What happened
On 3 March 2010, a Reims Cessna F172F Skyhawk, registration G-ASWL, was conducting a training flight from Manchester Barton Airport to Swansea Airport. During the return leg of the flight, the aircraft was approximately 8 nm north of Swansea when the engine RPM suddenly dropped from its cruise setting to 1,500. Although the instructor took control and applied carburettor heat, the engine power did not recover, and the instructor subsequently reported that fuel levels in both tanks had fallen to less than a quarter full.
After transmitting a MAYDAY call, the instructor identified a suitable field for an emergency landing. During the approach, the engine power remained at 1,500 RPM. The aircraft touched down on its main wheels at approximately 55 kt. As the nosewheel was lowered, it sank into the soft ground, causing the aircraft to tip forward and invert. The student pilot, who was wearing full restraints, escaped without injury, but the instructor sustained minor facial injuries because he was not wearing his diagonal shoulder strap.
The investigation
Investigators examined the aircraft and the flight conditions. Meteorological data indicated a temperature of 6°C and a dew point of -1° and clear skies, conditions that present a moderate risk of carburettor icing. An aviation surveyor noted deep ruts in the ground caused by the landing.
During the recovery process, the aircraft was disassembled, revealing that only approximately five litres of fuel remained in the left tank and one litre in the right tank. This amount was less than the manufacturer's minimum usable fuel specification. While the tanks appeared intact, the low levels suggested a potential fuel leak may have occurred. Additionally, the student pilot noted that the fuel gauges had indicated critically low levels prior to departure, a concern that was not addressed by the instructor.