be difficult for a pilot of an aircraft to determine the duration during which the electrical energy source is capable of delivering the electrical power required by the hybrid power plant. The pilot's workload then increases in trying to estimate this duration, which can be problematic in an emergency situation.

[0014] The present invention then aims to assist the pilot of an aircraft comprising a hybrid power plant in order to reduce his workload.

[0015] The present invention relates firstly to a method for monitoring an energy level of an electrical energy source, this electrical energy source being capable of delivering a reference electrical power PPe / during a predetermined reference duration DTRef for a predetermined reference load level NRef of the electrical energy source, and comprising: - at least one electrical energy storage device, - at least one sensor, and - a calculator.

[0016] The method according to the invention is remarkable in that it comprises the following steps: - acquisition of at least one parameter of the electrical energy source, via said at least one sensor, - calculation of a main consumption duration DTprin during which the electrical energy source is capable of providing an electric current carrying the reference electrical power PRef, as a function of said at least one parameter of the electrical energy source, using the calculator, and - main display of main symbols indicating the main consumption time DTprin.

[0017] In this way, the method according to the invention makes it possible to monitor the electrical energy source using one or more parameters of this electrical energy source.

[0018] The source of electrical energy may, for example, belong to a hybrid power plant of an aircraft.

[0019] The electrical energy source may comprise a single energy storage device or several energy storage devices, possibly rechargeable. Such an energy storage device may comprise a battery for example.

[0020] The electrical energy source also comprises one or more sensors intended to monitor the operation and state of the electrical energy source by measuring the value of one or more parameters. The sensors make it possible to measure, on the one hand, one or more first parameters relating directly to the electrical energy source itself and, on the other hand, one or more second parameters relating to the electric current flowing in the electrical energy source.

[0021] The first parameter(s) may be chosen from a charge level, a temperature and an aging of the electrical energy source, while the second parameter(s) are chosen from an electrical intensity and an electrical voltage of an electrical current flowing in the electrical energy source.

[0022] The charge level takes, for example, the form of a coefficient expressed as a percentage equal to the current quantity of electrical energy contained in the electrical source divided by the maximum quantity of electrical energy that it can contain. Aging is a coefficient representing the efficiency and / or the yield of the electrical energy source as a function of its duration of use. Aging is for example equal to the number 1 when the electrical energy source is new and decreases during the life of the electrical energy source, together with the duration and conditions of use, for example according to a predetermined law.

[0023] Furthermore, when the electrical energy source comprises at least two electrical energy storage devices, the parameter(s) comprise one or more of previously cited parameters, and relating to each of these storage devices.

[0024] The computer is connected to the sensors by a wired or wireless connection and receives one or more signals carrying information relating to this or these parameters of the electrical energy source.

[0025] The computer then calculates the main consumption duration DTprin using this or these parameters. The main consumption duration DTprin can for example be determined using one or more laws or charts stored in a memory of the computer or in a memory connected to the computer. These laws or charts take into account for example the parameters of the electrical energy source, in particular its temperature and its aging.

[0026] The main symbols may indicate the main consumption duration DTprin by including the numerical value of this main consumption duration DTprin. Alternatively or additionally, the main symbols may display this main consumption duration DTprin in relation to the reference duration DTRef. The main symbols then include, for example, a bar graph, a disc, a scale, or others.

[0027] The main symbols indicating the main consumption duration DTprin can be displayed on a screen present on the electrical energy source, or on a remote screen, for example present in the cockpit of an aircraft equipped with the monitored electrical energy source.

[0028] Thanks to this main display of the main symbols, an operator, or even the pilot of an aircraft, quickly visualizes the main consumption duration DTprin available for the electrical energy source, according to the parameter(s) of the source, and in particular its charge level, and can then optimize the use of the electrical energy supplied by the electrical energy source.

[0029] In addition, the main symbols may include an alert zone corresponding to a predetermined final consumption duration DTfin during which the electrical energy source is capable of providing an electrical current carrying the reference electrical power PRef, before the electrical energy source no longer contains electrical energy, and is then not capable of providing electrical energy.

[0030] The alert zone is represented for example with a specific color, different from the color used for the other main symbols. This alert zone thus makes it possible to clearly and distinctly indicate the last percentages of electrical energy that the electrical energy source can provide.

[0031] The method according to the invention may also comprise an estimation of at least one additional consumption duration DTcomp during which the electrical energy source is capable of providing an electric current carrying an additional electrical power Pcomp different from the reference electrical power. PRef depending on the parameter(s) of the electrical energy source and the additional electrical power Pcomp, and an additional display of additional symbols indicating the additional consumption duration DT comp.

[0032] Indeed, the electrical energy source is not always used to deliver the reference electrical power PRef. Therefore, when the electrical energy source is used to deliver a different electrical power and, for example, lower than the reference electrical power PRef, an operator knows that the electrical energy source can deliver such electrical power for a duration greater than the main consumption duration DTprin, without any other information.

[0033] Similarly, if the electrical energy source delivers an electrical power greater than the reference electrical power PRef, an operator sees, using the complementary symbols, that the electrical energy source can deliver such electrical power for a duration less than the main consumption duration DTprin.

[0034] The complementary display of the complementary symbols can thus indicate one or more complementary consumption durations DTcomp associated respectively with one or more complementary electrical powers Pcomp. This complementary display advantageously allows the operator to have a more precise idea of the duration during which the electrical energy source can provide such electrical power, even if this electrical power is not exactly equal to one of the complementary electrical powers Pcomp for which the complementary consumption duration DTcomp is displayed. This complementary electrical power Pcomp can for example correspond to a predetermined particular use.

[0035] The method according to the invention may also comprise a calculation of a value of electrical power received or delivered by the electrical energy source as a function of the parameter(s), and an additional display of the value of electrical power received or delivered.

[0036] This value of electrical power received or delivered can be determined using the second parameters of the electrical current flowing in the electrical energy source, using the electrical voltage and the electrical intensity of this electrical current. This value of electrical power received or delivered can also be determined using measurements at the level of the electrical machine which is powered by the source, for example using measurements of a motor torque of an output shaft of the electrical machine and a rotation speed of this electrical shaft.

