History of the Flight
On 30 October 2014, a Piper PA-28-140 Cherokee (registration G-COLH) was completing a private flight from Wellesbourne Mountford Airfield near Stratford-upon-Avon to Full Sutton Airfield near York. The pilot, aged 19 with 121 hours of flying experience (2 hours on type), assessed the surface wind as directly across the single grass runway (04/22) and elected to land on Runway 04. Visibility was good, but recent rain had left the grass surface soft and wet. The final approach was flown with full flap (40°) at approximately 75 kt. The aircraft mass was about 872 kg, roughly 10% below the maximum permitted.
Late on final, the pilot noticed a flock of birds on the runway. Expecting them to disperse, she continued the approach. As the aircraft descended through about 100–150 ft, the birds rose into its path. The aircraft struck at least two birds; one hit the left wing and another struck the propeller, leaving bird remains on the passenger-side windscreen. Concerned for the aircraft's condition, the pilot continued the approach. The aircraft touched down all three wheels together some distance along Runway 04, just beyond a hard taxiway crossing the grass runway. The pilot applied wheel brakes, but the aircraft skidded on the wet grass without decelerating. It overran the runway onto an adjacent field, encountered uneven ground, and overturned. The pilot and two passengers evacuated through the left cockpit window. One passenger sustained a hairline fracture of an arm.
Airfield Information
Full Sutton Airfield has a single grass runway designated 04/22. The published landing distance available on Runway 04 is 772 m. A hard taxiway (formerly a runway) crosses Runway 04 about 420 m from the start, leaving approximately 330 m of runway beyond the taxiway.
Performance Considerations
The manufacturer's Pilot's Operating Manual for the PA-28-140 provides landing performance data for a standard aircraft at maximum mass (975 kg) on a level paved runway in zero wind with 40° flaps, using an approach speed of 62 kt and touching down on the main wheels at 48–56 kt. The landing distance from 50 ft in these conditions is 330 m.
Guidance from the CAA (Safety Sense Leaflet 7c and AIC 127/2006) notes that manufacturer's figures are achieved by highly experienced pilots in ideal conditions with a new aircraft. Actual conditions require factoring; typical factors for this case include a 10% mass decrease (0.9 multiplier), wet grass (1.35 to 1.6 depending on grass length), tailwind (1.2 for a 10% tailwind component), soft ground (1.43), and an additional safety factor (1.43). Using the pilot's details and a tailwind up to 5 kt, the expected landing distance from 50 ft was between 600 m and 710 m before accounting for increased approach speed or a safety factor.
Discussion
The pilot, with limited experience, faced a critical situation just before landing and had to decide between continuing to land further along the runway or going around. Uncertainty over the aircraft's condition and the shock of the event influenced her decision to continue. The pilot did not intend to land long, but it was a consequence of that decision. The lack of braking action on wet grass combined with the reduced available runway beyond the taxiway led to the overrun.