What happened
On May 6, 1972, a Standard Libelle glider, registration HB-10 and 09, departed from Buttwil for a training flight. After being towed and releasing the tow rope at approximately 500 m/AG near Horben, the pilot climbed to 1400 m/MS using thermal currents. Due to a light north wind, the aircraft drifted south of the Lindenberg ridge. Seeking better visibility and thermals, the pilot navigated toward Rooterberg and later Meggen, but found no significant lift in those areas.
At an altitude of 1100 m/MS, the pilot decided to perform an outlanding on a mown field near Hinter-Barbrämen, located west of Küssnacht a. Rigi. The field was approximately 180 meters long and 37 meters wide, flanked on both sides by electrical power lines. While attempting a left turn at 150 m/AG to align with the field, the pilot initiated the final approach too early, resulting in an excessively high flight path. To correct this, the pilot attempted a full left circle approximately 250 meters before the landing site. This maneuver was executed poorly, causing the aircraft to drift to the left.
As the aircraft flew over houses near the approach path, the left wing tip struck an electrical insulator on a power line at an altitude of approximately 8 m/AG. Although the pilot managed to level the wings after the impact, the Standard Libelle struck the ground heavily at 12:15 PM.
The investigation
The investigation confirmed that the pilot held a valid glider license with endorsements for passenger and aerobatic flight, as well as a special permit for motor gliders. The pilot had 326:48 total flight hours, with 14:54 hours on the involved aircraft type. There was no evidence of health issues affecting the pilot's performance during the flight. The aircraft was found to be airworthy and in compliance with all regulations, with no pre-existing technical defects identified.
Findings
- The primary cause of the accident was the collision with electrical power lines resulting from an imprecise landing approach.
- The pilot's control inputs during the corrective left circle were imprecise, leading to a lateral drift toward the power lines.
- The pilot's psychological state may have been influenced by a previous incident in 1971 involving a collision with a flagpole, which reportedly triggered a sense of panic during the maneuver.