What happened
On 13 March 2005, a modified Jodel DR1051, registration G-AYGD, was performing a private flight from Cardiff International Airport. After receiving clearance for an immediate takeoff from Runway 30, the pilot began the takeoff roll from an intersection while a passenger jet was lining up on the full length of the runway.
During the takeoff, the pilot intentionally delayed raising the tail wheel due to the existing crosswind. However, as the tail wheel was lifted, the aircraft experienced a significant leftward yaw. Despite the application of full right rudder and differential braking, the pilot could not maintain directional control. The pilot subsequently reduced power to idle to manage the aircraft's excursion onto the grass area adjacent to the runway. As the aircraft encountered a shallow ditch at the edge of the runway, the undercarriage collapsed. There were no injuries to the pilot or the two passengers on board.
The investigation
The investigation examined the aerodynamic forces acting on the aircraft during the transition from a three-point stance to a level attitude. It was established that the sudden yaw occurred precisely as the tail wheel was raised. The investigation identified several contributing aerodynamic factors that led to the loss of control, including the effects of propeller wash, the reduction in directional stability inherent when the tail wheel is raised, asymmetric blade effect, torque reaction, and gyroscopic forces resulting from the aircraft's forward pitch.