Health monitoring system

Abstract

A method of performing health monitoring for an aircraft having a variable pitch propeller system, the method comprising: receiving aircraft flight information; performing a virtual pitch operation to determine a virtual propeller pitch or a virtual blade angle as a function of 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 monitoring process using the virtual propeller pitch or virtual blade angle and the measured propeller pitch or blade angle to determine a health of at least one component of the aircraft, wherein the at least one component is different from the blade.

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] It is very important to monitor the health of an aircraft and its systems to reduce the likelihood of component failure during flight. However, acquiring data so that health monitoring can be performed reliably can be difficult. Summary of the invention

[0003] According to a first aspect, a method for performing health monitoring for an aircraft with a variable pitch propeller system is provided, the method comprising: receiving aircraft flight information; performing a virtual pitch operation 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 monitoring process using the virtual propeller pitch or the virtual blade angle and the measured propeller pitch or blade angle to determine a health status of at least one component of the aircraft, wherein the at least one component is different from the blade.

[0004] By performing a virtual pitch calculation to determine a virtual propeller pitch or virtual blade angle, a useful data source for aircraft health monitoring may be provided, for example, using differences between measured and virtual values ​​to indicate that a component of the aircraft is not operating as expected.

[0005] Determining the health status may include propeller gearbox fault detection and / or propeller pitch change actuator fault detection.

[0006] The health monitoring process may be performed during flight. The health monitoring process may be performed while the aircraft is on the ground.

[0007] The health monitoring process may include comparing a virtual propeller pitch or a virtual blade angle with a measured propeller pitch or blade angle. An unhealthy condition may be determined if the difference between the virtual value and the measured value exceeds a threshold.

[0008] The measured propeller pitch may be determined using the measured blade angle and propeller rotational speed. The method may comprise measuring the blade angle and the propeller rotational speed.

[0009] 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.

[0010] 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.

[0011] 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.

[0012] The method may include sensing aeronautical information.

[0013] 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.

[0014] The aviation information may include environmental information. The environmental information may include the aircraft altitude. The environmental information may include the ambient air density. The environmental information may include the ambient temperature.

[0015] Aeronautical information can include any additional information such as pitch, yaw and roll angles, angle of attack, X, Y or Z acceleration, weight, etc...

[0016] Aircraft flight information may include propeller drive power information.

[0017] The propeller drive power information may include engine parameters. The engine parameters may include engine torque. The engine parameters may include engine rotation speed. The engine parameters may include engine power.

[0018] The propeller drive power information may include propeller parameters. The propeller parameters may include propeller rotation speed. The propeller parameters may include propeller drive torque. The propeller parameters may include propeller drive power.

[0019] The virtual pitch operation may include a propeller power calculation performed on the propeller drive power information to determine a virtual propeller pitch or a virtual blade angle.

[0020] The input shaft propeller power may be calculated using the propeller rotational speed and the absorbed propeller torque. The input shaft propeller power may be calculated using the aircraft airspeed, propeller thrust, and propeller efficiency. The input shaft propeller power may be calculated using the engine rotational speed and the engine torque. The calculation using the propeller rotational speed and the absorbed propeller torque is preferred.

[0021] 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.

[0022] The method may include sensing propeller drive power information from an engine of the aircraft, the engine being configured to drive a propeller.

[0023] 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 rotation speed.

[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 operational. 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] According to a second aspect, a health monitoring system for a variable pitch propeller system of an aircraft is provided, the health monitoring system comprising: a virtual pitch sensor configured to receive aircraft flight information and perform a virtual pitch operation to determine a virtual propeller pitch or a virtual blade angle based on the aircraft flight information; at least one physical sensor configured to measure the propeller pitch or the blade angle; and a health monitoring processor configured to perform a health 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 the at least one component is different from the blade.

[0026] Determining the health status may include propeller gearbox fault detection and / or propeller pitch change actuator fault detection.

