Flight History
On 17 May 1992, the pilot of the Standard Cirrus glider HB-1234 departed from Luzern-Beromünster airfield at 1519 local time under aerotow. The tow reached approximately 1050 m above sea level, but due to an altimeter mis-setting (QNH set to 1040 hPa instead of the actual 1024 hPa), the pilot believed the altitude was about 1300 m. After releasing near Hildisrieden, the pilot attempted to exploit weak thermals but continuously lost height. With visibility of only 4 km and a gusty northeast wind of 5–10 knots, he decided to return to the airfield.
While flying over a small forest near the hamlet of Schopfen at about 100 m above ground, the pilot realized he could not reach the airfield on a direct approach. He initiated a turn into the downwind leg. During this turn, the glider stalled and entered a spin, striking the ground with the nose at the edge of a field. The aircraft rebounded, rotated 180°, and impacted again tail-first in a meadow, resulting in its destruction. The pilot sustained serious injuries.
Findings
- The pilot held a valid glider pilot license.
- Flight training was minimal: in 1990, he flew 4 flights totaling 4:45 hours; in 1991, 3 flights totaling 5:54 hours. In the 90 days prior to the accident, he had no flight time.
- No evidence of pre-existing medical issues was found.
- The glider was certified for VFR operations, and no technical defects were identified that could have caused the accident.
- Mass and center of gravity were within limits.
- The altimeter was set to a QNH of 1040 hPa, which was 16 hPa higher than the actual pressure of 1024 hPa, causing an over-read of approximately 150 m.
- Weather at the accident site: 2–3/8 cumulus clouds with base around 1500 m, visibility about 4 km, wind from northeast at 5–10 knots gusty, temperature 21°C, dew point 13°C.
Cause
The accident was caused by the glider falling below minimum flight speed at low altitude, leading to a stall during a turning maneuver.
Probable Cause (from source)
"Falling below minimum flight speed at low altitude."