Method and system for assisting driving of rotorcraft in fuel economy mode

Abstract

A system for assisting the driving of a rotorcraft (10) comprising two engines, the first engine of which is in a standby state to ensure that the aircraft is operating in a fuel economy mode (so-called ECO mode) and the second engine remains operating in said ECO mode, a system allowing the pilot to activate the ECO mode, the flight computer (20) is configured to check in real time that conditions authorized to enter the ECO mode are satisfied: the sum of the powers provided by the engines is less than the maximum continuous power, the rotational speed N2 of the power turbine of the second engine is greater than a determined speed threshold between 80% and 90% of the maximum speed of the engines, the altitude of the aircraft is greater than a minimum value, and the speed of the aircraft is greater than the minimum value. The minimum value allows for a transient phase of autorotation during reactivation of the backup engine in the event of a failure of the operating engine, as well as no serious failure detected.

Description

Technical Field

[0001] The present invention relates to the field of assisted control of rotorcraft, in particular helicopters or drones, and more particularly to a fuel economy mode or "ECO mode" consisting in, for example, placing one of the two engines of a twin-engine aircraft in standby mode in order to save fuel during cruising or waiting flight and search phases (loitering). Background Art

[0002] Climate change is a major concern for many legislators and regulators worldwide. Specifically, states have already adopted, are currently adopting, or will soon adopt various measures to limit carbon emissions. In particular, an ambitious standard applies to both new and existing aircraft, requiring the implementation of technical solutions to bring them into compliance with existing regulations. In recent years, civil aviation has been committed to contributing to the fight against climate change.

[0003] Technological research has led to significant improvements in the environmental performance of aircraft. The applicant considers factors influencing all stages of design and development to achieve components and aviation products that consume less energy, are more environmentally friendly, and can be integrated and used in civil aviation with only a moderate environmental impact, with the goal of improving aircraft energy efficiency. Therefore, the applicant is committed to reducing its impact on the climate by using environmentally friendly methods that minimize greenhouse gas emissions and utilizing corresponding development and manufacturing processes, thereby reducing the environmental footprint of its activities.

[0004] This ongoing research and development effort also focuses on next-generation aircraft engines, lightweighting of aircraft (particularly through the materials used and lighter onboard equipment), the development of electronic technologies to provide propulsion, and ultimately, aviation biofuels.

[0005] In this context, it is known that twin-engine aircraft, during the cruise or loitering phase, use the engines in a fuel economy mode (so-called ECO mode), either with the combustion chambers of the engines open or closed. In this mode, which is used, for example, in rotary twin-engine aircraft, one of the aircraft's engines is in standby mode.

[0006] However, if used improperly, this mode of operation can lead to premature wear of the engines that provide propulsion power to the aircraft, particularly the hot parts of gas turbines, a phenomenon known as endocreep.

[0007] Authorization and subsequent maintenance of ECO mode is necessary for safety reasons and includes performing safety tests (or safety checks) to determine the values ​​of engine parameters and then checking whether these engine parameters are within suitable operating ranges to enable and subsequently maintain ECO mode.

[0008] However, performing such a safety check requires a certain amount of time and is therefore particularly restrictive for the pilot, who must maneuver the aircraft to stabilize the engine ratings and thermal management. Summary of the Invention

[0009] The subject of the present invention is therefore a method for assisted driving that alleviates the above-mentioned drawbacks and allows optimizing the use of the ECO mode to save fuel. The invention also aims to ensure that the ECO mode can be used in complete safety.

[0010] These objectives are achieved by a method for assisting the piloting of a rotorcraft comprising two engines, a first engine of which is in standby state to ensure the operation of the aircraft in a fuel economy mode (so-called ECO mode), the second engine remaining operational in said ECO mode, the method being characterized in that, in order to allow the pilot to activate the ECO mode, the flight computer of the aircraft checks in real time that the following conditions for authorizing entry into the ECO mode are met: the sum of the powers supplied by the engines is less than the maximum continuous power, the rotation speed N2 of the power turbine of the second engine is greater than a determined speed threshold, the altitude of the aircraft is greater than a minimum value that allows the transition phase of automatic rotation during the reactivation of the standby engine in the event of a failure of the operating engine, and the absence of detected serious faults.

