What happened
On 09 November 2003, a Thunderbird 4 was performing a takeoff from Runway 20 at Bapsfontein Aerodrome. The pilot initiated the rotation at a speed of 55 mph. While climbing at an indicated airspeed of 65 mph, the aircraft suffered a sudden loss of engine power at an altitude of approximately 100 feet above ground level.
In response to the engine failure, the pilot attempted a glide approach, following the extended centerline of Runway 20. During the landing sequence, the nose wheel contacted a mound in an open field near the aerodrome. This impact caused the nose landing gear to detach from the airframe. The momentum of the landing caused the aircraft to overturn, eventually coming to rest in an inverted position.
The investigation
The investigation focused on the mechanical state of the engine and the circumstances of the power loss. An inspection of the ignition system was conducted by an approved person. This examination revealed significant failures within the spark plug set, specifically that four plugs failed to produce a spark and an additional four plugs were found to be unserviceable.
Records indicated that the aircraft's annual inspection had been completed on 25 August 2003, with only 6.4 flight hours accumulated since that certification. The aircraft's Authority to Fly was valid at the time of the incident.
Findings
- The primary cause of the engine failure was defective spark plugs.
- The loss of power occurred during the initial climb phase at a low altitude.
- The separation of the nose landing gear and the subsequent inversion were caused by the aircraft striking a mound during the emergency landing.