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There has to be more to the story.The F-22 has a problem with uncommanded nose gear retraction that happened at engine shutdown. I believe there was an electrical system transient during engine shutdown that somehow told the nose gear to retract. The short term fix was for the crewchief to go under the fuselage back by the main gear, then approach the nose gear from the rear to pin it before shutdown, carefully avoiding the inlet suction from the running engines. The problem was eventually fixed and this engine running gear pinning because unnecessary.In this case on the F-35, the nose gear retracted well after engine shutdown, with the pilot out of the cockpit going down the ladder. Electrical power should be off at this time. I’m not a landing gear designer, but most are driven hydraulically to the down position with linkage going over center to lock the gear down. Pinning of the gear usually doesn’t happen until the recovery inspection, before any aircraft towing operations. In this case, some stored hydraulic pressure must have been applied to the linkage to move out of the over center position, then gravity takes over. What allowed the hydraulic fluid to flow into the gear actuator (failed isolation valve?) after power was removed is where the investigation will focus. Pinning the gear would have prevented the mishap, but only as a secondary method.
There has to be more to the story.
The F-22 has a problem with uncommanded nose gear retraction that happened at engine shutdown. I believe there was an electrical system transient during engine shutdown that somehow told the nose gear to retract. The short term fix was for the crewchief to go under the fuselage back by the main gear, then approach the nose gear from the rear to pin it before shutdown, carefully avoiding the inlet suction from the running engines. The problem was eventually fixed and this engine running gear pinning because unnecessary.
In this case on the F-35, the nose gear retracted well after engine shutdown, with the pilot out of the cockpit going down the ladder. Electrical power should be off at this time. I’m not a landing gear designer, but most are driven hydraulically to the down position with linkage going over center to lock the gear down. Pinning of the gear usually doesn’t happen until the recovery inspection, before any aircraft towing operations. In this case, some stored hydraulic pressure must have been applied to the linkage to move out of the over center position, then gravity takes over. What allowed the hydraulic fluid to flow into the gear actuator (failed isolation valve?) after power was removed is where the investigation will focus. Pinning the gear would have prevented the mishap, but only as a secondary method.