[0027] 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.

[0028] The health monitoring system may include an environmental sensing device configured to sense aeronautical information.

[0029] 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.

[0030] 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.

[0031] Aircraft flight information may include propeller drive power information.

[0032] The propeller drive power information may include engine parameters. The engine parameters may include engine output torque. The engine parameters may include engine rotation speed. The engine parameters may include engine output mechanical power.

[0033] The propeller drive power information may include propeller parameters. The propeller parameters may include propeller rotation speed. The propeller parameters may include propeller drive torque. The propeller parameters may include propeller drive power.

[0034] The virtual pitch operation may include a propeller power calculation performed on the propeller drive power information to determine a virtual propeller pitch or a virtual blade angle.

[0035] The input shaft propeller power may be calculated using the propeller rotational speed and the absorbed propeller torque. The input shaft propeller power may be calculated using the aircraft airspeed, propeller thrust, and propeller efficiency. The input shaft propeller power may be calculated using the engine rotational speed and the engine torque. The calculation using the propeller rotational speed and the absorbed propeller torque is preferred.

[0036] 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.

[0037] 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.

[0038] 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 rotation speed.

[0039] 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 operational. The aircraft flight information verification process may include determining that the sensor is within an operating range.

[0040] According to a third aspect, there is provided a variable pitch propeller system comprising the health monitoring system described above.

[0041] According to a fourth aspect, there is provided an aircraft comprising a variable pitch propeller system.

[0042] The method of the first aspect may include any of the features and / or functional steps described with respect to the second, third and / or fourth aspects. The health monitoring system of the second aspect may include any of the features and / or functional steps described with respect to the first, third and / or fourth aspects. The variable pitch propeller system of the third aspect may include any of the features and / or functional steps described with respect to the first, second and / or fourth aspects. The aircraft of the fourth aspect may include any of the features and / or functional steps described with respect to the first, second and / or third aspects.

[0043] According to a fifth aspect, there is provided a method of operating a variable pitch propeller system for an aircraft, the method comprising:

[0044] Receive aircraft flight information;

[0045] performing a virtual pitch calculation to determine a virtual propeller pitch or a virtual blade angle according to the aircraft flight information; and

[0046] In response to a low virtual propeller pitch or virtual blade angle being determined, a pitch protection procedure is performed.

[0047] 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.

[0048] The method may include sensing aeronautical information.

[0049] 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.

[0050] The aviation information may include environmental information. The environmental information may include the aircraft altitude. The environmental information may include the ambient air density. The environmental information may include the ambient temperature.

[0051] Aircraft flight information may include propeller drive power information.

[0052] Aeronautical information may include any additional information such as aircraft pitch, yaw and roll angles, angle of attack, X, Y or Z acceleration, weight.

[0053] The propeller drive power information may include engine parameters. The engine parameters may include engine torque. The engine parameters may include engine rotation speed. The engine parameters may include engine power.

[0054] The propeller drive power information may include propeller parameters. The propeller parameters may include propeller rotation speed. The propeller parameters may include propeller torque. The propeller parameters may include propeller power.

[0055] The virtual pitch operation may include a propeller power calculation performed on the propeller drive power information.

[0056] 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.

[0057] The method may include sensing propeller drive power information from an engine of the aircraft, the engine being configured to drive a propeller.

[0058] 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 rotation speed.

[0059] The pitch protection process may include controlling a variable pitch propeller system to increase propeller pitch and / or blade angle.

[0060] The pitch protection process may include bypassing the pitch controller of the variable pitch propeller system.

[0061] 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 operational. 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.

[0062] The method may include, in response to a low virtual propeller pitch or a virtual blade angle not being determined, controlling the propeller pitch according to a pitch control process. 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.

[0063] The method may include sensing a blade angle from the propeller.

[0064] 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 differential control. The pitch control process may include any one of proportional control and / or integral control and / or differential control or 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 foreseeable.

