What happened
On the evening of June 22, 2003, a Diamond DA 40 D "Diamond Star TDI", registration F-GNJV, was performing a local flight departing from the Falaise airfield. Shortly after takeoff from runway 06, while climbing through approximately 600 feet, the pilot experienced a sudden and significant loss of engine power. Despite attempts to adjust the power lever, the engine failed to respond. The pilot subsequently executed an emergency landing in a nearby field characterized by tall crops.
The impact caused substantial damage to the aircraft, specifically affecting the nose gear, the right main landing gear, and the propeller. There were 3 persons on board (the pilot and two passengers); the pilot sustained injuries during the event.
The investigation
The investigation focused on the engine performance and the fuel system of the aircraft, which had been delivered new to the flying club on June 3, 2003. It was noted that the engine, a Thielert TAE 125-01 with fewer than 100 flight hours, had previously exhibited difficulties with hot starts. Specifically, a fuel pump replacement had been performed by the engine manufacturer one week prior to the accident.
Investigators examined the fuel system design and the possibility of vapor lock. The engine manufacturer investigated the hypothesis that a vapor bubble had formed within the fuel circuit.
Findings
- The primary cause of the engine power loss was a design flaw in the fuel system.
- Specifically, a faulty non-return thermostatic valve within the fuel filter allowed for the formation of a vapor bubble, leading to the sudden loss of power during the climb.
- The aircraft was operating under a provisional permit to fly at the time of the accident.