A hybrid aircraft architecture and power management method

Abstract

It is disclosed a hybrid aircraft power management method, wherein the hybrid aircraft comprises: - a plurality of electric power sources, comprising: o at least two turbogenerators each comprising an internal combustion engine and at least one electrical generator, and o at least a complementary power source, and - a plurality of electric propulsion units, each electric propulsion unit being connected to at least two turbogenerators and at least a complementary power source, and wherein the hybrid aircraft power management method comprises: - determining, for a considered flight, a flight power plan, and - based on the determined flight power plan, operating the electric power sources during the flight, wherein the flight power plan comprises a sequence of successive flight phases corresponding to respective electrical needs of the aircraft, and, for each flight phase, a respective subset of active electric power sources, wherein the subset of active electric power sources corresponding to a phase is determined to provide an amount of electrical power meeting the aircraft's electrical needs of the flight phase.

Description

A HYBRID AIRCRAFT ARCHITECTURE AND POWER MANAGEMENT METHODTECHNICAL FIELD

[0001] The present disclosure relates to a hybrid aircraft power management method and a hybrid aircraft power architecture. It finds notable application in aircraft dedicated to short to medium-haul flights.TECHNICAL BACKGROUND

[0002] In the context of adapting human activities in order to reduce their carbon emissions and mitigate climate change, there is a growing need to reduce the carbon footprint of aviation. As a consequence, intensive research is done on several levers that may contribute in said carbon footprint reduction, such as alternative fuels and alternative propulsive systems, embarking means such as electrical batteries or hydrogen fuel cells to progressively replace the use of kerosene-based turbomachines.

[0003] Accordingly, some hybrid propulsion architectures have been disclosed, comprising batteries coupled to electric propulsors, that complement or replace turbomachines. Such architectures are typically operated in order to rely as much as possible on the batteries and use the turbomachines in critical conditions or to prevent failure of the batteries.

[0004] It has also been disclosed in US 11 ,465763 a hybrid-electric, single aisle aircraft that has been designed in order to realize a significant reduction in emissions from commercial aviation.

[0005] This aircraft is propelled by a hybrid-electric propulsion architecture, comprising at least three electric propulsors coupled to a distribution bus, a plurality of energy storage units, and one or more gas turbine generators serving as rangeextending generators, where all energy storage units and gas turbine generators are also coupled to the distribution bus to contribute to propulsion of the aircraft.

[0006] This document defines three types of ranges depending on a “degree of hybridization” of the propulsion, ranging from a zero degree (full turboelectric propulsion) to a 100% degree (full battery propulsion). However, this document does not disclose any specific strategy for aircraft power management enabling such emission reductions.DESCRIPTION OF THE INVENTION

[0007] The present disclosure aims at improving the prior art.

[0008] In particular, an aim of the present disclosure is providing a hybrid aircraft power management and hybrid aircraft power architecture that enable significant reductions in fuel consumption, and more generally in energy consumption, as compared to the prior art.

[0009] To this end, it is disclosed a hybrid aircraft power management method, wherein the hybrid aircraft comprises:- a plurality of electric power sources of at least two different types, and- a plurality of electric propulsion units, each electric propulsion unit being connected to one or more electric power source of each type, and wherein the hybrid aircraft power management method comprises:- determining, for a considered flight, a flight power plan, and- based on the determined flight power plan, operating the electric power sources during the flight, wherein the flight power plan comprises a sequence of successive flight phases corresponding to respective electrical needs of the aircraft, and, for each flight phase, a respective subset of active electric power sources, wherein the subset of active electric power sources corresponding to a phase is determined to provide an amount of electrical power meeting the aircraft’s electrical needs of the flight phase.

[0010] According to the disclosed hybrid aircraft power management method, together with the configuration of the electric power sources and propulsion units, it is possible to use different sets of electrical power source to meet the aircraft’s electrical needs, at different phases of the flight. In particular, the definition of the flight power plan may enable adjusting the operated electrical power sources of each phase to maximize electric power generation efficiency, and hence reduce energy consumption, in particular fuel consumption.

[0011] In embodiments, the plurality of electric power sources comprises at least two turbogenerators each comprising an internal combustion engine and at least one electrical generator, and at least one complementary power source, and each electric propulsion unit is connected to at least two turbogenerators and at least one complementary power source.

[0012] In embodiments, the flight power plan further comprises, for each flight phase, an average electrical power value delivered by each active electric power source.

[0013] In embodiments, the flight power plan is determined to maximize efficiency of electric power generation by the electric power sources, during a determined time horizon, which can correspond to the duration of the flight or a duration exceeding the duration of the flight, for instance a duration of at least two consecutive flights.

[0014] In embodiments, the efficiency of electric power generation is defined as:wherein Pi(t) is the electric power delivered by a source i, Effi is the electric power generation efficiency of the source i, which may depend at least on the electric power delivered by the source, Ei is the available energy of the source i over the determined time horizon, and tf-to is the determined time horizon.

[0015] In embodiments:- determining the flight power plan is performed by a computer belonging to an Airline Information Services Domain, and- operating the electric power sources based on the flight power plan is performed by a computer belonging to an Aircraft Control Domain.

[0016] In embodiments, the method comprises an initial determination of the flight power plan before the flight, and at least one iteration of updating the flight power plan during the flight.

[0017] In embodiments, each iteration of updating the flight power plan during the flight is implemented by a software running on a pilot’s mobile computing device and interfaced with an Aircraft Control Domain through a secure gateway.

[0018] In embodiments, operating the electric power sources during the flight in accordance with the determined flight power plan comprises:- receiving real-time data including: o an amount of electrical power demand to meet the aircraft’s electrical needs, o operating conditions of the electric power sources, and- based on the received real-time data, and on the flight power plan, select a subset of active electric power sources to provide the amount of electrical power, and issue a power supply command for each selected power source, comprising an electrical power value to be delivered by each power source.

[0019] In embodiments, operating the electric power sources during the flight further may comprise issuing at least one extinction request of the internal combustion of aturbogenerator that was previously active and that is not within the selected subset of active electric power sources.

[0020] In embodiments, operating the electric power sources during the flight may may comprise issuing at least one activation request of the internal combustion engine of a turbogenerator within the selected subset of active sources and which was previously off.

[0021] In embodiments, selecting a subset of active electric power sources based on the received real-time data and on the flight power plan comprises: determining at least one candidate subset of electric power sources based on the received real-time data, such that the candidate subset of electric power sources is able to deliver the amount of electrical power, and, in view of the flight power plan, selecting the candidate subset of electric power sources that satisfies a determined criterion on the numbers of turbogenerators ignition or extinction.

[0022] In embodiments, the determined criterion is of minimizing the number of turbogenerator’s ignitions and extinctions over the whole flight.

[0023] In embodiments, selecting a subset of active electric power sources is performed by implementing pre-established deterministic rules.

[0024] In embodiments, the flight power plan comprises at least phases of takeoff, climb, cruise, descent and landing, where each phase is associated with a respective subset of active electric power sources.

[0025] In embodiments, the flight power plan comprises at least the following phases and associated subsets of active electric power sources: during take-off and climb phase, the subset of active power sources includes at least the two turbogenerators, during the cruise phase, the subset of active power sources includes one or two turbogenerator(s), depending on the mean altitude of the cruise, during the descent and landing phases, the subset of active power sources includes the at least one battery and the two turbogenerators are turned off.

[0026] In embodiments, the aircraft further comprises non-propulsive systems, and the aircraft’s electrical needs encompass propulsive and non-propulsive electrical needs.

