Protection system

Abstract

A method of operating a variable pitch propeller system for an aircraft, the method comprising: receiving aircraft flight information; performing a virtual pitch calculation to determine a virtual propeller pitch or a virtual blade angle from the aircraft flight information; and performing a pitch protection process in response to determining the low virtual propeller pitch or virtual blade angle.

Description

Technical Field

[0001] The present application relates to a pitch protection system, a pitch control system, a health monitoring system, a variable pitch propeller system, an aircraft and a method. Background Art

[0002] The pitch protection system for variable pitch propeller systems is designed to provide fail-safe behavior when the main control system fails. When the propeller overspeeds or the blade pitch displacement is below the minimum low pitch position in flight, the protection system may override the main control system. Variable pitch propeller systems typically have a complex architecture and are heavy, costly, and require high maintenance. They may require multiple sensors (e.g., blade angle sensors are required for each of the protection system and the main control system) or hydromechanical systems (e.g., blade angle sensors are required for the protection system and the main control system) with extensive maintenance and calibration requirements. Summary of the invention

[0003] In a first aspect, there is provided a method of operating a variable pitch propeller system for an aircraft, the method comprising:

[0004] Receive aircraft flight information;

[0005] performing a virtual pitch calculation to determine a virtual propeller pitch or a virtual blade angle based on aircraft flight information; and

[0006] A pitch protection procedure is performed in response to determining a low virtual propeller pitch or virtual blade angle.

[0007] By performing a virtual pitch calculation to determine a virtual propeller pitch or a virtual blade angle, the number of sensors may be reduced and the variable pitch propeller system may be simplified. Since the virtual pitch calculation is particularly accurate when the virtual propeller pitch is near a propeller pitch threshold (e.g., during flight), the virtual propeller pitch calculation may be particularly suitable for determining when to perform a pitch protection procedure.

[0008] When the virtual propeller pitch is below a propeller pitch threshold, a low virtual propeller pitch or a virtual blade angle may be determined. When the virtual blade angle is below a threshold, a low virtual propeller pitch or a virtual blade angle may be determined.

[0009] The aircraft flight information may include aeronautical information. The virtual pitch calculation may include aeronautical information calculations performed on the aeronautical information to determine a virtual propeller pitch or a virtual blade angle.

[0010] The method may include sensing aeronautical information.

[0011] The aeronautical information may include aircraft speed information. The aircraft speed information may include indicated airspeed. The aircraft speed information may include Mach number. The aircraft speed information may include true airspeed.

[0012] The aviation information may include environmental information. The environmental information may include aircraft altitude. The environmental information may include ambient air density. The environmental information may include ambient temperature.

[0013] Aeronautical information can include any additional information such as pitch, yaw and roll angles, angle of attack, X, Y or Z acceleration, weight, etc...

[0014] Aircraft flight information may include propeller drive power information.

[0015] The propeller drive power information may include engine parameters. The engine parameters may include engine torque. The engine parameters may include engine speed. The engine parameters may include engine power.

[0016] The propeller drive power information may include propeller parameters. The propeller parameters may include propeller speed. The propeller parameters may include propeller drive torque. The propeller parameters may include propeller drive power.

[0017] The virtual pitch calculation may include a propeller power calculation performed on the propeller drive power information to determine a virtual propeller pitch or a virtual blade angle.

[0018] The input shaft propeller power can be calculated from the propeller speed and the absorbed propeller torque. The input shaft propeller power can be calculated from the aircraft airspeed, propeller thrust and propeller efficiency. The input shaft propeller power can be calculated from the engine speed and engine torque. The calculation from the propeller speed and absorbed propeller torque is preferred.

[0019] The aircraft flight information may include aircraft system configuration information. The aircraft system configuration information may include configuration of aircraft flight control components. The aircraft control components may include flaps. The aircraft control components may include slats. The aircraft system configuration information may include landing gear status.

[0020] The method may include sensing propeller drive power information from an engine of the aircraft, the engine being configured to drive a propeller.

[0021] The aircraft flight information may not include the measured propeller pitch. The aircraft flight information may not include the measured blade angle. The aircraft flight information may not include the propeller speed.

[0022] The pitch protection process may include controlling the variable pitch propeller system to increase the propeller pitch and / or blade angle.

[0023] The pitch protection process may include bypassing the pitch controller of the variable pitch propeller system.

[0024] The virtual pitch calculation includes performing an aircraft flight information verification process to verify that the aircraft flight information is valid. The aircraft flight information verification process may include determining that the sensor is in operation. The aircraft flight information verification process may include determining that the sensor is within an operating range. The aircraft flight information verification process may include determining that the sensor is connected.

[0025] The method may include controlling the propeller pitch according to a pitch control process in response to not determining a low virtual propeller pitch or a virtual blade angle. The pitch control process may include receiving a measured blade angle from a blade angle sensor and controlling the pitch of the propeller in response to the measured blade angle.

[0026] The method may include sensing a blade angle of a propeller.

