Accident Overview
On Saturday, 29 August 1964, at approximately 10:35 Central European Time, a private flight departed from Birrfeld airfield in Switzerland. The aircraft, a Stinson 108-3 registered as HB-TRP, was piloted by a private pilot who was accompanied by three colleagues as passengers. During the takeoff run and initial climb, the pilot maintained an excessively nose-high attitude, preventing the aircraft from gaining proper speed. When the pilot initiated a left turn to avoid overflying an overhead railway line, the aircraft stalled and descended, impacting a potato field approximately 750 meters from the runway end.
Injuries and Damage
The pilot sustained a lumbar vertebra contusion, requiring an eight-day hospital stay and resulting in temporary disability. The front-seat passenger suffered various injuries, primarily to the head and limbs, and was unable to work for 14 days. The two rear-seat passengers were uninjured. The aircraft was completely destroyed by fire.
Aircraft and Pilot Information
The aircraft was a four-seat, single-engine high-wing monoplane with fixed tailwheel landing gear. Its maximum permissible takeoff weight was 1090 kg, and the center of gravity range was between 0.42 and 0.55 meters behind the wing leading edge. The aircraft was equipped with flaps and a stall warning horn that activated at speeds near the stall. According to the flight manual, the stall speed (power off) was 64.5 mph with flaps retracted and 61.4 mph with flaps extended. The aircraft had undergone an official condition check on 26 August 1964, which noted that the stall warning horn activated too late (at 52 mph instead of the correct speed). This issue had not been rectified by the accident date.
The pilot, born in 1941, held a private pilot license issued on 12 September 1962, with a type rating for the Stinson 108-3. His last medical examination was on 14 June 1962, and his license had expired due to the overdue examination. Total flight experience was approximately 64 hours and 340 landings, of which 6 hours 34 minutes and 41 landings were on the Stinson 108-3. In the prior six months, he had flown 3 hours 53 minutes and 13 landings. No health issues were identified at the time of the accident.
Flight Sequence
The pilot had reserved the aircraft on 28 August 1964 for a private passenger flight the following morning. He was unaware that his license had expired. On the morning of the accident, he arrived with his three colleagues. Pre-flight preparation was normal, and he was not informed about the pending stall warning horn issue. Fuel was added; engine warm-up and checks showed no anomalies.
Takeoff was from runway 26 with flaps set to takeoff position. After approximately 300 meters, the pilot lifted the aircraft off the ground and then briefly pushed the nose down. Near the runway end, he pulled back on the elevator to clear a road. At that moment, the stall warning horn sounded. The pilot momentarily pushed forward to silence it, then resumed the climb while adjusting the trim one turn nose-down. He then retracted the flaps, after which the aircraft began to sink noticeably. Despite normal engine operation, the aircraft barely gained altitude, reaching only about 30 meters. Approaching the railway line near Birr station at an altitude of roughly 35-40 meters, the pilot initiated a shallow left turn. During the turn, the aircraft stalled with low forward speed, struck the ground flat, bounced, and came to rest after rotating about 110 degrees left. The occupants evacuated, and the aircraft caught fire.
Investigation Findings
Examination of the wreckage revealed the elevator trim tab was set to approximately -10 degrees (nose-up trim). The trim indicator and crank were burned. Propeller deformation indicated high engine RPM at impact. The reconstructed takeoff weight was 1070 kg, with a center of gravity at 0.475 meters.
The investigation concluded that the pilot's expired license was not a causal factor. The primary cause was the pilot's decision to maintain an excessively nose-high attitude during takeoff and initial climb, combined with a nose-up trim setting, which led to a stall. The stall warning horn's delayed activation may have influenced the situation, but the pilot's actions after the horn sounded—minimal trim correction, resuming the climb, and retracting flaps—indicated a lack of awareness. The turn to avoid the railway line was deemed unnecessary and contributed to the stall.
Probable Cause
The accident is attributable to the pilot stalling the aircraft during takeoff and initial climb.