[0065] According to a sixth 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 virtual pitch calculations 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 a low virtual propeller pitch or a virtual blade angle being determined.

[0066] A low virtual propeller pitch or a virtual blade angle may be determined 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.

[0067] 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.

[0068] The protection system may include an environmental sensing device configured to sense aeronautical information.

[0069] 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.

[0070] 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 temperature.

[0071] Aeronautical information may include any additional information such as aircraft pitch, yaw and roll angles, angle of attack, X, Y or Z acceleration, weight.

[0072] Aircraft flight information may include propeller drive power information.

[0073] The propeller drive power information may include engine parameters. The engine parameters may include engine torque. The engine parameters may include engine rotation speed. The engine parameters may include engine power.

[0074] The propeller drive power information may include propeller parameters. The propeller parameters may include propeller rotation speed. The propeller parameters may include propeller thrust.

[0075] The virtual pitch operation may include a propeller power calculation performed on the propeller drive power information to determine a virtual propeller pitch or a virtual blade angle.

[0076] The protection 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 the propeller.

[0077] 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 rotation speed.

[0078] The pitch protection process may include controlling a variable pitch propeller system to increase propeller pitch and / or blade angle.

[0079] The pitch protection process may include bypassing the pitch controller of the variable pitch propeller system.

[0080] The virtual pitch calculation may include 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 operational. The aircraft flight information verification process may include determining that the sensor is within range.

[0081] 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 in separate units.

[0082] According to a seventh aspect, there is provided a variable pitch propeller system comprising the protection system described above.

[0083] 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 a low virtual propeller pitch or a virtual blade angle not being determined. 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.

[0084] The variable pitch propeller system may include a blade angle sensor configured to measure a blade angle from the propeller.

[0085] 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 differential control. The pitch control process may include any of proportional control and / or integral control and / or differential control.

[0086] The variable pitch propeller system may comprise a propeller. The variable pitch propeller system may comprise a drive unit for driving the propeller.

[0087] According to an eighth aspect, there is provided an aircraft comprising a variable pitch propeller system.

[0088] The method of the fifth aspect may include any of the features and / or functional steps described in relation to the sixth, seventh and / or eighth aspects. The protection system of the sixth aspect may include any of the features and / or functional steps described in relation to the fifth, seventh and / or eighth aspects. The variable pitch propeller system of the seventh aspect may include any of the features and / or functional steps described in relation to the fifth, sixth and / or eighth aspects. The aircraft of the eighth aspect may include any of the features and / or functional steps described in relation to the fifth, sixth and / or seventh aspects.

[0089] The systems and methods related to health monitoring in the first to fourth aspects may include any of the features and / or functional steps specified in relation to the systems and methods related to protection in the fifth to eighth aspects. In addition, the systems and methods related to protection in the fifth to eighth aspects may include any of the features and / or functional steps specified in relation to the systems and methods related to health monitoring in the first to fourth aspects.

[0090] The protection system and the health monitoring system may share a common virtual pitch sensor. The protection system and the health monitoring system may each include an independent 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

[0091] Various examples will now be described with reference to the accompanying drawings, in which:

[0092] Figure 1 A schematic diagram of an aircraft including a variable pitch propeller system is shown;

[0093] Figure 2 A cross-sectional view of a propeller is shown;

[0094] Figure 3 A method of operating a variable pitch propeller system is shown;

[0095] Figure 4 showing a schematic diagram of a second aircraft including a second variable pitch propeller system; and

[0096] Figure 5 A method of operating a second variable pitch propeller system is shown. DETAILED DESCRIPTION

[0097] 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.

[0098] 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 (e.g., the virtual pitch sensor and the protection processor) may be embodied in a single processor.

[0099] Pitch control system 20 (also referred to as a primary control system) includes a controller 32 , a propeller speed sensor 34 , and a blade angle sensor 36 .

