What happened
On May 11, 2008, at approximately 17:40, a Piper PA-J3 C 65 Cub, registered F-BGXC, was conducting a local flight near Ramillies, France. The aircraft was operated by a flying club and carried a pilot and one passenger. After completing an initial 45-minute flight, the pilot departed for a second local flight. Approximately fifteen minutes into this second leg, while cruising at an altitude of 1,000 feet, the engine began experiencing significant fluctuations in RPM. The pilot was unable to maintain level flight and subsequently performed an emergency landing in a nearby field. There were no injuries and no damage to the aircraft resulting from the landing.
The investigation
The investigation focused on the cause of the engine instability. Upon inspection of the aircraft on the ground, a mechanic discovered deposits within the fuel tanks, the fuel lines, and the fuel filter, which was found to be almost entirely obstructed.
Investigators determined that prior to the first flight of the day, the pilot noted that the fuel tanks contained only about ten liters of fuel and decided to refuel the aircraft. Because the fuel level in the storage tank was too low to utilize the club's standard refueling equipment, the pilot opted to use a manual Japy-type pump located on the tank. This specific pump is intended only for draining the bottom of the tank and does not include a filtration mechanism. To compensate for the lack of filtration, the pilot attempted to use a paper filter during the process. No other club members were present during this refueling procedure.
Findings
- The primary cause of the engine malfunction was the decision to use an inappropriate fuel pump for refueling the aircraft.
- The use of the manual pump allowed unfiltered fuel to enter the system, introducing contaminants into the fuel lines and tanks.
- The fuel filter became nearly blocked by deposits introduced during the refueling process.
- A delay in fuel delivery from the supplier had caused the storage tank level to drop, necessitating the use of the manual pump.
- The pilot was aware of the risks associated with bypassing the standard filtration system but chose to proceed with the refueling to ensure the flight could take place.