What happened
On September 14, 2003, a Cessna 152, registration F-GBQD, was conducting a flight from Brest to Pontoise via Quimper. During the descent toward Pontoise aerodrome, the pilot was instructed by air traffic control to descend to 2,500 feet. At this stage, the pilot noticed engine RPM fluctuations and observed that the engine would struggle or stall when the engine speed exceeded 2,000 RPM. After notifying the controller of the engine issues and his intention to perform a field landing, the pilot managed to stabilize the aircraft's speed at approximately 75 knots by limiting engine power. The aircraft landed on runway 05 at Pontoise approximately 3 hours and 22 minutes after departing Quimper. Upon landing, only three liters of fuel remained in the tanks.
The investigation
The investigation examined the fuel management and flight planning of the trip. The pilot had initially checked fuel levels using a pipette at various stages of the flight. After departing Brest, the pilot noted 100 liters of usable fuel. Following the leg to Quimper, the pilot measured 90 liters remaining. The pilot noted that the fuel consumption for the 36-minute leg from Brest to Quimper appeared unusually low (approximately 16.7 l/h), but attributed this to an error in his initial measurement at Brest rather than a change in consumption rates. For the final leg from Quimper to Pontoise, the pilot estimated a flight time of 2 hours and 30 minutes in zero-wind conditions. However, during the flight, a headwind increased the estimated flight duration by 10% to 20%, bringing the total estimated time to over three hours.
Findings
- The pilot failed to perform detailed meteorological research prior to departure, as conditions at the origin were favorable.
- There was an erroneous estimation of fuel consumption for the flight leg.
- The pilot exhibited confirmation bias, failing to properly monitor actual fuel consumption during the flight.
- The primary cause of the incident was the pilot's decision to continue the flight despite the increasing risk of fuel exhaustion.