[0027] According to another object, it is disclosed a hybrid aircraft power management device, for an aircraft comprising,- a plurality of electric power sources of at least two different types, and- a plurality of electric propulsion units, each electric propulsion unit being connected to one or more electric power source of each type, wherein the hybrid aircraft management device comprises at least a computer configured to:- determine, for a considered flight, a flight power plan, wherein the flight power plan comprises a sequence of successive flight phases corresponding to respective electrical needs of the aircraft, each flight phase being associated with a respective subset of active electric power sources determined to provide an amount of electrical power meeting the aircraft’s electrical needs, and- operate the electric power sources during the flight in accordance with the determined flight power plan, wherein the determination of the flight power plan is implemented to maximize electric power generation efficiency among the electric power sources, during a determined time horizon.

[0028] In embodiments, the hybrid aircraft power management device comprises a first computer, belonging to an Airline Information Services Domain configured to determine the flight power plan, and at least a second computer, belonging to an Aircraft Control Domain, configured to operate the electric power sources during the flight in accordance with the determined flight power plan.

[0029] In embodiments, the first computer comprises a pilot’s mobile computing device or a server located on the ground, and the first computer is configured for transmitting the flight power plan to the second computer through a secure gateway.

[0030] In embodiments, the hybrid aircraft power management device comprises:- A Flight Management System (FMS), configured to receive the flight power plan and to iteratively compute, for each of a plurality of sequences of the flight, based on the flight power plan and a position of the aircraft along the flight: o Longitudinal and lateral guidance commands, o a speed command, and o a power plan command comprising, a respective subset of active electric power sources and an average power to be delivered by each active electric power source for the upcoming sequence of the flight, and- a Power Management System (PMS), configured to receive the power plan command, and real-time data including: o an amount of electrical power demand to meet the aircraft’s electrical needs, and o operating conditions of the electric power sources, and to select a subset of active electric power sources to provide the amount of electrical power, and issue a power supply command for each selected power source, comprising an electrical power value to be delivered by each power source.

[0031] In embodiments, wherein the second computer, belonging to the Aircraft Control Domain, comprises the FMS and the PMS.

[0032] According to another object, it is disclosed a hybrid aircraft power architecture, comprising:- a plurality of electric power sources of at least two different types, and- a plurality of electric propulsion units, each electric propulsion unit being connected to one or more electric power source of each type, the hybrid aircraft power architecture further comprising a hybrid aircraft power management device according to the description above.

[0033] In embodiments, the turbogenerators are sized such that:- said at least two turbogenerators operate at a pre-determined high efficiency operating point during cruise at high altitude,- a subset of turbogenerators, including at most all turbogenerators minus one, operate at a pre-determined high efficiency operating point during cruise at intermediate altitude.

[0034] The disclosed aircraft power architecture, which can be classified as a series hybrid architecture, enables decoupling power generation from propulsion. This, in turn, enables operating the electric propulsion units on the one hand and the electric power sources on the other hand respectively at optimal operating points. The latter action is performed by suitably selecting various subsets of active electric power sources to provide the required electrical power for meeting the aircraft’s electrical needs. As a consequence of such selection, the turbogenerators can be operated within a high efficiency operating range during cruise, or completely shut off during taxi and descent. This enables significant reduction in fuel consumption as compared to traditional architectures in which the turbomachines were sized for the takeoffphase and therefore operated at a sub-optimal operating point during cruise, and when at idle. To permit such operation, turbogenerators have to be suitably sized.

[0035] In embodiments, the turbogenerators are sized such that:- said at least two turbogenerators operate in a pre-determined high efficiency range during cruise at high altitude, for a speed comprised between 120 % and 150 % of the stall speed at said altitude,- a subset of turbogenerators including at most all turbogenerators minus one, operate in a pre-determined high efficiency range during cruise at intermediate altitude, for a speed comprised between 120 % and 150 % of the stall speed at said altitude.

[0036] In embodiments, the high efficiency operating point corresponds to a delivered electric power comprised between 90 and 100% of the maximal deliverable power.

[0037] According to another object, it is disclosed a mobile computing device, comprising a display, an input interface, a processor and a memory, wherein the memory stores, for at least one considered flight, a flight power plan, comprising, a sequence of successive flight phases corresponding to respective electrical needs of the aircraft, and, for each flight phase, a respective subset of active electric power sources, wherein the subset of active electric power sources corresponding to a phase is determined to provide an amount of electrical power meeting the aircraft’s electrical needs of the flight phase, and wherein the mobile computing device is configured for transmitting, to a computer belonging to an Aircraft Command Domain, the flight power plan through a secure gateway.

[0038] In embodiments, the mobile computing device is further configured for receiving, during the flight, data regarding the flight and operating conditions of the aircraft, and for updating the stored flight power plan according to the received data.

[0039] In embodiments, the mobile computing device is further configured for displaying, on the display, a notice of updated flight power plan.

[0040] In embodiments, the mobile computing device is configured for displaying a notice of updated flight power plan only when:- updating the flight power plan is responsive to an action from the pilot, or,- when the updated flight power plan increases efficiency of electric power generation over the flight of an amount exceeding a predetermined threshold, and the aircraft is in one among a list of predetermined flight phases.

[0041] In embodiments, the mobile computing device is further configured for: Receiving, via the input interface, a command from the pilot responsive to displaying an updated flight power plan, and,In response to the pilot’s command, transmitting the updated flight power plan to the computer belonging to the Aircraft Command Domain, through the secure gateway.

[0042] According to another object, it is disclosed a Power Management System, for a hybrid aircraft comprising: a plurality of electric power sources of at least two different types, a plurality of electric propulsion units, each electric propulsion unit being connected to one or more electric power source of each type, the Power Management System comprising a hardware device configured to operate in an Aircraft Control Domain, the Power Management System being configured to receive:- a power plan command comprising, for the upcoming sequence of a flight, a respective subset of active electric power sources and an average power to be delivered by each active electric power source,- real-time data including: o an amount of electrical power demand to meet the aircraft’s electrical needs, o operating conditions of the electric power sources, and being configured to select, based on the received real-time data and on the power plan command, a subset of active electric power sources to provide the amount of electrical power, and to issue a power supply command for each selected power sources, comprising an electrical power value to be delivered by each power source.

[0043] In embodiments, the Power Management System is configured to select the subset of active electric power sources by implementing pre-established deterministic rules.DETAILED DESCRIPTION OF THE DRAWINGS:

[0044] The present disclosure is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings, in which like reference numerals reference to similar elements and in which:

[0045] Figure 1 schematically represents a hybrid aircraft architecture according to an embodiment.

[0046] Figure 2a is an example of electric power generation efficiency of a turbogenerator according to the delivered power (expressed as a ratio of the maximal deliverable power), at constant operating parameters.

[0047] Figure 2b is an example of electric power generation efficiency of a battery according to the delivered power (expressed as a ratio of the maximal deliverable power).

[0048] Figure 3 schematically represents the main steps of a power management method according to an embodiment.

[0049] Figure 4 is an example decomposition of a typical flight in a plurality of flight phases.

[0050] Figure 5 schematically shows an example of part of a flight power plan for a flight, including the selected subsets of active electric power sources at each phase of the flight.

[0051] Figure 6 schematically shows an example of a command architecture of a hybrid aircraft, including a hybrid aircraft power management device according to an embodiment.

[0052] Figure 7 schematically shows an example of a mobile computing device according to an embodiment.

[0053] Figure 8 shows the main steps of a method implemented by a mobile computing device.DETAILED DESCRIPTION OF EMBODIMENTS

[0054] A hybrid aircraft power architecture and power management method will now be described. In embodiments, the aircraft is a fixed wing aircraft.

[0055] With reference to figure 1 , the hybrid aircraft power architecture 1 is a series hybrid architecture comprising a plurality of electric power sources 10, feeding with electrical power a plurality of electric propulsion unit 20, and a plurality of non- propulsive electric systems or appliances 40.

