What happened
On 31 May 2014, a DHC-1 Chipmunk with registration G-BCOO was performing a series of circuits at Hawarden Airfield. The flight, which originated from Sleap Airfield, carried two pilots. During the second touch-and-go attempt, the aircraft experienced a progressive and unstable lateral oscillation immediately after touchdown, causing it to swing across the runway centerline.
As the oscillation developed, the pilot in the rear seat took control from the handling pilot. In an attempt to stabilize the aircraft and initiate a go-around, the pilot applied full left rudder and brakes, and increased the throttle to approximately 1,500 rpm. However, the aircraft failed to respond to these inputs. Realizing the aircraft was leaving the paved surface, the pilot closed the throttle, allowing the aircraft to exit the runway onto the adjacent grass. The aircraft subsequently struck a taxiway marker board. There were no injuries to the crew.
The investigation
The investigation examined the environmental conditions and the decision-making process regarding the wind. At the time of the incident, the wind was reported by ATC as 9 kt from 340º, which included both a tailwind and a crosswind component. The pilot in command had previously noted that the wind might be unsuitable for the aircraft but decided not to request a runway change to avoid delays.
Investigators also looked into the handling of the aircraft. While the first touch-and-go had been successful, the second attempt coincided with the onset of the instability. The pilot in command noted that his experience with the DHC-1 Chipmunk had primarily been on a different aircraft equipped with more powerful and responsive braking systems, suggesting that the braking applied during the incident may have been insufficient to counteract the oscillation.