[0011] Similarly, in order to allow reactivation of the first engine and thus exit the ECO mode, at least one of the aforementioned conditions for entering the ECO mode or one of the following additional conditions must be false: the acceleration limit is not reached, the oil temperature TH is greater than a determined temperature threshold, which makes it possible to ensure rapid reactivation of the standby engine, the fuel temperature Tcarb is greater than a determined temperature threshold, which makes it possible to ensure rapid reactivation of the standby engine, and there is no loss of power to the running engine.

[0012] Thus, with ECO mode activated, the nominal values ​​and margins of the engine parameters are estimated directly based on the engine model implemented in the flight computer, and their updating and display can therefore be done more regularly and in a manner that is more transparent to the pilot.

[0013] Preferably, serious faults include data faults that prevent normal operation of the engine and / or its equipment, series faults, electrical system faults, faults that cause loss of engine control, control system faults, and hydraulic system faults.

[0014] Advantageously, the fulfillment or non-fulfillment of the authorization condition is displayed on an indicator disk comprising three power ranges, which respectively correspond to the fulfillment of the authorization condition, the possible fulfillment of the authorization condition and the non-fulfillment of the authorization condition.

[0015] Preferably, the speed of rotation N2 of the power turbine is greater than a threshold between 80% and 90% of the maximum speed of the engine, the oil or fuel temperature threshold is 5° C., and the minimum value of the minimum altitude is equal to 300 meters.

[0016] The present invention also relates to an assisted piloting system for implementing the above method, and an aircraft for implementing the assisted piloting system, preferably a twin-engine helicopter. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Other characteristics and advantages of the invention will become apparent from the description given below, made with reference to the accompanying single drawing, which shows, without any limitation, an exemplary embodiment of the invention and in which:

[0018] [ Figure 1 ] Figure 1 An aircraft including a system for assisting piloting in ECO mode according to an example of the present invention is schematically shown. DETAILED DESCRIPTION

[0019] The principle of the invention is based on the real-time determination of various parameters by the aircraft's flight computer, which are then synthesized to provide the pilot with a flight control indication on a screen in the aircraft's cockpit (e.g., a FLI for the first limit indicator) indicating whether entry into fuel economy mode (ECO mode) is authorized. Preferably, once this ECO mode is activated, the pilot can also access the indicator to find out whether it is authorized to maintain said mode.

[0020] For example, if the duration of the cruise phase is long enough, typically at least greater than 10 minutes, and the power requested during this phase is not too high (corresponding to an engine control temperature greater than 1400K), the pilot can enable ECO mode if all the authorization conditions defined by the flight computer are met.

[0021] To do this, with all engines operating and controlled conventionally according to their nominal speed and / or torque set points, it is recommended that the following flight parameters meet the authorization conditions to allow activation of ECO mode:

[0022] - the sum of the powers supplied by the engines, P, is less than the maximum continuous power (PMC),

[0023] the speed N2 of the power turbine of the operating engine is greater than a determined speed threshold (preferably corresponding to a threshold between 80% and 90% of the maximum speed of the engine),

[0024] - the altitude H is greater than a minimum value that allows the transition phase of autorotation during the reactivation of the standby engine in the event of failure of the operating engine (safety standard), typically an altitude Alt> 300 m, and

[0025] - No serious faults are detected (nonPa). The term "serious fault" is understood to mean the failure of certain data (NR, i.e. rotor, selector speed, fuel pressure) that prevents the normal operation of the aircraft and / or its equipment, failures of serial links (between computers and between computers and aircraft), failures of the electrical system, failures of the IGV, failures that can affect the control system (limited acceleration

[0026] / deceleration speed), hydraulic system failure and any other failure that could lead to loss of engine control. Having a rotation speed N2 greater than a threshold between 80% and 90% of the maximum engine speed makes it possible to cover the aircraft's cruising or holding flight phases as well as taxiing and ground idling phases.

[0027] In other words, a rotation speed N2 greater than 80% of the maximum speed of the engines makes it possible to ensure that the aircraft operates in a fuel-efficient mode (so-called ECO mode) during the taxiing and ground idling phases.

[0028] Similarly, a rotation speed N2 greater than 90% of the maximum engine speed ensures that the aircraft operates in a fuel-saving mode (so-called ECO mode) during the cruise phase. These authorization conditions for entering ECO mode must be cumulatively met before activation of ECO mode is permitted. To enter ECO mode, the computer of the engine being placed on standby preferably performs several checks. The first step is to check whether authorization has been received from the avionics system.