[0037] In this way, the operator can instantly know on the one hand whether the source is receiving an electric current, to be recharged, or whether it is providing a carrier electric current. of an electrical power, and on the other hand the quantity of energy that it receives or delivers. The operator is thus aware, for example, of the electrical power delivered in relation to the reference electrical power PRefd the operator can estimate the duration of consumption of this electrical power delivered in relation to the main consumption duration DTprin of which he is aware.

[0038] To facilitate awareness of the operation of the electrical energy source, when the electrical energy source receives electrical power, the value of the received electrical power is displayed with a first color, and when the electrical energy source delivers electrical power the value of the delivered electrical power can be displayed with a second color distinct from the first color.

[0039] Furthermore, the electrical energy source can equip an aircraft comprising a hybrid power plant and a lift rotor driven in rotation by the hybrid power plant via a mechanical transmission chain, the hybrid power plant comprising at least one thermal engine, at least one electrical machine, and the electrical energy source electrically connected to the electrical machine(s), via an electrical connection chain.

[0040] In this case, the method may comprise a determination of energy flow circulating in the mechanical transmission chain and the electrical connection chain, as well as a transfer display, for example on a screen present in the cockpit of the aircraft, of transfer symbols provided with figurines, respectively representing the lift rotor, the thermal engine(s), the electrical machine(s), and the electrical energy source as well as arrows representing the energy flows between the lift rotor and respectively the thermal engine(s), and the electrical machine(s), as well as between the electrical energy source and the electrical machine(s).

[0041] In this way, the aircraft pilot has a global vision of the exchange of mechanical power and electrical power in the hybrid power plant and towards the lift rotor.

[0042] Alternatively or additionally, the method according to the invention applied to an electrical energy source of such an aircraft may comprise a determination of at least one characteristic of the aircraft, an estimation of at least one descent rate and at least one distance achievable to the ground, using only electrical energy that can be delivered by the electrical energy source, and a descent display, for example on a screen present in the cockpit of the aircraft, of descent symbols representing at least one descent trajectory of the aircraft as a function of the descent rate of the aircraft and the distance achievable by the aircraft for landing. The descent symbols comprise at least one descent trajectory of the aircraft formed with a descent rate and an associated achievable distance.

[0043] The rate of descent of the aircraft and the achievable distance of the aircraft are determined in particular as a function of said at least one parameter of the electrical energy source, of the electrical power supplied by the electrical energy source to the electrical machine, of the characteristic(s) of the aircraft, for example using laws or charts stored in a memory of the computer or a memory connected to the computer.

[0044] In this way, the pilot has knowledge of one or more descent trajectories allowing the ground to be reached, associated with an achievable distance, with the associated descent rate, with a view to landing in particular. Such knowledge is particularly useful in the case where the lift rotor is driven solely by the electrical machine(s) powered by the electrical energy source, for example in the event of failure of the thermal engine(s).

[0045] In addition, during this estimation, several descent rates and several achievable distances can be estimated, being associated respectively with several distinct electrical powers that can be delivered by the electrical energy source. The descent symbols then comprise several descent trajectories associated respectively with these descent rates and these achievable distances. The descent symbols can also comprise a value of the electrical power making it possible to obtain the descent rate and the achievable distance associated with each displayed descent trajectory.

[0046] A descent rate of the aircraft is for example determined using charts or laws stored in a memory of the computer or in a memory connected to the computer. These laws or charts, including in particular polars characterizing the flight and the performance of the aircraft, take into account one or more characteristics of the aircraft as well as the electrical power supplied by the electrical energy source to the electrical machine(s).

[0047] A descent trajectory may comprise only a slope according to the estimated descent rate if the energy level of the electrical power source is sufficient for the source to deliver the electrical power associated with this estimated descent rate until the aircraft reaches the ground. Alternatively, a descent trajectory may comprise a first slope according to this estimated descent rate corresponding to a flight during the duration of consumption of the electrical power of the electrical power source and a second slope at an autorotation descent rate to the ground corresponding to a flight without engine power. A reserve of electrical energy may further be kept specifically to be consumed during the landing phase itself, to slow down the descent of the aircraft for example.

[0048] The characteristic(s) of the aircraft may be chosen from a height of the aircraft relative to the ground, a mass of the aircraft, a forward speed of the aircraft and a vertical speed of the aircraft for example.

[0049] In addition, the descent rate and the achievable distance can be corrected as a function of a wind speed experienced by the aircraft. Indeed, in the event of a strong headwind, the achievable distance will be reduced. The value of the wind speed can be known and extracted from a weather report by the computer and / or available at the level of an avionics system of the aircraft.

[0050] The method according to the invention may also comprise a determination of a maximum achievable distance equal to the greatest of the previously estimated achievable distances, the maximum achievable distance being associated with an optimal descent rate and an optimal electrical power. Knowledge of this maximum achievable distance thus allows a pilot of the aircraft to estimate the achievable landing point furthest from its current position, independently of the relief which surrounds it.

[0051] The method according to the invention can then comprise a selection of a trajectory chosen from the displayed descent trajectories and the descent symbols comprise a descent marker representative of the gradient rate corresponding to the trajectory chosen on an artificial horizon instrument of the aircraft.

[0052] In this way, the pilot of the aircraft can check on the artificial horizon instrument whether the actual descent rate of the aircraft complies with and / or is consistent with the descent rate associated with the trajectory chosen to reach a landing area.

[0053] Alternatively or additionally, the method according to the invention may comprise a selection of a trajectory chosen from the displayed descent trajectories and the descent symbols comprise a power marker representative of the electrical power corresponding to the trajectory chosen on a power indication instrument of the aircraft.

[0054] In this way, the pilot of the aircraft can check on the power indication instrument whether the power consumed by the aircraft complies with and / or is in agreement with the electrical power associated with the trajectory chosen to reach a landing area. Such a power indication instrument is for example a first limitation indicator or a collective pitch indicator.

[0055] The method may also comprise a location of a current position of the aircraft, carried out for example using a satellite location device, and the descent symbols comprise a display of at least one achievable distance superimposed on a map of the environment of the aircraft from the current position of the aircraft, the map being for example stored in a memory of the aircraft. The displayed achievable distance(s) are chosen from the estimated achievable distances.

