What happened
On February 20, 1972, a Mystère 20 (registration HB-VCG) was operating a commercial flight from Samedan to Zurich and back. During the return leg, the crew encountered rapidly deteriorating weather conditions caused by a southern foehn wind. While navigating the Oberhalbstein region toward the Julier Pass, the pilot encountered heavy cloud cover and light snowfall, which significantly reduced visibility.
As the aircraft approached the Julier Pass, the pilot found it impossible to turn toward Samedan due to the lack of visual references. In an attempt to find a way through or under the clouds, the pilot descended to a very low altitude over the Silvaplanersee. While executing a sharp right-hand turn at approximately 100 meters altitude, the right wing of the Mystère 20 struck the frozen surface of the lake. The impact caused the tail section to break off, and the remaining fuselage slid approximately 200 meters across the snow. The crew and two passengers sustained two injuries, but there were no fatalities.
The investigation
SUST examined the flight history, weather reports, and the wreckage of the aircraft. The investigation established that the crew had sufficient experience and valid licenses, and the aircraft was airworthy with no technical malfunctions contributing to the crash. Investigators specifically ruled out an asymmetric deployment of the flight spoilers, determining that the position of the spoilers found in the wreckage was a result of the impact rather than a mechanical failure.
The investigation also reviewed the weather forecasts available to the crew. It was noted that while a forecast was available in Zurich, the crew had not reviewed the specific details regarding the closure of the Julier Pass for VFR flight. Furthermore, the investigation looked into the visibility limits and the difficulty of maintaining radio contact with Samedan Tower during low-altitude operations in mountainous terrain.
Findings
- The primary cause was the continuation of a VFR flight in mountainous terrain at an altitude and in visibility conditions that made a safe turnaround impossible.
- Inadequate weather study and unsuitable flight tactics contributed to the accident.
- The crew's decision to fly along the valley floor rather than staying on one side of the valley prevented them from being able to turn back at Bivio.
- The high speed of the aircraft made a safe turning radius impossible at such low altitudes and reduced the pilot's reaction time.
Safety action
- The investigation recommended increasing the minimum visibility requirements for high-speed aircraft operating in uncontrolled airspace to ensure sufficient time for maneuvering.
- A recommendation was made to improve the radio equipment and communication infrastructure at Samedan Airport, including the installation of automatic voice recording systems.