isolating/isolation valve

isolating/isolation valve

isolating/isolation valveclick for a larger image
Dual pump system with isolating valve.
Valves in the fuel or hydraulic systems to separate and isolate subsystems in case of any failure. For example, a fuel-isolation valve isolates the pump from its servocontrol system, except the overspeed governor. The valve permits the pump to operate at a full stroke in the event of a sudden drop in the engine RPM caused by a failure of the servosystem, which leads to the piston moving to the minimum stroke. It also is used as a safeguard against the total failure of the system during takeoff and is switched off once a safe height and speed have been achieved. If the isolation valve remains on in flight, it will result in significantly higher fuel consumption. Similarly, in some aircraft, the hydraulic-isolation valve isolates the main systems, like those lowering the undercarriage and the flaps, from the operation of other hydraulically operated systems in case of any leaks.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved