What happened
On 13 May 2017, a DH82A Tiger Moth, registration G-ANNG, was taxiing at Old Sarum Airfield in Wiltshire. The aircraft was positioned on the northern side of Runway 06/24. With the wind blowing from 210º at 16 knots, the pilot began a left turn from the parking area toward the active runway.
As the pilot initiated the engine start, the aircraft began moving across the dry, firm grass. Due to the surface conditions, a significant amount of power was needed to get the aircraft rolling, which resulted in excess speed as the turn commenced. The pilot attempted to correct the course using full right rudder and a burst of power to prevent a collision with other parked aircraft. However, because the aircraft featured a tailskid and lacked braking capabilities, the maneuver failed to arrest the turn. The G-ANert subsequently rolled into a stationary Avions Pierre Robin CEA DR300/180R, registration G-BVYM.
At the time of the impact, the occupants of the Robin aircraft were performing pre-start checks, and its engine was not running. There were no injuries to the crew of either aircraft, and both pilots were able to exit their cockpits without assistance.
The investigation
The AAIB examined the circumstances of the ground collision, focusing on the taxiing dynamics of the Tiger Moth. The investigation established that the aircraft was operating on a firm, dry grass surface. The investigators reviewed the pilot's actions, specifically the use of rudder and power to steer the aircraft during the turn.
Findings
- The collision occurred because the pilot was unable to steer the aircraft sufficiently to avoid the parked Robin DR300/180R.
- The lack of braking or steering capability on the Tiger Moth, combined with the firm grass surface, prevented the pilot from correcting the turn.
- The pilot's application of full nose-right rudder actually had the opposite effect of what was intended during the turn.
- The aircraft was taxiing with a quartering tailwind, which contributed to the difficulty in controlling the direction of travel.