Summary
On Friday, 13 August 1965, at 1321 MEZ, a glider pilot departed from Saanen-Gstaad airfield in a Ka-8 glider, registration HB-705, for a ridge soaring flight along the slopes of the Hornberg. After approximately 40 minutes of normal flight on the west slope, the pilot turned towards the south slope. Suddenly, the aircraft banked left and crashed into an isolated group of fir trees. The pilot sustained a minor abrasion to one leg. The glider was largely destroyed (80% damage). Three fir tree tops were shortened by about 120 cm.
Investigation
The preliminary investigation was completed on 24 September 1965, with the report submitted to the commission president on 21 September. The commission reviewed the evidence and issued a final report on 22 October 1965.
Pilot Information
The pilot, born in 1936, held a glider pilot license issued on 29 August 1963, valid until 21 October 1966. He also held private and commercial pilot licenses (motorized) obtained on 7 August 1962 and 13 November 1963, respectively. His glider training began in May 1963 at Spreitenbach. Total glider experience amounted to 6 hours and 55 minutes across 36 flights, of which 1 hour and 44 minutes (6 flights) were on the accident type. All but one flight were conducted at Spreitenbach. His total motorized flight experience was approximately 1200 hours. No evidence of any health impairment at the time of the accident was found.
Aircraft Information
The glider was a Ka-8, a single-seat high-wing aircraft of mixed construction, designed by Poppenhausen and manufactured by A. Schleicher, both in West Germany. It was owned and operated by the Segelfluggruppe Zürich of the Aero-Club der Schweiz, section Zürich. The airworthiness certificate was issued on 23 November 1963, valid until 21 November 1965. Maximum permissible takeoff weight was 310 kg; the actual weight on the accident flight was about 280 kg. The stall speed was 50 km/h, with a lower red line on the airspeed indicator at 55 km/h. The stall characteristics were described as docile. A barograph was carried on board. No technical defects were identified.
Terrain and Weather
The accident occurred on the gently rising terrain of the Gfellalp area on the south slope of the Hornberg, approximately 2.5 km northeast of Gstaad, near the third-class road from Hornkessel to Gfellalp. Coordinates: 590.250/148.230, elevation 1760 m above sea level. Weather at the time was fine with 2/8 cumulus clouds at about 2800 m, visibility over 50 km. Wind at 2000 m was 10–15 knots from the west, with slight gustiness. Good thermal conditions with updrafts up to 3 m/s were reported.
Flight Sequence
The pilot arrived in Saanen on 12 August 1965 to participate in a gliding camp organized by the Segelfluggruppe Zürich. On the morning of 13 August, after a 19-minute dual instruction flight, he launched at 1321 MEZ via aerotow for his first solo ridge flight at the Hornberg. After soaring on the west slope for about 40 minutes, he intended to fly around the south peak and over the Gfellalp area towards the east slope. During this maneuver, the aircraft abruptly banked left and descended into an isolated group of fir trees.
Barograph Data
After the initial climb, the barograph trace showed approximately 12 minutes of mostly level flight, followed by 8 minutes of altitude loss of 70 meters. In the final minute before the impact, the sink rate was about 0.5 m/s.
Discussion
Analysis of the flight path and barograph data, together with the local conditions, indicated that the pilot left the main area of lift while crossing the Gfellalp. It is considered probable that in attempting to maintain altitude, he approached the stall speed and then encountered a gust, resulting in a loss of speed. The pilot's lack of experience in gliding, particularly in mountain terrain, contributed to his unexpected encounter with this situation. Additionally, insufficient familiarity with the flight characteristics of the specific glider may have been a factor.
Conclusion
The investigation commission unanimously concluded: The accident is highly likely due to the glider pilot, still inexperienced in soaring flight, flying too slowly in mountainous terrain and thereby losing speed due to gust effects.