[0056] The plurality of electric power sources may include one or more power sources of at least two different types. The different types of electric power souces may include:- Electrical batteries,- Hydrogen fuel cells,- Turbogenerators.

[0057] When the electric power sources comprise at least one turbogenerator, each turbogenerator comprises an internal combustion engine 13. Each internal combustion engine may for instance be a turbomachine or a piston engine, and is configured to generate mechanical power from combustion of fuel. Each internal combustion engine typically comprises an output shaft (not shown).

[0058] Furthermore, each turbogenerator comprises at least one electrical generator 14 configured to convert mechanical power of the output shaft into electrical power. In embodiments, and as represented in the example of figure 1 , each turbogenerator comprises two electrical generators 14a, 14b, each electrical generator being configured to convert mechanical power of the output shaft of the internal combustion engine 13 into electrical power. In embodiments, each turbogenerator comprises an even number, greater than two, of electrical generators.

[0059] Each propulsion unit 20 comprises an electrical motor 21 , configured to convert electrical power provided by one or more of the power sources of each type, into mechanical power, and a propeller 22, rotatably driven by said motor.

[0060] In embodiments, an example of which is shown in figure 1 , the plurality of electric power sources 10 comprises at least two turbogenerators 1 1 , and at least one complementary power source 12. The at least one complementary power source 12 can include one or more batteries, or one or more hydrogen fuel cells able to generate electrical power. The number of turbogenerators 1 1 may be greater than 2, for instance the architecture may comprise four turbogenerators. The number of complementary power sources 12 may also be greater than two, for instance equal to 3 or 4.

[0061] In that configuration, each propulsion unit 20 is connected to at least two turbogenerators 11 , and to at least a complementary power source 12, enabling the propulsion unit 20 to be selectively fed with electrical power by any subset among said at least two turbogenerators 1 1 and complementary power source 12, which results in a decoupling between power production and propulsion. For instance, allpropulsion units 20 may be provided with electrical power delivered by one or two turbogenerators 11 , optionally complemented with electrical power provided by the complementary power source(s) 12.

[0062] The non-propulsive electric systems 40 encompass any system that requires electrical power for its operation, and which do not contribute to aircraft propulsion. These may include one or more of the following:- Avionics systems: all electronic devices and systems used for navigation, communication, and monitoring of the aircraft. This includes navigation computers, communication radios, radar systems, transponders, and flight control computers (including control computers, and sensors)- Electric actuators, such as those that may be required move flight control surfaces, to retract and extend the landing gear, to brake, to operate the doors- Lighting systems, such as navigation lights, landing lights, taxi lights, and cabin lighting.Environmental Control System (ECS), for maintaining a comfortable and safe environment within the aircraft cabin and avionics bay. It includes systems for air conditioning, pressurization, and heating, all of which require electrical power.Emergency Systems, which may include emergency lighting, emergency oxygen systems, and other safety-critical equipment.- Anti-lcing / De-lcing Systems,- Communication Systems, apart from avionics, such as intercoms and public address systems within the aircraft.- Cabin Systems: may include galley equipments (ovens, coffee makers, refrigerators,...), plus various amenities such as power outlets for passengers, in-flight entertainment systems, which may include displays, audio systems, and Wi-Fi connectivity.

[0063] In embodiments, the non-propulsive electrical systems 40 are also connected to each electric power source. In the embodiment described above, the non-propulsive electrical systems may be connected to said at least two turbogenerators 1 1 and to at least a complementary power source 12, also enabling that these non-propulsive systems be fed with electrical power by various subsets of said electric power sources. Alternatively, non-propulsive electric power may be provided by a specifically dedicated power source (not shown).

[0064] According to a particular embodiment, and as represented in figure 1 , the architecture 1 may comprise an even number of propulsion units 12, with the propellers 22 being symmetrically disposed on the wings with respect to the fuselage of the aircraft. Further, when the turbogenerators 11 each comprise two electrical generators 14, two groups comprising the same number of propulsion units 20 may be defined, and the two electrical generators of each turbogenerator may be connected respectively to a respective group of electrical propulsion unit. This is a way to ensure that each turbogenerator is indeed able to deliver electrical power to both group of propulsion units.

[0065] At least some of the electrical power sources 10 exhibit an electric power generation efficiency that is variable according to the electrical power delivered by the source. This is a case in particular for the turbogenerators 11 , and also for batteries. As a consequence, for said power sources, respective high-efficiency ranges may be defined, which are ranges of delivered electrical power for which the efficiency of the power source is maximum or near maximum. For instance, the high-efficiency range of a power source may be defined as a range of delivered electrical power for which the efficiency of the power source is comprised between its maximum efficiency and a sub-maximal efficiency, which may be defined for instance as equal to 80% or 90% of the maximal efficiency.

[0066] With reference to figure 2a, is shown a typical curve of electrical power production efficiency with delivered power, for a turbogenerator including an internal combustion engine. One can see that the electrical power efficiency increases with the delivered power, and that it is therefore preferable to operate the turbogenerator in a region corresponding to a high power ratio, i.e. to deliver a power near to the maximal deliverable power, in order to reach high efficiency.

[0067] According to a non-limiting example, a range of maximum efficiency, corresponding to the above-mentioned “pre-determined high efficiency range”, may be defined as a range of powers delivered by the turbogenerator comprised between of 60% to 100% of the maximal deliverable power, for instance between 80 and 100%.

[0068] With reference to figure 2b, is shown a typical curve of electrical power production efficiency against delivered power, for an electric battery. One can see that, contrary to a turbogenerator, the efficiency of a battery decreases with delivered power, such that it is preferable to operate the battery at low delivered powered in order to preserve efficiency. According to a non-limiting example, a range of maximumefficiency, corresponding to the above-mentioned “pre-determined high efficiency range”, may be defined as a range of powers delivered by a battery that is comprised between 0 and 60% of the maximal deliverable power of the battery, for instance between 0 and 30%.

[0069] Furthermore, the electric power generation efficiency of an electric power source, or the maximum deliverable power, may also vary according to operating parameters of the power source. Regarding turbogenerators 11 , the operating parameters having influence on their electric power generation efficiency comprise, but may not be limited to, operating conditions of the aircraft, including an ambient temperature, the aircraft’s altitude, and speed.

[0070] Regarding an electrical battery, the operating parameters having an influence on the electrical power efficiency may comprise an ambient temperature and / or a temperature of the battery.

[0071] Thus, figures 2a and 2b commented above are provided for constant operating parameters. In particular, the maximum available power and maximum production efficiency may change according to the operating conditions. However, the general evolution of power generation efficiency with delivered power remains unchanged, for a given electric power source, despite a change in operating conditions.

[0072] Back to figure 1 , the architecture 1 further comprises at least a hybrid aircraft power management device comprising a controller 30, configured to manage electrical power production and distribution according to the aircraft’s needs, and according to the method disclosed below.

[0073] The controller 30 may comprise one or more processors 31 (which may belong to a same computer or to different computers) and storage means 32 (magnetic hard disk, optical disk, electronic memory, or any computer readable storage medium) in which a computer program product is stored, in the form of a set of program-code instructions to be executed in order to implement all or part of the steps described below. Alternatively, or in combination thereof, the controller 30 can comprise one or more programmable logic circuits (FPGA, PLD, etc.), and / or one or more specialized integrated circuits (ASIC), etc., adapted for implementing all or part of said steps. In other words, the controller 30 comprises a set of means configured by software (specific computer program product) and / or by hardware (processor, FPGA, PLD, ASIC, etc.). In embodiments, the power management method isperformed by a controller 30 embarked on board the aircraft. Alternatively, the power management method may be performed in part by a controller located on the ground and in part by an embarked controller, as discussed in more details below.

