What happened
On January 2, 1972, a Cessna 337 Super Skymaster, registration SE-ESA, departed Nice, France, for a private flight to Samedan, Switzerland. The flight initially proceeded under Instrument Flight Rules (IFR). While navigating through Italian airspace, the pilot requested a lower altitude to transition to Visual Flight Rules (VFR). After descending to 1,000 feet near the Saronno VOR, the pilot canceled the IFR flight plan to continue the journey under VFR conditions.
As the aircraft progressed toward the Alps, it entered the Bregaglia Valley. Witnesses observed the aircraft flying at a very low altitude, between 100 and 200 meters, beneath a dense cloud layer. While performing a left-hand turn, the aircraft struck a snow-covered mountainside near Casaccia, west of the Maloja Pass. The impact destroyed the aircraft, and both the pilot and the passenger were killed.
The investigation
SUST examined the flight preparation, communication logs, and meteorological conditions. The investigation revealed that the pilot had requested weather information for Samedan via Zurich, but the response provided to Nice was incomplete and erroneous, failing to include critical warnings from the Samedan airport chief. Furthermore, the pilot was unable to establish contact with the Milano Information frequency to verify VFR conditions for the remainder of the route.
Investigators also reviewed the pilot's navigation documents, which included various charts but lacked specific approach plates for Samedan. The investigation noted that the pilot's experience in the Alps was limited, having performed only a few VFR crossings of the mountain range previously.
Findings
- The pilot operated with incomplete flight preparation due to receiving inaccurate and partial weather information.
- There was a significant misjudgment of the weather situation in the Alps, specifically regarding the cloud ceiling and visibility in the Bregaglia Valley.
- The aircraft collided with a mountainside while obscured by clouds during a turning maneuver.
- The transition from IFR to VFR was performed without confirmed weather clearance for the intended route.
- The pilot entered the valley at an altitude too low to safely execute a turning maneuver or clear the terrain under the prevailing cloud base.