Abstract: A propeller control unit (PCU) for controlling pitch angles of blades of a propeller, has: a pitch angle actuator; a servo valve hydraulically connected to the pitch angle actuator and to a first hydraulic fluid source; and a feather valve having a body movable within a cavity, the feather valve having a first actuation port and a second actuation port both in fluid communication with the cavity, the body between the first actuation port and the second actuation port, the body being movable to selectively hydraulically connect the pitch angle actuator to the servo valve through the feather valve or to hydraulically connect the pitch angle actuator to a drain line through the feather valve, the first actuation port and the second actuation port hydraulically connected to a second hydraulic fluid source independent from the first hydraulic fluid source.

Abstract: A propeller control unit for an aircraft propulsion system including a propeller is provided. The propeller control unit includes an actuator, a pump, a flow regulator, a pressure sensor, and a controller. The actuator is configured to control a pitch of each of the propeller blades. The pump is configured to direct hydraulic fluid to the actuator. The flow regulator is in fluid communication with the pump and configured to control a hydraulic fluid pressure of the hydraulic fluid downstream of the pump. The pressure sensor is disposed downstream of the pump and upstream of the actuator. The pressure sensor is configured to measure the hydraulic fluid pressure and generate a hydraulic fluid pressure signal. The controller includes a processor in communication with a non-transitory memory storing instructions, which instructions when executed by the processor, cause the processor to monitor the hydraulic fluid pressure signal.

Abstract: A propeller blade angle control circuit for a turboprop engine includes a propeller control unit controlling a supply of oil to modify an angle of propeller blades, a pump located upstream of the propeller control unit and providing the supply of oil from an engine oil return system to the propeller control unit, and a flow regulator between the pump and the propeller control unit, the flow regulator modulating a supply of oil to the propeller control unit. A bypass, downstream of the pump in the propeller blade angle control circuit, has an inlet fluidly coupled to the pump. The bypass is operable between a closed position and an open position in which a portion of the oil supplied to the propeller control unit is diverted away from the propeller blade angle control circuit. The open position is engaged when an oil pressure reaches a predetermined threshold.

Abstract: A rotor blade control system includes a main control valve having an inlet for receiving liquid and an outlet for issuing liquid to a rotor pitch change actuator. The main control valve is configured to control flow of liquid from the inlet to the outlet to modify pitch angle of rotor blades. A feathering system has a first conduit in fluid communication with the outlet of the main control valve, a second conduit in fluid communication with the rotor pitch change actuator, and a drain conduit in fluid communication with a liquid return system. The feathering system has a normal operation mode for supplying liquid from the main control valve to the rotor pitch change actuator, and a feathering mode for allowing drainage from the rotor pitch change actuator to the drain conduit across a range of flow rates.

Abstract: A method of operating a reverse thrust system of an aircraft engine, the method comprising: receiving a status signal indicative that the aircraft is on-ground or in-flight; and upon detecting that the aircraft is on-ground, overriding a protection module such that the reverse thrust system is operable regardless of the protection module being in an active state or in a disabled state, the protection module causing, absent the overriding, the reverse thrust system to be inoperable when in the active state. An aircraft comprising: an engine including a reverse thrust system; a thrust control input device configured for generating an input signal indicative of a reverse thrust demand; at least one sensor configured for generating at least one status signal indicative of the aircraft being in-flight or on-ground; and a control system electronically connected with the at least one sensor, the thrust control input device and the reverse thrust system.

Abstract: A sensor signal produced by a sensor as a feedback device rotates with a propeller about an axis and moves along the axis with adjustment of a blade angle of the propeller is received, the sensor signal indicative of a rotational speed and of the blade angle of the propeller. From the sensor signal, it is determined whether the rotational speed is within a predetermined range of a reference speed and an expected change in the blade angle has occurred in response to a command to adjust the blade angle to maintain the rotational speed at the reference speed. In response to determining that the rotational speed is within the predetermined range of the reference speed and the expected change in the blade angle has failed to occur in response to the command, inoperable movement of the feedback device along the axis is determined and an alert is output.

Abstract: A system and method for detecting fixed pitch operation of a variable pitch propeller of an engine are provided. A command signal for maintaining a rotational speed of the propeller at a reference speed is output. An actual value of at least one of the rotational speed and a blade angle of the propeller is obtained. From the actual value, it is assessed whether an expected change in the at least one of the rotational speed and the blade angle of the propeller has occurred in response to the command signal. Responsive to determining that the expected change in the at least one of the rotational speed and the blade angle of the propeller has not occurred in response to the command signal, operation of the propeller at fixed pitch is detected and an alert output accordingly.

Abstract: A failure detection method and system for a propeller control unit coupled to a propeller are provided. An actual value of a blade angle and/or a rotational speed of the propeller are obtained. A comparison between the actual value and a threshold is performed. In response to determining, based on the comparison, that the actual value exceeds the threshold, the propeller control unit is caused to adjust the blade angle to bring the blade angle and/or the rotational speed towards the threshold. A subsequent actual value of the blade angle and/or the rotational speed is obtained. From the subsequent value, it is determined whether the blade angle and/or the rotational speed has been brought towards the threshold. In response to determining that the blade angle and/or the rotational speed has failed to be brought towards the threshold, failure of the propeller control unit is detected and an alert is output.

Abstract: Methods and systems for validating a propeller control unit associated with a propeller having blades are provided. Actuation of a control valve of the propeller control unit is commanded to alter a pitch angle of the blades. One of an actual pitch angle of the blades and an actual rotational speed of the propeller is determined after a predetermined time delay has elapsed. The one of the actual pitch angle of the blades and the actual rotational speed of the propeller is compared to a corresponding one of a pitch angle threshold and a rotational speed threshold, the pitch angle threshold and the rotational speed threshold based on a commanded pitch angle. A warning signal is issued in response to determining one of the actual pitch angle failing to meet the pitch angle threshold and the actual rotational speed failing to meet the rotational speed threshold.

