What happened
On 30 November 2004, a Piper PA-30 Twin Comanche, registration G-AVPS, was performing a private flight from Gloucester Airport to Farley Farm Airstrip in Hampshire for a scheduled annual inspection. During the approach to the grass runway, the pilot performed a go-around after determining the aircraft was too high, notably leaving the landing gear in the extended position during the second attempt.
Upon landing on the wet grass, the aircraft initially appeared to touch down normally on all three wheels. However, as the pilot applied the brakes, the landing gear collapsed. The impact caused significant damage to the aircraft, including bent propellers, shock-loaded engines, and damage to the lower fuselage skin and landing gear mechanism. The pilot was uninjured and able to exit the aircraft without assistance.
The investigation
The investigation examined the landing gear's mechanical operation and the aircraft's maintenance history. It was noted that the pilot had experienced issues with the landing gear during previous flights, including instances where the nose gear only partially extended.
Technical analysis focused on the electric motor and screw jack system used to actuate the gear. Investigators found that while the green 'down locked' indicator light was illuminated in the cockpit, the nose gear was not actually secured in the down position. The investigation looked into the possibility of the drag link being forced over its mechanical stop, but no such damage was found, ruling out a heavy landing as the primary cause of the mechanical failure.
Findings
- The nose gear was not locked down prior to touchdown.
- A misalignment of components or accumulation of dirt allowed the limit switches to trigger the 'down locked' light before the nose gear drag link had moved over centre.
- During the landing roll, the nose gear leg folded rearwards because the drag link failed to resist the rearward force.
- This movement exerted extreme loads on the electric landing gear motor, tearing it from its mounting on the wing spar.
- The displacement of the motor pulled the main gear cables forward, causing the main landing gear to retract and resulting in the total collapse of the undercarriage.