Unfortunately for me, my 1976 P337 suffered a nose gear collapse during taxi tests during its annual :( Fortunately the shop's insurance is paying for all the repairs (new propellor, prop strike engine teardown, sheet metal, etc); the unfortunate aspect is that it's going to be three months (or more) until I get my airplane back...
But I have a question about the incident: the shop wrote up a root cause analysis for their insurance company and I'm curious about it, hence my question for you all: I'm puzzled that the downlocks wouldn't hold even if there is no hydraulic pressure -- I thought the point of downlocks or over-centered construction was to stay down even if there is no hydraulics.
Here's what they said (abbreviated slightly):
Identified circuit breaker ‘LG MTR’ for the ‘Landing Gear Motor’ was ‘tripped’. With the pump motor de-energized, the hydraulic pressure in the landing gear system would not be maintained at operating pressure and would have decayed over time, resulting in the landing gear doors to begin to open and the nose landing gear actuator to unlock during taxi. Once the actuator was unlocked, the movement during taxi caused the nose landing gear to collapse.
... the circuit breaker had been manually pulled to the ‘OFF’ position during maintenance activity four (4) days before the occurrence and not reset. ...
So, in your collective experience and wisdom, is there a problem with the downlocks? I.e. should the downlocks have stayed locked even without hydraulic pressure and thus this collapse should not have happened? I care about the answer because if there's a problem with the downlocks, then the landing gear system has some problem that needs to be fixed (in addition to all the damage).
Thanks for your knowledge and advice,
- Bjorn