What happened
On 29 June 2009, a Piper PA-28-236 Dakota, registration G-FRGN, was returning to a private airstrip at North Moreton, Oxfordshire, following a flight from Oxford Airport. The weather conditions were generally good with light easterly winds, though recent heavy rain showers had left the 800 m grass runway with patches of standing water.
During the approach to Runway 35, the pilot noted a crosswind from the right. The aircraft touched down approximately 200 m into the runway. About 100 m after touchdown, the pilot applied the brakes, but the aircraft failed to decelerate. Believing the braking system had failed, the pilot attempted to steer the aircraft to the left. However, due to a lack of directional control, the aircraft overran the end of the runway and struck a hedge. The impact caused damage to the port wing, propeller, engine mountings, and caused the nose landing gear to shear off. The pilot was uninjured and exited the aircraft via the standard exit.
The investigation
The investigation established that the pilot was unaware of the recent heavy rain shower and the resulting slippery condition of the grass surface prior to landing. The investigation noted that while the typical landing distance for this aircraft on this runway is approximately 350 m with moderate braking, the presence of water significantly altered the aircraft's performance.
Findings
- The aircraft skidded on the wet grass surface upon touchdown.
- The pilot had not realized the runway was wet, which would have prompted an earlier touchdown and more immediate braking.
- The primary cause was the loss of braking effectiveness and directional control due to the wet, slippery grass surface.
- Guidance from the CAA suggests that landing distances on wet grass can increase by as much as 60%, a factor that contributed to the overrun.