What happened
On April 3, 1971, a private pilot operating a SIAI-Marchetti S-205-18F, registration HB-ELN, arrived at Thun Aerodrome with three passengers for a short recreational flight. During the takeoff roll, the pilot noted poor acceleration. Approximately halfway down the runway, the aircraft lifted off at a high angle of attack without gaining sufficient altitude. This maneuver caused the aircraft to roll toward the right wing and veer off the runway.
Rather than aborting the takeoff, the pilot continued the roll, crossing the runway boundary. A second attempt to lift off resulted in the aircraft flying at a low altitude and high pitch, eventually breaching three fences. The aircraft finally came to a stop on a nearby football field, where it collided with a parked Austin Cooper and a bicycle. There were no fatalities among the four occupants, though the aircraft was destroyed.
The investigation
Investigators examined the aircraft's condition, the pilot's experience, and the environmental factors at the time of the accident. The SIAI-Marchetti S-205-18F was found to be airworthy, with its weight and center of gravity within permissible limits. The propeller controls were set to low pitch/high RPM, and the parking brake was released.
The pilot had recently completed only two training sessions on this specific type, totaling approximately 90 minutes of instruction and 20 landings. The investigation also reviewed the runway conditions, noting the grass strip was dry and sufficient in length for the takeoff weight, and confirmed that the weather was clear with light winds.
Findings
- The pilot attempted to rotate the aircraft at an insufficient airspeed, which triggered the stall warning.
- The high angle of attack during the initial lift-off significantly hindered the aircraft's ability to accelerate.
- The pilot failed to execute a timely aborted takeoff despite the aircraft veering off the runway after the first failed attempt.
- The pilot's lack of thorough preparation for a takeoff at near-maximum weight and the decision to rotate without regard for rotation speed indicated inadequate familiarity with the aircraft type.