[0074] When a controller 30 embarked on board the aircraft implements part or all of the power management method, said controller is preferably connected to a plurality of sensors (not shown) embarked onboard the aircraft, a plurality of computers (not shown) and inceptors (not shown), in order to be able to receive realtime data relative to the operation of the aircraft. Furthermore, said controller may also comprise at least one remote communication interface 33 enabling the reception of data (such as for instance, updates regarding weather or air traffic during the flight) from the ground, and emission of data to the ground.

[0075] With reference to figure 6, which shows an exemplary command architecture of the aircraft according to embodiments, the controller 30 may encompass a plurality of computers comprising at least one computer in an AISD domain (ground computer GRD or embarked mobile computing device 9) and at least one computer in an ACD domain (PMS).

[0076] As known to the skilled person, a domain refers to a functional or operational area within the aircraft’s system architecture or operation. A domain groups systems, data or components that share similar purposes or characteristics. Domains are subject to specific security requirements according to the criticality of the aircraft operations they relate to.

[0077] The aircraft domains in particular include the Airline Information Services Domain (AISD), encompassing important but non-critical functions and systems that are not essential for the immediate safety and operation of the aircraft. This domain provides services and connectivity between independent systems that manage:- passenger entertainment,- crew scheduling and communication,- flight scheduling and reporting,- maintenance and performance monitoring reports, Internet connectivity for passengers.

[0078] The Aircraft Control Domain consists of secure and safety-critical systems and networks whose primary functions are to support the safe operation of the aircraft. It includes systems that directly impact the safety of flight and navigation of the aircraft, such as:Flight Management System (FMS)- Autopilot,Flight Controls Engine control, Communication with Air T raffic Control,- Aircraft sensors and actuators.

[0079] Different security requirements apply to these two domains, and the communication between these domains is subject to stringent rules defined in the following standards: ED-202A / DO-326A "Airworthiness Security Process Specification", ED-203A / DO-356A "Airworthiness Security Methods and Considerations" and ED-204 / DO-355 "Information Security Guidance for Continuing Airworthiness".

[0080] Thus, when the controller 30 comprises at least one computer in the ACD and one computer in the AISD, it also comprises a secure gateway 99 enabling communication between the two computers according to protocols that abide by the standards mentioned above, which guarantee the security of the ACD.

[0081] With reference to figures 3 to 5, a hybrid aircraft power management method will now be described. As mentioned, this method may be implemented by at least one controller 30.

[0082] The method comprises a step 100 of determining, for a considered flight, a flight power plan.

[0083] As shown schematically in figure 5, a flight power plan comprises a sequence of successive flight phases defining the aircraft’s route for the flight, from origin to destination of the flight, including a plurality of successive points along the aircraft’s route and the coordinates of these points. The sequence of successive flight phases takes into account time and spatial constraints (such as, for instance, maximum duration for the flight, geographical constraints related to mountainous areas, weather forecast, etc.), as well as parameters of the flight (such as the type of aircraft and configuration of the electric power sources and propulsion units, and the load of the aircraft), where each flight phase corresponds to respective electrical needs of the aircraft. The flight power plan thus includes a flight plan, as conventionally known to the skilled person. Furthermore, the flight power plan comprises a power plan comprising, for each flight phase, a respective subset of active electric power sources, which is determined to meet the aircraft’s electrical needs of the phase. The subsetof active electric power sources may be expressed as an active (“ON”) or inactive (“OFF”) state for each electric power source during a phase of the flight. The power plan may also comprise the electrical power, for instance average electrical power, delivered by each source of the subset during the phase. This average electrical power value may be expressed as an absolute power value delivered by a source, or as a percentage of the maximum power deliverable by the source.

[0084] A subset of active selected power sources 10 may include at least one electric power source 10 among all the electric power sources of the aircraft, and may include all the electric power sources 10, when necessary.

[0085] According to non-limiting examples, the subset of active electric power sources may include a single turbogenerator 11 , two turbogenerators 11 , a single turbogenerator complemented 11 by the complementary power source 12, or the complementary power source(s) 12 only.

[0086] Each flight phase of the flight plan may further be defined by additional parameters including the aircraft horizontal and / or vertical trajectory and speed during the phase.

[0087] The electrical needs of the aircraft associated with each flight phase include at least the propulsive needs, i.e. the electrical power necessary for the propulsion units to enable the aircraft to implement the trajectory associated with the phase. In embodiments, the electrical needs of the aircraft may include the propulsive needs as well as at least some of the non-propulsive needs, such as for instance needs of critical non-propulsive systems, which can include, but may not be limited to, de-icing or anti-icing systems. In embodiments, the electrical needs of the aircraft include all propulsive and non-propulsive needs of the aircraft.

[0088] The subset of active electric power sources associated with each phase is defined according to the aircraft’s electrical need for the phase.

[0089] In embodiments, the flight power plan is determined based on at least one criterion on electric power generation efficiency. In embodiments, the flight power plan is determined to maximize efficiency of electric power generation by the electric power sources, during a determined time horizon. The determined time horizon is typically the duration of the flight. However, the determined time horizon may exceed the duration of the flight and may encompass at least one subsequent flight, i.e. at least two consecutive flights.

[0090] The efficiency of electric power generation can be defined as follows:where Pi(t) is the electric power delivered by a source i at time t, Effi is the electric power generation efficiency of the source i, Ei is the available energy of the source i over the determined time horizon, and tf-to is the determined time horizon.

[0091] As explained above, the electric power generation efficiency Effi of a source i is variable with the delivered power at least for turbogenerators and batteries, and may also vary depending on operating parameters of the power source. Regarding the energy Ei, said energy typically corresponds to the available energy over the whole flight, and thus corresponds, for the turbogenerators, to the total potential energy represented by the quantity of fuel available for the flight. For electric batteries, the energy corresponds to the total energy deliverable by the batteries over the flight.

[0092] The problem of finding the best flight power plan can be formulated as an optimization problem that seeks the maximum energy efficiency as defined above, under time and spatial constraints, to perform the mission from origin to destination.

[0093] The decision variables may include those related to the aircraft’s trajectory, speed, active power sources and electrical power delivered by each source along the trajectory.

[0094] Although many numerical methods exist to perform the optimization, the underlying optimization algorithm can be described as follows.

[0095] First, the method starts with an initial guess for a mission profile, in which a predetermined number of phases may be used, along with a predetermined set of rules determining the subsets of power sources delivering the electrical power, and for given external operational conditions (takeoff and landing altitude, temperature, ...).

[0096] The predetermined phases may for instance include the six following principal flight phases which are generally defined for a flight plan, and which are represented in figure 3:Taxiing P1 , which corresponds to the movement of the aircraft on the ground under its own power, to reach a runway from an airport’s gate or to reach an airport’s gate from the runway, thus a flight typically comprises two taxiing phases, one before takeoff and one after landing,- Takeoff P2, where the aircraft leaves the ground and becomes airborne,Ascent or climb P3, which is the phase during which the aircraft increases its altitude, and which follows the takeoff and precedes the cruise,Cruise P4, which is the phase of the flight when the aircraft levels off after the climb. The cruise may itself comprises a plurality of distinct flight phases, according to different needs of the aircraft of the cruise, corresponding for instance to various speeds or altitudes of the aircraft,Descent P5, which is phase during which the aircraft decreases its altitude after cruise and before landing, andLanding P6, which is the phase at which the aircraft reaches the ground.

