What happened
On 10 July 2016, a Reims Cessna F1-82P Skylane, registration G-DATG, was conducting a private flight from Oxford Kidlington Airport to a private grass airstrip near Westcott, Buckinghamshire. The flight included the pilot and two passengers.
Upon arrival, the pilot encountered a blustery crosswind. To manage the wind, the pilot chose a flap setting of 20° instead of the standard 40°. This resulted in an unstable approach with fluctuating airspeeds. The aircraft touched down approximately 30 metres into the 540-metre strip. Despite applying heavy braking, the aircraft could not be stopped within the available distance. The aircraft overran the end of the grass strip, crossed a hedge and a small ditch, and came to rest on a minor road. The impact caused substantial damage to the engine, propeller, fuselage, wings, and landing gear, while the pilot and one passenger sustained minor injuries.
The investigation
The AAIB examined the pilot's pre-flight performance calculations, which were generated using a computer programme. The investigation found that the software used by the pilot's group had several critical flaws. Specifically, the programme applied a 15% increase for grass runways, which was lower than the 20% factor recommended by the aircraft manufacturer. Furthermore, the programme failed to account for runway slope and provided a ground roll figure that incorrectly assumed a dry, paved surface regardless of the actual runway type.
Investigators also reviewed the approach dynamics, noting that the pilot's decision to use a reduced flap setting and the lack of a stabilized approach contributed to a higher-than-ideal touchdown speed. The investigation also considered the possibility of a tailwind component and the impact of the crosswind on braking effectiveness.
Findings
- The pilot's landing performance calculations were inaccurate due to reliance on a flawed performance programme that underestimated the required distance for a grass surface and ignored runway slope.
- The approach was unstable, characterized by airspeed fluctuations and a non-standard flap configuration.
- The pilot prioritized managing the crosswind over maintaining the correct landing configuration and speed.
- A potential plan continuation bias may have influenced the decision to proceed with the landing despite the deteriorating approach conditions.