Introduction
On 27 July 1967, a Rhönlerche II glider registered as HB-721 was involved in an accident at Grenchen Airport. The aircraft, owned by the Segelfluggruppe Grenchen, sustained 40% damage, and the pilot suffered a minor injury to the right ankle. No ground damage occurred.
Aircraft and Pilot
The glider was a twin-seat, strut-braced high-wing design powered by lift. Its empty weight was 223 kg, with a maximum load of 177 kg and a maximum takeoff weight of 406 kg. The student pilot, born in 1948, held a learner's permit for motor and glider flight issued on 27 October 1965. At the time of the accident, he was participating in a glider course (S-20, Level II) in Grenchen. His total flight experience was 7 hours 7 minutes over 61 flights, including 64 minutes solo. His flight instructor, born in 1924, held a glider pilot license and a provisional glider instructor permit.
Sequence of Events
The flight instructor assessed favorable thermal conditions near the Jura slope based on a barogram taken by another student at 1350 local time and decided to send the student pilot on a local glider flight. The tow pilot launched with the student at 1459 local time and released 4 km north of the airport over a forest edge near Bettlach at approximately 600 m above ground level after a 6-minute tow. Although the tow pilot circled within a thermal zone, the student experienced immediate strong sink after release. He initially flew toward Solothurn but then turned right toward the airport, flying over the airport buildings at about 120 m AGL.
Intending to land on Runway 07, which was active due to the bise wind, the student abandoned the approach after sighting a Piper landing on the same runway. He turned left and then right, deciding to land with a tailwind on the glider runway. However, upon noticing a tow train ready for takeoff, he changed his plan again and flew along the southern boundary of the airport, then turned right to land crosswind to the runway in a northerly direction. During the turn, at approximately 6-7 m AGL, the glider stalled over the right wing and struck the ground at 1510 local time.
Damage and Injuries
The pilot sustained a minor injury to the right ankle. The glider was 40% damaged, and no ground damage was recorded.
Probable Cause
The accident is attributed to the still-inexperienced student pilot, who, after inappropriate approach maneuvers over the airport, initiated a turn at too low speed and low altitude, resulting in a stall and subsequent loss of control.