[0029] The computer also performs a consistency check to verify that the request to enter ECO mode has been correctly formulated and to avoid untimely activation of ECO mode. The computer also checks for the presence of one or more critical faults. These faults include, for example, faults that could affect the operation of ECO mode, the operation of the engine, or the operation of the system for reactivating an engine that was placed in standby mode.

[0030] Once all of these checks have been performed, and only if these conditions are met, the first engine preferably gradually shifts to ECO mode. Upon entering ECO mode, the power of the first engine is preferably gradually reduced until it reaches minimum power. The first engine maintains operation at minimum power for a period of time, for example, between one and two minutes. Next, the engine starter is activated to check the operation of ECO mode. If the starter is functioning properly, the first engine is placed in standby mode.

[0031] like Figure 1As shown, in the aircraft 10, when all engines are running and controlled at their nominal set points, the flight computer 20 can calculate the power that should be provided by the engines that remain running in the ECO mode (estimated ECO power). In addition, by adding the power provided by each engine and using the engine model installed in the flight computer, it is possible to determine what engine parameters (N1, TC, and torque) correspond to this power and the degree of damage to the engines that remain running.

[0032] Specifically, an engine model implemented in a computer is used to evaluate the health status of the second engine that remains in operation in real time, and to determine in real time whether the second engine that remains in operation in the ECO mode can provide the power required to continue the flight.

[0033] All of this data can be used to determine whether entry into ECO mode is permitted, and whether it is recommended. They can also be displayed (continuously or upon request, for example, in the first limit indicator dial 22) to assist the pilot in positioning himself within the power range 100 most suitable for, for example, ECO mode (the lower ranges show the selectable possible power range 102 and the prohibited power range 104, respectively). Thus, if ECO mode is activated, the pilot has access to a temporary view of the engine parameters. Thus, he can predict the margin of available power relative to the maximum available power in ECO mode, as well as the fuel consumption savings associated with operation of all engines. This indicator can be correlated with several parameters (N1, TC, torque, power, etc.).

[0034] Likewise, when ECO mode is activated, the engines and the entire electrical system dedicated to reactivating the backup engine are monitored to initiate reactivation of the backup engine if necessary. Thus, the flight computer can continuously monitor the overall status of the engines and electrical systems and, in particular, determine in real time whether all conditions for maintaining ECO mode are met. If a failure or loss of power is detected in the operating engine, the backup engine will be reactivated.

[0035] Note that the aforementioned authorization to enter ECO mode is not necessarily subject to the same conditions, and therefore not necessarily calculated in the same manner, as the authorization to remain in ECO mode (or any request to exit ECO mode). For example, the engine in standby will be reactivated (thereby causing exit from ECO mode) if at least one of the following conditions for maintaining ECO mode becomes false, namely:

[0036] - the engine is running with a power less than the maximum established power, usually PMC,

[0037] - the speed N2 of the power turbine of the running engine is greater than a determined speed threshold,

[0038] - the altitude H is greater than a minimum value that allows a transition phase of autorotation during reactivation of the standby engine in case of failure of the operating engine (safety standard), usually Alt>300 m,

[0039] - there are no detected serious faults (nonPa),

[0040] - Acceleration limits are not reached, which are essentially surge protection limits, gas generator acceleration limits, or fuel flow rates greater than or equal to the maximum flow rate, typically 500

[0041] kg / h.

[0042] - the oil temperature Th is greater than a certain temperature threshold, making it possible to ensure rapid reactivation of the standby engine, typically Th>5°C,

[0043] - the fuel temperature Tcarb is greater than a determined temperature threshold, making it possible to ensure rapid reactivation of the standby engine, typically Tcarb>5°C, and,

[0044] - No loss of power to the running engine.

[0045] When the aircraft is in ECO mode and a fault is detected, if the detected fault prevents the normal operation of ECO mode or threatens to freeze the normal operation of ECO mode, the engine in ECO mode will exit ECO mode. This type of fault is considered critical to the operation of ECO mode. Therefore, the criticality of one or more faults has an impact on the exit from ECO mode. If a single fault occurs that prevents the normal operation of ECO mode, it will trigger the exit from ECO mode.

