What happened
On September 24, 2007, a Cessna 152, registration CS-AYX, departed from Cascais for a recreational VFR flight with the pilot and a passenger on board. The flight was intended to be a two-hour trip, and the pilot had recorded an estimated endurance of four hours and thirty minutes on the flight plan.
Approximately one hour and twenty-five minutes into the flight, while flying at 2,500 feet near the Arrábida mountain range and the city of Setúbal, the engine suffered a partial loss of power, operating only at low RPM. The pilot attempted standard emergency procedures, including applying carburetor heat and advancing the throttle, but the engine failed to regain power. Consequently, the pilot was forced to perform an emergency landing in an unprepared agricultural field.
During the approach, the pilot reported the emergency to Lisbon Approach and shut down the engine once the landing was assured. The aircraft came to a stop within approximately twenty meters, sustaining light damage to the engine cowlings, the nose gear structure, and the left wingtip. Both occupants exited the aircraft uninjured.
The investigation
The GPIAAF investigation focused on the engine failure and the fuel levels at the time of the incident. Maintenance inspections of the aircraft revealed that the engine, a Lycoming O-235, functioned normally during testing and showed no signs of mechanical malfunction. No fuel leaks or cracks were found in the fuel system.
Upon examining the fuel tanks at the crash site, investigators found that the right tank was empty and the left tank contained only approximately three liters of fuel. The investigation also reviewed the pilot's pre-flight actions and the aircraft's flight logs. It was noted that the pilot had checked for the presence of fuel but had not accurately verified the quantity, relying instead on a visual estimate of the fuel level relative to the tank height.
Findings
- The primary cause of the incident was engine power loss due to fuel exhaustion.
- The pilot's pre-flight inspection failed to accurately determine the remaining fuel quantity, as the pilot relied on a visual estimate rather than using a fuel dipstick.
- The flight plan incorrectly stated an endurance of four hours and thirty minutes, which was not supported by the actual fuel remaining in the tanks.
- The pilot's lack of confidence in the fluctuating fuel gauges led to a failure to perform periodic fuel quantity checks during the flight.
- The aircraft's recent flight history indicated that the remaining fuel was insufficient to meet the planned flight duration.