What happened
On August 8, 1965, a Cessna 170B, registration D-ELEK, departed Samedan Airport in Switzerland for a flight to Augsburg, Germany. The aircraft was carrying a pilot and three passengers. During the takeoff roll, which was noted as being significantly longer than expected, the aircraft encountered a headwind of 10 to 15 knots.
Shortly after lifting off, the aircraft reached an altitude of approximately 15 to 50 meters. The pilot attempted a steep climb, which caused the airspeed to decay. As the aircraft flew toward the St. Moritz valley threshold, it encountered descending air currents in the lee of the terrain. While attempting a left-hand turn to navigate the valley, the aircraft lost sufficient airspeed and entered a stall. The left wingtip struck the ground, resulting in the total destruction of the aircraft. The four occupants sustained light to heavy injuries.
The investigation
The investigation examined the aircraft's weight, engine performance, and the pilot's flight maneuvers. It was determined that the Cessna 170B was approximately 4% to 5% over its maximum allowable takeoff weight. The investigation also noted that the engine's performance appeared to be below specification, as a previous check had shown a maximum RPM of only 2100, whereas the manual requires 2230 to 2330 RPM.
Investigators also reviewed the pilot's flight experience and the environmental conditions, specifically the presence of the Maloja wind and the terrain-induced downdrafts near the St. Moritz valley edge.
Findings
- The aircraft was overloaded, which increased the takeoff roll and reduced the safety margin for climbing.
- The pilot initiated a too rapid climb immediately after takeoff, which depleted the aircraft's kinetic energy and led to a dangerous drop in airspeed.
- The aircraft eventually entered a stall during a turning maneuver.
- The pilot failed to verify the takeoff weight against the aircraft's limitations, likely due to an assumption that the low amount of additional baggage would offset the weight of the full fuel tanks.
- Environmental factors, including descending air currents near the valley threshold, contributed to the loss of altitude.