1969 Jodel D 11 HB-SOW Accident at Gruyères Airfield

Incident Overview and Flight Details On May 24, 1969, a Jodel D 11 aircraft with the registration HB-SOW crashed shortly before the threshold of runway 36 at the Gruyères airfield in Switzerland. The aircraft was operating a private flight from Porrentruy to Gruyères, with the pilot intending to make an intermediate landing before returning to Schmitten. The aircraft impacted the ground at 17:03 local time, approximately 120 meters south of the runway threshold and 35 meters east of the extended centerline. ## Aircraft and Occupants The aircraft, a 1959-built Jodel D 11 with a 90-horsepower Continental C 90-12 F engine, was owned and piloted by a private pilot born in 1917. The pilot held a valid private pilot license and had a total flight time of 645 hours and 15 minutes, with 6 hours and 56 minutes in the preceding three months. The passenger, born in 1927, held no aviation credentials. At the time of the accident, the aircraft had 434 operating hours and 814 landings on its airframe. ## Accident Sequence and Probable Cause During the final approach, the pilot initiated a left slip at a low altitude, reducing engine power to idle. The pilot reported feeling the approach was too high and initiated a second slip. The aircraft then pitched over the right wing and impacted the ground. The official investigation concluded that the accident occurred because the pilot exceeded the allowable angle of attack during a slip initiated at low altitude. Witnesses observed the aircraft with its nose high and left wing low during the slip, followed by a sudden roll to the right. ## Investigation Findings Blood tests taken from both occupants indicated an alcohol concentration of 0.5 to 0.6 promille for the pilot and 0.8 to 0.9 promille for the passenger. A forensic medical report noted that at the pilot's level, even alcohol-tolerant individuals experience mild impairment, including euphoria, reduced self-control, and decreased attention. The wreckage examination revealed no pre-existing technical defects. The first ground contact was made by the right wing's underside, followed by the forward fuselage impacting at a 40-degree longitudinal tilt. The aircraft then rotated 90 degrees to the right before coming to rest perpendicular to the direction of flight.