[0046] However, if the detected fault does not affect the operation of the ECO mode or the power availability of the engines remaining in operation, or does not pose a risk of affecting the operation of the ECO mode or the power availability of the engines remaining in operation, then the ECO mode is preferably maintained. For example, if a failure occurs in the flight recorder system, this does not pose an obstacle to continuing the ECO mode. On the other hand, if a fault occurs in the system for measuring the rotational speed of the power turbine of the operating engine, then the ECO mode is preferably not maintained and exited without waiting for the occurrence of a new fault. This is because a single fault could cause damage to the engines remaining in operation.

[0047] It is also noted that several indications related to ECO mode may be issued in such a manner as to inform the pilot regarding the use of ECO mode (ECO mode activated, ECO mode authorized, ECO mode interrupted), such as an indication related to the transition to the standby phase; and / or an indication related to the engine being on standby; and / or an indication related to a reactivation being in progress (and the type of reactivation); and / or an indication related to an interruption of a reactivation.

[0048] Note that although reference is primarily made to conventional twin-engine applications, the present invention is naturally applicable to multi-engine and UAV applications, where recommendations for engine usage may also be made to the pilot or flight control system.

Claims

1. A method for assisting the piloting of a rotorcraft (10) comprising two engines, a first engine of which is in a standby state to ensure operation of the aircraft in a fuel economy mode, so-called ECO mode, the second engine remaining operational in said ECO mode, The method is characterized in that, allowing the pilot to activate the ECO mode, the flight computer (20) of the aircraft checks in real time that the following conditions for authorizing entry into the ECO mode are met: - the sum of the powers supplied by the engines is less than the maximum continuous power, - the rotational speed N2 of the power turbine of the second engine is greater than a determined speed threshold, said speed threshold being between 80% and 90% of the maximum speed of said engine, - the aircraft's altitude is greater than a minimum value that allows the transition phase of autorotation during reactivation of the standby engine in the event of a failure of the operating engine, - and the absence of any detected serious faults.

2. The method according to claim 1, wherein To allow reactivation of the first engine and thus exit the ECO mode, at least one of the aforementioned conditions for entering ECO mode or one of the following additional conditions must be false: - the acceleration limit is not reached, - the oil temperature TH is greater than a determined temperature threshold, making it possible to ensure a rapid restart of the standby engine use, the fuel temperature Tcarb is greater than a determined temperature threshold, making it possible to ensure rapid reactivation of the standby engine, - and running engines with no loss of power.

3. The method according to claim 2, wherein The oil or fuel temperature threshold is 5°C.

4. The method according to any one of claims 1 to 3, wherein The serious faults include data faults that prevent the normal operation of the engine and / or its equipment, series faults, electrical system faults, faults that cause engine loss of control, control system faults and hydraulic system faults.

5. The method according to any one of claims 1 to 4, wherein The satisfaction or non-satisfaction of the authorization condition is displayed on an indicator disk (22) including three power ranges (100, 102, 104), which respectively correspond to the satisfaction of the authorization condition, the possible satisfaction of the authorization condition and the non-satisfaction of the authorization condition.

6. The method according to any one of claims 1 to 5, wherein The minimum value of the altitude is 300 meters.

7. A system for assisting the piloting of a rotorcraft (10) comprising two engines, the first of which is in standby state to ensure that the aircraft operates in a fuel economy mode, so-called ECO mode, the second engine remaining operational in said ECO mode, said method being characterized in that it allows the pilot to activate said ECO mode, comprising a flight computer (20) configured to check in real time that the following conditions for authorizing entry into the ECO mode are met: the sum of the powers supplied by the engines is less than the maximum continuous power, the rotation speed N2 of the power turbine of the second engine is greater than a determined speed threshold, said speed threshold being between 80% and 90% of the maximum speed of the engines, the altitude of the aircraft being greater than a minimum value allowing a transition phase of automatic rotation during the reactivation of the standby engine in the event of a failure of the operating engine, and the absence of detected serious faults.

8. The system according to claim 7, wherein: Also included is an indicator panel (22) connected to the flight computer and configured to display in three power ranges (100, 102, 104), the three power ranges corresponding to satisfaction of the authorization condition, possible satisfaction of the authorization condition, and non-satisfaction of the authorization condition, respectively.

9. An aircraft (10), preferably a twin-engine helicopter, comprising a system for assisting piloting according to any one of claims 7 or 8.

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