On July 13, 1999, at 1310 Pacific daylight time, a Schempp-Hirth Nimbus-4DM motorized glider, N807BB, experienced an in-flight breakup while maneuvering near Minden, Nevada. The commercial glider pilot and a passenger were fatally injured, and the glider was destroyed. The glider had departed from Minden-Tahoe airport at 1240 and was operated by the owner/pilot under the provisions of 14 Code of Federal Regulations (CFR) Part 91. No flight plan was filed for the local area soaring flight. The glider was certificated in the United States in the experimental category for exhibition and racing, and it was also certificated in Germany in the standard class, utility category .
We determined that the probable cause of this accident was the pilot’s excessive use of the elevator control during recovery from an inadvertently entered spin and/or spiral dive during which the glider exceeded the maximum permissible speed, which resulted in the overload failure of the wings at loadings beyond the structure’s ultimate design loads.
