What happened
On March 28, 1999, a Robin DR 400-120, registration F-GAHE, was engaged in a multi-leg cross-country flight involving several aircraft. The flight itinerary included legs from Cherbourg to Old Sarum, then to Kemble, before returning to Cherbourg. During the final leg of the journey, the pilot contacted the control tower to request priority for a semi-direct approach.
While established on the base leg, the engine ceased operation. The pilot attempted an emergency landing in a nearby field, resulting in heavy damage to the aircraft. There were no injuries reported among the three occupants on board.
The investigation
The investigation focused on the engine failure and the fuel state of the aircraft. Investigators examined the flight logs and the aircraft's tachometer to determine the actual duration of the flight. While the pilot's records suggested a flight time of 1 hour and 42 minutes for the final leg, it was determined that the tachometer-based timer under-reported actual flight time because the engine was operated at lower RPMs (2400 RPM and 2200 RPM) to conserve fuel after the low-level warning light illuminated.
Furthermore, the investigation looked into the refueling process and the aircraft's weight. Although 78 liters of fuel had been added prior to the flight, it could not be confirmed that the 110-liter tank was completely full at departure. Additionally, the aircraft was found to have departed Cherbourg with a 18 kg overload.
Findings
- The primary cause of the engine failure was inadequate fuel management.
- The aircraft's fuel tank was found to be empty following the accident.
- The pilot's reliance on a tachometer-linked timer led to an inaccurate estimation of remaining flight time, as the timer does not account for time elapsed at reduced engine speeds.
- The aircraft was operating in an overloaded state during the initial departure.