What happened
On 23 November 1997, a Piper PA-28-161, registration G-BJBY, was engaged in a private flight from Old Sarum Airfield in Wiltshire. The flight was intended to be a short local excursion lasting approximately one hour. Before departure, the pilot performed performance calculations for a takeoff from the wet grass runway, assuming a flap setting of 25 degrees. These calculations suggested that sufficient runway length was available for the aircraft, which was carrying two passengers and 20 US gallons of fuel.
During the takeoff roll on Runway 06, the pilot observed that acceleration was slower than usual, though this was expected due to the soft ground conditions. As the aircraft reached 52 knots, the pilot initiated rotation. The aircraft struggled to lift off and maintained a very low rate of climb. Fearing there was insufficient distance to perform a safe abort, the pilot continued the takeoff attempt. Consequently, the aircraft struck a fence and the top of a mound at the end of the runway before coming to a sudden stop on nearby waste ground. The occupants, including the pilot and two passengers, sustained minor injuries.
The investigation
Investigators examined the wreckage and the flight parameters to determine why the aircraft failed to clear the obstacles. While the pilot's initial calculations were based on a 25-degree flap setting, physical evidence from the aircraft's flap quadrant revealed that the flaps were actually set to 40 degrees. The detente in the quadrant showed clear distortion consistent with this higher setting. This incorrect configuration significantly increased drag and contributed to the poor acceleration and climb performance observed during the takeoff run.
Findings
- The aircraft struck a fence and a mound at the end of the runway.
- The incorrect flap setting of 40 degrees was the primary factor in the degraded takeoff performance.