What happened
On 3 June 2011, a Piper PA-32RT-300 Cherokee Lance II, registration G-RHHT, was attempting a takeoff from Runway 06 hard at Wycombe Air Park. The aircraft was operating a private flight, carrying a pilot and four passengers, intended for the Isle of Man.
During the takeoff roll, the pilot rotated the aircraft at 65 KIAS using flap 2. As the aircraft became airborne, the pilot experienced a buffet and a sensation of "wallowing" in roll. The stall warning horn sounded, and the airspeed dropped from 67 to 60 KIAS. The aircraft adopted an extreme nose-up attitude, reaching a maximum height of approximately 4 metres before sinking back toward the ground. The aircraft subsequently struck a 15-foot-high hedge at the airfield boundary, causing the aircraft to come to rest inverted in a field. The pilot and passengers sustained minor injuries.
The investigation
The AAIB investigation examined the wreckage and the aircraft's performance capabilities. Physical evidence, including the state of the propeller and engine cowlings, confirmed the engine was producing high power at the time of impact. The investigation also analyzed the aircraft's weight and balance.
While the pilot had calculated the takeoff weight and centre of gravity (CG) to be within safe limits, the actual weights of the occupants and baggage placed the aircraft 186 lb over the maximum weight limit. Furthermore, the actual CG was 99.34 inches aft of the datum, which was 3.34 inches beyond the permitted aft limit. The investigation also reviewed the available runway length, noting that the declared takeoff distance available (TODA) was 735 m, while the unfactified takeoff distance required for the actual weight was 731 m.
Findings
- The aircraft was operating with a takeoff weight exceeding the maximum limit and a centre of gravity significantly behind the aft limit.
- The aft CG position reduced the longitudinal manoeuvre stability, making the aircraft unusually sensitive to pitch inputs.
- The proximity of the perimeter road at the end of the runway likely caused the pilot to subconsciously over-control the aircraft in pitch.
- The resulting high angle of attack and the drag produced by the ventral fin caused the aircraft to decelerate, making recovery impossible within the remaining runway length.