Accident Overview
On 16 September 2007, at approximately 1040 UTC, a Piper PA-28-140 Cherokee (registration G-AVGD) experienced a loss of engine power during the base leg turn at Deanland Airfield, Sussex. The aircraft was being operated as a commercial air transport passenger flight with one pilot and one passenger on board. Both occupants received minor injuries and were able to exit the aircraft unaided before emergency services arrived.
Flight History
The aircraft had recently been repaired following an accident in September 2006. The flight originated at Cranfield Airfield and was to Deanland. After joining the circuit and turning onto base leg, the pilot attempted to increase engine power to manage the rate of descent, but the engine did not respond to throttle inputs. The instructor, who was also on board, took control, switched fuel tanks, confirmed the electric fuel pump was on, and selected carburettor heat to hot, but the engine remained unresponsive. The instructor transmitted a MAYDAY and conducted a forced landing in a field approximately 750 metres northeast of the runway. During the landing, the aircraft passed through a hedge, causing the wings to separate from the fuselage.
Engine and Carburettor Heat System
The aircraft was powered by a single Lycoming O-320-E2A piston engine. The carburettor heat control cable had been replaced during the aircraft's rebuild. After the replacement, the control protruded more than 25 mm from the instrument panel when in the cold position. This condition had been reported to the engineering organisation but was not corrected before the accident. The commander noted that this protrusion likely prevented the carburettor air valve from reaching its fully hot position before the control reached its maximum travel, thereby limiting the effectiveness of carburettor heat in preventing or removing ice.
Pilot and Weather Conditions
The commander, aged 66, held a Private Pilot's Licence with 1,150 total flying hours, including 42 hours in the last 90 days and 15 hours in the last 28 days. The reported weather at the time was temperature +15°C and dew point +11°C, conditions conducive to carburettor icing at cruise and descent power settings, as indicated by CAA General Aviation Safety Sense Leaflet No. 14.
Probable Cause
The commander reported that, in his opinion, the most probable cause of the incident was carburettor icing. The AAIB bulletin noted that the carburettor heat control protrusion may have prevented full heat application, limiting its ability to prevent or remove ice.
Damage and Injuries
The wings separated from the fuselage during the hedge impact. Both the crew member and passenger received minor injuries.