Abstract: A propeller control unit (PCU) has: a pitch angle actuator; a valve operable to selectively fluidly connect the pitch angle actuator with a source of oil for controlling pitch angles of blades of a propeller and with a drain line for draining oil out of the pitch angle actuator for feathering the blades; and a bypass line having an inlet hydraulically between the valve and an inlet of the drain line, the bypass line having an outlet hydraulically between the inlet of the drain line and an outlet of the drain line.

Abstract: There is provided a method and a system for detecting and mitigating a propeller failure condition. An actual value of a rotational speed of the propeller and/or of a pitch angle of blades of the propeller is obtained. In response to determining that the speed is below a reference rotational speed for the propeller and/or determining that the pitch angle is above a pitch angle threshold, an actuator operatively connected to the blades is commanded to decrease the pitch angle to increase the speed towards the reference speed. After commanding of the actuator to decrease the pitch angle, a subsequent value of the speed and/or a subsequent value of the pitch angle is obtained. The actuator is commanded to hold the pitch angle in response to determining that the speed has failed to increase towards the reference speed and/or determining that the pitch angle has failed to decrease.

Abstract: Methods and systems for validating a propeller control unit associated with a propeller having blades are provided. Actuation of a control valve of the propeller control unit is commanded to alter a pitch angle of the blades. One of an actual pitch angle of the blades and an actual rotational speed of the propeller is determined after a predetermined time delay has elapsed. The one of the actual pitch angle of the blades and the actual rotational speed of the propeller is compared to a corresponding one of a pitch angle threshold and a rotational speed threshold, the pitch angle threshold and the rotational speed threshold based on a commanded pitch angle. A warning signal is issued in response to determining one of the actual pitch angle failing to meet the pitch angle threshold and the actual rotational speed failing to meet the rotational speed threshold.

Abstract: A propeller control unit (PCU) for controlling pitch angles of blades of a propeller, has: a pitch angle actuator; a servo valve hydraulically connected to the pitch angle actuator and to a first hydraulic fluid source; and a feather valve having a body movable within a cavity, the feather valve having a first actuation port and a second actuation port both in fluid communication with the cavity, the body between the first actuation port and the second actuation port, the body being movable to selectively hydraulically connect the pitch angle actuator to the servo valve through the feather valve or to hydraulically connect the pitch angle actuator to a drain line through the feather valve, the first actuation port and the second actuation port hydraulically connected to a second hydraulic fluid source independent from the first hydraulic fluid source.

Abstract: Methods and systems for fault detection of a fuel control unit of an engine are provided. Exceedance of at least one engine parameter beyond a safety threshold, associated with excessive fuel flow to the engine, is detected at an engine controller associated with the engine. The fuel control unit is commanded, via the engine controller, to implement a reduction in the fuel flow to the engine. Following the commanding of the fuel control unit, subsequent exceedance of the at least one engine parameter beyond the safety threshold is detected at the engine controller. A fault of the fuel control unit is determined at the engine controller, based on the subsequent exceedance. In response to determining the fault of the fuel control unit, at least one countermeasure to the fault of the fuel control unit is triggered by the engine controller.

Abstract: A failure detection method and system for a propeller control unit coupled to a propeller are provided. An actual value of a blade angle and/or a rotational speed of the propeller are obtained. A comparison between the actual value and a threshold is performed. In response to determining, based on the comparison, that the actual value exceeds the threshold, the propeller control unit is caused to adjust the blade angle to bring the blade angle and/or the rotational speed towards the threshold. A subsequent actual value of the blade angle and/or the rotational speed is obtained. From the subsequent value, it is determined whether the blade angle and/or the rotational speed has been brought towards the threshold. In response to determining that the blade angle and/or the rotational speed has failed to be brought towards the threshold, failure of the propeller control unit is detected and an alert is output.

Abstract: A sensor signal produced by a sensor as a feedback device rotates with a propeller about an axis and moves along the axis with adjustment of a blade angle of the propeller is received, the sensor signal indicative of a rotational speed and of the blade angle of the propeller. From the sensor signal, it is determined whether the rotational speed is within a predetermined range of a reference speed and an expected change in the blade angle has occurred in response to a command to adjust the blade angle to maintain the rotational speed at the reference speed. In response to determining that the rotational speed is within the predetermined range of the reference speed and the expected change in the blade angle has failed to occur in response to the command, inoperable movement of the feedback device along the axis is determined and an alert is output.

Abstract: A system and method for detecting fixed pitch operation of a variable pitch propeller of an engine are provided. A command signal for maintaining a rotational speed of the propeller at a reference speed is output. An actual value of at least one of the rotational speed and a blade angle of the propeller is obtained. From the actual value, it is assessed whether an expected change in the at least one of the rotational speed and the blade angle of the propeller has occurred in response to the command signal. Responsive to determining that the expected change in the at least one of the rotational speed and the blade angle of the propeller has not occurred in response to the command signal, operation of the propeller at fixed pitch is detected and an alert output accordingly.

Abstract: A propeller control unit (PCU) has: a pitch angle actuator; a valve operable to selectively fluidly connect the pitch angle actuator with a source of oil for controlling pitch angles of blades of a propeller and with a drain line for draining oil out of the pitch angle actuator for feathering the blades; and a bypass line having an inlet hydraulically between the valve and an inlet of the drain line, the bypass line having an outlet hydraulically between the inlet of the drain line and an outlet of the drain line.