Flight History
The pilot departed Buttwil airfield at 1110 MEZ on 6 May 1972, tow-launching the Standard Libelle HB-1009 for a training flight. After releasing the tow rope at approximately 500 m above ground near Horben, he used thermal updrafts to climb to 1400 m above mean sea level. A light north wind drifted the glider over the southern end of the Lindenberge. Seeking better visibility and being outside the Zurich TMA, the pilot flew towards the Rooterberg, hoping for good lift near cumulus clouds. Not finding sufficient thermals, he continued towards Meggen. Still without notable lift south of the Rooterberg ridge, he headed west of Küssnacht am Rigi. At an altitude of about 1100 m above mean sea level, he decided to perform an outlanding on a mowed meadow at Hinter-Barbrämen. The field measured approximately 180 meters in length and 37 meters in width and was flanked on both sides by electrical power lines.
Accident Sequence
At approximately 150 m above ground, the pilot began a left turn for the approach. He turned into the final leg too early, causing the approach to be too high. To correct, he executed a full left circle about 250 meters before the landing field. The circle was flown imprecisely, and the glider skidded to the left during the recovery. The aircraft cleared nearby houses with adequate height but was still in a skid. At about 8 meters above ground, the left wing tip struck an electrical power line situated northwest of the approach path, hitting an insulator. The pilot managed to return the glider to level attitude, but it contacted the ground hard at 1215.
Damage
The pilot sustained slight injuries. The glider HB-1009 was heavily damaged. Minor third-party damage occurred.
Pilot and Aircraft Information
The pilot, born in 1942, held a valid glider pilot license with endorsements for passenger flights and aerobatics, as well as a special permit for motor gliders. His total flying experience was 326 hours and 46 minutes, including 14 hours and 54 minutes on the Standard Libelle. In the preceding 90 days, he had flown 5 hours and 2 minutes total, with 1 hour and 5 minutes on the accident type. No health impairment was indicated. The aircraft was airworthy and certified for flight, with no evidence of pre-existing technical defects.
Weather Conditions
At the time of the accident, visibility was 10 to 20 kilometers. Wind was 5 knots from variable directions. Cloud cover was 3 to 5 eighths cumulus with bases between 1500 and 1800 meters above ground. Temperature was +18°C.
Investigation Findings
The investigation noted that the approach to the power line was caused by imprecise flight control. According to the pilot, memories of a previous collision with a flagpole in 1971 contributed to a panic reaction, which in turn led to imprecise control inputs.
Cause
The accident resulted from the pilot colliding with an electrical power line due to an imprecise landing approach.