[0100] Figure 2 The 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., included in a propeller unit). The propeller sensing device 28, the propeller speed sensor 34, and the blade angle sensor 36 are located remote from the pitch protection system 18 and the pitch control system 20.

[0101] 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 .

[0102] In normal use, the engine 16 provides mechanical power for driving the propeller 14, which can be used for aircraft thrust or braking. The pitch control system 20 controls the pitch of the propeller 14 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 via, 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.

[0103] The propeller pitch or blade angle depends on the drive power and the propeller rotation speed on the one hand and on the aerodynamic configuration of the aircraft and the flight conditions on the other hand. For each set of these parameters there is a unique propeller pitch.

[0104] In some cases, a malfunction of the propeller control system 20 may cause the propeller pitch to be 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.

[0105] 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.

[0106] In the aircraft flight information receiving stage 102 , the virtual pitch sensor 22 receives the aircraft flight information.

[0107] 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 .

[0108] Aeronautical information includes aircraft speed information. Aircraft speed information includes indicated airspeed. Aircraft speed information includes Mach number. Aircraft speed information includes true airspeed.

[0109] Aviation information includes environmental information. Environmental information includes aircraft altitude. Environmental information includes ambient air density. Environmental information includes ambient temperature.

[0110] 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.

[0111] In other examples, aeronautical information may not be sensed directly. For example, satellite data may be used to determine aircraft speed data.

[0112] Aircraft flight information includes propeller drive power information.

[0113] The propeller drive power information includes engine parameters. The engine parameters include engine torque. The engine parameters include engine rotation speed. The engine parameters include engine power.

[0114] During the aircraft flight information receiving phase 102 , the engine sensing device 30 measures engine parameters.

[0115] The propeller drive power information includes propeller parameters. The propeller parameters include propeller rotation speed. The propeller parameters include propeller thrust.

[0116] During the aircraft flight information receiving phase 102 , the propeller sensing device 28 measures propeller parameters.

[0117] 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.

[0118] 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 operational, within range, and / or connected. The aircraft flight information verification process may include cross-checking with data from another sensor. In the event that a sensor is not operational, not within range, and / or not connected, or the aircraft flight information verification process fails for another reason, some aircraft flight information may not be used in the virtual pitch calculation. In this case, the pitch control and / or protection system may generate an alert, and the alert may be sent to the pilot and / or sent as maintenance information available on the aircraft and / or sent wirelessly to a maintenance platform.

[0119] 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.

[0120] The virtual pitch operation includes an aeronautical information calculation performed on the aeronautical information. The virtual pitch operation 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 operation can be implemented by a neural network or other machine learning technology, mapping and / or lookup table.

[0121] An illustrative example of virtual blade angle calculation is presented here as follows:

[0122] Example input parameters:

[0123] Aircraft altitude (ALT)

[0124] Aircraft speed (AS)

[0125] ●Ambient temperature (Tamb)

[0126] ●Propeller rotation speed (NP)

[0127] ●Propeller drive torque (TQ)

[0128] The true airspeed (TAS), air density (ρ) and Mach number (Mn) may be determined by calculation, lookup tables, interpolation, machine learning, neural networks or any other suitable method based on the ambient temperature (Tamb), aircraft speed (AS) and altitude (ALT) or based on other parameters that are physically equivalent thereto.

[0129] The advance ratio J can be calculated by calculation, lookup table, interpolation, machine learning, neural network or any other suitable method based on the true airspeed (TAS), propeller speed (NP) and propeller diameter Or it can be determined based on other parameters that are physically equivalent.

[0130] The propeller shaft horsepower (SHP) may be determined from the propeller rotational speed (NP) and the propeller drive torque (TQ) or from other parameters physically equivalent thereto by calculation, lookup tables, interpolation, machine learning, neural networks, or any other suitable method.

