What happened
On 26 March 2023, a Pioneer 3/00, registration G-OWBA, was conducting a training flight at North Weald Aerodrome in Essex. During the landing roll, the aircraft experienced a sudden leftward veer approximately five seconds after a smooth touchdown. The instructor on board noted that the left wing subsequently made contact with the runway surface, causing the aircraft to depart the paved area and strike a runway light. There were no injuries to the two crew members on board.
The investigation
Investigators examined the aircraft and determined that the left main landing gear had collapsed. Specifically, the threaded bar of the left main landing gear jack screw had buckled and fractured near its outboard end. This failure meant that the landing gear was not in the down and locked position, forcing the load through the extension/retraction mechanism rather than the over-centre mechanism.
During the inspection, investigators also found a scuff mark inside the wheel well, suggesting the tyre had contacted the interior wall. It was discovered that the tyre installed on the aircraft was two inches wider than the dimensions specified in the maintenance manual.
Findings
- The primary cause of the gear collapse was that the left main landing gear was not properly locked in the down position.
- While the exact reason for the failure to lock could not be confirmed due to component damage, it is believed the gear may not have been correctly configured following a recent replacement of the extension/retraction mechanism components.
- A previous flight had involved an issue with the right main gear indication, which the crew believed was a microswitch adjustment issue; however, this may have been an early sign of the gear not reaching full travel.
- An incorrect, oversized tyre was fitted to the aircraft, though this was not determined to be the cause of the gear failure.