[0027] The pitch control process may include linear control. The pitch control process may include proportional control. The pitch control process may include integral control. The pitch control process may include derivative control. The pitch control process may include any one of proportional control and / or integral control and / or differential control and any combination thereof. The pitch control process may include nonlinear control. The pitch control process may include deterministic control. The pitch control process may include lead-lag control. Other types of control are also foreseeable.

[0028] According to a second aspect, a protection system for a variable pitch propeller system is provided, the protection system comprising: a virtual pitch sensor configured to receive aircraft flight information and perform a virtual pitch calculation to determine a virtual propeller pitch or a virtual blade angle based on the aircraft flight information; and a processor configured to perform a pitch protection process in response to determining a low virtual propeller pitch or a virtual blade angle.

[0029] When the virtual propeller pitch is below a propeller pitch threshold, a low virtual propeller pitch or a virtual blade angle may be determined. When the virtual blade angle is below a threshold, a low virtual propeller pitch or a virtual blade angle may be determined.

[0030] The aircraft flight information may include aeronautical information. The virtual pitch calculation may include aeronautical information calculations performed on the aeronautical information to determine a virtual propeller pitch or a virtual blade angle.

[0031] The method may include sensing aeronautical information.

[0032] The aeronautical information may include aircraft speed information. The aircraft speed information may include indicated airspeed. The aircraft speed information may include Mach number. The aircraft speed information may include true airspeed.

[0033] The aviation information may include environmental information. The environmental information may include aircraft altitude. The environmental information may include ambient air density. The environmental information may include ambient temperature.

[0034] Aeronautical information can include any additional information such as pitch, yaw and roll angles, angle of attack, X, Y or Z acceleration, weight, etc...

[0035] Aircraft flight information may include propeller drive power information.

[0036] The propeller drive power information may include engine parameters. The engine parameters may include engine torque. The engine parameters may include engine speed. The engine parameters may include engine output mechanical power.

[0037] The propeller drive power information may include propeller parameters. The propeller parameters may include propeller speed. The propeller parameters may include propeller drive torque. The propeller parameters may include propeller drive power.

[0038] The virtual pitch calculation may include a propeller power calculation performed on the propeller drive power information to determine a virtual propeller pitch or a virtual blade angle.

[0039] The input shaft propeller power can be calculated from the propeller speed and the absorbed propeller torque. The input shaft propeller power can be calculated from the aircraft airspeed, propeller thrust and propeller efficiency. The input shaft propeller power can be calculated from the engine speed and engine torque. The calculation from the propeller speed and absorbed propeller torque is preferred.

[0040] The aircraft flight information may include aircraft system configuration information. The aircraft system configuration information may include configuration of aircraft flight control components. The aircraft control components may include flaps. The aircraft control components may include slats. The aircraft system configuration information may include landing gear status.

[0041] The method may include sensing propeller drive power information from an engine of the aircraft, the engine being configured to drive a propeller.

[0042] The aircraft flight information may not include the measured propeller pitch. The aircraft flight information may not include the measured blade angle. The aircraft flight information may not include the propeller speed.

[0043] The pitch protection process may include controlling the variable pitch propeller system to increase the propeller pitch and / or blade angle.

[0044] The pitch protection process may include bypassing the pitch controller of the variable pitch propeller system.

[0045] The virtual pitch calculation includes performing an aircraft flight information verification process to verify that the aircraft flight information is valid. The aircraft flight information verification process may include determining that the sensor is in operation. The aircraft flight information verification process may include determining that the sensor is within an operating range.

[0046] The protection system may be included in a protection unit. The virtual pitch sensor and the protection processor may be embodied in a single processor. The virtual pitch sensor and the protection processor may be located in separate units.

[0047] According to a third aspect, a variable pitch propeller system is provided, the variable pitch propeller system comprising the above-mentioned protection system.

[0048] The variable pitch propeller system may include a pitch controller configured to control the propeller pitch according to a pitch control process in response to not determining a low virtual propeller pitch or a virtual blade angle. The pitch control process may include receiving a measured blade angle from a blade angle sensor and controlling the pitch of the propeller in response to the measured blade angle.

[0049] The variable pitch propeller system may include a blade angle sensor configured to measure a blade angle of the propeller.

[0050] The pitch control process may include linear control. The pitch control process may include proportional control. The pitch control process may include integral control. The pitch control process may include derivative control. The pitch control process may include any of proportional control and / or integral control and / or differential control.

[0051] The variable pitch propeller system may include the propeller. The variable pitch propeller system may include a drive unit for driving the propeller.

[0052] According to a fourth aspect, there is provided an aircraft comprising a variable pitch propeller system.

[0053] The method of the first aspect may include any one of the features and / or functional steps described with respect to the second aspect, the third aspect, and / or the fourth aspect. The protection system of the second aspect may include any one of the features and / or functional steps described with respect to the first aspect, the third aspect, and / or the fourth aspect. The variable pitch propeller system of the third aspect may include any one of the features and / or functional steps described with respect to the first aspect, the second aspect, and / or the fourth aspect. The aircraft of the fourth aspect may include any one of the features and / or functional steps described with respect to the first aspect, the second aspect, and / or the third aspect.

