What happened
The pilot encountered a malfunction while attempting to lower the landing gear. Upon activating the extension mechanism, the circuit breaker for the landing gear motor tripped immediately. The pilot reset the breaker and, after allowing a brief cooling period, attempted to extend the gear again, but the breaker popped once more with identical results.
Unable to fully deploy and lock the landing gear through normal means, the pilot utilized the emergency extension system. Despite this effort, the aircraft touched down with the landing gear only partially extended. The structural integrity of the gear was compromised upon impact, resulting in a collapse of the landing gear assembly.
The investigation
A thorough examination of the damaged components revealed significant mechanical failure within the landing gear actuating system. Several bearings with part number 5201KD were found to be broken and had become jammed between the worm gear and the gearbox housing. This obstruction prevented proper operation of the mechanism.
Further inspection indicated that there was little to no lubricant remaining in the actuator. The actuator had accumulated 4,538 hours of operation since new and had never been overhauled. This exceeded the manufacturer's recommended overhaul interval of 2,000 hours, suggesting that wear and lack of maintenance contributed to the bearing failure.
Findings
The primary factors leading to the incident were the broken bearings in the landing gear actuating system and the lack of lubrication. The failure was exacerbated by the actuator operating well beyond its recommended overhaul period. The repeated tripping of the circuit breaker prevented normal gear extension, forcing reliance on emergency systems which could not fully compensate for the mechanical jam.