What happened
On 23 August 2003, a Piper PA-28-181 Cherokee Archer II, registration G-BXWO, was preparing for a flight from Redhill Airfield, Surrey, to Deauville, France. The aircraft was part of a larger group of ten aircraft traveling to Biarritz. At the time of departure, the aircraft was loaded with four occupants and was within its maximum takeoff weight, though its centre of gravity was positioned very close to the aft limit.
During the takeoff roll on Runway 26 L, the aircraft exhibited slow acceleration. An air traffic controller observed that the aircraft was maintaining an unusually nose-high attitude, with the nose oleable almost fully extended. As the aircraft reached an altitude of approximately 50 feet, the crew experienced an uncommanded drop in engine RPM. This was immediately followed by the activation of the stall warning and a wing drop.
Recognising the inability to clear obstacles, the pilot in the right seat took control, reduced throttle, and lowered the nose to perform an emergency landing straight ahead. The aircraft struck the ground heavily on the right main landing gear, causing the gear to collapse and detach. There were no injuries to the four occupants.
The investigation
The investigation focused on the cause of the engine power loss and the aircraft's handling characteristics during takeoff. An examination of the engine by an engineering firm found no mechanical faults capable of explaining the power reduction. However, investigators discovered that the engine primer pump was in the unlocked position. Subsequent full-power engine tests demonstrated that when the primer pump is left unlocked, the maximum attainable RPM decreases by 100 RPM. Although the crew stated the primer had not been used for the start, the unlocked state was identified as a factor in the engine's performance.