Circumstances
On 16 September 1959, a Piper Super Cub PA-18A-150, registration HB-OPT, owned by the Swiss Life Saving Society and operated by the Swiss Air Rescue Guard, departed from Speck airfield at 1315 hours on a search mission for a missing hiker in the Andeer area. The aircraft carried a pilot and a passenger who served as the mission commander. The flight was not reported to the Federal Air Office as required, and no waivers were sought for minimum altitude exemptions. The aircraft was overloaded by 30 kg at departure.
Flight Sequence
The search was conducted in three phases over the mountains west of Andeer. During the final phase, the aircraft flew at altitudes as low as tree-top level, violating the prescribed minimum altitude of 150 meters above ground. At approximately 1515 hours, the aircraft entered the terrain bowl of Lai Lung lake at an altitude of no more than 50 meters above ground, coming from a general northerly direction. While crossing Alp Durnan, the aircraft struck the rising terrain in a near-horizontal attitude with high engine RPM, significant sink rate, and low forward speed. The cockpit clock stopped at 1515, and the variometer indicated a sink rate of 7 m/s.
Aircraft and Pilot Information
The aircraft was a Piper Super Cub PA-18A-150, serial number 18-4814, powered by a Lycoming O-320 engine of 150 hp and a Sensenich M-74 DM-56 metal propeller. Its maximum takeoff weight was 794 kg; at the time of the accident, the weight was 780 kg. The center of gravity was within limits. No pre-existing mechanical defects were found. The pilot, born 1926, held a restricted commercial pilot license valid from May 1959. He had 171 hours and 28 minutes of flying experience, with 9 hours 59 minutes on the accident aircraft. He had no formal mountain or rescue training. The passenger, born 1928, was an experienced mission commander and parachutist but not a pilot.
Weather Conditions
At the time of the accident, the weather was characterized by light to moderate cloud cover at 2800–3200 meters above sea level and visibility between 10 and 40 km due to haze. Light south winds of 6–15 km/h were present, with possible gusts up to 30 km/h from the Splügen pass, which could have generated downdrafts of 2–3 m/s on the slopes and up to 5 m/s on steep faces.
Cause
The report states that the accident occurred because insufficient speed and altitude reserve were available, and the aircraft encountered a zone of unfavorable winds. No other contributing factors were identified.