INTEGRATED ALTERNATE GEAR EXTENSION AND GROUND-CREW DOOR OPENING/ CLOSING SYSTEM FOR AN AIRCRAFT

In an aircraft having an alternate gear extension system as a backup for use by the pilot in the event of failure of the main gear extension system, a ground-crew operated subsystem is integrated with the pilot's alternate gear extension equipment for enabling the ground-crew to open and close the gear door by controls accessible on the underside of the aircraft fuselage. The integration of these two functions involves dual use of certain of the electrical and hydraulic components so that frequent and scheduled operation of the door opening function by ground-crew personnel automatically exercises the alternate gear extension mode to ensure its operability as a safety backup to the main gear extension system. The added components of the ground-crew door control function include a safety valve and an associated safety valve latch that prevent subsequent and unexpected door closure under conditions in which hydraulic actuator pressure is not available at the instant a door is commanded closed, but becomes available at a subsequent time.