Monitoring of aircraft propulsion systems

Abstract

The invention relates to a method for monitoring a propulsion system (102) of an aircraft (100), the method comprising:-calculating a margin of a parameter (NG, T4x) of a thermal chain (TH) as a margin (PMD1, PMT1) of the thermal chain (TH); -calculating a margin of the parameter (IBAT) of the electrical chain (ELEC), taking at least a portion of the margin as the margin of the electrical chain (ELEC); adding the margin (PMD1, PMT1) of the thermal chain (TH) to the margin of the electrical chain (ELEC) to obtain a total margin (ePMD) of the propulsion system (102); and-transmitting the total margin to a display device (AF) of the aircraft (100) such that the display device (AF) displays the total margin (ePMD).

Description

Technical Field

[0001] The present invention relates to hybrid propulsion systems for aircraft, and more particularly to parallel hybrid propulsion for helicopters. Background Art

[0002] A non-hybrid propulsion system generally comprises a thermal chain for driving a rotary propulsion unit of the aircraft, for example, in the case where the aircraft is a helicopter, for driving a main rotor and an anti-torque rotor.

[0003] The propulsion system has several certified speeds which define the power limits. It is known that the available power margin can be calculated for each speed. To this end, the power margins for several parameters in the thermal chain are calculated and the minimum margin is selected from them.

[0004] In addition, the aircraft includes a flight control indicator designed to display synthetic information to the pilot so that he can always know the power margin available before reaching the power limit of the certified speed. This indicator is called the "first limit indicator (indicateur de première limite, IPL)" and informs the pilot of the remaining power margin.

[0005] Furthermore, on the basis of the thermal chain redundancy, the hybrid propulsion system also comprises an electrical chain for driving the rotary propulsion unit. Such redundancy enables the aircraft to land in satisfactory safety conditions in the event of a thermal chain failure. A typical application example is a parallel hybrid helicopter propulsion system consisting of a turboshaft engine and an electric motor, which together drive the main rotor and the anti-torque rotor. However, the invention is more widely applicable to hybrid aircraft propulsion systems that do not necessarily have such rotors.

[0006] The object of the present invention is to adapt the calculation of the power margin to the case of a hybrid propulsion system. Summary of the invention

[0007] A method for monitoring a propulsion system of an aircraft is proposed, the propulsion system comprising a rotary propulsion unit and a thermal chain for driving the rotary propulsion unit, the method comprising: - calculation of a threshold value of a parameter of the thermal chain, which parameter must remain below said threshold value in order for the power provided by the thermal chain to be below a predefined maximum power; - calculating a margin of the parameter of the thermal chain relative to a threshold value of the parameter of the thermal chain, wherein the margin is taken as the margin of the thermal chain; Characterized in that the propulsion system further comprises an electrical chain, the electrical chain being used to drive the rotary propulsion unit in parallel with the thermal chain, the method further comprising: - calculating a threshold value of a parameter of the electrical chain, which parameter must remain below said threshold value in order for the power supplied by the electrical chain to be below a predefined maximum power; - calculating a margin of a parameter of the electrical chain relative to a threshold value of the parameter of the electrical chain, wherein at least a part of the margin is used as the margin of the electrical chain; - Add the margin of the thermal chain to the margin of the electrical chain to obtain the total margin of the propulsion system; - transmitting the total margin to a display device of the aircraft so that the display device displays the total margin; and wherein the propulsion system has at least one certified operating speed, the at least one certified operating speed defining a non-zero power supply duration of the electrical chain, the method further comprising: - checking whether the energy storage source of the electric chain is sufficiently charged to enable the electric chain to maintain a parameter with a minimum margin at the threshold value of this parameter for a defined power supply duration; and - If the electrical energy storage source is sufficiently charged, the margin of the electrical chain is added to the margin of the thermal chain to obtain the total margin.

[0008] The invention may also include one or more of the following optional features in any technically possible combination.

[0009] Optionally, the method further comprises: - calculating, for each of a plurality of parameters of the electrical chain, a threshold value below which this parameter must remain in order for the power supplied by the electrical chain to be below a predefined maximum power; and - for each of a plurality of parameters of the electrical chain, calculating a margin of the parameter relative to a threshold value of the parameter; and - determining a minimum margin among a plurality of margins of a plurality of parameters in the electrical chain, wherein the minimum margin is taken as the margin of the electrical chain.

[0010] Also optionally, the propulsion system has at least one certified operating speed, the at least one certified operating speed defining a threshold value for each of a plurality of parameters in the thermal chain, the method further comprising: - Calculate the margins for each parameter in the electrical chain; and - determining a minimum margin among a plurality of margins of a plurality of parameters in the thermal chain, wherein the minimum margin is taken as the margin of the thermal chain.

[0011] Optionally, the method further comprises: - If the electrical energy storage source is not sufficiently charged, the overall margin is set equal to the margin of the thermal chain.

