The subject matter of this specification can be embodied in, among other things, an actuator apparatus includes an output member configured to actuate between a first positional configuration and a second positional configuration, a source fluid reservoir, a fluid velocity resistor configured to provide a predetermined resistance to fluid flow, a fluid velocity fuse configured to flow fluid flows having a first predetermined range of fluid velocities and to block fluid flows having second predetermined range of fluid velocities, and a fluid actuator assembly configured to urge fluid flow from the source fluid reservoir through the fluid velocity resistor and the fluid velocity fuse based on actuation of the output member.

An assembly is provided for an aircraft propulsion system with an axial centerline. This assembly includes a nacelle structure and a thrust reverser system. The nacelle structure includes a fan cowl, where a forward cavity extends axially into the nacelle structure from an aft end of the fan cowl. The thrust reverser system includes a sleeve, a cascade structure, a blocker door and a linkage. The sleeve is configured to translate axially along the centerline and relative to the nacelle structure between a forward stowed position and an aft deployed position. The cascade structure, the blocker door and the linkage are at least partially within the forward cavity when the sleeve is in the forward stowed position. The cascade structure is fixedly attached to the sleeve. The linkage extends between and is pivotally attached to the cascade structure and the blocker door.

A thrust reverser assembly for a gas turbine engine including a core engine, a nacelle surrounding at least a portion of the core engine defining a bypass duct between the nacelle and the core engine where an outer door movable between a stowed position and a deployed position extends outwards from the nacelle and a blocker door movable between a stowed position and an deployed position extends into an airflow conduit defined by the bypass duct to deflect air outwards.

A hydraulic lock apparatus includes a hydraulic actuator, a pressure storage device connected to the hydraulic actuator, and a control valve configured to actuate to a first position and a second position. The control valve fluidly isolates the pressure storage device from the hydraulic actuator when the control valve is in the first position. The control valve fluidly connects the pressure storage device to the hydraulic actuator when the control valve is in the second position.

A system and method can include a rotational component, a fluid pump, and a shaft transferring rotational power toward the fluid pump. A fluid circuit can include a valve and the fluid pump wherein pump is configured to motivate fluid toward the valve disposed downstream of the pump. The system can be configured to raise fluid pressure at the pump outlet by closing the valve to thereby effect an increased braking load on the shaft. The rotational component can be an electric machine mechanically coupled to a gas turbine engine. The fluid circuit can include a heat exchanger configured to transfer heat between the rotational component and the fluid. The system can include a second heat exchanger configured to transfer heat from the fluid to a heat sink. A processing system can be configured to receive a command to increase the hydraulic braking load to the rotational component by closing the valve to raise fluid pressure at the pump outlet based on a braking command.

The subject matter of this specification can be embodied in, among other things, an actuator apparatus includes an output member configured to actuate between a first positional configuration and a second positional configuration, a source fluid reservoir, a fluid velocity resistor configured to provide a predetermined resistance to fluid flow, a fluid velocity fuse configured to flow fluid flows having a first predetermined range of fluid velocities and to block fluid flows having second predetermined range of fluid velocities, and a fluid actuator assembly configured to urge fluid flow from the source fluid reservoir through the fluid velocity resistor and the fluid velocity fuse based on actuation of the output member.

A gas turbine engine has a compressor section with a low pressure compressor and a high pressure compressor having a downstream end. A cooling air system includes a tap from a location upstream of the downstream most location. The tap passes air to a boost compressor, and the boost compressor passes the air back to a location to be cooled. The boost compressor is driven by a shaft in the engine through an epicyclic gear system. A speed control changes the relative speed between an input and an output to the epicyclic gear system.

A thrust reverser assembly for a gas turbine engine including a core engine, a nacelle surrounding at least a portion of the core engine defining a bypass duct between the nacelle and the core engine where an outer door movable between a stowed position and a deployed position extends outwards from the nacelle and a blocker door movable between a stowed position and a deployed position extends into an airflow conduit defined by the bypass duct to deflect air outwards.

A gas turbine engine has a compressor section with a low pressure compressor and a high pressure compressor having a downstream end. A cooling air system includes a tap from a location upstream of the downstream most location. The tap passes air to a boost compressor, and the boost compressor passes the air back to a location to be cooled. The boost compressor is driven by a shaft in the engine through an epicyclic gear system. A speed control changes the relative speed between an input and an output to the epicyclic gear system.

A braking system for the low pressure spool of a gas turbine engine includes a braking assembly connected to the low pressure spool and reversibly configurable between an actuated state and an unactuated state. The braking assembly in the unactuated state allows rotation of the low pressure spool without interference. The braking assembly in the actuated state applies a force opposing the rotation of the low pressure spool. A method of controlling the speed of rotation of a low pressure spool and a method of controlling the speed of rotation of low and high pressure spools are also discussed.