Aircraft and Pilot Information
The aircraft involved was a 1978 Reims Cessna F172N Skyhawk, registration G-BSHR, powered by a Lycoming O-320-H2AD piston engine. The pilot held a Private Pilot Licence, was 28 years old, and had 342 hours total flying experience, including 40 hours on type. The flight was a training sortie with only the pilot on board.
History of Flight
On the day of the accident, 3 November 2001, the aircraft had been flown for 1 hour 5 minutes earlier that morning without issue and was not refuelled before the accident flight. After a thorough pre-flight check, including fuel sampling, the pilot was cleared for takeoff from Exeter. During initial climb, ATC cleared the pilot to operate west of the airfield at altitudes up to 2,500 feet. The pilot levelled at 2,000 feet to maintain separation from cloud base. Shortly after changing the fuel tank selector from BOTH to LEFT, the engine began to run roughly. The pilot immediately re-selected BOTH and requested a rejoin at the departure airfield. While positioning for approach at approximately 1,800 feet and 80 KIAS, the engine suffered a total loss of power. The pilot attempted three unsuccessful airborne engine restarts with different fuel tank selections (LEFT, RIGHT, BOTH), after which the propeller stopped. The pilot selected a field, transmitted a Mayday call to Exeter Radar, and prepared for an emergency landing with full flap. After touchdown, the pilot applied back pressure to keep the nose wheel from digging into soft ground, but the aircraft became airborne again and struck a hedge and trees. The pilot evacuated with minor injuries.
Meteorological Conditions
A Meteorological Office aftercast for 1200 hrs on 3 November 2001 indicated a weak ridge of high pressure over southern England with a slack air mass over the Exeter area. Visibility was 25 km, with few cumulus clouds between 2,000 and 2,500 feet. At 2,000 feet, the temperature was 8°C and dewpoint 7°C, giving 93% humidity. These conditions plotted on a carburettor icing probability chart indicated a probability of serious carburettor icing at any engine power setting.
Wreckage Examination
During recovery, reasonable quantities of fuel were found in and around both fuel tanks. AAIB inspection found no obvious faults: the gascolator contained AVGAS free of contamination and water, the gascolator filter was exceptionally clean, the engine rotated freely with good compressions, and all controls (throttle, mixture, carburettor heat, fuel selector) functioned correctly. The carburettor air intake filter was clean. The engine was removed and run on a test bed for 1 hour 19 minutes, during which no faults were identified.
Previous Occurrence
On 2 May 2001, the same pilot experienced a similar engine failure while flying a Cessna 152 (G-BMFZ). He descended from 3,000 to 2,000 feet, noted power loss, applied carburettor heat (which worsened the situation), then returned to cold air, resulting in an engine stoppage. He performed a successful forced landing in a sports field; the aircraft was undamaged and no injuries occurred. Checks revealed no cause, and the aircraft was returned to service. The Meteorological Office aftercast for that incident also showed conditions conducive to serious carburettor icing.
Additional Observations
During wreckage recovery, it was noted that both wings had folded rearwards, forcing the inboard ends of the flaps into the rear passenger cabin at approximately rear seat passenger head height.