[0056] The pilot of the aircraft can thus clearly visualize, on the map, the distance that he can travel in the event of failure of the thermal engine(s), using only the electrical energy that can be supplied by the electrical energy source. He can thus, for example, choose a landing zone for an emergency landing, depending on the distance that can be reached by the aircraft.

[0057] The present invention also relates to a source of electrical energy, and comprising: - at least one electrical energy storage device, - at least one sensor, and - a calculator.

[0058] This electrical energy source is capable of delivering a reference electrical power PRef for a predetermined reference duration DTRef for a predetermined reference charge level NRef and can apply the method as previously described, the computer being configured to implement this method.

[0059] The present invention finally relates to an aircraft comprising a hybrid power plant and a lift rotor driven in rotation by the hybrid power plant via a mechanical transmission chain, the hybrid power plant comprising at least one heat engine, at least one electric machine, and an electrical energy source electrically connected to the electric machine, via an electrical connection chain. The electrical energy source is capable of delivering a reference electrical power P7?e / for a predetermined reference duration DTRef for a predetermined reference charge level NRef and comprises at least one electrical energy storage device, at least one sensor and a computer.

[0060] The electrical energy source may apply the method as previously described, the computer being for example configured to implement this method. The computer may be dedicated to carrying out this method or shared to execute other functions in the aircraft, or even be integrated into an avionics system of the aircraft.

[0061] 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: - [Fig.l], a view of an aircraft equipped with an electrical energy source according to the invention, - [Fig.2], a view of an aircraft equipped with an electrical energy source according to the invention, - [Fig. 3], a block diagram of a method according to the invention, and - Figures 4 to 11, exemplary views of the displays according to the method according to the invention.

[0062] Elements present in several distinct figures are assigned a single reference.

[0063] Figures 1 and 2 represent examples of sources 10 of electrical energy equipping a hybrid power plant 20 of an aircraft 1.

[0064] Whatever the embodiment, the source 10 of electrical energy comprises at least one storage device 11, 12 of electrical energy, at least one sensor 13-17, and a computer 9.

[0065] According to a first example shown in [Fig. 1], the electrical energy source 10 comprises a single electrical energy storage device 11. According to a second example shown in [Fig. 2], the electrical energy source 10 comprises two electrical energy storage devices 11, 12 arranged electrically in parallel with each other.

[0066] In the context of the invention, a source 10 of electrical energy may also comprise more than two electrical energy storage devices 11, 12. When a source 10 comprises at least two electrical energy storage devices 11, 12, these may be electrically arranged in parallel with each other and / or in series.

[0067] A storage device 11, 12 may comprise, for example, an electric battery, possibly rechargeable, or a supercapacitor.

[0068] Independently of the examples shown, the electrical energy source 10 is capable of delivering an electrical current carrying a reference electrical power PRef for a predetermined reference duration DTRef for a predetermined reference charge level NRef. The charge level of the source 10 characterizes the quantity of electrical energy that the source 10 contains. This electrical current is characterized by an electrical intensity and an electrical voltage.

[0069] Of course, the electrical energy source 10 is also capable of delivering an electrical power different from the reference electrical power PRef. For example, the reference duration DTRef may be equal to two minutes and the reference charge level A7?e / may be equal to eighty percent (80%).

[0070] The sensors 13-17 of the electrical energy source 10 measure one or more parameters of this electrical energy source 10. The sensors 13-17 may in particular be arranged at the level of the electrical energy source 10 to measure one or more first parameters relating directly to the electrical energy source 10 itself, as well as one or more second parameters relating to the electrical current flowing in the electrical energy source 10.

[0071] Such a sensor 13-17 can provide a raw signal carrying raw measurements made by this sensor 13-17. Such a sensor 13-17 can also include an integrated computer in order to process these raw measurements, for example via filtering or sampling. usual, or even the application of transformations, and provide a processed signal carrying these raw measurements thus processed.

[0072] For example, an electrical energy storage device 11,12 may comprise a temperature sensor 13,13', possibly equipped with a thermocouple, for measuring an internal temperature of this electrical energy storage device 11,12.

[0073] In a complementary or alternative manner, an electrical energy storage device 11, 12 may comprise a charge sensor 14, 14' making it possible to measure an electrical charge level of this electrical energy storage device 11, 12, namely the quantity of electrical energy that it contains.

[0074] In a complementary or alternative manner, an electrical energy storage device 11, 12 may comprise an aging sensor 15, 15' for measuring an aging level of this electrical energy storage device 11, 12. Such an aging sensor 15, 15' may for example comprise a calculator configured to perform a calculation of the aging level of the electrical energy storage device 11, 12 as a function of internal parameters, such as its internal resistance and its state of charge for example. The aging level may be taken into account to determine the value of the maximum electrical intensity of an electric current that this electrical energy storage device 11, 12 can supply.

[0075] In a complementary or alternative manner, an electrical energy storage device 11, 12 may comprise an intensity sensor 16, 16', possibly equipped with an ammeter, for measuring an electrical intensity of an electric current flowing in the electrical energy storage device 11, 12, namely entering or leaving this storage device 11, 12.

[0076] In a complementary or alternative manner, an electrical energy storage device 11, 12 may comprise a voltage sensor 17, 17', possibly equipped with a voltmeter, for measuring an electrical voltage at the terminals of the electrical energy storage device 11, 12, and corresponding to the electrical voltage of the electrical current entering or leaving the electrical energy storage device 11, 12.

[0077] The computer 9 can be dedicated solely to the operation of the source 10. Alternatively, the computer 9 can be shared to perform other functions of the aircraft 1, or even be integrated into an avionics system 4 of the aircraft 1, as shown in [Fig. 2]. In both cases, the computer 9 is connected by wire or wireless means to the sensors 13-17 of the electrical energy source 10 to receive the signals emitted by the sensors 13-17.

[0078] The computer 9 may comprise, for example, at least one processor and at least one memory, 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 computer. The term processor may designate both a central unit of processing known by the acronym CPU, a graphics processing unit GPU, a digital unit known.