[0012] Also optionally, if the electrical energy storage source is not fully charged, the margin of the parameter is set to zero.

[0013] Also optionally, if the electrical energy storage source is not sufficiently charged, the margin of the parameter is taken to be equal to the state of charge divided by the predefined power supply duration.

[0014] Also optionally, the method further includes: transmitting the margin of the thermal link to a display device for displaying to a pilot in the aircraft.

[0015] A computer program capable of being downloaded from a communication network and / or recorded on a computer-readable medium is also proposed, characterized in that, when the program is executed on a computer, the computer program comprises instructions for executing the steps of the method according to the invention.

[0016] An aircraft is also proposed, comprising: - a propulsion system for an aircraft, the propulsion system comprising a rotary propulsion unit, and a thermal chain for driving the rotary propulsion unit; - display device; and - a computer designed to implement the method according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The invention will be better understood with the aid of the following description, which is given by way of example only and is made with reference to the accompanying drawings, in which: - Figure 1 Functional diagram of an aircraft for implementing the invention, - Figure 2 For monitoring Figure 1 A block diagram of a method for a propulsion system of an aircraft is shown, and - Figure 3 for Figure 1 A view of the aircraft's first limit indicator. DETAILED DESCRIPTION

[0018] Reference Figure 1 , an example of an aircraft 100 embodying the present invention will now be described.

[0019] The aircraft 100 may be a fixed-wing or rotary-wing aircraft (such as in the case where the aircraft is a helicopter), or may be a vertical take-off and landing (VTOL) aircraft.

[0020] Thus, the aircraft includes a propulsion system 102 .

[0021] The propulsion system 102 includes at least one rotary propulsion unit 104. In the case where the aircraft is a helicopter, the propulsion system 102 includes, for example, two rotary propulsion units: a main rotor designed to enable lift, control and propulsion, and an anti-torque rotor designed to counteract the torque caused by the main rotor. Alternatively, the rotary propulsion unit 104 may be a propeller or a fan.

[0022] The propulsion system 102 further comprises a thermal chain TH for driving each rotary propulsion unit 104. In the example shown, the thermal chain TH comprises a single turboshaft engine TM. Alternatively, the thermal chain TH may comprise several turboshaft engines.

[0023] In particular in the case where the aircraft is a helicopter, the propulsion system 102 also comprises, for example, a main gearbox BTP comprising an input shaft A1 connected to the thermal chain TH and an output shaft connected to the rotary propulsion unit 104 .

[0024] The propulsion system 102 also includes an electrical chain ELEC for each rotary propulsion unit 104. The electrical chain ELEC includes, for example, an electrical energy storage source BAT and a motor M connected to the electrical energy storage source BAT. The electrical energy storage source BAT may include one or more basic power sources, such as one or more chemical batteries or any other type of electrical energy storage device. Similarly, the motor M may include one or more basic motors. The motor M is designed to operate selectively, on the one hand as a motor receiving power from the electrical energy storage source BAT, and on the other hand as a generator supplying power to the electrical energy storage source BAT to recharge the electrical energy storage source BAT. Alternatively, the motor M may be designed to operate only as a motor.

[0025] Due to the presence of the thermal chain TH and the electrical chain ELEC, the propulsion system 102 is referred to as a hybrid system.

[0026] In the case of a so-called parallel hybrid as shown in the figure, the main gearbox BTP comprises a second input shaft A2 connected to the electric chain ELEC, in particular to the electric machine M.

[0027] The aircraft 100 also comprises a computer CALC for controlling the propulsion system 102 , more specifically the thermal link TH and the electrical link ELEC.

[0028] The propulsion system 102 has at least one certified operating speed. This means that the engine manufacturer guarantees that, for each speed, the thermal chain TH and the electrical chain ELEC are each able to provide the maximum power associated with that speed (called the limit), possibly for a predefined duration associated with that speed. This duration is limited and can be zero. In the absence of an associated duration, the manufacturer guarantees that the maximum power can be reached for as long as necessary and in any case for very long durations, for example up to the typical duration of the mission.

[0029] The maximum power and duration may be different for the thermal chain TH and the electrical chain ELEC. Thus, generally, each speed defines the maximum power and possible duration of the thermal chain TH on the one hand and the electrical chain ELEC on the other hand.

[0030] Each limit may be "controlled", ie indicative. It is then up to the pilot to comply with the limit according to information in the user manual of the propulsion system 102. If the power requested by the pilot exceeds the driving limit, the computer CALC is designed to allow the propulsion system 102 to exceed the driving limit.

[0031] Each limit may alternatively be "controlled", ie the computer CALC is designed to prevent the limit from being crossed, even if the pilot requests the computer CALC to cross the limit. Controlled limits are sometimes called "butées".

[0032] For example, propulsion system 102 may have one or more of the following speeds.

