Synopsis
During a touch-and-go at Hawarden Airfield, a DHC-1 Chipmunk 22 experienced an unstable oscillation after touchdown, causing it to deviate left and right of the runway centerline. The pilot in command (PIC) took control but was unable to prevent the aircraft from leaving the paved surface onto adjacent grass, where it struck a taxiway marker board. Neither pilot was injured, and both exited the aircraft without assistance.
History of the Flight
The aircraft, registered G-BCOO, was being flown from Sleap Airfield to Hawarden Airfield with the intention of conducting circuits upon arrival. Two pilots were on board, both co-owners. Pilot A, who had extensive tailwheel experience and was the PIC, occupied the rear seat. Pilot B, in the front seat, held a Commercial Pilot's Licence but lacked tailwheel experience and had not completed differences training for the DHC-1 Chipmunk.
Upon arrival, Runway 22 was in use with a surface wind of 10 kt from 330°, variable between 290° and 350°, resulting in tailwind and crosswind components. Pilot A later noted concern that the wind might not be suitable, but considered the crosswind within the aircraft's 10 kt limit and the runway long enough for the tailwind component. It was agreed that Pilot B would perform a touch-and-go, with Pilot A following through on the controls.
After a successful first approach and touch-and-go, the aircraft departed into a left-hand circuit. Pilot B began an approach for a second touch-and-go; ATC reported wind as 9 kt from 340°. Following touchdown, a progressively unstable oscillation developed, causing the aircraft to deviate either side of the runway centerline. Pilot A took control, applying full left rudder and brakes with no response. He then advanced the throttle to approximately 1,500 rpm intending to go-around, but again the aircraft did not respond. Deciding no further corrective action could be taken within the remaining paved area, he closed the throttle and allowed the aircraft to depart the runway onto grass. The aircraft remained upright and came to rest about 30 m from the runway. No injuries occurred, but it later became apparent the aircraft had struck a taxiway marker board, damaging the left trailing edge flap, left elevator, lower left wing surface, and one propeller blade. The Airport Fire Service attended, though the aircraft was taxied to the ramp under its own power and both pilots vacated without assistance.
Discussion
Pilot A was aware of the Hawarden Airfield AIP entry warning of turbulence from factory buildings with wind speeds exceeding 15 kt. He speculated that local wind strength where the oscillation developed might have been stronger than reported by ATC. He also noted that he had considered requesting a runway change upon arrival but decided against it due to potential delays, though in retrospect he believed a change might have been prudent. Additionally, he considered that allowing Pilot B to handle the aircraft near its crosswind limit may have been ill-advised, but he had been impressed by Pilot B's handling during the first approach and touchdown. Pilot A's previous experience on another DHC-1 Chipmunk with more powerful brakes led him to consider that he might have applied insufficient braking.