Incident Details
On 7 June 1998 at 1641 hours UTC, a Piper PA-34-200T, registration G-CTWW, was involved in an incident at RAF Shawbury, Shropshire. The aircraft had two Continental LTSIO-360-EB1 piston engines and was manufactured in 1979. The flight was private, with one pilot and two passengers on board. No injuries were reported. The pilot held a Private Pilot's Licence with an IMC Rating, was 48 years old, and had 792 total flying hours, including 30 hours on type.
Sequence of Events
The pilot had just completed three landings at Welshpool and was departing the circuit with two passengers, both pilots. During the climb-out, a passenger commented that the right landing gear leg did not appear retracted. The pilot recycled the landing gear three or four times, but the right wheel remained in what appeared to be a locked down position. Upon rejoining the circuit at Welshpool, the pilot lowered the landing gear and confirmed three green lights indicating 'down and locked'. However, on touchdown, the right landing gear leg began to collapse. The pilot applied full power, aborted the landing, and commenced a go-around.
The pilot then performed a low fly-past at Welshpool for an experienced instructor on the ground, who observed that the right leg appeared to be 'dangling' at an unusual angle. The pilot elected to divert to a longer and wider runway with comprehensive emergency support, choosing RAF Shawbury, nearby. The instructor telephoned Shawbury to give advance notice to emergency services. As it was a Sunday, organizing emergency services took time, allowing the pilot to plan his emergency landing.
Before landing, the pilot shut down the right engine and feathered its propeller. In the landing flare, he cut the left engine and landed with power and electrics off, door catches open, and fuel off. The crosswind helped keep the right wing up during the landing roll, and little further damage occurred.
Aircraft Damage
The right landing gear was destroyed, and the right flap, propeller, and right wing skin were damaged (the wing upper skin was holed). A licensed engineer inspected the aircraft and confirmed that no further damage had occurred at Shawbury beyond that caused in the first landing at Welshpool.
Engineering Findings
The engineer found that the trunnion pin, which retains the aft face of the mounting at the top of the right landing gear leg, had migrated rearwards. This eventually allowed the top of the leg to move upward under landing loads, puncturing the wing upper skin. The trunnion pin is normally held in place by a retaining bolt running through its center and a barrel nut mounted in the upper part of the landing gear leg. After the accident, the trunnion pin and retaining bolt were found loose in the aft portion of the wing, but the barrel nut was not found, and it could not be determined at what point it had departed from the leg.