What happened
On 18 August 2002, during a De Havilland Moth Club rally weekend at Woburn Abbey, a DH60G Gipsy Moth, registration G-AALY, was attempting a departure from a temporary grass runway. The flight was intended to be a formation takeoff alongside a Tiger Moth to a local airstrip for an overnight stay.
As the aircraft accelerated down Runway 19, it encountered a mound located approximately halfway along the 550-metre strip. This caused the aircraft to bounce, resulting in a high angle of attack. The aircraft briefly became airborne before descending back onto the runway. Seeking smoother ground to assist acceleration, the pilot steered toward the right side of the strip. However, the aircraft had already travelled too far to safely abort the takeoff.
In an attempt to clear a nearby lake, the pilot maintained full power, hoping to utilize ground effect. As the aircraft crossed the lake, it became apparent that the aircraft would not clear a four-foot bank on the opposite side. The aircraft subsequently stalled due to the high angle of attack. The right lower wing made contact with the water, causing the aircraft to rotate 180 degrees before coming to rest nose-down in approximately three feet of water. There were no injuries to the pilot or the passenger.
The investigation
The investigation examined the aircraft's configuration and the pilot's decision-making process. The aircraft was operating at a takeoff weight of 748 kg, which was below its maximum allowable weight of 839 kg, and the center of gravity was within limits.
Investigators looked into the impact of the runway surface and the pilot's actions following the initial bounce. The pilot noted that the aircraft was equipped with a cruise pitch propeller and a more powerful engine than standard, which had influenced his expectations regarding acceleration. The pilot also identified several contributing factors, including dehydration, hurried pre-departure preparations, and a desire to maintain formation with the lead aircraft.
Findings
- The unexpected bounce caused by a mound on the runway was the primary catalyst for the sequence of events.
- The pilot's reluctance to push the control stick forward after the bounce, potentially due to fear of a secondary bounce, contributed to the high angle of attack.
- Environmental and physiological factors, such as high temperatures affecting performance and pilot dehydration, influenced the outcome.
- The pilot's decision to continue the takeoff despite insufficient remaining runway distance led to the excursion into the lake.