[0054] According to a fifth aspect, a method for performing health status monitoring on an aircraft with a variable pitch propeller system is provided, the method comprising: receiving aircraft flight information; performing a virtual pitch calculation to determine a virtual propeller pitch or a virtual blade angle based on the aircraft flight information; receiving a measured propeller pitch or blade angle from at least one physical sensor associated with the propeller; and performing a health status monitoring process using the virtual propeller pitch or the virtual blade angle and the measured propeller pitch or blade angle to determine the health status of at least one component of the aircraft, wherein at least one component is different from the blade.

[0055] Performing a virtual pitch calculation to determine a virtual propeller pitch or virtual blade angle may provide a useful data source for aircraft health monitoring, e.g., a difference between a measured value and a virtual value may indicate that a component of the aircraft is not operating as expected.

[0056] Determining the health status may include propeller gearbox fault detection and / or propeller pitch change actuator fault detection.

[0057] The health monitoring process may be performed during flight. The health monitoring process may be performed while the aircraft is on the ground.

[0058] The health monitoring process may include comparing a virtual propeller pitch or a virtual blade angle to a measured propeller pitch or blade angle. When the difference between the virtual value and the measured value exceeds a threshold, poor health may be determined.

[0059] The measured propeller pitch may be determined from the measured blade angle and propeller speed. The method may comprise measuring the blade angle and the propeller speed.

[0060] The health monitoring process may include determining a failure of a component. The health monitoring process may include determining a wear condition of a component.

[0061] The component of the aircraft may be an aircraft system. The aircraft system may include a mechanical system of a propeller. The aircraft system may include a hydraulic system of a propeller. The aircraft system may include an electrical system of a propeller. The aircraft system may include a propeller gearbox.

[0062] The aircraft flight information may include aeronautical information. The virtual pitch calculation may include aeronautical information calculations performed on the aeronautical information to determine a virtual propeller pitch or a virtual blade angle.

[0063] The method may include sensing aeronautical information.

[0064] The aeronautical information may include aircraft speed information. The aircraft speed information may include indicated airspeed. The aircraft speed information may include Mach number. The aircraft speed information may include true airspeed.

[0065] The aviation information may include environmental information. The environmental information may include aircraft altitude. The environmental information may include ambient air density. The environmental information may include ambient temperature.

[0066] Aeronautical information can include any additional information such as pitch, yaw and roll angles, angle of attack, X, Y or Z acceleration, weight, etc...

[0067] Aircraft flight information may include propeller drive power information.

[0068] The propeller drive power information may include engine parameters. The engine parameters may include engine torque. The engine parameters may include engine speed. The engine parameters may include engine power.

[0069] The propeller drive power information may include propeller parameters. The propeller parameters may include propeller speed. The propeller parameters may include propeller drive torque. The propeller parameters may include propeller drive power.

[0070] The virtual pitch calculation may include a propeller power calculation performed on the propeller drive power information to determine a virtual propeller pitch or a virtual blade angle.

[0071] The input shaft propeller power can be calculated from the propeller speed and the absorbed propeller torque. The input shaft propeller power can be calculated from the aircraft airspeed, propeller thrust and propeller efficiency. The input shaft propeller power can be calculated from the engine speed and engine torque. The calculation from the propeller speed and absorbed propeller torque is preferred.

[0072] The aircraft flight information may include aircraft system configuration information. The aircraft system configuration information may include configuration of aircraft flight control components. The aircraft control components may include flaps. The aircraft control components may include slats. The aircraft system configuration information may include landing gear status.

[0073] The method may include sensing propeller drive power information from an engine of the aircraft, the engine being configured to drive a propeller.

[0074] The aircraft flight information may not include the measured propeller pitch. The aircraft flight information may not include the measured blade angle. The aircraft flight information may not include the propeller speed.

[0075] The virtual pitch calculation includes performing an aircraft flight information verification process to verify that the aircraft flight information is valid. The aircraft flight information verification process may include determining that the sensor is in operation. The aircraft flight information verification process may include determining that the sensor is within an operating range. The aircraft flight information verification process may include determining that the sensor is connected.

[0076] According to a sixth aspect, a health status monitoring system for a variable pitch propeller system of an aircraft is provided, the health status monitoring system comprising: a virtual pitch sensor, which is configured to receive aircraft flight information and perform virtual pitch calculations to determine a virtual propeller pitch or a virtual blade angle based on the aircraft flight information; at least one physical sensor, which is configured to measure the propeller pitch or the blade angle; and a health status monitoring processor, which is configured to use the virtual propeller pitch or the virtual blade angle and the measured propeller pitch or blade angle to perform a health status monitoring process to determine the health status of at least one component of the aircraft, wherein at least one component is different from the blade.

[0077] Determining the health status may include propeller gearbox fault detection and / or propeller pitch change actuator fault detection.

[0078] The aircraft flight information may include aeronautical information. The virtual pitch calculation may include aeronautical information calculations performed on the aeronautical information to determine a virtual propeller pitch or a virtual blade angle.

[0079] The health monitoring system may include an environmental sensing device configured to sense aeronautical information.

