Flight Sequence
On Saturday, 8 September 1973, a student pilot at Fricktal-Schupfart airfield conducted a thermal instruction flight with his instructor from 1355 to 1510 hours (MEZ). At 1644 hours, he started a solo circuit flight lasting 9 minutes, which was normal except for minor details. At 1758 hours, he began a second solo flight with the following task from his instructor: exam program, fly a figure-eight while being towed, after release perform three full circles to the right (maximum one minute), flown in the downwind area, normal landing pattern, approach with a sideslip to the right, and then a spot landing. The student flew four circles instead of three. The flight was largely normal until the final approach. At about 90 meters above ground in the final approach, the glider entered a dive and continued into an inverted attitude. After a subsequent climbing inverted attitude, it rolled to the right, collided with two trees, and struck the ground at 1808 hours about 300 meters east of runway 26.
Injuries and Damage
The pilot was seriously injured. The glider was destroyed. Minor third-party damage occurred.
Pilot Information
The pilot, born 1934, held a student pilot license valid for gliders. His total glider experience was 9 hours 34 minutes, of which 6 hours 43 minutes were on the accident type. Glider training began on 23 July 1973 in Schupfart. The last medical examination was on 8 June 1973, with a result of fit. No incidents were recorded in the Federal Air Office files. During the accident flight, he wore a light sleeveless vest and flew without head covering. Due to retrograde amnesia, he could not recall the accident sequence.
Aircraft Information
The glider, a Rhönlerche II registered HB-623, was airworthy and certified for operation. No pre-existing technical defects were found. The maximum permissible takeoff weight was 400 kg; the actual weight was 307 kg. The permissible center of gravity range was 365–540 mm; the actual CG was 440 mm. Weight and CG were within limits.
Witness Observations
According to several witnesses, the glider entered a dive at about 90 meters above ground in the final approach, then transitioned to inverted flight, then to a climbing inverted attitude, rolled to the right, and crashed.
Flight Test
A flight test with a Rhönlerche II showed that this glider can be put into a dive with a small hand force on the control stick. Although the test did not include pushing the glider from the dive into inverted flight, it is assumed that this is possible with relatively low control forces.
Weather Conditions
Wind: weak, predominantly from SW, 2–5 kt. Visibility: approximately 10 km. Cloud cover: 1/8–2/8 altocumulus and cirrus. Temperature: 23°C. Sun position: azimuth 271°, elevation 7°.
Assessment
The transition of the glider into a dive and subsequently into inverted or climbing inverted flight likely represented an unintentional maneuver. It is presumed that the pilot suffered a disturbance of consciousness from unknown reasons and subsequently lost control of the glider.
Probable Cause
Uncontrolled flight attitude in the landing final approach due to loss of consciousness of the pilot.