[0079] The electrical energy source 10 may also comprise a display 15, for example a screen, for displaying several symbols comprising one or more indications of the charge level of the electrical energy source 10. This display 15 may for example be remote in the cockpit of the aircraft 1, when the electrical energy source 10 equips a hybrid power plant 20 of this aircraft 1. Alternatively, the display 15 may be integrated into the electrical energy source 10.

[0080] In all cases, the display 15 is connected by wire or wireless means to the computer 9.

[0081] Signals, electrical or optical, analog or digital, can then be transmitted, on the one hand, by the sensors 13-17 to the computer 9 and, on the other hand, by the computer 9 to the display 15.

[0082] As mentioned previously, the source 10 of electrical energy can equip a hybrid power plant 20 of an aircraft 1. The hybrid power plant 20 drives one or more rotors 2 in rotation, for example a lift rotor, a tail rotor or a propeller, via a mechanical transmission chain 5. The mechanical transmission chain 5 can in particular comprise a main power transmission box 25.

[0083] The hybrid power plant 20 may comprise at least one thermal engine 21, 22 mechanically connected to the mechanical transmission chain 5, as well as at least one electrical machine 23, 24 also mechanically connected to the mechanical transmission chain 5.

[0084] The electrical machine(s) 23, 24 are electrically connected to the electrical energy source 10, via an electrical transmission chain 6, so as to be powered by an electrical current delivered by the electrical energy source 10.

[0085] Such an electrical machine 23, 24 can operate in motor mode to transform electrical energy supplied by the electrical energy source 10 into mechanical energy transmitted to the lift rotor 2, via the mechanical transmission chain 5. The electrical machine 23, 24 can also operate in generator mode to transform mechanical energy supplied by the thermal engine(s) 21, 22 and / or the lift rotor 2, via the mechanical transmission chain 5, into electrical energy transmitted to the electrical energy source 10 via an electrical transmission chain 6, and intended to recharge the electrical energy storage device(s) 11, 12 of the source 10.

[0086] In this way, the thermal engine(s) 21, 22 as well as the electrical machine(s) 23, 24 can jointly or independently drive the rotor 2 in rotation, via the mechanical transmission chain 5. The source 10 of electrical energy can in particular be used to compensate for a breakdown of the thermal engine(s) 21,22 by supplying the electrical machine(s) 23,24 in order to drive the rotor 2 in rotation.

[0087] According to the example shown in [Fig. 1], the hybrid power plant 20 comprises a heat engine 21 and an electric machine 23. According to the example shown in [Fig. 2], the hybrid power plant 20 comprises two heat engines 21, 22 and two electric machines 23, 24. Alternatively, such a hybrid power plant 20 may comprise one or more heat engines 21, 22 and / or one or more electric machines 23, 24.

[0088] The aircraft 1 also comprises an avionics system 4 centralizing various information relating to the flight and operation of the aircraft 1, obtained using standard sensors and / or computers (not shown). The avionics system 4 can then display this information for the attention of a pilot of the aircraft 1. This information centralized by the avionics system 4 comprises, for example, a height relative to the ground, a forward speed and a vertical speed of the aircraft 1 measured by dedicated sensors, respectively by a height sensor, such as a radiosonde for example, a forward speed sensor such as an anemometer and a vertical speed sensor such as a variometer.

[0089] When the computer 9 is dedicated solely to the operation of the source 10, the computer 9 is connected by wire or wireless means to this avionics system 4. Such information relating to the flight and operation of the aircraft 1 can thus be transmitted to the computer 9, using electrical or optical, analog or digital signals.

[0090] In addition, instructions or a computer program may be stored in a memory of the computer 9 or in a memory connected to this computer 9. The computer 9 may then execute these instructions or this program to implement a method for monitoring an energy level of the electrical energy source 10.

[0091] [Fig.3] represents a block diagram of this method for monitoring an energy level of an electrical energy source 10. This method may comprise the following steps.

[0092] First of all, the method comprises an acquisition 110 of at least one parameter of the source 10 of electrical energy, carried out by means of the sensors 13-17, 13'-17'.

[0093] In this way, one or more first parameters relating to the source 10 of electrical energy, and in particular relating to the storage device(s) 11, 12 of electrical energy, and / or one or more second parameters relating to the electrical current flowing in the source 10 of electrical energy, and in particular relating to the electrical current flowing in the storage device(s) 11, 12 of electrical energy, are acquired. Signals carrying these parameters are, for example, transmitted by the sensors 13-17,13'-17' to the computer 9, and possibly stored in a memory of the computer 9 or connected to the computer 9.

[0094] During this acquisition 110, if the source 10 of electrical energy comprises at least two electrical energy storage devices 11, 12, an acquisition of at least one parameter for each of these storage devices 11, 12 is carried out.

[0095] Following this acquisition 110, the method comprises a calculation 120, carried out by the computer 9 as a function of the parameter(s) of the electrical energy source 10 previously acquired, of a main consumption duration DTprin during which the electrical energy source 10 is capable of providing an electric current carrying the reference electrical power PRef. The main consumption duration DTprin is calculated using this or these parameters, and one or more laws or charts stored in a memory of the computer 9 or in a memory connected to the computer 9. The main consumption duration DTprin may in particular be equal to the quantity of energy contained in the electrical energy source divided by the reference electrical power PRef, the quantity of energy being defined by the charge level of the source as well as possibly by its temperature, or even its aging.

[0096] Then, the method comprises the main display 210, on the display 15, of main symbols 31 indicating the main consumption duration DTprin.

[0097] The main symbols 31 can indicate the main consumption duration DTprin by displaying this main consumption duration DTprin in relation to the reference duration DTRef. The reference duration DTRef has been previously stored in a memory of the computer 9 or in a memory connected to the computer 9.

[0098] The main symbols 31 may comprise various shapes, such as a bar graph, a disc, a scale, or the like.

[0099] [Fig.4] represents a first example of main symbols 31 comprising a bar graph comprising eight bars each representing a duration equal to one eighth of the reference duration DTRef. The totality of the bars thus representing the reference duration DTRef corresponding to a charge level of the source 10 equal to or greater than the reference charge level NRef.

