Summary
On Sunday, 5 July 1964, at 1701 MEZ, a Piper Cub J3C (registration HB-ODD) commenced a commercial passenger flight from Birrfeld Airport with one passenger on board. Simultaneously, a glider student on a Rhönlerche II (registration HB-576) began a training flight using a winch launch under the supervision of a glider instructor. During the initial climb, the powered aircraft collided with the winch cable that had been released by the glider student. The winch operator cut the cable, and the powered aircraft dragged the remaining cable along the ground. All pilots landed safely and were uninjured. A pedestrian sustained light injuries to the head and shoulders. The Piper Cub was substantially damaged, and two parked aircraft sustained minor damage.
Investigation
The investigation was conducted by the Swiss Aircraft Accident Investigation Commission. The pilot of the Piper Cub was born in 1942 and held a restricted commercial pilot license issued on 24 October 1963, valid until 27 September 1964. He began powered flight training in October 1962 and had approximately 265 hours and 1550 flights on powered aircraft, as well as 100 hours and 200 flights on gliders, mostly at Birrfeld. The glider instructor was born in 1929 and had been a glider instructor since 1961. The glider student was born in 1930. The winch operator was born in 1941 and was a German national. The chief flight instructor was born in 1935. The pedestrian was born in 1897.
Sequence of Events
At approximately 1700 MEZ, the pilot of the Piper Cub prepared for a commercial passenger flight. He paused briefly before entering the runway, observing no glider ready for launch. He then positioned his aircraft about 70 meters ahead and 40 meters to the right of the glider launch point. After waiting for sufficient separation from a towing aircraft, he applied full throttle at 1701 without rechecking the glider area. While the powered aircraft was still at the runway edge, the glider student on the Rhönlerche had become ready for launch. In the presence of the chief flight instructor, the glider instructor signaled the start to the winch operator. The instructor believed the powered aircraft pilot intended to wait at the runway edge. He did not monitor the powered aircraft further and noticed it only after it had lifted off and reached about 30 meters altitude. The winch operator had also seen the powered aircraft stopping at the runway edge and initiated the glider launch after the flagman repeated the start signal. When the glider reached about 170 meters altitude, the student released the cable. The relatively strong wind blew the cable, which was equipped with a braking parachute, to the right into the takeoff path of the powered aircraft, which had by then covered three-quarters of the runway and reached about 50 meters altitude. The cable caught the landing gear and came to rest diagonally over the cockpit. The winch operator immediately cut the cable. The aircraft dragged the remaining approximately 200 meters of cable over two parked aircraft (Stinson 108-3 HB-TRP and DH Chipmunk HB-TUF) and then over the road where the pedestrian was present. The pilot of the powered aircraft executed a turn and landed with a tailwind.
Damage
The pilots involved were uninjured. The pedestrian sustained light injuries to the head and shoulders, which did not result in incapacity for work. The Piper Cub HB-ODD was substantially damaged, with repair costs estimated at approximately 1000 Swiss francs (10% of its value). The two parked aircraft sustained minor damage to the left flap and rudder, respectively.
Cause
The accident is attributed to the absence of a central flight control.