A ram air turbine release system including a turbine defining a rotational axis including at least one notch therein for receiving a plunger to prevent rotation of the turbine mechanically by moving between a first position and a second position, and a first bearing system contacting at least a portion of an outer surface of the plunger configured to reduce friction produced when the plunder moves between the first positon and the second position.

A system includes a first fluid flow path configured to condition a pressurized medium and deliver the pressurized medium to one or more loads. The first fluid flow path including an air cycle machine. A second fluid flow path is configured to circulate a working fluid. The second fluid flow path includes a heat exchanger thermally coupled to the first fluid flow path. Within the heat exchanger, heat extracted from the pressurized medium is transferred to the working fluid. The second fluid flow path additionally includes a turbine operably coupled to the air cycle machine, a condenser, and a pump operable to circulate the working fluid through at least a portion of the second fluid flow path. The turbine is rotationally driven by expanding the working fluid across the turbine.

An air cycle machine includes a compressor in fluid communication with an output conduit, a first turbine operably connected to the compressor and fluidly coupling the compressor with the output conduit, a second turbine operably connected to the compressor and fluidly coupling the compressor with the output conduit, and a valve. The valve couples the compressor with the output conduit and has an open position and a closed position. In the open position the first turbine and the second turbine are fluidly connected in parallel between the compressor and the output conduit. In the closed position the first turbine is fluidly connected in series with the second turbine between the compressor and the output conduit. Air cycle machine systems and methods of controlling flow in air cycle machines are also described.

A starter air valve has a valve member and an actuator. A rotary spool valve has a rotatable valve body and an outer housing to selectively provide three modes of operation for the starter air valve. A first mode of operation connects air through the rotatable valve body to communicate with an actuator control, and to receive air back from the actuator control. The rotatable valve body then communicates the air to the actuator. In a second mode the rotatable valve body blocks communication between the actuator control and the actuator, and delivers air through a variable area port in a wall of the rotatable valve body to bypass the valve member. In a third mode the rotatable valve body blocks communication between the actuator and the actuator control, and connects air to the actuator without having passed to the actuator control. A starter air system is also disclosed.

A ram air turbine (RAT) system can include a generator configured to be turned by a RAT and to output an alternating current (AC) power, a generator control unit (GCU) configured to control an output of the generator, a rectifying module configured to rectify the AC power into a direct current (DC) power, and a DC load configured to receive the DC power from the rectifying module. The DC load can be operatively connected to the GCU to provide feedback from the DC load to the GCU. The GCU can be configured to control the output of the generator as a function of the feedback to prevent stalling of the RAT and/or doorbelling current and/or voltage in the system caused by disconnecting the generator from the DC load.

A compound engine assembly for use as an auxiliary power unit for an aircraft and including an engine core with internal combustion engine(s), a compressor having an outlet in fluid communication with an engine core inlet, a bleed conduit in fluid communication with the compressor outlet through a bleed air valve, and a turbine section having an inlet in fluid communication with the engine core outlet and configured to compound power with the engine core. The turbine section may include a first stage turbine having an inlet in fluid communication with the engine core outlet and a second stage turbine having an inlet in fluid communication the first stage turbine outlet. A method of providing compressed air and electrical power to an aircraft is also discussed.

A compound engine assembly for use as an auxiliary power unit for an aircraft and including an engine core with internal combustion engine(s), a compressor having an outlet in fluid communication with an engine core inlet, a bleed conduit in fluid communication with the compressor outlet through a bleed air valve, and a turbine section having an inlet in fluid communication with the engine core outlet and configured to compound power with the engine core. The turbine section may include a first stage turbine having an inlet in fluid communication with the engine core outlet and a second stage turbine having an inlet in fluid communication the first stage turbine outlet. A method of providing compressed air and electrical power to an aircraft is also discussed.

A system and method for controlling a position of an inlet door of an auxiliary power unit are provided. A first control signal comprising instructions for opening the inlet door to a selected one of at least a first position and a second position is output. A possible failure in a feedback signal associated with the selected one of the at least first position and second position is detected and a second control signal comprising instructions for opening the inlet door to the other one of the at least first position and second position is then output.

A release mechanism comprises a locking body mounted for reciprocating movement in a first axial direction between a locked position and a released position. A force transmitting element is coupled to the locking body for transmitting a force (F) to the locking body for moving the locking body from the locked position to the released position. A biasing element acts on the locking body in a direction for moving the locking body from the released position to the locked position. The locking body comprises a slot having a first slot portion extending in said first direction, and a second slot portion extending transversely from one side of said first slot portion at an end thereof. The slot slidably receives an actuating element therein.

A transmission device for a hybrid aircraft comprising a turboshaft engine including a gas generator, a free turbine, and a main rotor, the device comprising a first reversible electric machine coupled to a shaft of the free turbine by way of a first deactivatable coupling means, and to the main rotor, and a second reversible electric machine coupled to a shaft of the gas generator by way of a second deactivatable coupling means, and coupled to the main rotor by way of a third deactivatable coupling means, the second deactivatable coupling means being able to be activated when the second electric machine rotates in a first direction of rotation, and the third deactivatable coupling means being able to be activated when the second electric machine rotates in a second direction of rotation opposite to the first direction of rotation.