What happened
On 3 July 2014, a HAPI Cygnet SF-2A, registration G-BWFN, was conducting a private local flight from Abbots Bromley Airfield. The flight, which included the pilot and one passenger, proceeded normally following takeoff from Runway 23. However, as the aircraft reached approximately 450 ft above ground level, the engine began making popping noises and suffered a loss of power.
Due to the low altitude, the pilot immediately focused on selecting a landing site rather than performing troubleshooting. After selecting a field to avoid cattle, the aircraft descended toward the landing area. During the descent, the propeller ceased rotation entirely. The pilot noted that the aircraft's handling characteristics changed significantly, with increased drag and sluggish controls due to the lack of propeller slipstream. Upon touchdown, the landing gear collapsed and the right wing struck the ground. Both the pilot and the passenger sustained minor injuries but were able to exit the aircraft unassisted.
The investigation
An investigation into the engine failure was conducted by the pilot and a Light Aircraft Association inspector. The examination of the electrical and fuel systems revealed no mechanical or electrical faults. Consequently, the investigation focused on atmospheric conditions and engine operation.
While the pilot had recorded warm ambient temperatures, data from a nearby airport indicated a lower temperature and a dewpoint of 14°C. It was noted that the aircraft's temperature gauge might have provided an inaccurate reading because the aircraft had been sitting in the sun. The investigation also considered the impact of the aircraft idling on the grass prior to takeoff and the potential for high humidity.
Findings
- The engine failure was likely caused by carburettor icing.
- The temperature and dewpoint spread at the time of the accident presented a moderate risk for icing.
- The aircraft's temperature gauge may have been misleading due to solar heating while parked.
- The collapse of the landing gear was caused by the rough ground conditions during the forced landing.