What happened
On 17 December 2012, an Alpi Aviation Pioneer 400, registration G-CGAJ, departed from a private airstrip near Abergavenny for a flight to Gloucestershire Airport. The aircraft was carrying one pilot and one passenger. Shortly after takeoff, the pilot attempted to retract the landing gear, but the landing gear actuator circuit breaker tripped.
After resetting the breaker, the pilot found it tripped again immediately. Attempts to manually operate the gear were unsuccessful. Fearing the gear was not fully locked, the pilot proceeded to Gloucestershire Airport to utilize better emergency facilities. During the approach, the pilot received visual confirmation from the Air Traffic Control Tower that all three gear legs appeared to be down. However, upon touchdown, the left main and nose landing gear collapsed. The aircraft veered off the left side of the runway and struck a disused concrete manhole cover, resulting in damage to the left wing, flap, and landing gear. There were no injuries to the occupants.
The investigation
An engineer from the Light Aircraft Association examined the aircraft the following day. The inspection revealed that all three landing gear screw jacks had fractured. The investigation established that the left main landing gear jack had likely failed during the takeoff phase. Because the overcentre mechanism had not been properly engaged, the motor end of the fractured screw rotated several times before jamming against the rear spar, which caused the electrical circuit breaker to trip.
Findings
- The primary cause of the gear failure was the fracture of the landing gear screw jacks.
- The failure was attributed to the jacks being subjected to improper loads because the overcentre mechanisms were not properly engaged.
- The mechanical failure of the left main gear jack during takeoff led to the subsequent electrical trip and the inability to manipulate the gear manually.