Synopsis
On 14 January 2007, a Gulfstream AA-5B (registration G-BTII) suffered a loss of directional control during engine start at Biggin Hill Airfield, Kent. The aircraft swung left, its left wing contacting an adjacent parked Piper PA-28 and its right wing striking a concrete shed. The pilot, the only person on board, was uninjured. The aircraft sustained damage to both wings, while the adjacent aircraft had damage to its left wing.
Sequence of Events
The pilot completed pre-start checks, including setting the parking brake to ON. After starting the engine, the aircraft began to move forward. Despite repeatedly operating the toe brakes, the aircraft continued to turn left. The pilot, preoccupied with monitoring instruments, looked up to find the aircraft heading toward a hangar. He applied the brakes, which resulted in a 90° left turn, avoiding the hangar but now heading toward the perimeter fence. He then located the throttle and mixture controls and pulled both fully back, stopping the engine. The aircraft continued turning toward the parked Piper PA-28. The collision occurred with G-BTII's left wing sliding under the left wing of the parked aircraft and the right wing hitting the shed wall.
Aircraft Examination
After the accident, the co-owner and pilot tested the brakes on the apron. The right wheel brake was marginally less effective than the left, but the aircraft could be steered and braked normally at various speeds. The pilot noted that the aircraft had not flown for a month and was parked outside in wet weather, possibly causing a temporary sticking of the right brake caliper piston.
Pilot's Comments
The pilot stated that the engine was likely running faster than the normal 1,200 rpm idle after start, but he did not have a chance to reduce power due to his focus on avoiding a collision. He also thought he might have inadvertently applied a combination of brake and rudder in panic. Additionally, the parking brake was set to ON, which should have locked out the toe brakes, but the sharp left turns suggested the parking brake was not fully engaged and left brake pressure was being applied.
Video Analysis
The pilot provided CCTV footage from the airfield showing the incident in time-lapse photographs taken approximately two seconds apart. The quality did not show the propeller start, but a sudden nose-down attitude change indicated the engine starting and running at relatively high speed. The first forward movement occurred two seconds later, and the aircraft made a 90° turn over the next ten seconds before the collision after an additional three to four seconds. The total time from first observable movement to impact was about 13-14 seconds.