[0033] The propulsion system 102 may have a continuous speed C associated with a controlled limit PMC (Puissance Maximum Continue), which is the maximum power that the thermal chain TH can deliver continuously, ie throughout the duration of a mission of the aircraft 100 , or even several missions.

[0034] The propulsion system 102 may have a driving limit PMD TH (PMD at maximum take-off power) and driving limit PMD ELEC The associated maximum takeoff speed D, the piloting limit PMD TH The hot link TH can be used for a predefined duration T_PMD TH Delivered power within the driving limit PMD ELEC The electrical chain ELEC can be used for a predefined duration T_PMD ELEC The power delivered during the duration T_PMD TH and T_PMDELEC Typically it is of the order of several minutes (usually of the order of fifteen to thirty minutes).

[0035] The propulsion system 102 may have a PMT with a controlled limit TH (PMT is Puissance Maximum Transitoire maximum transient power) and controlled limit PMT ELEC The associated maximum transient speed T, controlled limit PMT TH is the maximum instantaneous power that the hot chain TH can deliver, controlled by the limit PMT ELEC is the maximum instantaneous power that the electric chain ELEC can deliver. For the maximum transient speed T, the duration of the thermal chain TH and the duration of the electric chain are both zero.

[0036] In order to calculate the different information to be displayed to the pilot (as will be explained in more detail later), the aircraft 100 comprises several measurement systems.

[0037] More specifically, the aircraft 100 firstly comprises a system S for monitoring the thermal chain TH. TH , the system S TH Designed to measure at least one parameter of the thermal chain TH that has an influence on the power supplied by the thermal chain TH. For example, the speed NG of the gas generator of the turboshaft engine TM, and / or the temperature T4x of the gas driving one or more power turbines of the turboshaft engine TM, and / or the torque C provided by the turboshaft engine or the engine of the thermal chain TH TM .

[0038] The aircraft 100 also comprises a system S for monitoring the electrical chain ELEC ELEC , the system S ELEC Designed to measure at least one parameter of the electrical chain ELEC having an influence on the power supplied by the electrical chain ELEC.

[0039] In the following, parameters that have an influence on the power provided by the thermal chain TH and the power provided by the electrical chain ELEC are referred to as main parameters.

[0040] Measuring system ELEC Including for example System S BAT , the system S BAT For measuring at least one parameter of the electric energy storage source BAT, such as the current I supplied by the electric energy storage source BAT to the motor M BAT and / or the state of charge SOC of the electrical energy storage source BAT. BAT or in addition to the measuring system S BAT In addition, the measurement system S ELEC Including for example System S M , the system SM For measuring at least one parameter of the motor M, such as the torque C provided by the motor M M . Measuring system S ELEC It is also designed, for example, to measure at least one other so-called auxiliary parameter of the electrical chain ELEC, for example by the measuring system S BAT Measured temperature T of the electrical energy storage source BAT BAT and / or the charging power PR of the energy storage source BAT. For example, according to the current I BAT and the voltage measured at the terminals of the electrical energy storage source BAT to calculate the charging power PR.

[0041] The aircraft 100 also comprises, for example, an external monitoring system S0 designed to measure at least one atmospheric parameter surrounding the aircraft 100 , such as the atmospheric pressure P0 and / or the atmospheric temperature T0 .

[0042] The aircraft 100 also comprises a display device AF designed to display information transmitted by the computer CALC.

[0043] The aircraft 100 may also include an input device SA designed to allow the pilot to input information to the computer CALC, in particular the target service life DDV_cible. The input device SA may take various forms, such as a (potentiometer-type) adjustment knob on the aircraft dashboard, an input keyboard on the screen, etc.

[0044] Reference Figure 2 , an example of a method 200 for monitoring a propulsion system 102 according to the present invention will now be described.

[0045] During a step 202 , the computer CALC receives the measured values ​​of each parameter.

[0046] In the example shown, the computer CALC receives: - Main parameters of hot chain TH: NG, T4x, C TM The measured values ​​of NG_m, T4x_m, C TM _m, -Main parameters of electrical chain ELEC BAT , C M The measured value I BAT _m, C M _m, - Auxiliary parameters T of the electrical chain ELEC BAT , SOC measurement value T BAT _m, SOC_m, and -Measured values ​​P0_m, T0_m of atmospheric parameters P0, T0.

[0047] During a step 204, the computer CALC calculates, for each speed and for each main parameter of the hot chain TH, the threshold value below which the main parameter in question must remain in order for the power supplied by the hot chain TH to be lower than the maximum power of this hot chain TH at the speed in question. This calculation is based, for example, on one or more other measured parameters, such as one or more atmospheric parameters.

[0048] In the example shown, the computer CALC uses, for example, the measured values ​​P0_m, T0_m: - For the continuous speed C, calculate the thresholds NG_C, T4x_C and C TM _C, - For takeoff speed D, calculate the thresholds NG_D, T4x_D and C TM _D, and - For the transient speed T, calculate the thresholds NG_T, T4x_T and C TM _T.

