Incident Overview
An airplane experienced a landing with its landing gear retracted. The aircraft had recently undergone replacement of the landing gear transmission as well as maintenance on the gear system. Following the landing, the aircraft was lifted from the runway, and the landing gear was extended manually.
Post-Accident Examination
A post-accident investigation revealed that the gear motor circuit breaker had popped. Further examination indicated that the gear motor was binding due to insufficient adjustment between the transmission and the gear motor. This binding caused the circuit breaker to trip, preventing the gear from extending electrically.
Manual Extension System
The airplane is equipped with a manual extension system that also serves as a secondary gear position indicator. When the landing gear is moving via electrical actuation, the manual extension system moves simultaneously. In this instance, the manual extension functioned as intended after the aircraft was raised from the runway, allowing the gear to be extended manually.
Findings
The investigation identified that the binding of the gear motor, resulting from inadequate adjustment between the newly installed transmission and the gear motor, was the direct cause of the circuit breaker activation. No other contributing factors were cited in the source.