[0097] The predetermined rules determining the subset of active electrical power sources associated with each phase may for instance be the following, in particular in the case where the aircraft comprises two turbogenerators and when the complementary power source includes a battery:- when P < Pcomp, where P is the estimated power for the phase, PCOmp is the amount of electrical power available from the battery, and said power from the battery PCOmp can be supplied over the whole current flight phase (Pn), then the subset of active power sources consists in the battery only,- when Pcomp < P < PTG where PTG is the power available from a single turbogenerator 1 1 at the estimated aircraft’s operating conditions for the phase, then the subset of active power sources consists in a single turbogenerator 1 1 ,- when PTG < P < PTG + Pcomp , then the subset of active power sources consists in a single turbogenerator and the battery,- when PTG + A P < P < 2* PTG , then the subset of active power sources consists in two turbogenerators, and- when 2* PTG < P, then the subset of active power sources consists in two turbogenerators and the battery.

[0098] Once an initial flight power plan is defined, an aircraft performance model, which can calculate energy used based on flown mission profile, is evaluated on said initial power plan.

[0099] The output is aggregated into the objective function, corresponding to the function given above regarding efficiency of electric power generation.

[0100] The feasibility of the constraints, such as those imposed on flight duration, or spatial constraints (related for example to the flight over mountainous areas, with the required margins) are then evaluated.

[0101] If the proposed mission profile is feasible, and a predetermined convergence criterion has been achieved, the optimization procedure terminates, providing in output the optimal mission profile and the related flight power plan.

[0102] If the proposed mission profile is not feasible, or the convergence criterion is not achieved, then the parameters of the phases are then changed (e.g. phase duration, speed, altitude), and the above-mentioned procedure is repeated.

[0103] Examples of convergence criterion include: optimality criteria for the objective function within a given tolerance, rate of change of input variables within a given tolerance, etc.

[0104] Therefore, it should be noted that, within the context of the present disclosure, the phases of a flight power plan may not be limited to the above-listed flight phases P1 to P6. In particular, some of the above phases may be themselves decomposed into phases, according to the corresponding electrical power needs, including propulsive and non-propulsive needs. Notably, the cruise and climb phases may be decomposed into a plurality of phases.

[0105] In embodiments, the flight power plan is determined 100 at least once before the flight.

[0106] When generated before the flight, decision variables such as payload and energy to be loaded (for instance, fuel) can be included in the set of the decision variables to be optimized.

[0107] In embodiments, the first determination 100 of the flight power plan, before the flight, is performed by a computer belonging to the AISD, i.e. with lower safety requirements than the ACD. Said first determination may in particular be performed by a computer located on the ground, denoted GRD in figure 6, or by a mobile computing device 9, such as a tablet, that may be embarked by the pilot.

[0108] Implementing the flight power plan determination in the AISD Domain enables:Benefitting from abundant data, including data relative to weather forecast applicable to the flight and, optionally, to at least one subsequent flight of the aircraft, airport data (availability of runway, of battery charging devices etc.)Benefiting from more important computational resources that the embarked computational resources,Benefitting from more frequent updates than in the ACD Domain, considering the lower requirements for certification.

[0109] With reference to figure 7 is schematic representation of an example of a mobile computing device 9. The mobile computing device may be a laptop or tablet, to be used by the pilot and embarked in the cockpit of the aircraft during the flight.

[0110] The mobile computing device 9 may include a display 90, for instance a screen that may or may not be tactile, an input interface 91 , which may include one or more buttons, touch pad, or correspond to the touch screen 90, a processor 92 and a memory 93. Furthermore, the mobile computing device 9 is configured for communicating to a computer belonging to an Aircraft Command Domain, for instance a Flight Management System FMS, through the secure gateway 99.

[0111] The flight power plan determined at step 100, ahead of the flight, may be stored in the memory 93 of the mobile computing device 9. Once the pilot is installed in the aircraft’s cockpit, the pilot may establish a communication between the mobile computing device 9 and the FMS through the secure gateway 99 to send the flight power plan to the FMS.

[0112] Back to figure 3, in embodiments, the method may also include updating 1 10 the flight power plan during the flight. Regarding updates performed during the flight, some of the above-mentioned variables might be excluded from the set of decision variables to be optimized, such as the payload and energy to be loaded. Moreover, the computation of an updated flight power plan may be performed taking into account actualized variables including the amount of remaining fuel, the remaining load of the batteries, the remaining distance of the flight, the current speed and altitude of the aircraft, etc.

[0113] In embodiments, updating 110 the flight power plan during the flight may be performed at regular intervals, i.e. at a frequency which may be comprised between once per minute and once per hour, for instance of once every five or ten minutes. In that case, the computations for determining an optimal flight power plan may be performed at said regular intervals, and the flight power plan selected for the flight is changed only when the results of the computations differ from the currently implemented flight power plan by a predetermined threshold.

[0114] Alternatively or in combination, updates of the flight power plan may be required by the pilot during the flight. For instance, the circumstances of the flight, in particular, the weather conditions, may change during the flight and cause the pilot or Air Traffic control to require a change in the aircraft’s trajectory, leading to a different energy management strategy.

[0115] In embodiments, updating 110 the flight power plan during the flight may be implemented on the pilot’s mobile computing device 9. The main steps of this update are described below with reference to figure 8.

[0116] The pilot’s mobile computing device 9 may receive 1 11 , during the flight, updated information regarding the flight’s conditions (weather, destination, trajectory) and updated information regarding the aircraft’s operation (available fuel, state of charge of the batteries, etc.). This information is gathered by the systems belonging to the ACD domain and transmitted to the pilot’s computing device through the secure gateway 99. The pilot’s mobile computing device 9 may then compute an updated flight power plan, taking into account the received updated information, during step 112. When an updated flight power has been computed, a notice informing the pilot of the same, and providing information regarding the updated flight power plan, may be displayed on the display during a step 1 13.

[0117] In embodiments, in order to avoid disturbing the pilot, displaying the updated flight power plan is restricted to the following cases:- when the updating of the flight power plan is responsive to an action from the pilot (which may be consecutive to a change in the flight’s conditions),- or when the updating of the flight power plan is not responsive to an action from the pilot but the updated flight power plan provides an increase in efficiency of electric power generation by an amount exceeding a predetermined threshold, and the aircraft is in one among a list of predetermined flight phases.

[0118] The predetermined flight phases are phases during which the workload of the pilot is relatively low as compared to the other flight phases and may include cruise.

[0119] Once an updated flight power plan is displayed on the mobile computing device, the method comprises receiving 114 a pilot’s command provided at the mobile computing device’s input. The pilot’s command may be a validation of the updatedflight power plan or an alternative order (e.g. denying the updated flight power plan, and returning to the previously computed flight power plan).

[0120] When the pilot has validated the updated flight power plan, the mobile computing device may then transmit the same to a computer of the ACD, for instance the FMS, during a step 115.

[0121] Back to figure 2, once the flight power plan is determined or updated, the method then comprises operating 200 the electric power sources during the flight, based on said determined flight power plan, and in particular based on the power plan included in the flight power plan. This step is implemented by at least a controller 30 that is embarked on board the aircraft.

[0122] Operating the power source is based on the determined flight power plan, but also takes into account real-time data in order to ensure permanently meeting the aircraft’s electrical needs, i.e. at least the aircraft’s propulsive needs, and possibly also non-propulsive needs.

[0123] Accordingly, operating 200 the electric power sources comprises a substep 210, which can be implemented throughout the flight, at a determined frequency, during which the controller 30 receives data, preferably real-time data, including:- An amount of electrical power to meet the aircraft’s propulsive needs, and optionally part or all non-propulsive needs, herein after denoted Pr, and- Operating conditions of the electric power sources.- The amount of electrical power to meet the aircraft’s propulsive and non- propulsive needs may comprise:

[0124] On the one hand, a request of electrical power supply for the electric propulsion units 20, i.e. a value of electrical power to be delivered to each electric propulsion unit to enable meeting the propulsive needs of the aircraft. The request of electrical power supply for the electric propulsion units 20 may be obtained from a command of the pilot on the aircraft’s throttle, which is converted into a request for thrust and then into a request for electrical power.