[0049] During a step 206 , the computer CALC calculates, for each speed and each main parameter of the heat source TH, the difference between the measured value and the threshold value of the main parameter in question, this difference forming the margin of the main parameter in question.

[0050] In the example shown, the computer CALC: - For the continuous speed C, calculate the margins ΔNG_C, ΔT4x_C and ΔC TM _C, - For takeoff speed D, calculate the margins ΔNG_D, ΔT4x_D and ΔC TM _D, and - for the transient speed T, calculate the margins ΔNG_T, ΔT4x_T and ΔC TM _T.

[0051] In step 208, the computer CALC calculates, for each speed of finite duration (possibly zero) and for each main parameter of the electric chain ELEC, a threshold value below which the main parameter in question must remain in order for the power supplied by the electric chain ELEC to be lower than the maximum power of this electric chain ELEC at the speed in question. This calculation is based, for example, on one or more other measured parameters, such as one or more atmospheric parameters.

[0052] In the example shown, the computer CALC is based on the measured values ​​SOC_m, T BAT _m, P0_m and T0_m: - For takeoff speed D, calculate threshold I BAT _D and C M _D, and - Calculate the threshold I for the instantaneous speed TBAT _T and C M _T.

[0053] Therefore, no threshold is calculated for the continuous speed C of the electric chain ELEC.

[0054] During a step 210 , the computer CALC calculates, for each speed and each main parameter of the electric chain ELEC, of ​​finite duration (possibly zero), the difference between the measured value and the threshold value of the main parameter in question, this difference forming an intermediate margin for the main parameter in question.

[0055] In the example shown, the computer CALC: - Calculate the intermediate margin ΔI for takeoff speed D BAT _D′ and ΔC M _D′, and -Calculate the intermediate margin ΔI for the transient speed T BAT _T′ and ΔC M _T′.

[0056] In step 212, the computer CALC converts the margins calculated in steps 206 and 210 into the same unit, which may be the unit of any physical quantity. Preferably, the physical quantity is "meaningful" to the pilot and directly related to the pilot's driving. For example, the unit chosen is power, so the margin is converted into a power margin. After conversion in this way, the margins can be compared and / or summed. The power is, for example, the mechanical power provided.

[0057] For example, the current margin I BAT Multiply the voltage of the energy storage source BAT and the efficiency of the motor M to convert the current margin I BAT Expressed as power.

[0058] For example, the torque margin C M Multiply the torque margin C by the rotation speed of the motor M M Expressed as power.

[0059] For example, the parameters of the thermal chain TH can be converted into power using a model of a turboshaft engine TM and assuming that all other parameters of the engine are constant.

[0060] Furthermore, during step 212, a threshold value of a main parameter of the electrical chain ELEC (in the example shown, parameter I BAT and C M The threshold value) is also converted into the selected unit, for example into power.

[0061] During a step 214, for each speed having a non-zero finite duration associated with the electric chain ELEC, the computer CALC checks whether the electric energy storage source BAT is sufficiently charged to enable the electric chain ELEC to provide the power threshold of this parameter during the associated duration. In particular, to evaluate the charge of the electric energy storage source BAT, for example, a measurement SOC_m of the state of charge SOC of the electric energy storage source BAT can be used. Alternatively, a State Of Energy (SOE) measurement can be used.

[0062] For example, for takeoff speed D and current I BAT , the computer CALC checks whether: SOC ≥ I BAT _D×T_PMD ELEC , I BAT _D is expressed in power, T_PMD ELEC is the maximum duration of the take-off speed D of the electrical chain.

[0063] If the electrical energy storage source BAT is fully loaded, the margin of the main parameter in question is considered to be equal to its intermediate margin. In this case, for example, the parameter I BAT The margin ΔI BAT _D is considered equal to the intermediate margin ΔI BAT _D′.

[0064] Otherwise, the margin of the main parameter in question is considered to be smaller than the intermediate margin.

[0065] In the first example, the parameter margin is considered to be zero. In this case, for example, if SOC BAT _D×T_PMD ELEC , then parameter I BAT The margin ΔI BAT _D is considered to be zero.

[0066] In a second example, if the electrical energy storage source BAT is not sufficiently charged, the parameter margin is considered equal to the state of charge SOC divided by the duration associated with the speed of the electrical chain ELEC. In this case, for example, if the SOC BAT _D×T_PMD ELEC , then parameter I BAT The margin ΔI BAT _D is considered equal to SOC / T_PMD ELEC .

[0067] During step 216, for each speed having an associated zero duration, the margin of the main parameter in question is then considered equal to its intermediate margin. In this case, for example, parameter I BAT The margin ΔI​​BAT _T is considered equal to the intermediate margin ΔI BAT _T′.

[0068] During step 218, when several parameters of the thermal chain TH are used, the computer CALC compares the margins of these parameters for each state to select the smallest margin. The selected margin is taken as the margin of the thermal chain TH.