[0131] The power coefficient (Cp) can be calculated based on the propeller shaft horsepower (SHP), propeller rotation speed (NP), air density (ρ), and propeller diameter by calculation, lookup table, interpolation, machine learning, neural network, or any other suitable method. Or it can be determined based on other parameters that are physically equivalent.

[0132] The virtual blade angle can be determined by calculation, lookup table, interpolation, machine learning, neural network or any other suitable method based on Mach number (Mn), advance ratio J, power coefficient (Cp) or other parameters physically equivalent thereto and the aerodynamic model ("aerodeck") of the propeller. The principle of virtual blade angle determination here relies on "inverse aerodeck", that is, the inverse method of the conventionally performed method is used to determine the aircraft performance (e.g., Mach number (Mn), advance ratio J, power coefficient (Cp)) based on the aerodynamic characteristics of the propeller (geometry).

[0133] 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 more refined virtual blade angle determination, the aircraft high lift configuration (flaps, slats, THSA) and attitude (Nz, yaw, GW, ...) may also be taken into account.

[0134] This virtual blade angle determination example is illustrative only and is 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.

[0135] The virtual pitch calculation implements equations based on the lift line solution. This solution involves vortex theory where vorticity is shed from the blade cross section as the propeller moves through the air. Several such solutions have been developed. The following references can be used to calculate the equations:

[0136] Goldstein S. "On the Vortex Theory of Screw Propellers." (1929)

[0137] Locke CNHYeatman D. "Tables for Use in an Improved Method ofAirscrew Strip Theory Calculation"(1934)

[0138] McCormick BW "Aerodynamics of V / STOL Flight" (1967)

[0139] Ladden, Gilmore "Advanced V / STOL Propeller Technology" Vol.II (1971)

[0140] Baskin VE, Vildgrube L..S., Vozhdayev YS, Maykapar CI "Theory of the lifting airscrew" (1973)

[0141] These references are given as examples.

[0142] In other examples, the aircraft flight information does not include all of the information described above. Some of the aircraft flight information may be determined based on other aircraft flight information. For example, engine power may be determined based on engine torque and engine rotational 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 a virtual propeller pitch or a virtual blade angle. Any combination of the listed aircraft flight information may be used. The list presented herein is not exhaustive.

[0143] By performing a virtual pitch operation, the number of sensors may be reduced and the variable pitch propeller system may be simplified (eg, because blade angle sensors are not included in the pitch protection system).

[0144] 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.

[0145] In the event that 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 causes the pitch control phase 108 to be implemented.

[0146] In the pitch control phase 108, the pitch control system 20 controls the pitch of the propeller 14 according to the pitch control process, as described above. The method 100 is then performed again. The method 100 may be performed periodically.

[0147] In case the virtual propeller pitch is less than the propeller pitch threshold, a low virtual propeller pitch or virtual blade angle is determined. In the pitch protection stage 110, the protection processor 24 implements a pitch protection process.

[0148] In the presence of a small pitch (ie in the case of a move towards reverse), 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 in the case of a move towards feathering).

[0149] During the pitch protection process, the protection processor 24 controls the propeller 14 to increase the propeller pitch. In particular, the protection processor 24 bypasses the pitch control system 20, wherein 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. To increase the blade angle, the protection processor 24 can de-energize the actuator of the pitch control system 20, which can open the valve, thereby allowing 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.

[0150] During the pitch protection process, if the fault that caused the low pitch event is corrected or removed, the pitch control system 20 may again control the pitch of the propeller 14 according to the pitch control process.

[0151] Figure 4 A second aircraft 110 is shown. The second aircraft 110 includes many of the features of the aircraft 10. Repeated descriptions of common features are omitted, and only the differences are described here.

[0152] Second aircraft 110 includes a second variable pitch propeller system 112 that, like variable pitch propeller system 12 , includes propeller 14 , engine 16 , and pitch control system 20 .

[0153] 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 operation 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 the blade angle.

[0154] 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.

[0155] 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 those phases are omitted.

