What happened
While on final approach, the crew extended the landing gear and confirmed it was down and locked, noting three green lights on the instrument panel. This sequence of events was corroborated by the cockpit voice recorder. However, upon touchdown, the left main landing gear either collapsed or retracted.
The investigation
Investigators examined the landing gear components, including the actuator rods, rod ends, down lock rollers, and cams, finding them all to be undamaged. During a post-incident examination of the hydraulic power pack, the unit produced a loud noise, and hydraulic pressure was observed fluctuating between 500 and 1,200 PSI. While an internal inspection and functional test of the hydraulic power pack revealed no discrepancies, it was noted that procedural errors occurred during the testing process which may have invalidated the results.