What happened
On October 17, 2008, a STODDAR-HAMILTON GLASSAIR III SH-3R, registration G-BODI, was performing a local flight from the Robledillo de Mohernando Aerodrome. The flight began with a standard inspection and refueling process. After takeoff from runway 01, the aircraft climbed to 4,000 feet and proceeded northeast.
During the return to the aerodrome, while the pilot was executing a turn to align with the downwind leg of runway 19, several engine explosions were heard. The pilot reported an engine failure via radio and continued the circuit. During the final approach turn, the engine stopped completely. The pilot attempted an emergency landing in a field located approximately 500 meters from the threshold of runway 19. Upon touchdown with the landing gear extended, the aircraft struck the ground, causing it to capsize and come to rest in an inverted position.
The investigation
The investigation focused on the fuel delivery system and the sequence of events leading to the engine stoppage. Investigators examined the fuel tanks, including the main wing tank, the forward tank, and the two auxiliary tip tanks. While the engine itself was found to be intact and capable of rotation, investigators discovered that fuel was not reaching the filter from any of the selector valve positions.
Crucially, the investigation found that the electrical auxiliary fuel pump was switched off in the cockpit. Although fuel was present in the lines connecting the tanks to the selector valve, there was no fuel found between the filter and the mechanical pump, or between the mechanical pump and the injector servo. The investigation also noted that the pilot had not deployed the flaps, as the control lever was in the OFF position.
Findings
- The engine failure was triggered by a lack of fuel flow to the engine during the final stages of the landing circuit.
- The electrical auxiliary fuel pump was disconnected, which interrupted the fuel supply.
- The aircraft's auxiliary wingtip tanks lacked a system to ensure consistent fuel delivery during uncoordinated maneuvers.
- It is believed that fuel movement during the turns in the landing circuit, combined with the inactive auxiliary pump, caused the interruption in engine power.
- The use of flight helmets by the occupants prevented more serious injuries during the impact.