[0156] During the health monitoring phase 206, the health monitoring processor 124 performs a health monitoring process. During the health monitoring process, the health monitoring processor 124 compares the virtual propeller pitch to the measured propeller pitch.

[0157] In this example, the measured propeller pitch is determined using physical sensors, such as signals measured from pulse pick-offs from targets located on the blades and propeller aft bulkhead. In other examples, the blade pitch can also be measured using a transmission tube trailing contact sensor in a system configuration where the transmission tube translation follows the displacement of the propeller pitch actuator. In this case, the actuator is coupled to the blade trunnion pin through a dedicated kinematic device to convert the blade pitch at the blade level into an axial displacement of the actuator and, therefore, the transmission tube.

[0158] Based on the comparison between the virtual propeller pitch and the measured propeller pitch, the health monitoring processor determines a wear condition of a component of the aircraft, which in this example is an aircraft system. In some examples, an unfavorable health condition may be determined if a difference (e.g., a difference) between a virtual value (e.g., virtual propeller pitch) and a measured value (e.g., measured propeller pitch) exceeds a threshold.

[0159] 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, where the at least one component is different than a blade.

[0160] At least one component may be a propeller gearbox and / or a propeller pitch change actuator. Indeed, a failure of the propeller gearbox and / or the propeller pitch change actuator will result in a difference between the virtual propeller pitch and the measured propeller pitch and, therefore, will be detected by the present health monitoring method. The health monitoring method will not necessarily enable the isolation of faulty components, however, groups of components may be isolated based on the virtual blade angle model parameter values. The advantage of this method is not only that faults at the propeller blade level may be detected, but also that faults of components that physically interact with the propeller - as non-exhaustive examples, propeller drive (e.g., gearbox), propeller pitch change actuator system.

[0161] The propeller gearbox is used to adapt the engine rotation speed to the optimum speed required by the propeller. Due to the much larger diameter of the propeller and the need to maintain the blade tip speed below the speed of sound, the propeller usually rotates at a much smaller RPM than the engine. The propeller gearbox is a mechanical device that uses gears to reduce the output speed (propeller shaft) from a higher input speed (input shaft). The gearbox may include two stages. The first stage gearbox may include a first stage gear and a first stage pinion. The second stage gearbox may include planetary gears. Planetary gears are gear systems that combine an epicyclic gear train with planets that engage both a sun gear and a ring gear. The second stage gearbox may include a gear carrier. The gearbox may include an idler gear shaft. The gears may be helical gears or gearwheels or bevel gears. The gear shaft is usually guided in the gearbox housing using roller bearings or ball bearings. The torque meter is usually installed at the input of the gearbox, which means that the torque meter measures the input torque of the gearbox rather than the actual output torque that drives the propeller.

[0162] The gearbox fault may be a first stage gear fault, a first stage pinion fault, a planet fault, an input shaft fault or a propeller shaft fault and / or a ball bearing or roller bearing fault. A gearbox fault will affect the transmission efficiency between the inlet and the outlet of the gearbox, which means that the ratio between the output torque of the gearbox and the input torque of the gearbox will decrease. For a given input torque, less propeller drive torque is available. This gearbox efficiency drop will be detected by health monitoring (via comparison of virtual pitch with actual pitch). For example, a 20% drop in efficiency is equivalent to 1 degree of blade angle pitch.

[0163] In a propeller system architecture utilizing a transfer tube trailing contact sensor to measure blade pitch where transfer tube translation follows propeller pitch actuator displacement, a propeller pitch change actuator fault may be, for example:

[0164] - Deformation of yoke / plate 40 (actuator-blade mechanical connection)

[0165] -Transmission pipe 44 displacement (control module – actuator hydraulic connection)

[0166] - deformation of the feedback lever 46,

[0167] - Feedback measurement failure (out of range and / or wrong valid signal).

[0168] 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.

