What happened
On Sunday, June 18, 2000, a Cessna 172 H, registration F-GFMU, was conducting a flight departing from Autun with an intended stop in Saulieu before returning to Autun. The pilot initially estimated the flight duration would be approximately 45 minutes. After passing over Saulieu, the pilot decided to extend the trip to include visits to Avallon and Clame to Clamecy, increasing the total planned flight time to one hour.
Approximately 45 minutes into the flight, as the aircraft approached Autun, the pilot noted engine roughness, which was interpreted as a sign of impending fuel starvation. The pilot subsequently performed an emergency landing in a field near Ouroux-en-Morvan. During the landing roll, the nose gear struck a ditch, causing it to collapse. The aircraft sustained damage to the engine cowling, the nose gear, and the left wing leading edge. There were no fatalities among the two occupants.
The investigation
The investigation focused on the fuel levels and the discrepancy between the pilot's estimated endurance and the actual fuel remaining. Post-accident inspection revealed that the fuel tanks were empty. The aircraft's tachometer indicated a flight duration of 48 minutes since the previous flight log entry.
Prior to the flight, the pilot had estimated the aircraft's endurance at 90 minutes, based on an operator-provided average consumption rate of 30 liters per hour. This estimation was derived by comparing fuel gauge readings with refueling records and flight durations recorded in the logbook. However, the investigation found that a physical visual check of the fuel levels was not performed before departure.
Findings
- The investigation established that the aircraft was experiencing a higher fuel consumption rate than the operator's standard estimate. While the pilot used a figure of 30 liters per hour, the actual average consumption over the previous 20 flight hours was greater than 37 liters per hour.
- At 75% power, the aircraft's flight manual indicates consumption rates of 32 liters per hour at 2500 feet and 30 liters per hour at 5000 feet. Based on the actual consumption rate, the maximum endurance for the flight was only approximately 44 minutes.
- The pilot failed to perform a precise visual verification of the fuel quantity in the tanks before takeoff, relying instead on calculated estimates and logbook data.