Incident Overview
The pilot reported that during the final approach, the landing gear was extended normally. However, upon touchdown, the landing gear completely collapsed. The aircraft was subsequently examined to determine the cause of the failure.
Post-Crash Examination
A post-crash examination of the aircraft revealed that the alternator belt was loose. This condition allowed the battery to discharge sufficiently that the electric hydraulic pump could not fully extend the landing gear. The landing gear had not reached its fully locked position before touchdown.
Functional Test
After the examination, the aircraft was placed on jacks and auxiliary power was applied. Under these conditions, the landing gear cycled through extension and retraction without any discrepancies, confirming that the gear system itself was functional and the issue was related to the electrical power supply.
Probable Cause
The probable cause is the loose alternator belt, which led to battery drain and resulted in the electric hydraulic pump being unable to completely extend the landing gear.