What happened
On 29 October 2006, a Quad City Ultralights Challenger II, registration G-MYRJ, was conducting a private flight departing from Clench Common, Wiltshire. During the initial stages of the flight, while the aircraft was approximately 300 feet above the ground performing a right turn onto the cross-wind leg of the circuit, the engine suddenly ceased operation.
In response to the loss of power, the pilot initiated a left turn to reach the nearest suitable landing area. The aircraft landed in a field; however, the ground surface had become soft due to recent rainfall. As the aircraft came to a stop, the left main and nose landing gears collapsed into the soft earth, causing damage to the landing gear assembly. There were no injuries to the pilot or the passenger on board.
The investigation
Following the incident, the engine was removed from the aircraft and sent to an overhaul agent for inspection. The examination revealed that the engine had seized. While the pilot initially believed the seizure might have been caused by thermal expansion due to an overly lean fuel mixture, the investigation uncovered several maintenance discrepancies.
Investigators found that the cylinder bolt heads had been worn by the use of an incorrect socket size, a replacement bolt of the wrong length had been used for the disc valve, and a small-end bearing was missing a roller. Additionally, the connections between the oil reservoir and the cross-shaft gear chamber had been incorrectly installed in a reversed orientation. Although these issues indicated a poor standard of maintenance, the investigation determined that none of these specific defects were the direct cause of the engine failure.
Findings
- The engine failure occurred during the takeoff circuit at a low altitude.
- The landing gear sustained damage because the soft ground surface caused the wheels to sink upon arrival.
- The engine had experienced a seizure, though the specific underlying cause of the seizure remained unidentified.
- The engine showed evidence of substandard maintenance practices, including incorrect bolt usage and improper component assembly.