Limited flow thrust reverser actuating
The subject matter of this specification can be embodied in, among other things, an engine assembly includes a nacelle configured to at least partially surround an engine, and a thrust reverser coupled to the nacelle, the thrust reverser having a thrust-reversing element movable relative to the nacelle between a stowed position and a deployed position, a hydraulic actuator operably coupled to move the thrust-reversing element between the stowed position and the deployed position, and a fluid control system configured to operate the hydraulic actuator, the fluid control system having an electrohydraulic servo valve operable to selectively route fluid between a pressurized fluid source, the hydraulic actuator, and a fluid return reservoir, and a bypass fluid line providing fluid communication between the hydraulic actuator and the fluid return reservoir independent of the electrohydraulic servo valve.
1. A method of operating an engine thrust reverser comprising a thrust-reversing element movable between a stowed position and a deployed position, the method comprising:
transitioning the thrust-reversing element from the stowed position to the deployed position by:
conveying a primary fluid flow from a pressurized fluid source to a hydraulic actuator coupled to the thrust-reversing element;
conveying a secondary fluid flow from a fluid return reservoir to the hydraulic actuator, the secondary fluid flow being separate from the primary fluid flow; and
while conveying the primary fluid flow and the secondary fluid flow, operating an electrohydraulic directional control servo valve, the operating comprising:
configuring the electrohydraulic directional control servo valve to a first deploy stage in which the pressurized fluid source is fluidically connected to a deploy chamber of the hydraulic actuator and the fluid return reservoir is fluidically connected to a stow chamber of the hydraulic actuator;
controllably routing, through the electrohydraulic directional control servo valve in the first deploy stage, fluid from the pressurized fluid source to the deploy chamber;
configuring the electrohydraulic directional control servo valve to a second deploy stage in which the pressurized fluid source is fluidically connected to the deploy chamber and the stow chamber is fluidically connected to the deploy chamber;
controllably routing, through the electrohydraulic directional control servo valve, fluid from the stow chamber to the deploy chamber;
configuring the electrohydraulic directional control servo valve to a stow stage; and
routing, through the electrohydraulic directional control servo valve, fluid from the pressurized fluid source to the stow chamber; and
unidirectionally communicating, by a check valve, fluid from the stow chamber to the deploy chamber; and
permitting, by the check valve, fluid flow from the fluid return reservoir to the hydraulic actuator, wherein the check valve resides on a bypass fluid line providing fluid communication between the hydraulic actuator and the fluid return reservoir independent of the electrohydraulic directional control servo valve; and
inhibiting, by the check valve, fluid flow from the deploy chamber to the fluid return reservoir.
2. The method of claim 1 , further comprising limiting, by the electrohydraulic directional control servo valve, the primary fluid flow to a predetermined flow threshold that is based on a predetermined maximum deployment speed for the transitioning.
3. The method of claim 2 , further comprising receiving a position feedback signal representative of a position of the thrust-reversing element, wherein the predetermined flow threshold is based on the predetermined maximum deployment speed for the transitioning.
4. The method of claim 1 , further comprising:
operating an isolation control valve to selectively inhibit or permit fluid flow between the electrohydraulic directional control servo valve, the pressurized fluid source and the fluid return reservoir;
configuring a piloted check valve to a first pilot stage, where fluid flow from the fluid return reservoir to the hydraulic actuator through a bypass fluid line providing fluid communication between the hydraulic actuator and the fluid return reservoir independent of the electrohydraulic directional control servo valve is inhibited; and
configuring the piloted check valve to a second pilot stage, where fluid flow from the fluid return reservoir to the hydraulic actuator is permitted.
5. The method of claim 4 , further comprising:
controlling a solenoid valve coupled to both the isolation control valve and the piloted check valve; and
concurrently controlling, by the solenoid valve, operation of the isolation control valve and the piloted check valve.
6. The method of claim 5 , further comprising:
receiving a thrust-reverser-deploy command;
controlling the solenoid valve based on the receiving; and
initiating, by the solenoid valve, transition of the piloted check valve from the first pilot stage to the second pilot stage.
7. The method of claim 1 , wherein the check valve is configured to permit fluid flow when a pressure in the deploy chamber of the hydraulic actuator is less than a pressure at the fluid return reservoir.