[0080] The aeronautical information may include aircraft speed information. The aircraft speed information may include indicated airspeed. The aircraft speed information may include Mach number. The aircraft speed information may include true airspeed.

[0081] Aeronautical information may include environmental information. Environmental information may be related to environmental conditions. Environmental information may include aircraft altitude. Environmental information may include ambient air density. Environmental information may include ambient air temperature.

[0082] Aircraft flight information may include propeller drive power information.

[0083] The propeller drive power information may include engine parameters. The engine parameters may include engine output torque. The engine parameters may include engine speed. The engine parameters may include engine output mechanical power.

[0084] The propeller drive power information may include propeller parameters. The propeller parameters may include propeller speed. The propeller parameters may include propeller drive torque. The propeller parameters may include propeller drive power.

[0085] The virtual pitch calculation may include a propeller power calculation performed on the propeller drive power information to determine a virtual propeller pitch or a virtual blade angle.

[0086] The input shaft propeller power can be calculated from the propeller speed and the absorbed propeller torque. The input shaft propeller power can be calculated from the aircraft airspeed, propeller thrust and propeller efficiency. The input shaft propeller power can be calculated from the engine speed and engine torque. The calculation from the propeller speed and absorbed propeller torque is preferred.

[0087] The aircraft flight information may include aircraft system configuration information. The aircraft system configuration information may include configuration of aircraft flight control components. The aircraft control components may include flaps. The aircraft control components may include slats. The aircraft system configuration information may include landing gear status.

[0088] The health monitoring system may include a propeller power sensor configured to sense propeller drive power information. The power sensor may be configured to sense propeller drive power information from an engine of the aircraft, the engine being configured to drive a propeller.

[0089] The aircraft flight information may not include the measured propeller pitch. The aircraft flight information may not include the measured blade angle. The aircraft flight information may not include the propeller speed.

[0090] The virtual pitch calculation includes performing an aircraft flight information verification process to verify that the aircraft flight information is valid. The aircraft flight information verification process may include determining that the sensor is in operation. The aircraft flight information verification process may include determining that the sensor is within an operating range.

[0091] According to a seventh aspect, a variable pitch propeller system is provided, the variable pitch propeller system comprising the above health status monitoring system.

[0092] According to an eighth aspect, there is provided an aircraft comprising a variable pitch propeller system.

[0093] The method of the fifth aspect may include any one of the features and / or functional steps described in relation to the sixth aspect, the seventh aspect, and / or the eighth aspect. The health status monitoring system of the sixth aspect may include any one of the features and / or functional steps described in relation to the fifth aspect, the seventh aspect, and / or the eighth aspect. The variable pitch propeller system of the seventh aspect may include any one of the features and / or functional steps described in relation to the fifth aspect, the sixth aspect, and / or the eighth aspect. The aircraft of the eighth aspect may include any one of the features and / or functional steps described in relation to the fifth aspect, the sixth aspect, and / or the seventh aspect.

[0094] The systems and methods related to health status monitoring in aspects 5 to 8 may include any of the features and / or functional steps specified for the systems and methods related to protection in aspects 1 to 4. In addition, the systems and methods related to protection in aspects 1 to 4 may include any of the features and / or functional steps specified for the systems and methods related to health status monitoring in aspects 5 to 8.

[0095] The protection system and the health monitoring system may share a common virtual pitch sensor.The variable pitch propeller system and / or the aircraft may include a protection system and a health monitoring system. BRIEF DESCRIPTION OF THE DRAWINGS

[0096] Various examples will now be described with reference to the accompanying drawings, in which:

[0097] Figure 1 A schematic diagram of an aircraft including a variable pitch propeller system is shown;

[0098] Figure 2 A cross-sectional view of a propeller is shown;

[0099] Figure 3 A method of operating a variable pitch propeller system is shown;

[0100] Figure 4 a schematic diagram showing a second aircraft including a second variable pitch propeller system; and

[0101] Figure 5 A method of operating a second variable pitch propeller system is shown. DETAILED DESCRIPTION

[0102] Figure 1 An aircraft 10 is shown. The aircraft 10 includes a variable pitch propeller system 12. The variable pitch propeller system 12 includes a propeller 14, an engine 16, a pitch protection system 18, and a pitch control system 20.

[0103] The pitch protection system 18 includes a virtual pitch sensor 22, a protection processor 24, an environmental sensing device 26, a propeller sensing device 28, and an engine sensing device 30. Each of the environmental sensing device 26, the propeller sensing device 28, and the engine sensing device 30 includes a plurality of sensors configured to measure aircraft flight information as described below. It should be understood that several of the components may be embodied in a single processor (e.g., the virtual pitch sensor and the protection processor).

[0104] Pitch control system 20 (also referred to as a main control system) includes a controller 32 , a propeller speed sensor 34 , and a blade angle sensor 36 .

[0105] Figure 2The propeller 14 is shown in greater detail, highlighting the location of a propeller sensing device 28, a propeller speed sensor 34, and a blade angle sensor 36 that are located with the propeller 14 (e.g., contained in a propeller unit). The propeller sensing device 28, the propeller speed sensor 34, and the blade angle sensor 36 are located at a location remote from the pitch protection system 18 and the pitch control system 20.

