History of the Flight
The pilot flew the aircraft from its base at Sywell, Northampton to Wycombe Air Park with one passenger, intending to pick up three more passengers and fly to the Isle of Man. After arrival, the pilot consulted with the pilot of another IOM-bound aircraft. The accident aircraft was refuelled to 60 USG. The pilot met three passengers by the aircraft and loaded their overnight bags with his own in the rear baggage compartment. The passengers boarded; one sat in the front right seat, one in a mid-row rear-facing seat, and two in the rear seats. The pilot started the aircraft and taxied to Runway 06 for takeoff, following the other aircraft, which took off without incident. The accident aircraft lined up at the start of Runway 06 and commenced takeoff at 1243 hrs. The pilot used Flap 2, consistent with the short-field takeoff technique. Acceleration and engine indications appeared normal.
Witness Information
The front right seat passenger recalled the takeoff seemed normal until rotation, when the aircraft "did not feel right" and was not climbing. She saw the airspeed drop from 67 to 60 KIAS. Two rear passengers heard a loud "buzzer" (later identified as the stall warning horn) sounding until impact. One rear passenger noted a steep "tail down" attitude and deceleration after takeoff. Two independent pilots witnessed the crash: both recalled a high nose-up attitude immediately after takeoff (approximately 30° nose-up). One saw the aircraft "wallowing" in roll. Both reported it reached a maximum height of about 4 m before sinking back to the ground in a nose-up attitude and striking the hedge.
Meteorological and Aerodrome Information
The ATCO recorded surface wind from 030° at 10 kt, few clouds at 3500 ft, temperature 22°C, and QNH 1031 mb. The ATCO passed a surface wind of 040° at 14 kt when clearing the aircraft for takeoff. Wycombe Air Park Runway 06 hard has a declared takeoff run available (TORA) and takeoff distance available (TODA) of 735 m. The boundary hedge, approximately 15 ft high, was 789 m from the start of the takeoff run.
Wreckage and Impact Information
The aircraft passed through the northern boundary hedge near its eastern end, coming to rest inverted in a cultivated field with the fuselage oriented about 90° to the direction of travel. The left wing separated at the root attachment and remained in the hedge. The right wing/fuselage joint sustained substantial disruption, but the wing remained attached. The left flap came to rest between the left wing and the remainder of the wreckage. The fuselage, vertical stabilizer, and engine mounting sustained relatively light distortion. The engine cowlings had minimal damage. Markings on the perimeter track and a fragment of the ventral fin confirmed the aircraft was in a tail-down attitude as it approached the hedge. The propeller showed repeated blade strikes, gross distortion, leading edge impacts, and surface scoring. Cut foliage was found on top of the engine and between cylinders, indicating high power at impact. No evidence of mechanical failure was found; all valves and the inertia magneto operated correctly. The flap operating lever was found in the Flap 2 position.
Weight and Balance and Performance
The pilot calculated a takeoff weight of 3,526 lb and CG of 95.75 inches using assumed weights. Analysis using actual weights gave a takeoff weight of 3,786 lb and CG of 99.34 inches aft of datum, exceeding the weight limit by 186 lb and the aft CG limit by 3.34 inches. The unfactored takeoff distance required at actual weight with Flap 2 was 731 m, only 4 m less than the declared TODA. The CAA recommends increasing unfactored takeoff distance by 33%, which would require 871 m, 136 m longer than available. The aircraft's CG position would have significantly reduced longitudinal manoeuvre stability, making the aircraft unusually sensitive and light in pitch control. The Pilots' Operating Handbook states that if CG is too far aft, the airplane may rotate prematurely or tend to pitch up during climb, and longitudinal stability will be reduced.
Conclusion
The pilot attempted to take off with the aircraft's weight and center of gravity outside the flight envelope and a marginal runway length. These factors probably combined to cause the pilot to over-control the aircraft in pitch, resulting in the aircraft failing to gain height after takeoff and striking the hedge.