Accident Details
On 18 May 1962 at approximately 1520 Central European Time, a Bücker 131 Jungmann, registration HB-USP, collided with a rock ledge in the Val Tremola about 750 meters south of the Gotthard Pass summit. The aircraft was destroyed, and the pilot was not injured. No ground damage occurred.
Pilot Information
The pilot, born in 1940, held a private pilot license valid until 20 October 1963. He began motor flight training in October 1957 and had accumulated approximately 160 flight hours over 500 flights, of which about 21 hours and 45 flights were on the accident type. He had no instrument flight training. The investigation found no indications of health issues at the time of the accident.
Aircraft Information
HB-USP was a Bücker 131 Jungmann, a two-seat sport and training biplane of mixed construction, manufactured by Dornier-Werke A.G. in Altenrhein in 1940. It was powered by a 105-horsepower Hirth HM A-2 engine with an Infanger wooden propeller. The aircraft had a valid airworthiness certificate until 28 September 1962 and was not approved for instrument flight. Its takeoff weight at the time was 535 kg, within the maximum of 670 kg, and the center of gravity was within limits. The investigation found no technical defects.
Weather Conditions
The weather was characterized by a south föhn (Südstau) condition, with fog over the Gotthard and Val Tremola. On the north side, the cloud base was at approximately 2300 meters with 3/8 stratus; on the south side, 6/8 stratus at about 1500 meters. Visibility was 50 km on the north side and 6-10 km below the fog on the south side. Wind was SSE at 15-20 knots with no significant gusts.
Flight and Accident Sequence
The pilot planned to fly from Zurich-Kloten to Locarno. After a previous attempt was abandoned due to weather, he departed at 1440 on 18 May 1962. He climbed to about 3000 meters into the Reuss valley. Near Hospental, the weather deteriorated, with clouds at 2800 meters and fog over the pass. The pilot continued, then entered fog before reaching the pass. He attempted a left turn to regain visibility but abandoned it due to terrain proximity. He continued south in fog, hoping to clear the pass. At 1520, he felt a jolt and lost control; the aircraft came to rest in deep snow seconds later.
Investigation Findings
The aircraft struck a rock ledge with its left wheel, rotated, and impacted the slope with its right wing, then slid about 120 meters downhill. The pilot was uninjured. The investigation found no technical issues and no health concerns. The commission concluded that the accident was a classic case of a pilot attempting a visual flight across the Alps in marginal weather, continuing into instrument conditions, and losing orientation.
Probable Cause
The collision with terrain resulted from the pilot continuing a visual flight into instrument meteorological conditions and losing orientation.