What happened
On August 14, 2013, a Jodel D140A Mousquetaire, registration F-BIZF, was performing a banner towing flight near Lacanau, France. The aircraft departed from Andernos-les-Bains to conduct low-altitude advertising maneuvers. While flying near the southern shore of Lake Moutchic at approximately 300 feet, the aircraft encountered heavy turbulence. During this period, the engine began to sputter and subsequently failed. The pilot attempted an emergency landing on the surface of the lake. The impact with the water was severe enough to break the landing gear and resulted in one minor injury to the pilot.
The investigation
The investigation focused on the fuel system and the sequence of events leading to the engine failure. Examination of the wreckage revealed that the fuel selector was set to the rear tank, which was full, while the front tank contained a very low amount of fuel. The auxiliary pump was found in the "ON" position.
Evidence indicated that the pilot had intentionally departed with the front tank as the primary source, intending to switch to the rear tank once the fuel was depleted. However, while attempting to manage the fuel switch during heavy turbulence, the pilot executed an aggressive left turn to exit the turbulent area and check the banner attachment. The investigation established that the low fuel level in the front tank, combined with the aircraft's high pitch attitude during towing and the lateral forces of the maneuver, caused the fuel to shift away from the fuel strainer. This led to air entering the fuel line and the unpriming of the fuel pump.
Findings
- Inadequate fuel management, specifically the decision to use the front tank during towing operations, which is contrary to recommended procedures.
- The unpriming of the fuel system caused by the combination of low fuel levels, high pitch attitude, and an aggressive maneuvering response to turbulence.
- Low altitude at the time of the engine failure, which left the pilot with minimal options for recovery.
- Pilot fatigue at the end of the flying season may have acted as a contributing factor to the procedural error.