[0069] For example, the margin of the hot chain TH is: PMC for the continuous speed C, PMD1 for the take-off speed D, and PMT1 for the transient speed T.

[0070] During a step 220 , when using several parameters of the electric chain ELEC, the computer CALC compares the margins of these parameters for each speed in order to select the smallest margin.

[0071] For example, the margin of the electrical chain ELEC is: denoted as ΔP for takeoff speed D ELEC _PMD, for transient speed T, denoted as ΔP ELEC _PMT.

[0072] During a step 222 , the computer CALC adds, for each speed, the minimum margin of the thermal chain TH to the minimum margin of the electrical chain ELEC, this addition forming the overall margin of the propulsion system 102 for the speed in question.

[0073] For example, for takeoff speed D, the total margin is ePMD, and is equal to: ePMD = PMD1 + ΔP ELEC In a similar manner, for the transient speed T, the total margin is recorded as ePMT and is equal to: ePMT = PMT1 + ΔP ELEC _PMT.

[0074] The computer CALC transmits the total margin associated with each speed to the display device AF during a step 224. Furthermore, the computer CALC may transmit the margin of the thermal chain TH separately for each speed (without transmitting the margin of the electrical chain ELEC).

[0075] In the example shown, the computer CALC delivers: margins ePMD and margin PMD1 for the take-off speed D, and margin ePMT for the transient speed T. For the continuous speed C, the computer CALC delivers margin PMC.

[0076] In step 226 , display device AF displays the received margin. Display device AF also displays the total power provided by propulsion system 102 .

[0077] Furthermore, during flight, the computer CALC is designed so that the power provided by the propulsion system 102 is allocated to the needs of the aircraft (e.g., the power required by the main rotor and the anti-torque rotor to perform the maneuvers commanded by the pilot) before recharging the electric energy storage source BAT. When the power provided by the thermal link TH decreases, the recharging of the electric energy storage source BAT is reduced to ensure that the pilot has access to power. This operation can be performed automatically so that the pilot only needs to focus on the flight. However, in this case, when flight conditions permit (e.g., in cruise flight or during descent close to landing), it may be useful to provide the pilot with summary information to help the pilot manage the recharging of the electric energy storage source BAT.

[0078] To this end, during step 228, the computer CALC calculates the maximum charging power of the electric energy storage source BAT, for example based on measured parameters such as the state of charge SOC of the electric energy storage source BAT, the temperature T of the electric energy storage source BAT BAT and the atmospheric temperature T0. This maximum charging power is calculated, for example, by a mathematical function or a table consisting of values ​​depending on the relevant parameters and is stored in a memory accessible to the computer CALC. This limit can be expressed as power (in Watts), current or any other quantity or measurement unit chosen by the designer.

[0079] In a step 230 , the computer CALC receives a measurement of the charging power PR from the electrical energy storage source BAT.

[0080] In step 232 , the computer CALC calculates the difference between the charging power measurement value PR and the maximum charging power, which forms a transient charging power margin ΔPR.

[0081] In step 234 , the computer CALC transmits the transient charging power margin ΔPR to the display device AF.

[0082] In step 236 , the display device AF displays the instantaneous charging power margin ΔPR to the pilot.

[0083] In step 238, the computer CALC calculates the difference between the target state of charge SOC* and the measured value SOC_m of the state of charge SOC, which difference forms the energy remaining to be recharged. The parameters of the energy storage source BAT (for example, the voltage at the terminals of the energy storage source BAT and the current I BAT )’s measured values ​​and the mathematical model of the energy storage source BAT to measure the state of charge SOC.

[0084] In step 240, the computer CALC calculates the maximum charging power distribution of the electric energy storage source BAT until the target state of charge SOC*. The parameters of the electric energy storage source BAT (e.g., the voltage at the terminals of the electric energy storage source BAT and the current I BAT ) and a mathematical model of the electrical energy storage source BAT to calculate the distribution.

[0085] In a step 242 , the computer CALC receives a measurement of the charging power PR from the electrical energy storage source BAT.

[0086] During a step 244 , the computer CALC calculates the charging power profile by selecting for each point the minimum value between the maximum charging power profile and the current power.

[0087] In step 246, the computer CALC obtains the remaining recharging time TR by calculating the integral of the ratio between the remaining energy to be charged and the charging power profile. In practice, the integral can be obtained by the control system by calculating the sum of the intervals of the discretized power trajectory.

[0088] In a step 248 , the computer CALC transmits the remaining recharging time TR to the display device AF.

[0089] In step 250, the display device AF displays the remaining recharging time TR.

[0090] In addition, the service life (or conversely, the damage rate) of the turboshaft engine TM depends on its power demand. This service life mainly depends on the rotation speed of the rotating components (for example, the speed of the gas generator NG, the free turbine, etc.: NTL / N2) and the temperature T4x.