[0100] Thus, the filled squares jointly illustrate the main consumption duration DTprin while the empty square(s) represent the quantity of electrical energy from the source 10 already consumed. According to this first example, the source 10 of electrical energy has a main consumption duration DTprin equal to half the reference duration DTRef.

[0101] [Fig.5] shows a second example of the main symbols 31 comprising a disc. A full disc, i.e. one filled entirely, represents the duration of reference DTRef corresponding to a load level of source 10 equal to or greater than the reference load level NRef. When the main consumption duration DTprin is less than the reference duration DTRef, then an angular sector appears, for example, empty, and corresponds to the quantity of electrical energy from source 10 already consumed. According to this first example, the source 10 of electrical energy has a main consumption duration DTprin equal to three-quarters of the reference duration DTRef.

[0102] Independently of these forms, the main symbols 31 may also comprise main indexes 36 comprising numerical values corresponding to different values of the main consumption duration DTprin, as shown in FIGS. 4 and 5.

[0103] In addition, the main symbols 31 may include an alert zone 37 corresponding to a final consumption duration DTfin during which the electrical energy source 10 is capable of providing an electrical current carrying the reference electrical power PRef, before the electrical energy source 10 is no longer capable of providing electrical energy. Such an alert zone 37 is shown hatched in FIGS. 4 and 5, and corresponds to one eighth of the reference duration DTRef and is for example equal to 15 seconds. The final consumption duration DTfin is predetermined, and therefore independent of the parameter(s) of the source 10. In practice, such an alert zone 37 may be represented with a distinctive color, for example orange or red, and distinct from the color used to fill the boxes or angular sectors of the graphical representation of this main graph 31.

[0104] Thanks to this main display 210 of the main symbols 31, an operator or a pilot of the aircraft 1 clearly and quickly visualizes the main consumption duration DTprin during which the source 10 can provide the reference electrical power PRef II can thus optimize the use of the electrical energy that the source 10 of electrical energy comprises, in particular depending on the duration and the requirement of the flight until a landing in the case of an aircraft 1. The pilot can for example use a part of this electrical energy, while conserving a quantity of electrical energy to compensate for a possible breakdown of one or more thermal engines 21, 22.

[0105] This main display 210 advantageously takes into account the actual conditions of use of the electrical energy source 10 thanks to the parameters acquired from the source 10, and in particular its temperature, its charge level and its aging level, as well as the electrical current circulating in the source 10, whether the latter provides an electrical current to drive the rotor 2, or receives an electrical current to recharge the electrical energy storage device(s) 11, 12.

[0106] Furthermore, the method according to the invention may comprise an estimation 130 of at least one additional consumption duration DTcomp during which the source 10 of electrical energy is capable of providing an electric current carrying a complementary electrical power Pcomp different from the reference electrical power PRef. This estimation is carried out by the computer 9, as a function of the parameter(s) of the source 10 of electrical energy and the complementary electrical power Pcomp. The method according to the invention may also comprise a complementary display 220, on the display 15, of complementary symbols 32 indicating this complementary consumption duration DTcomp associated with this complementary electrical power Pcomp. The computer 9 may for example carry out a rule of three between the complementary electrical power Pcomp, the reference electrical power PRef and the main consumption duration DTprin to estimate the complementary consumption duration DTcomp.

[0107] The electrical energy source is not always requested to deliver the reference electrical power PRef. Therefore, it is not always obvious for an operator, or even a pilot of the aircraft 1, to estimate the duration during which the electrical energy source 10 is capable of delivering an electrical power different from the reference electrical power PRef, this lower electrical power possibly being higher or lower than the reference electrical power PRef.The additional display 220 of additional symbols 32 advantageously makes it possible to indicate one or more additional consumption durations DTcomp associated respectively with one or more additional electrical powers P comp, which allows the operator to know exactly the duration of use of such an additional electrical power Pcomp and to have a more precise idea of the duration of use of an electrical power different from the reference electrical power PRef and. of an additional electrical power Pcomp, this electrical power being able to be situated between an additional electrical power Pcomp and the reference electrical power PRef or between two additional electrical powers Pcomp.

[0108] [Fig.6] represents the main symbols 31, in the form of a bar graph provided with the main indexes 36, as well as the complementary display 32 for two complementary electrical powers Pcomp respectively equal to 50% and 75% of the reference electrical power PRef. The complementary display 32 also includes complementary indexes 38 comprising numerical values corresponding to different values of the complementary consumption duration DTcomp associated respectively with these complementary electrical powers P comp.

[0109] Furthermore, the method according to the invention may comprise a calculation 140 of a value of electrical power received or delivered by the source 10 of electrical energy carried out by the calculator 9 as a function of at least one parameter of the source 10 of energy. electrical, as well as an additional display 230, on the display 15, of this value 33 of electrical power received or delivered.

[0110] The operator or pilot of the aircraft 1 can thus easily see, on the one hand, whether the source 10 of electrical energy delivers electrical power to drive, for example, the lift rotor 2 or receives electrical power transmitted by the electrical machine(s) 23, 24, and, on the other hand, the value of this electrical power delivered or received.

[0111] Furthermore, to facilitate the understanding of the operator or pilot of the operating mode of the electrical energy source 10, distinct colors may be used for the additional display 230 of this value of electrical power received or delivered depending on whether the electrical energy source 10 receives or delivers this electrical power. A “-” sign and possibly a “+” sign may also be displayed in front of the value of the electrical power received or delivered, depending on whether the electrical energy source 10 receives or delivers this electrical power.

[0112] The main symbols 31 shown in [Fig.6] also include the additional display 230 of an electrical power value with a “-” sign corresponding to the electrical power received by the electrical energy source 10.

[0113] In the specific case where the source 10 of electrical energy equips an aircraft 1, the method may comprise a determination 150, by the computer 9, of the energy flows circulating in the mechanical transmission chain 5 and the electrical connection chain 6. The determination 150 essentially aims to determine the direction of circulation of the energy flows in the mechanical transmission chain 5 and the electrical connection chain 6, namely between on the one hand the lift rotor 2 and on the other hand the thermal engine(s) 21, 22, the electrical machine(s) 23, 24 as well as between the electrical machine(s) 23, 24 and the source 10 of electrical energy. The energy flow in the mechanical transmission chain 5 is unidirectional from the thermal engine(s) 21, 22 to the rotor 2 while it can be bidirectional between the electrical machine(s) 23, 24 and the rotor 2. The energy flow in the electrical connection chain 6 is bidirectional.

