Introduction
On 30 July 1964 at 1648 MEZ, two gliders, a Rhönlerche II (registration HB-573) and a Mucha Standard SZD-22B (registration HB-659), collided in mid-air over the Oberwalder Blasen ridge near Oberwald in the canton of Valais, Switzerland. The collision occurred during a glider training camp organized by the Akademische Fluggruppe Zürich (AFG) in cooperation with the Sportfluggruppe Swissair (SFS).
Pilots
The pilot of HB-573, born in 1943, was a student glider pilot holding a learner's permit since 2 April 1964. He had accumulated 11 hours and 59 landings, including 21 solo flights on the accident type. He was described as reliable and disciplined, accustomed to good airspace observation. No health issues were found.
The pilot of HB-659, born in 1939, held a glider pilot license since 21 August 1962. His total glider experience was 93 hours and 47 minutes with 243 landings, of which 25 hours were on the accident type. He had 26 hours of powered flight. Instructors noted him as disciplined but with somewhat irregular performance, requiring more flights than average to reach training milestones. He was involved in a previous landing accident on 5 July 1964 when his aircraft overturned during rollout after an overly long landing. No health issues were found at the time of the accident.
Aircraft
HB-573 was a two-seat, strutted high-wing glider of mixed construction, built in 1955 by Schleicher in Poppenhausen, West Germany. Its permissible gross weight was 400 kg; at the time of accident it weighed approximately 300 kg. HB-659 was a single-seat, cantilever shoulder-wing glider of wooden construction, built in 1960 by ZSLS No. 5 Krosno in Poland. Its permissible gross weight was 350 kg; it weighed approximately 340 kg at the time. Both aircraft had valid airworthiness certificates.
Weather
The weather at the accident site was: 4/8 cumulus cloud cover with base at 3400 m above sea level; visibility 30 to 50 km; wind at 2000 m from 300° at 5–10 kt, at 3000 m from 320° at 10 kt; moderate thermic turbulence in places. The sun elevation was 32° at an azimuth of 263°.
Sequence of Events
The glider camp ran from 20 July to 8 August 1964 at Münster in the Upper Valais. The pilot of HB-573 made his first flight in the camp on 22 July, an alpine familiarization flight and a check flight dual with an instructor. Between 22 and 30 July, he flew eight solo flights, including circuits and short glides. On 30 July, his instructor authorized a flight limited to ¾ hour, with instructions to stay near Oberwalder Blasen and return to the launch site if altitude dropped below 800 m above the start (2100 m). He was towed to 2600 m and released at 1644.
The pilot of HB-659 began flying in the camp on 25 July. He completed a required circuit and a short glide, after which he was cleared for further flights. By 30 July, he had flown two one-hour glides and a 20-minute dual flight. On the afternoon of 30 July, he was launched six minutes before HB-573 and released at 2100 m over the Blasen at 1634. The tow pilot of HB-573 saw HB-659 about 200–300 m above him during the tow, flying along the Blasenalp down-valley, then lost sight.
Three non-aviator witnesses on the ground in Oberwald, about 2 km from the collision, provided varying accounts. One saw both gliders circling in opposite directions, sinking at different rates and approaching each other. The other two saw a yellow glider (HB-573) flying straight up-valley while a red glider (HB-659) turned across its path. The first witness identified the faster-descending aircraft as red but later considered possible color confusion due to sunlight.
At collision, the left wings of both aircraft made frontal contact. HB-573 lost the outer half of its left wing and immediately entered a steep spin, crashing at 2100 m on the Blasen slope. HB-659 continued straight briefly, then its outer left wing detached. The pilot of HB-659 was thrown from his seat by his opening parachute and landed about 100 m southwest of his wreckage, which came to rest at 2080 m on the same slope, 500 m southwest of the HB-573 wreckage.
Damage and Injuries
The pilot of HB-573 was found dead in the wreckage, still strapped in. The pilot of HB-659 sustained severe injuries from impact with the tail of the falling HB-659, including a serious concussion with retrograde amnesia. He was incapacitated for four months.
Investigation
The investigation concluded that the collision was due to insufficient airspace observation by both pilots. Additionally, it was noted that the glider camp lacked the required authorization for training outside Birrfeld airfield.