What happened
On April 21, 2013, a Gardan GY80-180, registration F-BNQJ, departed from Castelnaudary for a local sightseeing flight over the Cathar castles. The aircraft was carrying a pilot and three passengers. Approximately fifteen minutes into the flight, while cruising at 4,000 feet, the engine suddenly failed and the propeller entered a windmilling state.
After attempting to restart the engine without success, the pilot declared an engine failure to air traffic control and prepared for an emergency landing in a nearby field. During the final approach, the aircraft struck and severed a telephone line. The impact caused the aircraft to be destroyed. The pilot and one passenger sustained slight injuries, while the remaining two passengers were uninjured.
The investigation
The investigation focused on the cause of the engine failure and the circumstances of the impact. Investigators examined the wreckage and the landing site, noting that the telephone line was obscured from the pilot's view by a tree hedge bordering the field.
Technical analysis of the engine and fuel system revealed that the fuel pressure gauge had dropped to zero during the flight. While the engine was not producing power at the time of impact, no mechanical malfunction was found in the Lycoming O-360-A engine or the fuel selector. Investigators also found a pin located in the upper fuel tank vent. This pin was a common practice used by the aircraft owners during ground storage to prevent debris from clogging the vents, but it was still in place during the flight.
Findings
- The engine failure was preceded by a total loss of fuel pressure, with no fuel found in the carburetor or fuel lines at the time of the investigation.
- The upper fuel tank vent was obstructed by a pin, which the pilot likely failed to remove before takeoff. While ground tests showed that the lower vent could still provide adequate airflow, the investigation could not definitively rule out that the obstruction caused the fuel starvation.
- The pilot's attention may have been diverted during the pre-flight inspection due to the presence of the passengers, leading to the oversight of the vent pin.
- The collision with the telephone line was caused by the aircraft's trajectory being destabilized during the final approach, and the line itself was hidden by vegetation.