[0091] Two damage modes are usually considered: cyclic fatigue and creep.

[0092] The computer CALC includes a cycle fatigue counter FC and a creep counter EF.

[0093] Cyclic fatigue is initiated by mechanical stresses caused by centrifugal accelerations experienced by the rotating components (compressor(s), high-pressure turbine(s), low-pressure turbine(s).

[0094] The cycle fatigue counter FC is designed to count the cycles of speed NG over time. For each mission (i.e., the period of time the aircraft is turned on), these cycles typically include the main cycle between start (zero speed NG) and maximum mission speed and partial cycles during the mission.

[0095] For example, the cycle fatigue counter FC is designed to calculate the increment dC_FC at each time step based on the measured value NG_m of the speed NG at that time step and the historical values ​​of the measured values ​​of the speed NG by implementing the predefined damage law f1: dC_FC=f1(NG_m, previous measurement value).

[0096] Creep characterizes the expansion of the turbine blades on a turboshaft engine TM. Creep is caused by the combined effect of centrifugal acceleration and the high temperatures to which the rotating parts are subjected. Creep therefore depends on the power the pilot requires from the engine and on the atmospheric conditions P0, T0.

[0097] The creep counter EF is designed to calculate at each time step an increment dC_EF from the measured values ​​NG_m of the speed NG and the measured values ​​T4x_m of the temperature T4x at that time step by implementing a predefined damage law f2: dC_EF=f2(NG_m, T4x_m).

[0098] When one of the counters FC, EF reaches a predefined threshold value (denoted C_FC_max for the cycle fatigue counter FC and C_EF_max for the creep counter EF), maintenance of the turboshaft engine TM must be performed.

[0099] To enable pilots to manage their flights to achieve the desired service life, the following steps can be implemented.

[0100] In step 252, the input device SA receives the target service life DDV_cible from the propulsion system 102 and transmits it to the computer CALC. The target service life DDV_cible is input by the pilot, for example, and can be adjusted before each flight according to the compromise between the operating costs of the aircraft and the services provided in the mission (onboard load and flight duration).

[0101] During a step 254 , the computer CALC receives a target useful life DDV_cible.

[0102] In a step 256 , the computer CALC calculates, for each counter FC, EF, the maximum rate of increment of the counter FC, EF that remains below a predefined threshold value during the target useful life DDV_cible.

[0103] In a first example, the maximum increment rate is calculated assuming that the wear is linear over the entire target service life DDV_cible. Therefore, the maximum increment rate dC_FC_max of the cycle fatigue counter FC is given by: dC_FC_max=C_FC_max / DDV_cible, and the maximum increment rate dC_EF_max of the creep counter EF is given by: dC_EF_max=C_EF_max / DDV_cible. Therefore, the maximum increment rate is constant as long as the target service life DDV_cible is not modified.

[0104] In a second example, each maximum increment rate is calculated "dynamically" based on the past use of the turboshaft engine TM. In this way, each maximum increment rate is calculated by taking into account the linear wear according to the current conditions, the current counter values ​​FC, EF and the part DDV_écoulée of the target service life DDV_cible that has already passed. The maximum increment rate dC_FC_max of the cycle fatigue counter FC is given by the following formula: dC_FC_max = (C_FC_max-C_FC_courante) / DDV_cible-DDV_écoulée), and the maximum increment rate dC_EF_max of the creep counter EF is given by the following formula: dC_EF_max = (C_EF_max-C_EF_courante) / DDV_cible-DDV_écoulée). It will be understood that DDV_cible-DDV_écoulée is equal to the remaining service life, recorded as DDV.

[0105] In this manner, if the turboshaft engines are frequently used at high power levels at the beginning of a mission (e.g., using the turboshaft engines at power levels close to power PMD during takeoff and climb), the maximum increment rate is adjusted downward to encourage the pilot to use the turboshaft engines less during the remainder of the flight.

[0106] In step 258, the computer CALC calculates a threshold value NGmax_FC for the speed NG as a function of the cyclic fatigue counter FC and the maximum rate of increment of the cyclic fatigue counter FC. More specifically, knowing the history of the measured values, by converting the inverse damage law f1 -1 Applied to the maximum incremental rate dC_FC_max to calculate the threshold NGmax_FC: NGmax_FC = f1 -1 (dC_FC_max).

[0107] During a step 260 , the computer CALC calculates a threshold value NGmax_EF for the speed NG and a threshold value T4xmax_EF for the temperature T4xmax as a function of the function f2 of the creep counter EF and of the maximum rate of increment of the creep counter EF. More specifically, by converting the inverse damage law f2 -1 Applied to the maximum incremental inverse damage law f2 -1 To calculate the threshold NGmax_EF and the threshold T4xmax_EF: (NGmax_EF, T4xmax_EF) = f2- 1 (dC_EF_max). It will be appreciated that since the speed NG and the temperature T4x are interrelated through the operation of the turboshaft engine TM, the inverse damage law f2 -1 Only one possible combination of NGmax_EF, T4xmax_EF is given.

