What happened
On 25 June 2008, a Beech A36 Bonanza, registration G-CDJV, was performing a private flight departing from Lydd Airport. Following takeoff, the pilot retracted the landing gear, but a loud mechanical noise occurred and the green light for the left landing gear failed to illuminate. After two attempts to recycle the gear, the nose and right gear lights showed 'down and locked', but the left gear remained unconfirmed. After a low pass to verify the gear's position with air traffic control, the pilot returned to Lydd to land.
During the return approach, the pilot attempted to manually extend the gear using the emergency handle but encountered a mechanical limit. Upon touchdown, the pilot attempted to use aileron control to keep the weight off the left gear. However, as the aircraft slowed to approximately 10 knots, the left landing gear collapsed. The left flap made contact with the ground, causing the aircraft to veer off the runway. There were no injuries to the pilot.
The investigation
Investigators examined the landing gear assembly and discovered that the extension/retension rod for the left gear had bent in two places. The investigation established that the landing gear downlock had failed to engage. Further inspection of the lock mechanism revealed that the pivot was restricted by corrosion and a lack of lubrication, and the uplock roller had become seized.
Engineers noted that a similar incident had occurred on a different aircraft, a Beech 58 Baron, where a nearly identical rod failure was caused by a seized uplock roller. The investigation found that while the manufacturer's manual suggests more frequent inspections for aircraft operating in humid or damp environments, the Beech A36 Bonanza lacked specific inspection requirements for the landing gear lock mechanisms in its flight manual or maintenance schedules.
Findings
- The left landing gear collapsed because the downlock mechanism failed to engage.
- The failure was caused by the left landing gear extension/retraction rod bending due to the seized state of the uplock roller and a lack of movement in the lock mechanism pivot.
- Corrosion and insufficient lubrication prevented the mechanism from functioning correctly.
- There were no specific requirements in the aircraft's maintenance schedule or flight manual to inspect the landing gear lock mechanisms or the uplock rollers.