What happened
On 7 March 2007, a Pioneer 300, registration G-TREX, was conducting a private cross-country flight from Gloucestershire Airport to Bembridge Airfield. While on the downwind leg for landing on Runway 30, the pilot activated the landing gear extension. Although the green indicator light signaled that the gear was down and locked, the nose gear failed to remain stable upon touchdown. As the aircraft's nose was lowered, the nose gear collapsed, causing the propeller to strike the ground. The aircraft subsequently slid to a halt with the lower cowling resting on the runway. There were no injuries to the pilot or the passenger.
The investigation
Investigators examined the aircraft's nose gear mechanism to determine why the gear failed to lock. The inspection revealed that the nose gear extension screwjack had been obstructed by a wiring loom. It was determined that the indicator and switch wires possessed excessive slack within the console tunnel. When the pilot operated the gear extension, the screwjack moved in a manner that caught these loose wires. The mechanism subsequently dragged a total of ten wires into the unprotected screwjack, causing it to jam. This obstruction prevented the gear from reaching full extension and stopped the over-centre downlock from engaging. The physical stress of the landing load was applied directly to the screwjack, causing it to shear and resulting in the collapse.
Findings
- The nose gear failed to lock because the extension screwjack was jammed by a wiring loom.
- Loose wiring in the console tunnel allowed the screwjack to snag and pull multiple wires into the mechanism.
- The mechanical failure of the screwjack was caused by the landing loads being applied to the jammed component, leading to a shear failure.