[0108] During a step 262 , the computer CALC calculates an upper limit PEsup of an operating variable of the turboshaft engine TM, such as the power provided by the turboshaft engine TM, based on the thresholds NGmax_FC, NGmax_EF, T4xmax_EF and with the aid of a model of the turboshaft engine TM.

[0109] For example, the computer CALC uses a model of the turboshaft engine TM to calculate the mechanical power that the turboshaft engine TM can deliver without exceeding these thresholds NGmax_FC, NGmax_EF, T4xmax_EF as an upper limit PEsup.

[0110] In step 264 , the computer CALC calculates a lower limit PEinf using the damage law in the partial cycle.

[0111] For example, the computer CALC uses a model of the turboshaft engine TM to calculate as lower limit PEinf the mechanical power that the turboshaft engine TM can deliver without falling below the threshold NGmin_FC, T4xmax_EF (without taking into account a shutdown of the turboshaft engine TM).

[0112] In a step 266 , the computer CALC transmits the current value of the mechanical power provided by the propulsion system 102 , the lower limit PEinf and the upper limit PEsup to the display device AF.

[0113] In step 268, the display device AF displays the current value, the lower limit PEinf and the upper limit PEsup of the provided mechanical power.

[0114] Reference Figure 3 , showing an example of a display device AF.

[0115] In this example, the power provided by the system is indicated by rotating pointer 302 .

[0116] The margins PMC, PMD1, ePMD, PMT1, ePMT are indicated as marks along the travel 304 of the rotating pointer 302, as are the lower limit PEinf and the upper limit PEsup.

[0117] It should also be noted that the present invention is not limited to the above-described embodiments. In fact, it will be apparent to those skilled in the art that various modifications may be made to the above-described embodiments based on the teachings just disclosed.

[0118] In the foregoing detailed presentation of the invention, the terms used should not be construed to limit the invention to the embodiments disclosed in this specification, but should be construed to include all equivalent solutions that a person skilled in the art can anticipate by applying their common sense to the implementation of the teachings just disclosed.

Claims

1. A computer-implemented method (200) for monitoring a propulsion system (102) of an aircraft (100), the propulsion system (102) comprising a rotary propulsion unit (104) and a thermal chain (TH), the thermal chain (TH) being used to drive the rotary propulsion unit (104), the method (200) comprising: - calculating (204) threshold values ​​(NG_D, T4x_D, NG_T, T4x_T) of parameters (NG, T4x) of the thermal link (TH), below which the parameters (NG, T4x) must remain in order for the power provided by the thermal link (TH) to be below a predefined maximum power (PMD TH , PMT TH ); - calculating (206) a margin of the parameters (NG, T4x) of the thermal chain (TH) relative to threshold values ​​(NG_D, T4x_D, NG_T, T4x_T) of the parameters of the thermal chain, wherein the margin is taken as the margin (PMD1, PMT1) of the thermal chain (TH); Characterized in that the propulsion system (102) further comprises an electrical chain (ELEC), the electrical chain being used to drive the rotary propulsion unit (104) in parallel with the thermal chain (TH), and the method (200) further comprises: - Calculate (208) the parameters (I) of the electrical chain (ELEC) BAT , C M ) threshold (I BAT _D, C M _D,I BAT _T, C M _T), the parameter (I BAT , C M ) must remain below the threshold (I BAT _D, C M _D,I BAT _T, C M _T) so that the power provided by the electrical chain (ELEC) is lower than a predefined maximum power; - calculating (210) the parameters (I) of the electrical chain (ELEC) BAT , C M ) relative to the threshold value of the parameter of the electrical chain (I BAT _D, C M _D,I BAT _T, C M _T), wherein at least a part of the margin is used as a margin of the electrical chain (ELEC); - adding (222) the margin (PMD1) of the thermal chain (TH) to the margin of the electrical chain (ELEC) to obtain the overall margin (ePMD) of the propulsion system (102); - transmitting (224) the total margin (ePMD) to a display device (AF) of the aircraft (100), so that the display device (AF) displays the total margin (ePMD); and wherein the propulsion system (102) has at least one certified operating speed, the operating speed defining a non-zero power supply duration of the electrical chain (ELEC), the method (200) further comprising: - checking whether the electric energy storage source (BAT) of said electrical chain (ELEC) is sufficiently charged to enable said electrical chain (ELEC) to maintain said parameter with a minimum margin at said parameter threshold value for a defined power supply duration; and If the electrical energy storage source is sufficiently charged, the margin of the electrical chain (ELEC) is added to the margin (PMD1) of the thermal chain (TH) to obtain the total margin (ePMD).