[0106] In other examples, blade angle sensor 36 may also be located remotely from propeller 14 , such as with other components of pitch control system 20 .

[0107] During normal use, the engine 16 provides mechanical power to drive the propeller 14, which can be used for aircraft thrust or braking. The pitch of the propeller 14 is controlled by the pitch control system 20 according to the pitch control process. During the pitch control process, the propeller speed sensor 34 measures the propeller speed. The blade angle sensor 36 measures the blade angle. The controller 32 receives the propeller speed and the blade angle and controls the propeller pitch. The controller 32 changes the blade angle (for example, by controlling the blade angle actuator 38 through, for example, a mechanical, hydraulic or electromechanical system) to control the propeller pitch. In this example, the controller 32 uses the propeller speed and the blade angle to implement proportional-integral-derivative control to achieve the target propeller pitch. In other examples, the controller can implement nonlinear control.

[0108] The propeller pitch or blade angle is a function of the drive power and propeller speed on the one hand, and of the aircraft aerodynamic configuration and flight conditions on the other hand. Each set of such parameters has a unique propeller pitch.

[0109] In some cases, a malfunction of the propeller control system 20 may result in the propeller pitch being too low, resulting in low propeller pitch, which may cause aircraft controllability issues. As described below, in the event of low propeller pitch, the pitch protection system 18 performs a pitch protection procedure.

[0110] Figure 3 A method 100 of operating a variable pitch propeller system 12 is shown. The method includes an aircraft flight information receiving phase 102, a virtual pitch calculation phase 104, a virtual propeller pitch comparison phase 106, a pitch control phase 108, and a pitch protection phase 110.

[0111] In the aircraft flight information receiving stage 102 , the virtual pitch sensor 22 receives aircraft flight information.

[0112] The aircraft flight information includes aeronautical information. In the aircraft flight information receiving phase 102 , the aeronautical information is measured by the environment sensing device 26 .

[0113] The aviation information includes aircraft speed information. The aircraft speed information includes indicated airspeed. The aircraft speed information includes Mach number. The aircraft speed information includes true airspeed.

[0114] Aviation information includes environmental information. Environmental information includes aircraft altitude. Environmental information includes ambient air density. Environmental information includes ambient temperature.

[0115] Aircraft flight information includes pitch, yaw and / or roll angles. Aeronautical information includes angle of attack. Aircraft flight information includes X, Y and Z accelerations. Aircraft flight information includes aircraft weight. Aircraft flight information includes aircraft control surface (e.g., flaps and / or slats) status. Aircraft flight information includes landing gear status.

[0116] In other examples, aeronautical information may not be directly sensed. For example, satellite data may be used to determine aircraft speed data.

[0117] Aircraft flight information includes propeller drive power information.

[0118] The propeller drive power information includes engine parameters. The engine parameters include engine torque. The engine parameters include engine speed. The engine parameters include engine power.

[0119] During the aircraft flight information receiving phase 102 , the engine sensing device 30 measures engine parameters.

[0120] The propeller drive power information includes propeller parameters. The propeller parameters include propeller speed. The propeller parameters include propeller thrust.

[0121] During the aircraft flight information receiving phase 102 , the propeller sensing device 28 measures propeller parameters.

[0122] Aircraft flight information does not include measured propeller pitch. Aircraft flight information does not include measured blade angle. The pitch protection system does not include a blade angle sensor.

[0123] The aircraft flight information receiving phase 102 may include an aircraft flight information verification process. The aircraft flight information verification process may include determining that the sensor is in operation, in range, and / or connected. The aircraft flight information verification process may include cross-checking with data from another sensor. If the sensor is not in operation, not in range, and / or not connected or the aircraft flight information verification process fails for other reasons, some aircraft flight information cannot be used for virtual pitch calculation. In this case, the pitch control and / or protection system may generate an alarm and send the alarm to the pilot and / or send it as maintenance information available on the aircraft and / or send it wirelessly to the maintenance platform.

[0124] In the virtual pitch calculation stage 104 , the virtual sensor 22 performs a virtual pitch calculation to determine a virtual propeller pitch or a virtual blade angle according to the aircraft flight information.

[0125] The virtual pitch calculation includes an aeronautical information calculation performed on the aeronautical information. The virtual pitch calculation includes a propeller power calculation performed on the propeller drive power information to determine a virtual propeller pitch or a virtual blade angle. The virtual pitch calculation can be implemented by a neural network or other machine learning technology, a map and / or a lookup table.

[0126] An illustrative example of virtual blade angle calculation is given below:

[0127] Example input parameters:

[0128] ●Aircraft altitude (ALT)

[0129] ●Aircraft speed (AS)

[0130] ●Ambient temperature (Tamb)

[0131] ●Propeller speed (NP)

[0132] ●Propeller drive torque (TQ)

[0133] The true airspeed (TAS), air density (ρ) and Mach number (Mn) may be determined based on the ambient temperature (Tamb), aircraft speed (AS) and altitude (ALT) or based on other parameters physically equivalent thereto, by calculation, lookup tables, interpolation, machine learning, neural networks or any other suitable method.

