What happened
On 13 February 2003, a Socata TBM 700B, registration N700VA, arrived at Oxford Airport for a private flight. After taxiing to a hangar, the pilot parked the aircraft outside and shut down the engine. Although the parking brake was engaged, the aircraft was not secured with chocks.
Approximately 50 minutes later, the pilot returned to the aircraft and observed it rolling forward at a walking pace. In an attempt to halt the movement, the pilot positioned himself in front of the plane and used the propeller to push against the aircraft. During this effort, the pilot stepped backward into a tree located at the edge of the pavement. The momentum of the aircraft forced the pilot into the tree, resulting in a serious injury involving a fractured shoulder blade. Nearby staff activated the crash alarm, and bystanders eventually arrived to push the aircraft away from the trapped pilot.
The investigation
The AAIB examined the braking mechanism of the Socata TBM 700B. The system requires the pilot to turn a control knob while simultaneously applying pressure to both toe brake pedals; failure to apply sufficient pedal pressure results in only partial braking. While the pilot maintained that he had applied the brake with full pressure, the maintenance organization noted that insufficient pedal pressure during engagement leads to incomplete braking.
Maintenance checks following the incident revealed no mechanical faults in the braking system. To investigate whether heat-related issues played a role, technicians performed a test where the brake was applied to a hot aircraft and left overnight; the brake held securely the following morning. The manufacturer could not provide a reason for why the brake might have slipped after 50 minutes, though they noted previous instances where operators failed to apply enough pedal pressure when engaging the knob.
Findings
- The aircraft was parked on a slight slope without the use of wheel chocks.
- The pilot was unable to see the tree due to low light conditions as it was getting dark.
- The specific cause of the brake slippage could not be determined.