What happened
On 14 January 2007, a Gulfstream AA-5B, registration G-BTII, was parked at Biggin Hill Airfield in Kent. The pilot began the engine start sequence while keeping feet on the toe brakes. Shortly after the engine started, the aircraft began moving forward. The pilot attempted to stop the movement by repeatedly applying the brakes, but the aircraft instead performed a 90-degree turn to the left.
As the aircraft turned, the pilot momentarily looked at the cockpit instruments to locate the throttle and mixture controls. During this period, the aircraft continued its trajectory toward a parked Piper PA-28. To avoid hitting the nose and propeller of the adjacent aircraft, the pilot ceased braking, which caused the aircraft to head toward the perimeter fence. The sequence ended when the left wing of G-BTII slid under the wing of the parked Piper PA-28, and the right wing struck a nearby concrete shed. There were no injuries to the pilot.
The investigation
Investigators reviewed CCTV footage from the airfield, which provided time-lapse images of the event. The pilot noted that the engine was likely running at a higher RPM than the standard 1,200 rpm setting, though he was unable to adjust the power due to the sudden movement. The pilot also suggested that his panicked application of the brakes might have involved simultaneous use of the rudder.
An examination of the aircraft was conducted by a co-owner. The investigation found that the right wheel brake was slightly less effective than the left, though it remained functional at various speeds. There was also a possibility that the right brake caliper piston had temporarily stuck due to the aircraft being parked outside in wet weather. Additionally, while the parking brake was set to the ON position, evidence suggested it was not fully engaged, allowing the toe brakes to generate some left brake pressure.
Findings
- The engine was likely operating at a higher-than-normal RPM during the start sequence.
- The pilot's focus on avoiding a hangar collision led to a decision to stop braking, which redirected the aircraft into the adjacent plane.
- The parking brake may not have been fully engaged, allowing the toe brakes to influence the aircraft's direction.