What happened
On August 5, 2005, a Cessna 172N, registration EC-HXC, was conducting a commercial banner towing operation near Almería Airport. The aircraft had departed from Vélez-Málaga Aerodrome and had been in flight for approximately two hours. While performing a right-hand turn to return to the base, the engine began to sputter and subsequently failed.
The pilot, flying at an altitude of approximately 500 feet, immediately released the banner and retracted the flaps to maximize the glide ratio. The pilot directed the aircraft toward the beach to perform an emergency landing. The aircraft struck the water approximately 10 meters from the shore, traveled 12 meters on its landing gear, and then the nose gear collapsed. The aircraft then slid 10 meters, nose-down, before flipping into an inverted position. It slid another 15 meters while upside down and finally came to a rest after traveling a further four meters on land. The pilot was the sole occupant and escaped the wreckage uninjured, though the aircraft sustained major damage.
The investigation
The investigation focused on the cause of the engine failure and the fuel system state. Post-accident inspections of the engine and fuel system revealed no mechanical defects or systemic failures. Investigators found approximately 50 liters of fuel in the left tank and 35 liters in the right tank. At the time of inspection, the fuel selector valve was in the closed position.
The pilot reported that during the flight, he had switched the fuel selector from the 'BOTH' position to the 'RIGHT' tank because he observed an asymmetry in fuel consumption between the two tanks. He noted that the engine failure occurred seconds after completing the right-hand turn.
Findings
- The engine failure was caused by a lack of fuel supply to the engine.
- The pilot's decision to switch to the right tank was based on fuel sight gauge readings that suggested an imbalance; however, post-accident measurements showed the right tank actually contained less fuel than the left, suggesting the gauges provided misleading information.
- While it was considered that fuel sloshing during a long-duration turn could have uncovered the fuel pickup, the remaining fuel volume made this unlikely.
- The investigation concluded that the most probable cause was that the pilot erroneously left the fuel selector valve in the closed position after switching tanks, thereby cutting off the fuel flow to the engine.