[0114] The directions of the energy flows in the mechanical transmission chain 5 can be defined for example using engine torque measurements on the thermal engine(s) 21, 22 and on the electrical machine(s) 23, 24 using torque meters. The direction of the energy flows in the electrical connection chain 6 can be defined using one or more second parameters relating to the electric current flowing in the electrical energy source 10.

[0115] The method then comprises a transfer display 240, on the display 15, of transfer symbols 34 provided with figurines 51-54 respectively representing the rotor of support 2, the thermal engine(s) 21,22, the electrical machine(s) 23,24 and the source 10 of electrical energy as well as arrows 61-63 representing the directions of circulation of these energy flows as shown in [Fig.7].

[0116] [Fig.7] represents the case of the aircraft 1 of [Fig.l], during an operation in which the engine 21, represented by a first figurine 51, and the electrical machine 23, represented by a second figurine 52, jointly drive in rotation the lift rotor 2, represented by a third figurine 53, the source 10 of electrical energy, represented by a fourth figurine 54, electrically supplying the electrical machine 23. The main symbols 31 can be displayed simultaneously with these transfer symbols 34 to indicate in particular the main consumption duration DTprin.

[0117] Thanks to these transfer symbols 34, the pilot of the aircraft 1 easily and instantly visualizes the energy exchanges within the mechanical 5 and electrical 6 transmission chains, as well as the operating mode of the electrical energy source 10, as an energy supplier or receiver.

[0118] In the specific case where the source 10 of electrical energy equips the aircraft 1, the method may comprise a determination 160 of characteristics of the aircraft 1, using the avionics system 4 and / or usual sensors of the aircraft 1 capable of determining these characteristics such as the height of the aircraft 1 relative to the ground, its forward speed and its vertical speed for example.

[0119] Then, the computer 9 can make an estimation 170 of at least one descent rate, then of at least one distance achievable by the aircraft 1 when the aircraft 1 uses only the electrical energy delivered by the electrical energy source 10. This estimation 170 is for example made from dedicated laws or charts stored in a memory of the computer 9 or in a memory connected to the computer 9. For this purpose, the computer 9 receives signals carrying information relating to the characteristic(s) of the aircraft 1 previously measured, as well as information relating to the parameter(s) of the electrical energy source 10 and can estimate one or more descent rates of the aircraft as a function of this or these characteristics of the aircraft 1, of the parameter(s) of the electrical energy source 10 and of one or more electrical powers that the electrical energy source 10 can supply to the electrical machine 23, 24.

[0120] This or these descent rates can be determined using charts or laws stored in a memory of the computer 9 or in a memory connected to the computer 9. These laws or charts can for example include polar curves characterizing the flight and the performance of the aircraft 9.

[0121] The computer 9 applies the characteristics of the aircraft 1 and an electrical power supplied by the source 10 of electrical energy to the electrical machine(s) 23,24 to these laws or charts to deduce the descent rate associated with this electrical power. A descent speed of the aircraft 1 using this electrical power and applying this descent rate can be determined simultaneously by the computer 9 using these laws and charts as a function of the characteristics of the aircraft 1 and the electrical power supplied by the electrical energy source 10. This operation can be repeated several times with different electrical powers.

[0122] Then, one or more distances achievable to the ground by the aircraft 1 are calculated by the computer 9 as a function of the estimated descent rate(s), the parameter(s) of the electrical energy source 10 and the characteristic(s) of the aircraft 1, in particular the height of the aircraft 1 relative to the ground. The consumption time associated with the electrical power used to determine the descent rate, and the descent speed corresponding to this electrical power and this descent rate are also taken into account as well as possibly a descent rate in autorotation of the aircraft 1.

[0123] Indeed, a descent trajectory 40 can be constructed by the computer 9 to the ground to determine the achievable distance. The achievable distance is then equal to the horizontal distance between the starting point of this descent trajectory, namely the current position of the aircraft 1, and the arrival point of this descent trajectory on the ground.

[0124] This descent trajectory 40 may comprise only a slope 45 according to the estimated descent rate if the consumption duration associated with the electrical power used to determine the descent rate allows the aircraft 1 to reach the ground directly at the associated descent speed.

[0125] Otherwise, the descent trajectory 40 comprises a first slope 46 according to this estimated descent rate corresponding to a flight during this consumption duration and to the descent speed, as well as a second slope 47 at an autorotation descent rate to the ground corresponding to a flight without engine power. The autorotation descent rate can be predetermined, before the flight, and possibly adjusted according to the current mass of the aircraft 1, using the laws or charts.

[0126] Furthermore, a reserve of electrical energy can be stored specifically to be consumed during the landing phase itself, to slow down the descent of the aircraft 1 for example at the moment of contact with the ground.

[0127] The estimation 170 may comprise one or more sub-steps, such as a sub-step 172 of constructing this descent trajectory 40 and / or a sub-step 174 of determining the descent speed associated with the estimated descent rate and the corresponding electrical power. A sub-step 175 of calculating the consumption duration associated with the electrical power corresponding to the descent rate estimated can also be carried out. This calculation sub-step 175 is carried out in an identical manner to the estimation 130 of at least one additional consumption duration DTcomp by considering the additional electrical power Pcomp equal to the electrical power corresponding to the estimated descent rate.

[0128] A sub-step 176 of calculating the autorotation descent rate can also be carried out by the computer 9, as a function of a current mass of the aircraft 1, provided for example by the avionics system 4 and a predetermined autorotation descent rate, stored in a memory of the computer 9 or in a memory connected to the computer 9.

[0129] The computer 9 can thus estimate during this estimation 170 a single descent rate relating to an electrical power, for example to the reference electrical power PRef, and the achievable distance corresponding to this descent rate. Alternatively, the computer 9 can estimate during this estimation 170 several distinct descent rates relating respectively to several distinct electrical powers, for example equal to the reference electrical power PRe / d to one or more complementary electrical powers Pcomp, then the achievable distances corresponding to each of these descent rates.

