What happened
On January 7, 2020, a Cessna 152, registration HB-CCN, departed Buttwil Airport (LSZU) for a private training flight. The pilot, who required supervision due to a lack of recent flight training, had arranged for a flight instructor to oversee the session. Shortly after takeoff from runway 34, the aircraft encountered deteriorating weather conditions. While the surrounding area had relatively good visibility, low-lying clouds and a "cap cloud" over the Lindenberg ridge created challenging conditions.
During the flight, the pilot performed several turns to return to the airfield. At one point, the aircraft entered Instrument Meteorological Conditions (IMC) as it flew through the cloud layer. While the pilot was maneuvering, an instructor on the ground attempted to establish radio contact multiple times, but the pilot did not respond. The aircraft eventually entered a continuous descent in a right-scale turn, striking the terrain in the Rüedikerwald, approximately 2 km southwest of Buttwil. The impact resulted in one fatality and the total destruction of the aircraft.
The investigation
SUST examined the flight path using radar records, eyewitness accounts, and aircraft logs. The investigation focused on the pilot's physiological state and the meteorological environment. Investigators analyzed the aircraft's performance, noting that the weight and balance were within limits and no technical malfunctions were found. The investigation also looked into the weather patterns, specifically the presence of localized cloud formations that obscured the terrain.
Findings
- The pilot had suffered a heart attack approximately 20 to 30 minutes before the accident, prior to takeoff. This medical event likely impaired the pilot's ability to operate the aircraft effectively.
- The aircraft was operating in Instrument Meteorological Conditions (IMC), which significantly increased the risk of spatial disorientation.
- The loss of control was caused by a combination of the pilot's medical impairment and spatial disorientation while flying in clouds.
- Localized weather, specifically cap clouds over the Lindenberg ridge, created much more difficult flying conditions than those reported at nearby airports.