What happened
On July 5, 1964, at Birrfeld Airfield, a Piper Cub J3C, registration HB-ODD, was preparing for a commercial passenger flight. As the pilot applied full power for takeoff, a glider, a Rhönlerche II with registration HB-576, was simultaneously undergoing a winch-assisted training takeoff nearby.
During the climb, the glider pilot released the winch cable. Due to strong winds, the trailing cable drifted into the flight path of the ascending Piper Cub J3C. The cable became entangled in the aircraft's landing gear and draped across the cockpit. The winch operator immediately severed the cable to mitigate further danger. However, the momentum caused the trailing cable to drag the motor aircraft across the airfield, striking two parked aircraft—a Stinson 108-3 (HB-TRP) and a DH Chipmunk (HB-TUF)—and crossing a public road where a pedestrian sustained minor injuries.
The investigation
The investigation examined the timing of the two departures and the visibility of the aircraft to the respective pilots. It was noted that the motor aircraft pilot did not observe the glider at the waiting area before applying power, likely due to cockpit visibility limitations. The flight instructor, while observing the motor aircraft at a standstill, did not maintain continuous surveillance as the glider began its takeoff roll. The winch operator was also found to be relying on the instructor's signal, assuming the airfield environment was clear.
Findings
- The collision occurred because the two aircraft departed simultaneously without coordination.
- The motor aircraft pilot failed to verify the status of the glider waiting area before initiating takeoff.
- The flight instructor did not sufficiently monitor the motor aircraft's movement during the glider's launch.
- The absence of a centralized air traffic control service was the primary factor allowing these uncoordinated operations to occur.
Safety action
- The investigation concluded that establishing a centralized flight control system would have been appropriate and necessary given the level of activity at the airfield to prevent such occurrences.