What happened
On June 26, 1998, at approximately 19:00, a QuickSilver MX2 ultralight aircraft, identified as 24-AB, was performing a local flight near the Saint-Crespin-et-Carlucet aerodrome. The pilot was conducting a routine flight following a period of aircraft maintenance. As the aircraft climbed to an altitude of approximately 15 meters, the number two cylinder of the Rotax 503 engine ceased to function. Recognizing the engine failure, the pilot attempted to maintain airspeed by pushing the control stick forward; however, the aircraft entered a stall. The resulting impact caused heavy damage to the aircraft and resulted in one injury to the pilot.
The investigation
The investigation focused on the engine's performance following a recent period of storage. The aircraft had been out of service for six months, during which time the owner had performed various re-servicing procedures, including a cleaning of the carburetors. Post-accident inspection of the carburetor for cylinder number two revealed that the float bowl was empty. Investigators determined that the fuel inlet needle valve was stuck in the closed position.
Findings
- The primary cause of the engine failure was an incomplete carburetor cleaning following the aircraft's six-month storage period.
- During long-term storage, fuel evaporation in the carburetor float bowl can leave behind oil residue, which may clog critical components.
- The engine's user manual does not provide specific instructions or procedures for cleaning the carburetor.