[0134] The pitch ratio J can be calculated based on the true airspeed (TAS), propeller speed (NP) and propeller diameter. Or it may be determined based on other parameters that are physically equivalent thereto, by calculation, lookup table, interpolation, machine learning, neural network or any other suitable method.

[0135] The propeller shaft horsepower (SHP) may be determined based on the propeller speed (NP) and the propeller drive torque (TQ), or based on other parameters physically equivalent thereto, by calculation, lookup table, interpolation, machine learning, neural network, or any other suitable method.

[0136] The power coefficient (Cp) can be calculated based on the propeller shaft horsepower (SHP), propeller speed (NP), air density (ρ), and propeller diameter. Or it may be determined based on other parameters that are physically equivalent thereto, by calculation, lookup table, interpolation, machine learning, neural network or any other suitable method.

[0137] The virtual blade angle can then be determined based on the Mach number (Mn), pitch ratio J, power coefficient (Cp) or other parameters physically equivalent thereto and the aerodynamic model ("flight deck") of the propeller, by calculation, lookup table, interpolation, machine learning, neural network or any other suitable method. The principle of virtual blade angle determination here relies on the "inverse flight deck", that is, using the inverse method as the method conventionally performed to determine the aircraft performance (e.g., Mach number (Mn), pitch ratio J, power coefficient (Cp)) based on the aerodynamic characteristics (geometry) of the propeller.

[0138] With respect to the above virtual blade angle determination example, it should be understood that fewer or more input parameters may be used, and fewer or more intermediate parameters may be determined in order to determine a more accurate or less accurate virtual blade angle. For example, in addition to the above parameters for determining a more accurate virtual blade angle, the aircraft high lift configuration (flaps, slats, THSA) and attitude (Nz, yaw, GW, ...) may also be considered.

[0139] This virtual blade angle determination example is merely illustrative and not limiting in any way. Any suitable alternative for performing the determination of the virtual blade angle based on aircraft flight information is also within the scope of the present invention.

[0140] The virtual pitch calculation can implement an equation based on a lift line solution. This solution involves vortex theory where vortices break off the blade sections as the propeller moves through the air. Several such solutions have been developed. The equations can be calculated using the following references:

[0141] Goldstein S. "On the vortex theory of propellers" (1929)

[0142] Locke CNH, Yeatman D. "Tables for improving the theoretical calculation method of propeller strips" (1934)

[0143] McCormick, B.W. "Aerodynamics of V / STOL Flight" (1967)

[0144] Ladden, Gilmore "Advanced V / STOL Propeller Technology" Volume II (1971)

[0145] Baskin VE, Vildgrube LS, Vozhdayev YS, Maykapar CI "Theory of lift air propellers" (1973)

[0146] These references are given by way of example only.

[0147] In other examples, the aircraft flight information does not include all of the above information. Some of the aircraft flight information may be determined by other aircraft flight information. For example, the engine power may be determined based on the engine torque and the engine speed. Some of the aircraft flight information mentioned above may be omitted entirely. The virtual pitch calculation may not use all of the aircraft flight information mentioned above to determine the virtual propeller pitch or virtual blade angle. Any combination of the listed aircraft flight information may be used. The list provided herein is not exhaustive.

[0148] By performing a virtual pitch calculation, the number of sensors may be reduced and the variable pitch propeller system may be simplified (eg, since blade angle sensors are not included in the pitch protection system).

[0149] In the virtual propeller pitch comparison stage 106, the protection processor 24 receives the virtual propeller pitch from the virtual pitch sensor 22. The protection processor 24 compares the virtual propeller pitch to a propeller pitch threshold value.

[0150] If the virtual propeller pitch is greater than or equal to the propeller pitch threshold, the protection processor 24 sends a control signal to the controller 32 , which results in the pitch control phase 108 being implemented.

[0151] In the pitch control phase 108, the pitch control system 20 controls the pitch of the propeller 14 according to the pitch control process described above. The method 100 is then performed again. The method 100 may be performed periodically.

[0152] If the virtual propeller pitch is less than the propeller pitch threshold, a low virtual propeller pitch or virtual blade angle is determined. The protection processor 24 implements the pitch protection process in the pitch protection stage 110 .

[0153] When there is a fine pitch (ie, moving in the opposite direction), a low virtual propeller pitch or virtual blade angle may be determined. Conversely, a higher propeller pitch or blade angle may be defined by a large pitch or angle (ie, moving towards feathering).

[0154] During the pitch protection process, the protection processor 24 controls the propeller 14 to increase the propeller pitch. Specifically, the protection processor 24 bypasses the pitch control system 20 so that the pitch control system 20 is no longer used to control the propeller pitch. In order to increase the propeller pitch, the protection processor 24 can reduce the propeller speed and / or increase the blade angle. In order to increase the blade angle, the protection processor 24 can de-energize the actuator of the pitch control system 20, so that the valve can be opened to allow the control fluid to reach the propeller 14 to increase the blade angle. In some examples, alternative features for increasing the blade angle can be used.

