What happened
On 30 October 2018, a Denney Kitfox Mk 2, registration G-BSDD, was conducting a private flight in the Lake District when the pilot identified a fuel leak near the engine's priming pump. Fearing the leak might lead to engine failure, the pilot decided to perform a precautionary landing in a field near Coniston, Cumbria.
During the descent, the pilot noted a fuel drip rate of approximately two drops per second. While on the base leg of the approach, the pilot configured the aircraft for landing. As the aircraft transitioned to final approach, the pilot observed the airspeed was 4t8 mph and increasing. To reduce speed, the pilot fully extended the flaps. To avoid navigating between two trees near the flight path, the pilot applied a brief burst of power before closing the throttle for the final descent.
At an altitude of approximately 15 to 20 feet, the left wing stalled, causing the aircraft to enter a left-hand descending turn. The wing tip struck the ground, followed by the propeller hitting the earth and the collapse of the left landing gear. The pilot escaped the aircraft without injury.
The investigation
The investigation examined the mechanical state of the aircraft and the pilot's approach technique. It was determined that the fuel leak originated from the shaft seals of the hand priming pump. The pilot suggested that the seals may have suffered premature wear due to the necessity of operating the pump while cranking the engine, a requirement caused by the limited capacity of the aircraft's lightweight battery.
Regarding the flight profile, the investigation looked at the use of flaps and power management. The pilot had previously used a technique involving a burst of power to manage three-point landings, which had led to a false sense of security regarding the aircraft's stability at low speeds when fully configured.
Findings
- The left wing stall was the primary cause of the impact.
- The pilot failed to monitor airspeed during the final stages of the approach.
- The pilot used the flaps as airbrakes to reduce speed rather than as lift-augmentation devices.
- The fuel leak was caused by worn shaft seals in the priming pump.
- The aircraft sustained damage including a distorted left wing tip, a propeller strike, and a collapsed left landing gear.