History of the Flight
The pilot, flying a circuit using short takeoff and landing techniques with the aircraft owner observing from the rear tandem seat, conducted the circuit below 500 ft AAL due to an adjacent military airfield. On the base leg, the pilot selected full flap and slowed to an indicated 45 mph. Turning onto final approach, the aircraft descended below the desired approach angle at less than 100 ft AAL. With the engine running slightly above idle, the pilot advanced the throttle steadily, but the engine failed to respond. Forced to land in a field of rapeseed adjacent to the airstrip, the right main landing gear collapsed on ground contact, and the aircraft decelerated abruptly, stopping 30 m short of the runway with the right wingtip resting on the ground. The occupants vacated the aircraft without assistance.
Pre-Existing Engine Issue
The owner reported that during practice landings over several weeks, the engine had twice failed to respond when the throttle was advanced rapidly from idle. After discussing with engineers, he concluded that rapid throttle advancement caused a rich cut. Although the issue did not recur in the three weeks before the accident flight, he briefed the pilot about it. The pilot had therefore kept the engine above idle and avoided rapid throttle movement.
Post-Accident Inspection
No evidence of a technical malfunction was found during the post-accident inspection. The engine was due to be stripped down and rebuilt during the aircraft's repair.
Pilot's Comments
The pilot, with considerable type experience, noted that the reason for the engine's lack of response to throttle movement is unknown. He does not believe carburettor (induction) icing was the cause, as this is not a problem to which this aircraft type is prone and because it was unlikely on a flight of such short duration. In his view, the accident highlights that if an aircraft exhibits an intermittent fault, it is prudent to initiate an appropriate technical investigation at the earliest opportunity.