[0155] After the pitch protection procedure, if the fault that caused the low pitch event is corrected or eliminated, the pitch control system 20 may again control the pitch of the propeller 14 according to the pitch control procedure.

[0156] Figure 4 A second aircraft 110 is shown. Second aircraft 110 includes many of the features of aircraft 10. Repeated descriptions of common features are omitted, and only the differences are described herein.

[0157] Second aircraft 110 includes a second variable pitch propeller system 112 , which is similar to variable pitch propeller system 12 , including propeller 14 , engine 16 , and pitch control system 20 .

[0158] Compared to the variable pitch propeller system 12, the second variable pitch propeller system 112 includes a health monitoring system 118 instead of the protection system 18. The health monitoring system 118 includes a virtual pitch sensor 22, an environmental sensing device 26, a propeller sensing device 28, and an engine sensing device 30, each of which operates in the same manner as those components of the pitch protection system 18, wherein the virtual pitch sensor 22 performs a virtual pitch calculation to determine a virtual propeller pitch or a virtual blade angle. The health monitoring system 118 includes a physical sensor 140 configured to measure the propeller pitch or blade angle.

[0159] The health monitoring system 118 also includes a health monitoring processor 124. The health monitoring processor 124 is configured to perform a health monitoring process using the virtual propeller pitch or the virtual blade angle to determine the health of the aircraft.

[0160] Figure 5 A method 200 of operating the second variable pitch propeller system 112 is shown. The method includes an aircraft flight information receiving phase 102, a virtual pitch calculation phase 104, and a health monitoring phase 206. The aircraft flight information receiving phase 102 and the virtual pitch calculation phase 104 are performed in the same manner as in the method 100, and repeated descriptions of these phases are omitted.

[0161] In the health monitoring stage 206, the health monitoring processor 124 performs a health monitoring process. In the health monitoring process, the health monitoring processor 124 compares the virtual propeller pitch with the measured propeller pitch.

[0162] In this example, the measured propeller pitch is determined using physical sensors, for example, from pulse-pickup measurement signals from targets located on the blades and on the propeller aft bulkhead. In other examples, the blade pitch can also be measured by a transfer tube aft contact sensor in a system configuration where the transfer tube translation follows the propeller pitch actuator displacement. In this case, the actuator is coupled to the blade trunnion pin by dedicated kinematics to transform the blade pitch at blade level into actuator and transfer tube axial displacement.

[0163] Based on the comparison between the virtual propeller pitch and the measured propeller pitch, the health monitoring processor determines the wear condition of the component of the aircraft (in this example, the aircraft system). In some examples, when the difference (e.g., the difference) between the virtual value (e.g., the virtual propeller pitch) and the measured value (e.g., the measured propeller pitch) exceeds a threshold, it can be determined that the health condition is poor.

[0164] The aircraft system may be a mechanical system, an electrical system, and / or a gearbox of the propeller 14. In some examples, the health monitoring process may include determining a failure of at least one component of the aircraft, wherein the at least one component is different than a blade.

[0165] At least one component may be a propeller gearbox and / or a propeller pitch change actuator. In fact, a failure of a propeller gearbox and / or a propeller pitch change actuator will result in a difference between the virtual propeller pitch and the measured propeller pitch and will therefore be detected by the current health monitoring method. The health monitoring method will not necessarily be able to isolate the failed component, however, it is possible to isolate groups of components based on the virtual blade angle model parameter values. The advantage of the method is that not only failures at the propeller blade level can be detected, but also failures of components that physically interact with the propeller: propeller drive (e.g. gearbox), propeller pitch change actuation system, to name only a non-exhaustive example.

[0166] The propeller gearbox is used to adapt the engine speed to the optimal speed required by the propeller. The propeller usually rotates at a much lower PRM than the engine due to the much larger diameter of the propeller and the need to maintain the blade tip speed at subsonic speed. The propeller gearbox is a mechanical device that uses gears to reduce the output speed (propeller shaft) relative to the higher input speed (input shaft). The gearbox can include two stages. The first stage of the gearbox can include a first stage gear and a first stage pinion. The second stage of the gearbox can include planetary gears. Planetary gears are gear systems that combine an epicyclic gear train with planetary gears that engage both a sun gear and a ring gear. The second stage of the gearbox can include a planet carrier. The gearbox can include an idler gear shaft. The gears can be helical gears or bull gears or bevel gears. The gear shaft is usually guided in the gearbox housing by roller bearings or ball bearings. Torque meters are usually installed at the input of the gearbox, which means that they measure the input torque of the gearbox, not the actual output torque that drives the propeller.

[0167] A gearbox fault may be a first stage gear failure, a first stage pinion failure, a planetary failure, an input shaft failure or a propeller shaft failure and / or a ball or roller bearing failure. A gearbox fault will affect the transfer efficiency between the inlet and outlet of the gearbox, which means that the ratio between the output torque of the gearbox and its input torque will decrease. For a given input torque, the available propeller drive torque is less. A reduction in gearbox efficiency will be detected by health status monitoring (via comparison of virtual pitch with actual pitch). For example, a 20% drop in efficiency is equivalent to a 1 degree pitching of the blade angle.

