What happened
On August 8, 2003, a Cessna RA F 150M, registration HB-CWT, departed Saanen aerodrome for a return flight to Lommis. After taking off from runway 08, the pilot initiated a left turn toward Schönried, attempting to climb directly toward the rising terrain. Witnesses observed the aircraft climbing at a very high angle of attack with a noticeably slow rate of climb.
As the aircraft approached the area near Schönried station, the pilot attempted a rapid left banking maneuver, likely intending to execute a turn-back. During this maneuver, the aircraft lost lift and plummeted into a meadow at an altitude of approximately 30 meters. The impact caused the aircraft to catch fire, resulting in two fatalities—the pilot and the passenger. The aircraft was destroyed in the crash.
The investigation
SUST examined the flight conditions, the pilot's experience, and the aircraft's performance. The investigation established that the pilot had relatively limited flight experience, with only 8.5 hours of flight time on the specific Cessna RA F 150M model. While the aircraft's maintenance was up to date and the engine showed no signs of mechanical failure, environmental factors played a critical role.
On the day of the accident, temperatures reached 28°C, significantly increasing the density altitude to approximately 5,484 feet. This high density altitude, combined with turbulent leeward winds and downdrafts from the mountains, severely degraded the aircraft's climb performance. The investigation also noted that the pilot did not utilize the valley basin as suggested by visual approach charts to gain necessary altitude.
Findings
- The primary cause was a collision with terrain resulting from a loss of control due to an inappropriate flight tactic during a mountain departure.
- The pilot's flight preparation was insufficient, failing to account for the impact of high temperatures on performance.
- There was an underestimation of wind conditions, specifically the turbulent downdrafts along the flight path.
- The pilot's limited experience with the aircraft type and mountain operations contributed to the error.
- The pilot likely fell below the minimum maneuvering speed during the turn, leading to the stall and subsequent descent.
Safety action
- The Federal Office of Civil Aviation should review whether visual approach charts for challenging airfields could be improved by including specific departure suggestions, warnings regarding performance limitations in high temperatures, or notices of hazardous wind conditions.
- The authorities should evaluate whether certain airfields should require a mandatory or recommended instructor briefing for pilots.