Mini Nimbus collision with tree near Schänis after low-altitude maneuver
On September 16, 1989, a Schempp-Hirth Mini Nimbus B collided with a tree near Schänis Flugplatz LSZX in Switzerland. After approximately two hours of flight, the pilot attempted to cross a ridge at low altitude. During the maneuver, the left wing struck the top of a tree, causing the glider to spiral and crash into the forest. The pilot sustained minor injuries, and the aircraft was destroyed. The investigation confirmed the accident resulted from flying below the minimum safe altitude during ridge soaring.
- Aerotow ridge soaring: The pilot aerotowed from Mollis and then spent about two hours soaring in weak thermals and ridge lift near the Chüemettler ridge.
- Weak ridge lift: Weak thermals and hang wind meant usable lift was only available close to the forested slope, encouraging flight very near the terrain.
- Low ridge height: The glider was flying relatively low, around 1300 m MSL, as it approached the Chüemettler ridge above Schänis.
- Low-altitude ridge crossing: While relatively low, the pilot decided to cross the Chüemettler ridge by turning right over the crest.
- Wing hits treetop: During the right turn over the ridge, the left wing struck the top of a fir tree about 22 m above ground, breaking off roughly 1.5 m of the treetop.
- Spiral into forest: Following the treetop strike, the glider entered a left spiral and descended uncontrolled into the forest about 50 m further on.
- Crash - minor injury: The glider crashed in the forest, destroying the aircraft and causing minor injuries to the pilot.