What happened
On 29 November 2007, an Aero AT-3 R100, registration G-SPAT, was parked at Elstree Aerodrome in Hertfordshire following a private flight from North Weald. After being stationary for approximately 30 minutes, the pilot performed pre-flight inspections and initiated the engine start-up sequence.
During the start-up process, the pilot observed that the engine RPM was higher than typical levels. Simultaneously, the aircraft began moving forward and veering toward the left. Despite the pilot's attempts to shut down the engine, the aircraft continued its trajectory, eventually striking a parked Piper PA-28R-200, registration G-AZDE. The collision resulted in no injuries to the pilot, but caused significant damage to both airframes.
The investigation
The investigation examined the mechanical state of the braking systems and the pilot's actions during the incident. The aircraft's parking brake is operated via a switch connected to a valve that maintains hydraulic pressure, and the investigation confirmed that operating the foot pedals has no braking effect while the parking brake is engaged. Post-accident testing of the brakes on G-SPTR confirmed they were fully functional and serviceable.
Findings
- The primary cause of the movement was the pilot's potential uneven application of the hydraulic main-wheel brakes during the start-up phase, specifically pressing the left pedal with more force than the right.
- The higher than normal engine RPM during start-up contributed to the increased momentum and difficulty in controlling the aircraft's movement.
- The collision caused damage to the propeller, spinner, engine cowling, exhaust, wing leading edges, and the left side of the fuselage of the Aero AT-3 R100.
- The Piper PA-28R-200 sustained damage to its right fuselage side, cargo door, and right flap.