Summary
On Easter Monday, 20 April 1981, at 1435 hours local time, a student pilot took off from Buttwil aerodrome in the Rhönlerche II glider HB-699, towed by a Varga 2150 A (HB-DCR). Approximately 1.5 km north of the field, the tow pilot released the tow cable due to repeated slight engine RPM drops. Both aircraft turned back. As the glider approached runway 16 threshold at about 60 m above ground, it turned left, pitched up, and stalled. The pilot recovered briefly but then pitched up again at low altitude, entering a maneuver similar to a reversal and crashed at 1442 hours. The pilot died that day from severe injuries. The glider was destroyed.
Flight History
The student pilot had started glider training on 7 September 1980. On 19 April 1981, he completed a check flight with an instructor who deemed him ready for the practical exam scheduled for 20 April. At 1341 hours, he flew a 13-minute practice flight, but the glide approach was too steep and the landing too long. At 1435 hours, he departed for another training flight to improve glide approaches. The tow was normal until the tow pilot experienced two brief RPM drops of 200–300 rpm each. After a third drop, he decided to release the cable at approximately 250 m above the field, about 1.5 km north of runway 16. He radioed the glider but received no confirmation. The tow pilot turned left 180° towards the field and saw the glider still attached to the cable, flying higher. Shortly after, the glider released the cable and approached runway 16 in a normal glide.
A pilot in another aircraft radioed that a glider was approaching from the opposite direction. Just before the runway threshold, at about 60 m above ground, HB-699 turned sharply left (east) into the Reuss valley. The pilot pulled up until the glider pitched nose-down and stalled. Just above the ground, the pilot recovered, but the glider then disappeared momentarily behind trees. When it reappeared, it executed a reversal-like maneuver and crashed from 30–40 m above ground at 1442 hours. The supervising glider instructor saw the aircraft only in the final phase and could not provide radio instructions.
The tow pilot made an approach to runway 34 but landed long and had to go around; a second attempt was successful. No further engine issues occurred after cable release. The accident site was about 400 m northeast of Buttwil airport (C-office) on the eastern slope of Lindenberg (coordinates 665'500/235'550, elevation approx. 680 m).
Personnel
The student pilot, a Swiss citizen born 1961, held a private pilot license (issued 22 August 1980, valid until 27 April 1981) with limited radiotelephony endorsement. He started glider training on 7 September 1980 and had 8 hours 47 minutes total glider time, including 5 hours 33 minutes solo. He also had 50 hours 24 minutes on powered aircraft. His last medical examination (27 April 1979) found him fit without restrictions.
The tow pilot, a Swiss citizen born 1952, held a private pilot license (issued 17 September 1980) and a glider pilot license (issued 28 June 1979). He had passed the towing check one day before the accident; this was his second tow flight after passing. He had 53 hours (205 landings) on powered aircraft and 49 hours 30 minutes (106 landings) on gliders. His last medical (5 June 1980) found him fit.
The glider instructor, a German citizen born 1939, had extensive experience: 662 hours 44 minutes (1588 landings) on gliders and 133 hours 9 minutes (608 landings) on powered aircraft. He held instructor and private pilot licenses.
Aircraft
HB-699 was a Rhönlerche II, a strutted shoulder-wing two-seat trainer in mixed construction, built by A. Schleicher in 1961 (serial number 1047). Owned by Segelfluggruppe Skylark, it had a valid airworthiness certificate and was last inspected on 6 July 1979. Total time was about 1400 hours with 5700 landings. Maximum weight 400 kg; accident weight approx. 350 kg. CG was at 0.534 m behind datum (allowable range 0.365–0.540 m). The tow aircraft HB-DCR was a Varga 2150 A, a two-seat low-wing all-metal design with fixed landing gear, built in 1980.
Cause
The official cause was flying below minimum flight speed at low altitude above ground. Contributing factors were: low experience of the glider student, rearward center of gravity, unexpected cable release by the tow pilot, and low towing experience of the tow pilot.