What happened
The aircraft encountered a critical mechanical issue while attempting to lower the landing gear. During this operation, a hydraulic line failure occurred, resulting in the complete loss of hydraulic fluid. Without pressure to operate the mechanism, the crew was unable to extend the gear and subsequently performed a gear-up landing.
The investigation
Post-accident examination revealed that the retaining ring of the main door actuator had failed. This failure allowed the piston to pop out of the actuator, compromising the hydraulic system's integrity. Investigators noted that there was an existing service letter addressing the inspection and replacement details for this specific circlip (retaining ring), indicating a known maintenance concern for this component.
Findings
The primary mechanical failure was identified as the failed retaining ring on the main door actuator. This component failure led directly to the hydraulic line rupture and subsequent fluid loss. The inability to maintain hydraulic pressure prevented the landing gear from deploying, necessitating the unflared touchdown.