2. The method (200) according to claim 1, comprising: - for each of a plurality of parameters of the electrical chain (ELEC), calculating a threshold value (I BAT _D, C M _D,I BAT _T, C M _T), the parameter (I BAT , C M ) must remain below the threshold (I BAT _D, C M _D,I BAT _T, C M _T) so that the power provided by the electrical chain (ELEC) is lower than a predefined maximum power (PMD ELEC , PMT ELEC ); - for each of a plurality of parameters of the electrical chain (ELEC), calculating (210) the parameter (I BAT , C M ) relative to the threshold value of the parameter (I BAT _D, C M _D,I BAT _T, C M _T) margin; as well as - determining a minimum margin among a plurality of margins of a plurality of parameters in the electrical chain (ELEC), wherein the minimum margin is taken as the margin (PMD1, PMT1) of the electrical chain (ELEC).

3. The method (200) according to claim 1 or 2, wherein: The propulsion system (102) has at least one certified operating speed (D, T), the at least one certified operating speed defining a threshold value (NG_D, T4x_D, NG_T, T4x_T) for each of a plurality of parameters (NG, T4x) of the thermal chain (TH), the method (200) comprising: - calculating (206) the margin of each parameter (NG, T4x) in said thermal chain (TH); and - determining a minimum margin among a plurality of margins of a plurality of parameters in the thermal chain (TH), wherein the minimum margin is taken as the margin of the thermal chain (TH).

4. The method (200) according to any one of claims 1 to 3, further comprising: - If the electrical energy storage source (BAT) is not sufficiently charged, setting the total margin (ePMD) equal to the margin (PMD1) of the thermal chain (TH).

5. The method according to any one of claims 1 to 3, wherein: If the electrical energy storage source (BAT) is not sufficiently charged, the margin of the parameter is set to zero.

6. The method according to any one of claims 1 to 3, wherein: If the electrical energy storage source (BAT) is not sufficiently charged, the margin of the parameter is set equal to the state of charge divided by the predefined power supply duration.

7. The method according to any one of claims 1 to 6, further comprising: The margin (PMD1) of the thermal link (TH) is transmitted (224) to the display device (AF) for display to a pilot in the aircraft (100).

8. A computer program capable of being downloaded from a communication network and / or recorded on a computer-readable medium, characterized in that The computer program comprises instructions for executing the steps of the method according to any one of claims 1 to 7 when the program is executed on a computer.

9. An aircraft (100), comprising: - a propulsion system (102) of the aircraft (100), the propulsion system (102) comprising a rotary propulsion unit (104), a thermal chain (TH) and an electrical chain (ELEC), the thermal chain (TH) being used to drive the rotary propulsion unit (104), the electrical chain (ELEC) being used to drive the rotary propulsion unit (104) in parallel with the thermal chain (TH); - display device (AF); as well as - a computer (CALC) designed to: Calculate (204) threshold values ​​(NG_D, T4x_D, NG_T, T4x_T) of the parameters (NG, T4x) of the thermal link (TH), the parameters (NG, T4x) must remain below the threshold values ​​(NG_D, T4x_D, NG_T, T4x_T) so that the power provided by the thermal link (TH) is below a predefined maximum power (PMD TH , PMT TH ); Calculating (206) a margin of the parameter (NG, T4x) of the thermal link (TH) relative to a threshold value (NG_D, T4x_D, NG_T, T4x_T) of the parameter of the thermal link, wherein the margin is taken as a margin (PMD1, PMT1) of the thermal link (TH); Calculate (208) the parameters (I BAT , C M ) threshold (I BAT _D, C M _D,I BAT _T, C M _T), the parameter (I BAT , C M ) must remain below the threshold (I BAT _D, C M _D,I BAT _T, C M _T) so that the power provided by the electrical chain (ELEC) is lower than a predefined maximum power (PMD ELEC , PMT ELEC ); Calculate (210) the parameters (I of the electrical chain (ELEC) BAT , C M ) relative to the threshold value of the parameter of the electrical chain (I BAT _D, C M _D,I BAT _T, C M _T), wherein at least a portion of the margin is used as a margin (ΔP ELEC _D, ΔP ELEC _T); · The margin (PMD1) of the thermal chain (TH) and the margin (ΔP ELEC _D) are added (222) to obtain an overall margin (ePMD) of the propulsion system (102); transmitting (224) the total margin (ePMD) to a display device (AF) of the aircraft (100) so that the display device (AF) displays the total margin (ePMD); and wherein the propulsion system (102) has at least one certified operating speed (D), the at least one certified operating speed (D) defining a non-zero power supply duration of the electrical chain (ELEC), the computer (CALC) being further designed to: - checking whether the electric energy storage source (BAT) of the electrical chain (ELEC) is sufficiently charged to enable the electrical chain (ELEC) to maintain the parameter at the threshold value of the parameter with a minimum margin for a defined power supply duration; - If the electrical energy storage source is sufficiently charged, the margin (ΔP ELEC _D) is added to the margin (PMD1) of the thermal chain (TH) to obtain the total margin (ePMD).

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