[0125] On the other hand, a request of electrical power supply for non-propulsive needs of the aircraft. Said data may include a current (i.e. instantaneous) power consumption of the non-propulsive equipments of the aircraft, and / or an operating mode of some non-propulsive, electrically intensive equipments, such-as de-icing equipments. Said data may also include operating parameters of the flight affectingthe use of some equipments, such as conditions of pressure and temperature outside the aircraft.

[0126] The operating conditions of the electric power sources 10 may include:- A current operating state of each electric power source 10, namely whether it is on or off (in particular for the turbogenerators, this refers to the operating state of the internal combustion engines),- A current value of electrical power provided by each electric power source 10,

[0127] Operating parameters affecting the electric power generation efficiency of each electric power source and which may include at least one or more of the following:- Ambient temperature,- Aircraft’s speed,- Aircraft’s altitude,- Temperature of each battery, when applicable.

[0128] The frequency at which the pieces of data listed above are received may for instance be comprised 1 and 100Hz, for instance between 1 and 50 Hz, for instance between 10 and 50Hz, for instance between 20 and 30Hz.

[0129] Operating 200 the electric power sources then comprises, based on the received data and the flight power plan, selecting 220 a subset of active electric power sources to provide the requested amount of electrical power, and issuing a power supply command for each selected power source, comprising an electrical power value to be delivered by each power source.

[0130] The selected subset of active electric power sources and the electrical power value delivered by the sources must permanently meet at least the aircraft’s propulsive needs. In embodiments, the subset’s selection is under the constraint of permanently meeting the propulsive needs and at least some non-propulsive needs, corresponding for instance to critical non-propulsive systems. In some situations, such as emergency situations, said constraints may lead to diverge from the flight power plan, to ensure aircraft’s safety to the detriment of power generation efficiency. As a non-limiting example, in case of default of a turbogenerator, a remaining turbogenerator and a battery may be used jointly to meet electrical needs of the aircraft even if the electric power generation efficiency of one or more of the sources is not maximal or within its high efficiency range.

[0131] However, when the real-time data correspond to the conditions taken into account for the elaboration of the flight power plan, the selected subset of power sources and delivered power comply with the flight power plan.

[0132] When the selected subset of power sources differs from the previously operated subset of power sources, step 200 may further include a step of issuing an activation or extinction request to at least one power source. In particular, it may include issuing at least one activation 230 request of the internal combustion engine of a turbogenerator within the selected subset of sources and which was previously off. Conversely, step 200 may also include issuing at least one extinction 240 request of the internal combustion of a turbogenerator that was previously active and that is not within the selected subset of electric power sources.

[0133] According to a non-limiting example, the controller is configured to select the subset of electrical power sources according to the following deterministic rules:When the received amount of electrical power Pris lower than the power available PCOmp (within the high-efficiency range) from the complementary power sources 12, and said power from the complementary power sources can be supplied over the whole current flight phase Pn, then the electric propulsion units 20 are fed only by the complementary power sources 12, and the internal combustion engines 13 of both turbogenerators are off. This can correspond for instance to the taxiing phases, as well as the descent and landing phases.- when the request of electrical power Pris higher than the power available from the complementary power sources, but lower than the power available from a single turbogenerator at current aircraft’s operating conditions, then the electrical power is supplied by a single turbogenerator. This can correspond for instance to a cruise phase.- when the request of electrical power Pris comprised between the power available PTG from a single turbogenerator at current aircraft’s operating conditions, and PTG + P comp , and Pcomp can be supplied by the complementary power sources over the whole current flight phase, then the electrical power is supplied by a single turbogenerator and the complementary power source.- when the request for electrical power Pris comprised between PTG + P comp and twice the power available from a single turbogenerator, then the electrical power is supplied by two turbogenerators,- when the request of electrical power is higher than twice the power available from a single turbogenerator at current aircraft’s operating conditions, then the electric propulsion units are fed at least by the two turbogenerators, complemented by the complementary power sources. This can correspond for instance to the take-off phase and climb phase.

[0134] In embodiments, step 220 is preferably implemented in order to reduce the number of activations and extinctions of the turbogenerators. Therefore, selecting a subset of electric power sources based on the received real-time data and on the flight power plan may comprise:- determining at least one candidate subset 221 of electric power sources based on the received real-time data, such that the candidate subset of electric power sources is able to deliver the required amount of electrical power, and, optionally, such that each electric power source of the subset operates in a respective high-efficiency range, and,- in view of the flight power plan, selecting 222 the candidate subset of electric power sources that satisfies a determined criterion on the numbers of turbogenerators ignition or extinction.

[0135] The determined criterion may be of minimizing the number of turbogenerator’s ignitions and extinctions over the whole flight.

[0136] Thus, according to an example, if a candidate subset comprises two turbogenerators and another candidate subset comprises one turbogenerator complemented by a battery, and if the next phase of the flight is operated with two turbogenerators, the controller can elect the first subset and activate a second turbogenerator,

[0137] A non-limiting illustrative example of selection of electric power sources over the flight is provided with reference to figure 5, according to which a typical flight can be performed with the following power management strategy, where the strategy is defined both by the selected sources which are used for providing electrical power to the propulsion units, and by the respective share of power provided by each power source:Taxi-out (P1), i.e. taxi to leave the airport’s gate and reach the runway, is carried out using only the complementary power source(s) 12. This phase can also be used to switch on the turbogenerators 11 .During take-off (P2), power is generated by turbogenerators 1 1 , with the complementary power sources that can add additional power, whenever required by the field performance at the given altitude and temperature. In case of turbogenerator failure after V1 , i.e. after reaching the speed beyond which takeoff should no longer be aborted, the complementary power sources can increase their contribution to the power distribution, hence minimizing field performance penalty.- During climb (P3), turbogenerators contribute to most of the power, while being operated in their respective efficiency ranges, and additional power is provided by the complementary power sources, if required.- Cruise (P4) can be carried out in different modes, depending on the altitude and speed: o For shorter missions, performed at lower altitudes (e.g. below FL100 which corresponds to approximately 3048 meters), one of the two turbogenerators 1 1 can be switched off. Power is therefore supplied by one turbogenerator 11 , optionally complemented by a complementary power source 12. o For longer missions, at higher altitudes, for instance comprised between FL100 and FL250 (corresponding approximately to 7620 meters), the two turbogenerators 11 continue to supply the power.During descent (P5), the active turbogenerators can be switched off. Power can be provided exclusively by the complementary power sources.In case of nominal approach and landing (P6), the end of the flight is performed exclusively relying on the complementary power sources.In case of go around, power required to gain altitude is provided by the complementary power sources, and one or more turbogenerators are switched on again. From there onwards, power from turbogenerators is used for further landing attempts, or to reach an alternative airport.

[0138] Back to figure 6, the systems of the ACD implementing parts of the abovedescribed method include a Flight Management System FMS.

[0139] The Flight Management System may receive the flight power plan determined at step 100 or updated at step 1 10 and transmitted, for instance, by the pilot’s mobile computing device 9. The FMS is configured to iteratively compute, for each of a plurality of sequences of the flight, based on the flight power plan and aposition of the aircraft along the flight (that the FMS can determine from data received from one or more sensors):- A 3D trajectory for the aircraft between two waypoints of the considered sequence of the flight, and longitudinal and lateral guidance commands for an Auto-Pilot system (not shown, part of a Flight Guidance System, itself part of Flight Control Computers FCC), enabling the Auto-Pilot to maintain the aircraft on the 3D trajectory,- A speed command for an Auto-Thrust system (not shown, part of the Flight Guidance System), and- A power plan command comprising a respective subset of active electric power sources and an average power to be delivered by each active electric power source for the upcoming sequence of the flight.

