A method and system for operating a gas turbine engine coupled to an aircraft propeller are described herein. The method comprises detecting a command for unfeathering the propeller, inhibiting shaft shear detection logic in response to detecting the command for unfeathering the propeller, detecting completion of the unfeathering of the propeller, and enabling the shaft shear detection logic in response to detecting the completion of the propeller unfeathering.

A propeller oil control system for a turboprop engine of an aircraft includes an engine control unit and a propeller oil controller. The engine control unit is operable to determine a flight phase of the aircraft and is configured to supply control commands. The propeller oil controller is coupled to receive a supply of oil and to discharge the oil at a discharge oil pressure. The propeller oil controller includes an electrohydraulic servo valve that receives the control commands moves to a plurality of positions between a first position and a mid-position, and a plurality of positions between the mid-position and a second position. The engine control unit only commands the electrohydraulic servo valve to move out of the first position when the engine control unit determines the aircraft is conducting a take-off roll or the aircraft is in flight.

A device for locking the pitch and for feathering adjustable-pitch fan blades of a turbine engine propeller, the device including an actuator having at least one movable portion designed to be coupled to pivots of the fan blades of the propeller in order to modify their pitch angle when it slides, a movable part having first mechanical device suitable for co-operating with the actuator when in a fan blade pitch-unlocking position in order to enable the actuator movable portion to slide over an extended actuator stroke; and second mechanical device suitable for co-operating with the actuator when in a fan blade pitch-locking position in order to enable the actuator movable portion to slide over an actuator stroke that is shorter than the extended actuator stroke, and an actuator.

A system for controlling a propeller having a plurality of blades having a primary control system and a backup control system. The primary control system including a sensor responsive to a propeller state, and a controller connected to the sensor and to an electrohydraulic control actuator. The electrohydraulic control actuator connected via a bypass valve to a hydraulic actuator that controls at least a blade angle of a blade of the propeller. The controller generating commands to the electrohydraulic control actuator based on at least the propeller state. The backup control system including a second controller, an electrohydraulic solenoid operably connected to the bypass valve. The backup control system operable to hydraulically disable the primary control system via the bypass valve upon the occurrence of a selected condition, the second controller modulates the operation of the electrohydraulic solenoid to control the bypass actuator based on the propeller state.

An aircraft comprising a fuselage and propelled by a turbine engine having two coaxial and contrarotating fans, the turbine engine comprising a power turbine having two contrarotating rotors, one of which drives a fan upstream from the turbine, the other a fan downstream from the turbine, each fan comprising a ring of blades, and the assembly of the fans and the power turbine being incorporated at the rear of the fuselage, in the extension of same. The aircraft comprises, for at least one of the fans, a device for blocking the rotation of the fan and a device configured to modify the pitch of the blades of the fan in such a way as to make it operate as a flow straightener with respect to the other fan.

A variable pitch propeller assembly operatively coupled with an engine and methods for controlling the pitch of a plurality of propeller blades thereof is provided. In one example aspect, the variable pitch propeller assembly includes features for combining overspeed, feathering, and reverse functionality in a single secondary control valve. The secondary control valve is operable to selectively allow a controlled amount of hydraulic fluid to flow to or from a pitch actuation assembly such that the pitch of the propeller blades can be adjusted to operate the variable pitch propeller assembly in one of a constant speed mode, a feather mode, and a reverse mode.

Methods and systems for slowing down an aircraft having a propeller. The method comprises operating the propeller at a reference speed with the propeller blades in a first position, applying a load to the propeller to slow down a rotational speed of the propeller when the propeller is in a windmilling state or just before the propeller enters the windmilling state, adjusting the propeller blades to a second position in response to the load being applied, to increase the rotational speed of the propeller back towards the reference speed, and operating the propeller at the reference speed with the propeller blades in the second position.

A system for controlling propeller pitch in the event of electro-hydraulic servo valve (EHSV) failure can include an actuator and a selection valve in fluid communication with the actuator. The selection valve can be fluid communication with a first EHSV having a first null state bias configured to bias the actuator to an increased-pitch position, and a second EHSV having a second null state bias configured to bias the actuator to a decreased-pitch position. The selection valve can be configured to selectively allow fluid communication between one of the first EHSV and actuator and/or the second EHSV and the actuator.

There is described herein methods and systems for testing a propeller feathering function. The method comprises monitoring a rotational speed over time of propeller blades of an aircraft, commanding an angle change of the propeller blades, comparing a post-angle change rotational speed of the propeller blades to an expected rotational speed without the commanded angle change and obtaining, by the processor, a rotational speed difference, and issuing a test passed signal when the rotational speed difference exceeds a threshold and a test failed signal when the rotational speed difference does not exceed the threshold.

The variable pitch propeller control system can have a source of adjustable, actuation hydraulic pressure, a feather valve openable to provide an actuation path of the actuation hydraulic pressure between the source and the actuator, and closeable to connect the actuator to a drain below the actuation hydraulic pressure and close the actuator path, and a bypass path parallel to the actuator path, the bypass path having a restricted flow area relative to a flow area of the actuator path.