[0130] Finally, a descent display 250, on the display 15, of descent symbols 35 displaying at least one descent trajectory 40 of the aircraft 1 towards the ground 7 is produced, as shown in [Fig.8].

[0131] The descent symbols 35 can then make it possible to display one or more trajectories 40 of the aircraft 1 constructed respectively with a pair comprising a descent rate and the associated achievable distance.

[0132] The method may also comprise a determination 178 of a maximum achievable distance. This maximum achievable distance is equal to the greatest achievable distance among the estimated achievable distances and is associated with an optimal descent rate and an optimal electrical power. The descent symbols 35 may then make it possible to display only a single so-called “optimal” descent trajectory 41 of the aircraft 1 constructed with a pair comprising the optimal descent rate and the maximum achievable distance. Alternatively, the descent symbols 35 may make it possible to display several descent trajectories 40 of the aircraft 1 constructed respectively with a pair comprising a descent rate and the associated achievable distance, including the optimal trajectory 41 of the aircraft 1. [Fig. 8] represents such an example of descent display 250.

[0133] For each trajectory 40 of the aircraft 1 displayed, the value(s) of the electrical power, the descent rate and / or the associated achievable distance, or even the associated consumption duration, may also be displayed. In addition, the descent rate and the achievable distance may be corrected by the computer 9 as a function of a wind speed experienced by aircraft 1, using laws or charts stored in a memory of aircraft 1 taking this wind speed into account. This wind speed is for example provided by the avionics system 4.

[0134] Thanks to the descent display 250, the pilot can view, on the descent symbols 35, the descent trajectory(s) 40 of the aircraft 1 permitted to the ground 7 by the electrical energy available in the electrical energy source 10. Thus, in the event of failure of the thermal engine(s) 21, 22, the pilot of the aircraft 1 can adapt the electrical power supplied by the electrical energy source 10 to reach a landing zone.

[0135] In this way, the method according to the invention advantageously makes it possible to increase the flight safety of the aircraft 1, following a failure of the thermal engine(s) 21, 22. The determination 160 of at least one characteristic of the aircraft 1 and the estimation 170 of at least one descent rate and at least one achievable distance, as well as the steps resulting therefrom, can be carried out in parallel in particular with the calculation 120 of the main consumption duration DTprin and the descent display 250. The estimation 170 can alternatively be carried out independently of these steps 120, 250, and therefore carried out following the acquisition 110 of at least one parameter from the source 10.

[0136] Furthermore, to help the pilot choose an achievable landing zone following such a failure, the method may also include a location 180 of a current position of the aircraft 1, carried out for example using a satellite location device on board the aircraft 1, and the descent symbols 35 include a display of one or more achievable distances, or even only the maximum achievable distance, superimposed on a map of the environment of the aircraft 1 from the current position of the aircraft 1. The map of the environment flown over by the aircraft 1 has for example been previously stored in a memory of the aircraft 1. According to the example of [Fig.9], two achievable distances are represented in the form of circles 71, 72 centered on the current position of the aircraft 1.A first circle 71 corresponds to the maximum achievable distance while a second circle 72 corresponds to an achievable distance associated with the reference electrical power PRef. This achievable distance associated with the reference electrical power PRef can make it possible to avoid an obstacle, such as a mountain, by initially allowing a substantially horizontal flight using the reference electrical power PRef, then subsequently performing a descent towards the ground 7.

[0137] Finally, the method according to the invention can also include an assistance display 260 on the display 15, of assistance symbols 80 to help the pilot of the aircraft 1 to follow a descent trajectory 40.

[0138] The method may for example comprise a selection 190 of a chosen trajectory. among the descent trajectories 40 and the assistance symbols 80 may include an artificial horizon 85 and a descent marker 82 representative of the gradient rate corresponding to the chosen trajectory, as shown in [Fig. 10]. The descent marker 82 may be displayed on an artificial horizon instrument of the aircraft 1.

[0139] Alternatively or in a complementary manner, the method may comprise the selection 190 of a trajectory chosen from the descent trajectories 40 and the assistance symbols 80 may comprise a power indicator 86 of the aircraft 1 and a power marker 83 representative of the electrical power associated with the chosen trajectory, as shown in [Fig. 11]. The power marker 86 may be displayed on a power indicating instrument of the aircraft 1.

[0140] The selection 190 of a trajectory chosen from the descent trajectories 40 can for example be carried out automatically by the computer 9, the chosen trajectory being for example the optimal trajectory. Alternatively, the selection 190 of a trajectory chosen from the descent trajectories 40 can be carried out manually by the pilot using a selection device such as a touch screen for example.

[0141] Naturally, the present invention is subject to numerous variations as to its implementation. Although several embodiments have been described, it is understood that it is not conceivable to exhaustively identify all possible modes. It is of course conceivable to replace a means described by an equivalent means without departing from the scope of the present invention and the claims.

Claims

Claims

1. Method for monitoring an energy level of an electrical energy source (10), said electrical energy source (10) being capable of delivering a reference electrical power (PRef) during a predetermined reference duration (DTRef) for a predetermined reference charge level (NRef) and comprising: - at least one electrical energy storage device (11, 12), - at least one sensor (13-17), and - a calculator (9), characterized in that said method comprises the following steps: - acquisition (110) of at least one parameter of said electrical energy source (10) via said at least one sensor (13-17), - calculation (120) of a main consumption duration (DTprin ) during which said electrical energy source (10) is capable of supplying an electric current carrying said reference electrical power (PRef),depending on said at least one parameter of said source (10) of electrical energy, and - main display (210) of main symbols (31) indicating said main consumption duration (DTprin).,

2. The method of claim 1, wherein said at least one parameter is selected from a charge level, a temperature, and an aging of said source (10) of electrical energy, as well as an electrical intensity and an electrical voltage of an electrical current flowing in said source (10) of electrical energy.

3. Method according to claim 2, wherein when said source (10) of electrical energy comprises at least two storage devices (11, 12) of electrical energy, said at least one parameter comprises one or more parameters relating to each of said storage devices (11, 12).

