What happened
On October 11, 2004, a Diamond DA 40 (registration F-GUVK) was conducting an instructional flight at Montpellier-Méditerranée airport. Following a previous 40-minute flight, the instructor and two students prepared for a second flight. During engine start-up, the instructor noted a smell of kerosene but found fuel gauges to be within expected ranges.
Shortly after takeoff, while passing 500 feet, the low fuel warning light illuminated. The instructor observed a drop in the main tank level and attempted to transfer fuel from the auxiliary tank to the main tank. However, the low fuel warning light reactivated, and the fuel levels continued to drop. The instructor decided to return to the airfield and requested a shortened circuit. During the final approach, at approximately 150 feet altitude, the engine lost power as the fuel gauges indicated zero. The instructor performed a successful engine-out landing with no injuries and no damage to the aircraft.
The investigation
Investigators examined the aircraft's fuel system and engine components. Post-flight inspections revealed that both fuel tanks were empty and a fuel leak was present under the fuselage. A fuel puddle had also been noted on the parking area prior to the flight.
Upon inspection of the engine, which featured a Thielert TAE 125-1 powerplant, investigators identified a significant leak at the R4-type high-pressure fuel pump. The examination revealed that the three screws securing the rear plate of the pump were loose. These screws had not been safety-wired or secured according to original assembly requirements, which allowed the seal to fail.
Findings
- The engine failure was caused by a fuel leak at the high-pressure pump.
- The leak was due to an inadequate assembly process for the R4 high-pressure pump, specifically the failure to secure the retaining screws.
- The leak only became active after the engine was started, explaining why the pre-flight checks did not detect the anomaly.
- A similar incident involving an R4 pump had occurred in June 2004, though the manufacturer had only updated assembly procedures for newer R5 models at that time.