[0169] In this case, the actuator is coupled to the blade trunnion pin 42 by means of a dedicated kinematic device to convert the blade pitch at the blade level into an axial displacement of the actuator and thus of the transmission tube.

[0170] If a fault is determined, the health monitoring system may generate an alert, and the alert may be sent to the pilot and / or sent as maintenance information available on the aircraft and / or sent wirelessly to a maintenance platform.

[0171] Health monitoring phase 206 may be performed during flight or on the ground after flight. Virtual pitch calculation phase 104 may also be performed during flight or on the ground 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.

[0172] In some examples, the variable pitch propeller system includes both the protection system 108 and the health monitoring system 118. In such examples, common virtual pitch sensor 22, environmental sensing device 26, propeller sensing device 28, and engine sensing device 30 components may be shared between the protection system 108 and the health monitoring system 118, for example, such that the components are common to the systems.

[0173] Although method steps and / or features have been described with respect to specific processors, controls, or sensors, the 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 on the same processor or across several different processors. Additionally, some processors may be located remotely from the aircraft and may communicate with components of the aircraft.

[0174] The various aspects of the devices disclosed in the various embodiments may be used alone, in combination, or in a variety of arrangements not specifically discussed in the foregoing embodiments, and therefore the present disclosure is not limited in its application to the details and arrangements of the components set forth in the foregoing description or shown in the accompanying drawings. For example, the aspects described in one embodiment may be combined in any manner with the aspects described in other embodiments. Although specific embodiments have been shown and described, it is apparent to those skilled in the art that changes and modifications may 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 for performing health monitoring for an aircraft having a variable pitch propeller system, the method comprising: Receive aircraft flight information; performing a virtual pitch calculation to determine a virtual propeller pitch or a virtual blade angle according to the aircraft flight information; receiving a measured propeller pitch or blade angle from at least one physical sensor associated with the propeller; as well as A health monitoring process is performed using the virtual propeller pitch or virtual blade angle and the measured propeller pitch or blade angle to determine a health condition of at least one component of the aircraft, wherein the at least one component is different than a blade.

2. The method of claim 1, wherein determining the health condition comprises propeller gearbox fault detection and / or propeller pitch change actuator fault detection. 3 . The method according to claim 1 , wherein the aircraft flight information comprises aeronautical information, and the virtual pitch operation comprises aeronautical information calculation performed on the aeronautical information for determining the virtual propeller pitch or the virtual blade angle. 4 . The method of claim 3 , wherein the method comprises sensing the aeronautical information. The method according to claim 3 or 4, wherein the aviation information comprises aircraft speed information.

6. The method according to any one of the preceding claims, wherein the aircraft flight information includes propeller drive power information, and the virtual pitch operation includes a propeller power calculation performed on the propeller drive power information to determine the virtual propeller pitch or virtual blade angle. 7 . The method of claim 6 , and comprising sensing the propeller drive power information from an engine of the aircraft, the engine being configured to drive the propeller.

8. A method according to any preceding claim, wherein the health monitoring process may comprise comparing the virtual propeller pitch or virtual blade angle with a measured propeller pitch.

9. A method according to any one of the preceding claims, wherein the health monitoring process comprises determining a fault or wear condition of the component of the aircraft.

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

11. The method according to any of the preceding claims, wherein the health monitoring process is at least partially performed during flight.

12. The method of any preceding claim, wherein the health monitoring process is at least partially performed while the aircraft is not in flight.

13. A health monitoring system for a variable pitch propeller system of an aircraft, the health monitoring 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 according to the aircraft flight information; at least one physical sensor configured to measure propeller pitch or blade angle; and A health monitoring processor is configured to perform a health monitoring process using the virtual propeller pitch or virtual blade angle and the measured propeller pitch or blade angle to determine a health condition of at least one component of the aircraft, wherein the at least one component is different than a blade.

14. A variable pitch propeller system comprising the health monitoring system according to claim 13 and comprising a propeller.

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

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