What happened
On 28 November 2010, a Gippsland GA8 Airvan, registration G-CDYA, was performing aerial work near Redland Airfield in Wiltshire. The aircraft was carrying eight passengers, including instructors and students, for a parachute jump operation.
Prior to departure, the aircraft had been parked outside overnight in freezing temperatures. Although the pilot had cleared the windscreen of frost, a layer of frost remained on the upper surface of the wings. During the takeoff roll on the grass runway, the pilot delayed rotation until 65 kt and subsequently selected full flaps.
As the aircraft crossed a hedge at the end of the runway, the pilot initiated a left turn for noise abatement. During this maneuver, the aircraft began to descend. The aircraft struck the ground with a left wing-low attitude, causing the landing gear to detach and the aircraft to skid through a ditch and into a field. The pilot sustained serious injuries, while the passengers escaped through the cockpit door after the sliding cabin door became jammed due to impact damage.
The investigation
Investigators examined the wreckage and analyzed GPS and video data from the flight. The investigation established that the aircraft's takeoff distance was significantly longer than calculated, likely due to a combination of reduced engine power and the effects of wing contamination.
Technical examination of the engine revealed it was producing approximately 50 bhp less than its rated value, though this was attributed to normal wear for an engine at 75% of its overhaul life. The investigation also found that the aircraft's stall warning system was functional, but the stall likely occurred at an angle of attack too low to trigger the warning horn.
Findings
- The aircraft stalled during a left turn due to frost on the wing upper surface, which reduced lift and increased the stalling speed.
- The stalling speed was likely higher than the expected 63 kt due to the presence of frost and the use of takeoff flaps.
- The takeoff performance was further compromised by the engine producing less power than specified.
- The aircraft rotated at a speed higher than the standard rotation speed (VR).