[0140] The command architecture further comprises Flight Control Computers FCC implementing conventional Flight Guidance system FG, including Auto-pilot and Autothrust systems, and outputting flight commands FC for Fly-by-Wire Electric Propulsive Units.

[0141] According to embodiments of the disclosure, the controller 30 further includes a Power Management System PMS, that is part of the Flight Control Computers FCC, and which is configured for receiving (in step 210), from the FMS, the power plan command, as well as real-time data representative of the aircraft’s operating conditions, including:- Active or inactive state of the electrical power sources,- Amount of (propulsive and non-propulsive) power demand to meet the aircraft’s electrical needs,- Operating conditions of the electric power sources (amount of power currently delivered, remaining fuel and state of charge of the batteries),Flight conditions (including weather, temperature...)

[0142] The PMS is configured for implementing step 200 described above of operating the electric power sources during the flight. The PMS is in particular configured for assessing the power plan command in view of the energetical situation of the aircraft. The PMS is configured for altering the power plan command in order to protect the aircraft, in order to ensure that the aircraft’s electrical needs are met. The PMS transmits instructions for operating the electrical sources through an Electrical Network Control Computer (not shown), whose function is to manage theelectrical network and transmit the instructions to the turbogenerators through the turbogenerators’ FADEC (Full Authority Digital Engine Control) and to the batteries through the batteries BMS (Battery Management System).

[0143] As the PMS has a critical function of commanding the electric power sources, it belongs to the Aircraft Control Domain, and as such it benefits from properties of availability and integrity of the components of this Domain. As a consequence, the PMS is configured to determine (step 220) the subset of active electric power sources by implementation of deterministic rules. By “rules” are meant instructions that dictate the actions to be taken by the PMS when certain conditions are meant, where said actions can include additional computations. Implementing deterministic rules responds to a requirement of safety for certification of the PMS in the Aircraft Control Domain.

[0144] Generally speaking, the PMS will not command the extinction of an active turbogenerator unless this extinction is planned in the power plan command. However, the PMS may order to switch on an additional turbogenerator when the instantaneous need for electrical power exceeds the need that has been forecasted in the power plan command. In this case, the PMS further takes into account:The current electrical power delivered by each active TG, and the maximum available power,- The current electrical power delivered by each battery,- The state of charge of each battery, and- The time before next ignition of an additional turbogenerator according to the flight power plan.

[0145] Below is a non-limiting example of rules that may be implemented by the PMS according to the number of turbogenerators that are active, considering an aircraft comprising only two turbogenerators. The same reasoning may be adapted easily when the aircraft comprises more than two turbogenerators:- When two / all the turbogenerators are active: o If all the TGs operate at their maximum power, the excess in electrical power demand is provided by the batteries / additional power sources. If the electrical power demand is lower than expected, the PMS sends an instruction for reducing the electrical power delivered by the TGs, o If at least one TG operates below its maximum power, the PMS sends an instruction for increasing the electrical power delivered by the TG.- When at least one TG is inactive, operates at its maximum power, and an supplementary electrical power is requested: o If the State of Charge (SoC) of the batteries does not enable delivering the supplementary electrical power, the PMS sends an ignition instruction to the inactive TG. o If the SoC of the batteries enable delivering the supplementary electrical power:■ If the supplementary electrical power request is temporary and it is not included in the power plan to ignite an additional TG within the duration of the supplementary electrical power request, the PMS instruct the batteries to provide the supplementary electrical power,■ Else, the PMS may instruct the ignition of an additional TG.

[0146] As can be readily understood from the above example, the possibility of activating one or two turbogenerators according to the needs for power, enables using the turbogenerators in their respective efficiency range, which is typically below the maximum power deliverable by each turbogenerator, over a longer duration than conventional flights.

[0147] Accordingly, the sizing of the turbogenerators may be reduced.

[0148] According to embodiments, the turbogenerators are therefore sized such that:- The at least two turbogenerators, i.e. the total number of turbogenerators of the aircraft, operate at a pre-determined high efficiency operating point during cruise at high altitude, and- A subset of turbogenerators, which comprises at most all turbogenerators of the aircraft minus one, can operate at a pre-determined high efficiency operating point during cruise at intermediate altitude.

[0149] Said sizing is preferably considered for a speed of the aircraft which is comprised between 120 % and 150% of the stall speed at said altitudes, the stall speed being expressed as a true air speed. In embodiments, the sizing is performed for a speed comprised between 120% and 150% of the stall speed, for instance equal to 140% of the stall speed.

[0150] The high efficiency operating point corresponds to a delivered electric power that is comprised between 90% and 100% of the maximal deliverable power,considered in continuous operating regime (being noted that the maximal deliverable power in non-continuous operating regime, such as takeoff, may be greater), and preferably between 95% and 100% of the maximal deliverable power, for instance equal to 100%.

[0151] Such a sizing is significantly reduced as compared to traditional thermal propulsion architectures in which turbomachines are sized according to takeoff power needs, and therefore oversized for cruise, thereby operating in sub-optimal power ranges during cruise.

Claims

CLAIMS1 . A hybrid aircraft power management method, wherein the hybrid aircraft comprises:- a plurality of electric power sources (10) of at least two different types, and- a plurality of electric propulsion units (20), each electric propulsion unit being connected to one or more electric power source (10) of each type, and wherein the hybrid aircraft power management method comprises:- determining (100), for a considered flight, a flight power plan, and- based on the determined flight power plan, operating (200) the electric power sources during the flight, wherein the flight power plan comprises a sequence of successive flight phases corresponding to respective electrical needs of the aircraft, and, for each flight phase, a respective subset of active electric power sources, wherein the subset of active electric power sources corresponding to a phase is determined to provide an amount of electrical power meeting the aircraft’s electrical needs of the flight phase.

2. The hybrid aircraft power management method according to claim 1 , wherein the plurality of electric power sources (10) comprises at least two turbogenerators (1 1 ) each comprising an internal combustion engine and at least one electrical generator (14), and at least one complementary power source (12), and each electric propulsion unit is connected to at least two turbogenerators and at least one complementary power source (12).

3. The hybrid aircraft power management method according to claim 1 or 2, wherein the flight power plan further comprises, for each flight phase, an average electrical power value delivered by each active electric power source.

4. The hybrid aircraft power management method according to any of claims 1 to 3, wherein the flight power plan is determined to maximize efficiency of electric power generation by the electric power sources, during a determined time horizon.

5. The hybrid aircraft power management method according to any of claims 3 to 4, wherein the determined time horizon is the duration of the flight or a durationexceeding the duration of the flight, for instance a duration of at least two consecutive flights.

6. The hybrid aircraft power management method according to claim 4 or 5, wherein the efficiency of electric power generation is defined as: wherein Pi(t) is the electric power delivered by a source i at time t, Effi is the electric power generation efficiency of the source i, Ei is the available energy of the source i over the whole flight, and tf-to is the determined time horizon.

7. The hybrid aircraft power management method according to any of the preceding claims, wherein:- determining (100) the flight power plan is performed by a computer belonging to an Airline Information Services Domain, and- operating (200) the electric power sources based on the flight power plan is performed by a computer belonging to an Aircraft Control Domain.

8. The hybrid aircraft power management method according to any of the preceding claims, comprising an initial determination (100) of the flight power plan before the flight, and at least one iteration (110) of updating the flight power plan during the flight.

9. The hybrid aircraft power management method according to the preceding claim, wherein each iteration of updating the flight power plan during the flight is implemented by a software running on a pilot’s mobile computing device and interfaced with an Aircraft Control Domain through a secure gateway.

