What happened
On 3 September 2000, a Grumman AA-5, registration G-BASG, was preparing for a private flight from a 480-metre grass airstrip on the Isle of Bute. The pilot, accompanied by one child passenger, had calculated the aircraft weight at 1,730 lb and intended to use 10° flaps for the departure.
Following standard power checks, the aircraft commenced its takeoff roll on Runway 27. While the initial acceleration appeared normal, witnesses noted that the engine began running roughly and misfiring after the aircraft had travelled approximately 50 to 60 metres. This engine instability intensified as the aircraft continued to gain speed.
As the aircraft reached roughly three-quarters of the runway length, the pilot closed the throttle and applied the brakes. Due to the insufficient speed gained during the roll, the aircraft failed to stop within the runway limits. At the end of the strip, a small undulation in the grass caused the aircraft to bounce. The aircraft then overran the runway, struck a fence, and slewed left for about 30 metres before coming to rest in a deep ditch. The aircraft was destroyed, though there were no injuries to the pilot or passenger.
The investigation
The investigation was based on the accident report submitted by the pilot. Investigators examined the takeoff performance and the mechanical state of the engine. It was noted that the runway featured a 1% downhill slope. Witnesses observed that the aircraft's speed at the moment the pilot decided to abort the takeoff was lower than what is typically observed during departures from this strip. The pilot concluded that the primary reason for the overrun was the loss of engine power, which had hindered the aircraft's ability to reach necessary takeoff speeds.