Background
On 24 May 1969 at 16:03, a training flight departed from Winterthur airfield in the Rhönlerche II glider, registration HB-708. The aircraft was owned by Segelfluggruppe Winterthur. The flight instructor, born in 1932, held a valid glider pilot license since 1953 and a glider instructor endorsement since 1956. He had accumulated 343 hours and 43 minutes of flight time and 1429 landings. The student pilot, born in 1937, held a learner's permit issued on 10 April 1968 and had begun training on 22 March 1969, logging 3 hours and 2 minutes over 48 flights—all dual instruction in the Rhönlerche type.
Sequence of Events
The glider was towed into the air by an aircraft, releasing at approximately 500 meters above ground near Wiesendangen, about 1 km northeast of the airfield. The instructor attempted to use weak thermal lift but was unsuccessful. At about 300 meters above ground, he instructed the student to return to the field. The student flew a circuit pattern, reaching about 120 meters above ground on the downwind leg. During the final turn onto the base leg, the student executed a 90-degree right turn. At approximately 30 meters above ground, with a headwind estimated at 30 km/h, the instructor determined that the glider could not safely reach the airfield. He decided to perform an off-field landing on a meadow west of the airfield. After a steep right sideslip, the glider touched down normally. After rolling 2–3 meters, the left wing collided with a hay rake parked about 15 meters from the right edge of the meadow.
Damage
Neither the instructor nor the student sustained injuries. The glider was heavily damaged. The hay rake and the ground were undamaged.
Investigation Findings
The investigation determined that both pilots held valid licenses and the glider was properly certified. The accident sequence indicated that both the student and the instructor were surprised by the distance of about 400 meters to the airfield and the low altitude of 30 meters. With the headwind and a 4-meter-high gravel mound that had to be cleared on the approach path, a safe landing on the field appeared doubtful. The instructor had little choice and was fortunate to be over a reasonably suitable meadow. Both pilots likely noticed the obstacle. It is possible that the aircraft drifted left during the right sideslip due to wind, and the rear-seat occupant's view of the landing area was restricted. After leveling the glider just before touchdown, the pilot could no longer avoid the collision.
Probable Cause
The accident was attributed to the instructor's misjudgment of the landing approach, with insufficient attention given to obstacle clearance during the off-field landing.