4. A method according to any one of claims 1 to 3, wherein said main symbols (31) comprise an alert zone (37) corresponding to a predetermined final consumption duration (DTfin) during which said source (10) of electrical energy is capable of providing an electrical current carrying said reference electrical power (PRef), before said source (10) of electrical energy is not capable of providing electrical energy.

5. Method according to any one of claims 1 to 4, wherein said method comprises an estimation (130) of at least one complementary consumption duration (DTcomp) during which said source (10) of electrical energy is capable of supplying an electric current carrying a complementary electrical power (Pcomp) different from said reference electrical power (PRef), as a function of said at least one parameter of said source (10) of electrical energy and of said complementary electrical power (PcompY and a complementary display (220) of complementary symbols (32) indicating said complementary consumption duration (DTcompY

6. Method according to any one of claims 1 to 5 wherein said source (10) of electrical energy equips an aircraft (1) comprising a hybrid power plant (20) and a lift rotor (2) driven in rotation by said hybrid power plant (20) via a mechanical transmission chain (5), said hybrid power plant (20) comprising at least one heat engine (21, 22), at least one electrical machine (23, 24) and said source (10) of electrical energy electrically connected to said at least one electrical machine (23, 24) via an electrical connection chain (6), said method comprises a determination (150) of energy flow circulating in said mechanical transmission chain (5) and said electrical connection chain (6), and a transfer display (240) of transfer symbols (34) provided with figurines (51-54) respectively representing said lift rotor (2), said at least one heat engine (21,22),said at least one electrical machine (23,24) and said source (10) of electrical energy as well as arrows (61-63) representing said energy flows between said lift rotor (2) and respectively said at least one heat engine (21,22) and said at least one electrical machine (23,24) as well as between said source (10) of electrical energy and said at least one electrical machine (23,24).,

7. Method according to any one of claims 1 to 6, in which said source (10) of electrical energy equips an aircraft (1) comprising a hybrid power plant (20) and a lift rotor (2) driven in rotation by said hybrid power plant (20) via a mechanical transmission chain (5), said hybrid power plant (20) comprising at least one heat engine (21, 22), at least one electrical machine (23, 24) and said source (10) of electrical energy electrically connected to said electric machine (23, 24) via an electrical connection chain (6), said method comprises a determination (160) of at least one characteristic of said aircraft (1), an estimation (170) of at least one descent rate and at least one distance achievable using only electrical energy that can be delivered by said source (10) of electrical energy as a function of said at least one parameter of said source (10) of electrical energy and of said at least one characteristic of said aircraft (1) of said aircraft (1),and a descent display (250) of descent symbols (35) representing at least one descent trajectory (40) of said aircraft (1) as a function of said descent rate and said achievable distance.,

8. Method according to claim 7, wherein during said estimation (170), several descent rates and several achievable distances are estimated, being associated respectively with several distinct electrical powers which can be delivered by said source (10) of electrical energy, and several descent trajectories (40) are displayed.

9. The method of claim 8, wherein said method comprises determining (178) a maximum achievable distance equal to the greatest of said achievable distances, said maximum achievable distance being associated with an optimal descent rate and an optimal electrical power.

10. Method according to any one of claims 8 to 9, wherein said method comprises a location (180) of a current position of said aircraft (1) and said descent symbols (35) comprise at least one achievable distance displayed superimposed on a map of the environment of said aircraft (1) from said current position of said aircraft (1), said at least one achievable distance displayed being chosen from said at least one estimated achievable distance.

11. A method according to claims 9 and 10, wherein said at least one displayed reachable distance comprises said maximum achievable distance and a reference achievable distance associated with said reference electrical power (PRef).

12. A method according to any one of claims 8 to 11, wherein said method comprises a selection of a trajectory (190) chosen from said descent trajectories (40) and an assistance display (260) of descent symbols (35) comprising an artificial horizon (85) and a descent marker 82 representative of said gradient rate corresponding to said chosen trajectory.

13. A method according to any one of claims 8 to 12, wherein said method comprises a selection (190) of a trajectory chosen from said descent trajectories (40) and an assistance display (260) of descent symbols (35) comprising a power indicator (86) of said aircraft (1) and a power marker representative of said electrical power corresponding to said chosen trajectory.

14. A method according to any one of claims 7 to 13, wherein said at least one descent trajectory (40) comprises a first slope (46) according to said estimated descent rate corresponding to flight with electrical power supplied by said source (10) of electrical energy and a second slope (47) at an autorotational descent rate to the ground corresponding to flight without engine power.

15. Method according to any one of claims 7 to 14, in which method comprises a step of constructing (172) said descent trajectory (40) and / or a step of determining (174) a descent speed of said aircraft (1) associated with said estimated descent rate and with said corresponding electrical power, and / or a step of calculating (175) a consumption duration associated with said electrical power corresponding to said descent rate.

16. Method according to any one of claims 7 to 15, wherein said characteristics of said aircraft (1) are chosen from a height relative to the ground, a forward speed, a vertical speed of said aircraft (1).

17. A method according to any one of claims 7 to 16, wherein said descent rate and said achievable distance are corrected as a function of a wind speed experienced by said aircraft (1).

18. Source (10) of electrical energy capable of delivering a reference electrical power (PRef) during a predetermined reference duration (DTRef) completed for a predetermined reference load level (NRef) comprising: - at least one electrical energy storage device (11, 12), and - at least one sensor (13-17), characterized in that said source (10) of electrical energy comprises a computer (9) configured to implement the method according to any one of claims 1 to 5.

19. Aircraft (1) comprising a hybrid power plant (20) and a lift rotor (2) driven in rotation by said hybrid power plant (20) via a mechanical transmission chain (5), said hybrid power plant (20) comprising at least one heat engine (21, 22), at least one electric machine (23, 24) and a source (10) of electrical energy electrically connected to said electric machine (23, 24) via an electrical connection chain (6), said source (10) of electrical energy comprising at least one storage device (11, 12) of electrical energy and at least one sensor (13-17), said source (10) of electrical energy being capable of delivering a reference electrical power (PRef) for a predetermined reference duration (DTRef) for a predetermined reference load level (NRef),characterized in that said source (10) of electrical energy comprises a computer (9) configured to implement the method according to any one of claims 1 to 17.,

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