Summary
On Sunday, 15 May 1960, a Piper Cub HB-OBX, piloted by a private pilot accompanied by his wife, departed Thun for Davos. During the final approach to land on runway 05 at Davos airfield, the aircraft lost speed, stalled, and crashed into a building material depot. The pilot sustained minor injuries; the passenger was uninjured. The aircraft was destroyed.
Aircraft and Crew
The aircraft was a Piper Cub J3C (L-4H), serial number 12.106, owned by the Sektion Berner Oberland of the Aero-Club der Schweiz. It was equipped with a Continental C-85-12 engine and a Sensenich TC-691 wooden propeller. The aircraft had a maximum takeoff weight of 580 kg and weighed 530 kg at the time of the accident. The center of gravity was within prescribed limits.
The pilot, born in 1925, held a private pilot license issued on 2 July 1957, valid until 20 October 1960. He had accumulated 96 hours and 7 minutes of flight time over 436 flights, with 3 hours and 7 minutes (13 flights) in 1960, including 1 hour and 26 minutes (4 flights) in the three days preceding the accident, all on the accident aircraft type. He was described as cautious and reserved. The passenger, born in 1923, was the pilot's wife and held no aviation credentials.
Flight History
On 13 May 1960, the pilot contacted the Davos airfield manager by telephone, obtaining landing permission and standard instructions. On 14 May, he received necessary authorizations from the club and flight instructor guidance. The instructor pointed out obstacles southwest of the field and noted that the higher elevation required a higher landing speed.
On the morning of 15 May, the pilot departed Thun at 07:44 CET with full fuel, flying via Susten, Oberalp, Reichenau, Thusis, and Filisur. He arrived over Davos at 09:40 at an altitude of about 2000 m (450 m above the field) in good weather with light southerly wind. He initially attempted an approach from the northeast, but came in too high and initiated a go-around. He then decided to land from the southwest.
Accident Sequence
Approximately 1.5 km southwest of the field at an altitude of about 100 m above ground, the pilot turned left toward the field and began a descending glide to the northeast. Witnesses described the approach as low and slow. During the glide, engine power was briefly increased. The aircraft was trimmed tail-heavy. As it passed over a shed just before the field boundary at low altitude, the left wing suddenly dropped, and the aircraft sank with little forward motion. According to the pilot, the airspeed indicator was at the red line at the critical moment. The engine power was increased at the last moment, but the aircraft struck the ground in a building material depot about 30 meters beyond the shed, with very low forward speed.
Damage
The aircraft was severely damaged in the forward fuselage and wings, and was not rebuildable. The engine remained usable. The pilot suffered a broken nasal bone and facial cuts; the passenger was uninjured. No significant ground damage occurred.
Findings
The accident was caused by loss of speed during the final approach. The aircraft's stall speed in level flight at idle power was approximately 35 mph indicated, with variation up to 40 mph. The airspeed indicator, replaced the day before the accident, was marked with a red line at 45 mph (72 km/h). The pilot's statement indicated that the indicated speed was at or below the red line at the critical moment.