Summary
On 10 April 1971 at approximately 1645 local time, the glider HB-796, a Ka-6 CR "Rhönsegler", crashed during an off-field landing near Köniz, Switzerland. The pilot sustained a minor head injury, and the aircraft was heavily damaged.
Investigation
The accident was reported to the Bureau of Aircraft Accident Investigation by telephone about half an hour after the occurrence. The investigation began at 1745 local time on the same day at the accident site.
Elements
Pilot
- Born 1942.
- Held a glider pilot license issued 14 September 1964, valid until 3 June 1972, with endorsements for tow flight, passenger flight, and instrument flight.
- Total flight experience: 203 hours 25 minutes and 241 landings, of which 86 hours 39 minutes and 45 landings on the accident type.
- In the last three months: 2 hours 29 minutes and 4 landings, flown on Ka-8 and Blanik.
- No previous off-field landings or special incidents.
Aircraft
- Owner and operator: Segelfluggruppe Bern des AeCS, Bern.
- Type: Ka-6 CR "Rhönsegler", single-seat high-wing standard class, wood construction.
- Year of manufacture: 1962, serial number 6008.
- Certificate of airworthiness issued 17 March 1971, valid until 31 March 1975.
Terrain
- Accident location: Gurtentäli, between Gurten (856 m) and Ulmizberg (937 m), 4.5 km west of Bern Airport.
- Coordinates: 600.290/195.350, elevation 630 m, municipality of Köniz.
- Valley floor consists of fields and meadows with several high-voltage and telephone lines.
Weather
- Bisenlage (easterly wind conditions).
- Airport weather at 1650 local: wind 030°/10 kt, visibility 7 km, cloud cover 3/8 at 3000 ft, temperature +18°C, QNH 1014 mb.
Accident Sequence
At 1545 local time, the pilot departed Bern Airport on a one-hour training flight under aero-tow. After release over the northern spur of the Längenberg, southwest of the airport, he reached approximately 1700 m and then flew to the Schwarzwasserbrücke, about 9 km behind the ridge, arriving there at 1250 m. Attempting to return to the windward side of the Längenberg, the pilot lost so much altitude that he was forced to land in the narrow and obstacle-rich Gurtentäli. Following the valley, he first crossed a 16 kV power line at a sharp angle from left to right, then accelerated to fly over a 220/380 V telephone line crossing the approach path. When pulling up to clear this last obstacle, he realized his speed was insufficient and decided to fly under the line. To avoid a pole on the left, he initiated a abrupt right turn, causing the right wingtip to catch in the soft arable land. The glider, with the left wing rising, tore the two telephone wires (spanning about 5 m high) and struck the ground hard with its nose.
Damage
- Pilot: slight injury (head wound).
- Aircraft: heavy damage (right wing destroyed, nose pushed in, fuselage broken behind the trailing edge).
- Third-party: broken telephone line and minor field damage.
Further Findings
Examination of the wreckage revealed no evidence of pre-existing defects.
Discussion
The pilot held a valid license and the aircraft had a valid certificate of airworthiness. The off-field landing became necessary because the pilot ventured too far behind the ridge of the Längenberg under the prevailing weather conditions and encountered downdrafts. The landing failed because the pilot decided to abandon the flight objectively too late, leaving no time to select a suitable field and execute a tactically correct approach.
Conclusion
The accident resulted from the pilot, after a too-late landing decision, contacting the ground with a wing while attempting to avoid an obstacle in the final approach.