What happened
On 7 May 2018, a DH87B Hornet Moth, registration G-ADLY, was preparing for a private flight from Earls Colne, Essex, to Goodwood, West Sussex. The weather conditions were calm with clear skies. Due to concerns regarding soft ground, the pilot elected to perform the takeoff using the 10-meter wide asphalt insert of Runway 24.
As the aircraft accelerated along the asphalt, the tail began to rise. In an attempt to maintain the aircraft's heading, the pilot applied right rudder and right differential brake. However, the right brake experienced a "snatching" sensation, which caused the aircraft to veer to the right and the nose to pitch downward. The pilot responded with full left rudder and aft stick to correct the deviation. This correction caused a significant swing to the left, moving the aircraft off the asphalt and onto the grass area south of the runway.
During the transition, the aircraft struck the Precision Approach Path Indicator (PAPI) structure. The pilot felt a slight bump before liftoff and managed to regain directional control approximately 10 meters into the grass, eventually reaching flying speed and climbing away. Upon landing at Goodwood, the pilot requested the fire service attend the aircraft as a precaution due to the braking issues experienced during the departure.
An inspection of G-ADLY revealed that a portion of the PAPI structure from Earls Colne was embedded in the right wing root. The right landing gear struts were damaged, and a small tear was found in the underside of the lower right wing fabric. There were no injuries to the pilot.
The investigation
The AAIB examined the mechanical operation of the aircraft's braking system and the pilot's decision-making process. The investigation established that the De Havilland Hornet Moth utilizes a hand lever for symmetric braking and rudder pedal deflection for differential braking.
Investigators looked into the pilot's experience and the choice of runway surface. While the pilot had significant experience with tailwheel aircraft, such as the Pitts Special, his experience on this specific type was limited to only 7 hours. The investigation also considered the impact of the narrow asphalt insert on the aircraft's maneuverability compared to the wider grass runway.