What happened
On September 24, 2007, at approximately 12:15 UTC, a Cessna 152, registration CS-AYX, was performing a recreational flight from Cascais. 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 was unable to restore power. Consequently, the pilot performed an emergency landing in an unpaved agricultural field near Aldeia Grande. During the approach, the pilot reported the emergency 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 mount, nose gear, engine cowling, and left wing tip. The pilot and passenger exited the aircraft uninjured.
The investigation
The GPIAAF investigation focused on the engine failure and the fuel state of the aircraft. Maintenance personnel inspected the engine at the scene and found it functioned normally at various power settings. No leaks or malfunctions were detected in the fuel system or the aircraft's components.
Investigators examined the fuel levels and found the right tank was empty, while the left tank contained only three liters of unusable fuel. The investigation also reviewed the pilot's pre-flight actions and the flight plan. It was noted that the pilot had checked for the presence of fuel but had not accurately measured the quantity. The pilot had estimated an endurance of four and a half hours in the flight plan, whereas the actual usable fuel available at takeoff was only sufficient for approximately 1 hour and 40 minutes of flight time.
Findings
- The primary cause of the incident was engine power loss due to fuel exhaustion.
- The pilot failed to verify the actual quantity of fuel in the tanks, relying instead on a visual estimate of the fuel level height.
- The flight plan contained an incorrect endurance calculation, significantly overestimating the remaining flight time.
- The pilot's lack of confidence in the fuel gauges, which were prone to needle oscillation, contributed to the failure to perform periodic fuel checks.
- The aircraft's previous flight, which lasted 2 hours and 50 minutes, had depleted the fuel levels significantly, a fact that could have been identified by reviewing the aircraft's logbook.