10. The hybrid aircraft power management method according to any of the preceding claims, wherein operating (200) the electric power sources during the flight in accordance with the determined flight power plan comprises:Receiving (210) real-time data including: o an amount of electrical power demand to meet the aircraft’s electrical needs, o operating conditions of the electric power sources, and- based on the received real-time data, and on the flight power plan, selecting (220) a subset of active electric power sources to provide the amount of electrical power, and issuing a power supply command for each selected power source, comprising an electrical power value to be delivered by each power source.11 . The hybrid aircraft power management method according to claim 10, wherein selecting (220) a subset of active electric power sources based on the received realtime data and on the flight power plan comprises:Determining (221 ) at least one candidate subset of electric power sources based on the received real-time data, such that the candidate subset of electric power sources is able to deliver the amount of electrical power, and,In view of the flight power plan, selecting (222) the candidate subset of electric power sources that satisfies a determined criterion on the number of turbogenerators ignitions or extinctions.

12. The hybrid aircraft power management method according to claim 11 , wherein the determined criterion is minimizing the number of turbogenerator’s ignitions and extinctions over the whole flight.

13. The hybrid aircraft power management method according to any of claims 10 to 12, wherein selecting a subset of active electric power sources is performed by implementing pre-established deterministic rules.

14. The hybrid aircraft power management method according to any of the preceding claims, wherein the aircraft further comprises non-propulsive systems (40), and the aircraft’s electrical needs encompass propulsive and non-propulsive electrical needs.

15. A hybrid aircraft power management device, for an aircraft comprising,- a plurality of electric power sources (10) of at least two different types, and- a plurality of electric propulsion units (20), each electric propulsion unit being connected to one or more electric power source (10) of each type,wherein the hybrid aircraft management device comprises at least a computer configured to:- determine, for a considered flight, a flight power plan, wherein the flight power plan comprises a sequence of successive flight phases corresponding to respective electrical needs of the aircraft, each flight phase being associated with a respective subset of active electric power sources determined to provide an amount of electrical power meeting the aircraft’s electrical needs, and- operate the electric power sources during the flight in accordance with the determined flight power plan, wherein the determination of the flight power plan is implemented to maximize electric power generation efficiency among the electric power sources, during a determined time horizon.

16. The hybrid aircraft power management device according to claim 15, comprising a first computer (9, GRD), belonging to an Airline Information Services Domain configured to determine the flight power plan, and at least a second computer, belonging to an Aircraft Control Domain, configured to operate the electric power sources during the flight in accordance with the determined flight power plan.

17. The hybrid aircraft power management device according to claim 16, wherein the first computer comprises a pilot’s mobile computing device or a server located on the ground, and the first computer is configured for transmitting the flight power plan to the second computer through a secure gateway.

18. The hybrid aircraft power management device according to any of claims 15 to 17, comprising:- A Flight Management System (FMS), configured to receive the flight power plan and to iteratively compute, for each of a plurality of sequences of the flight, based on the flight power plan and a position of the aircraft along the flight: o Longitudinal and lateral guidance commands, o a speed command, and o a power plan command comprising, a respective subset of active electric power sources and an average power to be delivered by eachactive electric power source for the upcoming sequence of the flight, and- a Power Management System (PMS), configured to receive the power plan command, and real-time data including: o an amount of electrical power demand to meet the aircraft’s electrical needs, and o operating conditions of the electric power sources, and to select a subset of active electric power sources to provide the amount of electrical power, and issue a power supply command for each selected power source, comprising an electrical power value to be delivered by each power source.

19. The hybrid aircraft power management device according to the combination of claims 16 and 18, wherein the second computer comprises the FMS and the PMS.

20. A hybrid aircraft power architecture (1 ), comprising:- a plurality of electric power sources (10) of at least two different types, and- a plurality of electric propulsion units (20), each electric propulsion unit being connected to one or more electric power source of each type, the hybrid aircraft power architecture further comprising a hybrid aircraft power management device according to any of claims 15 to 19.

21. The hybrid aircraft power architecture (1 ) according to claim 20, wherein the plurality of electric power sources comprises:- at least two turbogenerators (11 ) each comprising an internal combustion engine (13) and at least one electrical generator (14), and- at least a complementary power source (12), and each electric propulsion unit is connected to at least two turbogenerators (1 1 ) and at least a complementary power source.

22. The hybrid aircraft power architecture (1 ) according to claim 21 , wherein the turbogenerators (1 1 ) are sized such that:- said at least two turbogenerators operate at a pre-determined high efficiency operating point during cruise at high altitude,- a subset of turbogenerators, including at most all turbogenerators minus one, operate at a pre-determined high efficiency operating point during cruise at intermediate altitude.

23. The hybrid aircraft architecture (1 ) according to claim 21 or 22, wherein the turbogenerators are sized such that:- said at least two turbogenerators operate in a pre-determined high efficiency range during cruise at high altitude, for a speed comprised between 120 % and 150 % of the stall speed at said altitude,- a subset of turbogenerators, including at most all turbogenerators minus one, operate in a pre-determined high efficiency range during cruise at intermediate altitude, for a speed comprised between 120 % and 150 % of the stall speed at said altitude.

24. A mobile computing device (9), comprising a display (90), an input interface (91 ), a processor (92) and a memory (93), wherein the memory (93) stores, for at least one considered flight, a flight power plan, comprising, a sequence of successive flight phases corresponding to respective electrical needs of the aircraft, and, for each flight phase, a respective subset of active electric power sources, wherein the subset of active electric power sources corresponding to a phase is determined to provide an amount of electrical power meeting the aircraft’s electrical needs of the flight phase, and wherein the mobile computing device (9) is configured for transmitting, to a computer belonging to an Aircraft Command Domain (ACD), the flight power plan through a secure gateway (99).

25. A mobile computing device (9) according to claim 22, further configured for receiving, during the flight, data regarding the flight and operating conditions of the aircraft, and for updating the stored flight power plan according to the received data.

26. The mobile computing device (9) according to claim 23, further configured for displaying, on the display, a notice of updated flight power plan.

27. The mobile computing device according to claim 23 or 24, wherein the mobile computing device (9) is configured for displaying a notice of updated flight power plan only when:- updating the flight power plan is responsive to an action from the pilot, or,- when the updated flight power plan increases efficiency of electric power generation over the flight of an amount exceeding a predetermined threshold, and the aircraft is in one among a list of predetermined flight phases.

28. The mobile computing device (9) according to claim 24 or 25, further configured for:Receiving, via the input interface, a command from the pilot responsive to displaying an updated flight power plan, and,In response to the pilot’s command, transmitting the updated flight power plan to the computer belonging to the Aircraft Command Domain, through the secure gateway.

29. A Power Management System (PMS), for a hybrid aircraft comprising a plurality of electric power sources (10) of at least two different types, a plurality of electric propulsion units (20), each electric propulsion unit being connected to one or more electric power source (10) of each type, the Power Management System comprising a hardware device configured to operate in an Aircraft Control Domain, the Power Management System (PMS) being configured to receive:- a power plan command comprising, for the upcoming sequence of a flight, a respective subset of active electric power sources and an average power to be delivered by each active electric power source,- real-time data including: o an amount of electrical power demand to meet the aircraft’s electrical needs, o operating conditions of the electric power sources,and being configured to select, based on the received real-time data and on the power plan command, a subset of active electric power sources to provide the amount of electrical power, and to issue a power supply command for each selected power sources, comprising an electrical power value to be delivered by each power source.

30. The Power Management System (PMS) according to claim 27, being configured to select the subset of active electric power sources by implementing pre- established deterministic rules.

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