[0168] In a propeller system architecture where blade pitch is measured by a transfer tube aft contact sensor, where transfer tube translation follows propeller pitch actuator displacement, a propeller pitch variation actuator fault could be, for example:

[0169] - Yoke deformation / Plate 40 deformation (actuator-vane mechanical linkage)

[0170] - Transfer pipe 44 shift (control module - actuator hydraulic linkage)

[0171] - deformation of the feedback lever 46,

[0172] - Feedback measurement failure (out of range and / or wrong valid signal).

[0173] All of these faults result in a shift in the axial displacement measurement of the transfer tube 44. These faults will be detected by the health monitoring process.

[0174] In this case, the actuator is coupled to the blade trunnion pin 42 by dedicated kinematics to convert the blade pitch at blade level into an actuator and transfer tube axial displacement.

[0175] If a failure is determined, the health monitoring system may generate an alert and send the alert to the pilot and / or as maintenance information available on the aircraft and / or wirelessly to a maintenance platform.

[0176] Health monitoring phase 206 may be performed on the ground during flight or after flight. Virtual pitch calculation phase 104 may also be performed on the ground during flight or after flight. In some examples, health monitoring phase 206 and / or virtual pitch calculation phase 104 may be performed partially during flight and partially on the ground after flight.

[0177] In some examples, the variable pitch propeller system includes both the protection system 108 and the health monitoring system 118. In such examples, components of the common virtual pitch sensor 22, the environmental sensing device 26, the propeller sensing device 28, and the engine sensing device 30 may be shared between the protection device 108 and the health monitoring system 118, e.g., such components are common to the systems.

[0178] Although method steps and / or features have been described with respect to specific processors, controls, or sensors, these steps or features may be performed by the same component or across multiple components. For example, the virtual pitch sensor 22 and the protection processor 24 may be implemented in the same processor or across different processors. In addition, some processors may be located at a location remote from the aircraft and may communicate with components of the aircraft.

[0179] The various aspects of the equipment disclosed in the various embodiments can be used alone, in combination, or in various arrangements not specifically discussed in the previously described embodiments, so the application of the present disclosure is not limited to the details and arrangements of the components set forth in the previous description or shown in the drawings. For example, the aspects described in one embodiment can be combined with the aspects described in other embodiments in any way. Although specific embodiments have been shown and described, it is obvious to those skilled in the art that changes and modifications can be made without departing from the broader aspects of the present invention. The scope of the appended claims should not be limited to the embodiments set forth in the examples, but should be given the broadest reasonable interpretation consistent with the specification as a whole.

Claims

1. A method of operating a variable pitch propeller system for an aircraft, the method comprising: Receive aircraft flight information; performing a virtual pitch calculation to determine a virtual propeller pitch or a virtual blade angle based on the aircraft flight information; as well as A pitch protection procedure is performed in response to determining a low virtual propeller pitch or virtual blade angle.

2. The method according to claim 1, wherein: The aircraft flight information includes aeronautical information, and the virtual pitch calculation includes an aeronautical information calculation performed on the aeronautical information to determine the virtual propeller pitch or virtual blade angle.

3. The method according to claim 2, wherein: The method includes sensing the aeronautical information.

4. The method according to claim 2 or 3, wherein: The aviation information includes aircraft speed information.

5. A method according to any one of the preceding claims, wherein: The aircraft flight information includes propeller drive power information, and the virtual pitch calculation includes a propeller power calculation performed on the propeller power information to determine the virtual propeller pitch or virtual blade angle.

6. The method of claim 5, and comprising sensing the propeller drive power information from an engine of the aircraft, the engine being configured to drive the propeller.

7. A method according to any one of the preceding claims, wherein: The pitch protection process includes controlling the variable pitch propeller system to maintain or increase the propeller pitch and / or blade angle.

8. A method according to any one of the preceding claims, wherein: The pitch protection process includes bypassing a pitch controller of the variable pitch propeller system.

9. A method according to any one of the preceding claims, wherein: The virtual pitch calculation includes performing an aircraft flight information verification process to verify that the aircraft flight information is valid.

10. A method according to any preceding claim, and comprising, in response to not determining a low virtual propeller pitch or virtual blade angle, controlling the propeller pitch according to a pitch control process, the pitch control process comprising receiving a measured blade angle from a blade angle sensor and controlling the pitch of the propeller in response to the measured blade angle.

11. A method according to claim 10, comprising measuring the blade angle of the propeller.

12. A protection system for a variable pitch propeller system, the protection system comprising: a virtual pitch sensor configured to receive aircraft flight information and perform a virtual pitch calculation to determine a virtual propeller pitch or a virtual blade angle based on the aircraft flight information; as well as A protection processor is configured to execute a pitch protection process in response to determining a low virtual propeller pitch or virtual blade angle.

13. A variable pitch propeller system comprising a protection system according to claim 12 and comprising the propeller.

14. A variable pitch propeller system according to claim 12 or 13, and comprising a drive unit for driving the propeller.

15. An aircraft comprising a variable pitch propeller system according to claim 13 or 14.

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