What happened
On 20 November 2005, a Thruster T600N aircraft, registration G-CDBZ, was conducting a private flight from Sandown to a private grass airstrip at Little Atherfield Farm on the Isle of Wight. The pilot performed the approach at a speed of 55 kt, touching down roughly halfway down the runway, which was estimated to be between 500 and 600 metres in length.
At the time of the landing, the runway surface was wet and there was no wind. Despite the touchdown, the aircraft could not be brought to a halt within the airfield boundaries. The aircraft continued past the perimeter, driving through brambles before eventually coming to a stop in a ditch. While the pilot escaped without injury, the single passenger sustained a minor neck injury and was transported to a local hospital via ambulance as a precaution. The aircraft suffered a broken propeller and damage to the nose pod and upright spar.
The investigation
The investigation examined the landing performance requirements for the aircraft type. According to the manufacturer's manual, an approach speed of 45 kt is recommended for still or smooth conditions on a short, dry, level grass surface at ISA conditions, which should allow for a full stop within 279 m. The manual also specifies that the landing distance should be increased by 20% for wet grass, which would result in a required distance of approximately 335 m.
Investigators found that the pilot had previously used this airstrip and was familiar with the manual's quoted landing distances. However, the pilot's assessment of the required stopping distance was inaccurate for the specific conditions present during this flight.
Findings
- The pilot's reliance on a landing distance calculation that did not account for the reduced braking effectiveness of the wet grass led to an overrun.
- The aircraft touched down at 55 kt, which was higher than the recommended 45 kt for such conditions.
- The wet surface of the runway contributed to the inability to stop within the available runway length.