What happened
On 7 June 1998, a Piper PA-34-200T, registration G-CTWW, was departing the circuit at Welshpool following three completed landings. While climbing out with two passengers, the pilot was alerted by a passenger that the right landing gear leg appeared to be extended. In response, the pilot cycled the gear several times, but the right wheel remained in the downward position.
Upon returning to the circuit at Welshpool, the pilot lowered the gear and received three green lights, indicating the gear was down and locked. However, during the touchdown, the right landing gear leg collapsed. The pilot immediately applied full power to execute a go-around. To assess the situation, the pilot performed a low fly-past for an instructor on the ground, who noted the right leg was dangling at an abnormal angle.
Due to the mechanical instability, the pilot decided to divert to RAF Shawbury, a nearby airfield with a longer runway and greater emergency support. Before the final approach at Shawbury, the pilot shut down the right engine, feathered the propeller, and subsequently cut the left engine. The aircraft landed with power and electrics off, and fuel valves closed. A crosswind assisted in keeping the right wing elevated during the roll, preventing further significant damage.
The investigation
There were no fatalities and no injuries resulting from the incident. An inspection of the aircraft revealed damage to the right wing skin, the right flap, the propeller, and the destruction of the right landing gear.
An inspection by a licensed engineer determined that no additional damage occurred during the landing at Shawbury beyond what happened at Welshpool. The investigation focused on the trunnion pin, which secures the aft face of the right landing gear leg mounting. It was discovered that this pin had migrated rearwards. This movement allowed the top of the gear leg to shift upwards under landing loads, which ultimately punctured the upper wing skin.
Findings
- The trunnion pin, which is intended to be secured by a retaining bolt and a barrel nut, had moved out of position.
- The migration of the trunnion pin allowed the landing gear leg to move upward under the stresses of landing.
- While the trunnion pin and the retaining bolt were found loose in the aft wing, the barrel nut was missing, and its exact point of departure from the assembly could not be established.