What happened
On 20 December 2005, a Pioneer 300, registration G-OPFA, was involved in a landing gear collapse at Gloucester Airport. Following a routine flight, the pilot and passenger began taxiing back to the parking area. During the taxi, the pilot performed several sharp turns to both the left and right at ground speeds of approximately 12 kt. During these manoeuvres, the left landing gear collapsed, causing the left wing tip and tail to make contact with the ground. The propeller remained operational and did not strike the surface. The pilot immediately shut down the engine and notified the Aerodrome Fire Service.
The investigation
Technical examination of the aircraft revealed that the left screwjack had failed approximately two-thirds along its length. Additionally, distortion was noted on the nose and right screwjacks. The investigation established that a portion of the left jack had fallen downwards under gravity, which prevented the landing gear leg from retracting fully, though this also limited the overall damage to the airframe.
Further inspection of the electrical system revealed that the down-lock microswitch had been knocked out of adjustment. The pilot noted that it was sometimes necessary to remove the seat base to adjust seat belts, and it was possible that this microswitch had been inadvertently disturbed during such maintenance. The investigation also identified that the down-lock microswitch could signal a locked state before the mechanism had actually reached the over-centre position.
Findings
- The primary cause of the accident was the down-lock microswitch being knocked out of adjustment, which prevented the left landing gear operating mechanism from moving into the over-centre position.
- The failure of the left screwjack was a consequence of the landing gear leg not being properly locked in the down position.
- The investigation found no evidence that the sharp turns performed during taxiing directly caused the screwjack failure.