Primary finding
Probable cause
The flight's encounter with downdrafts. A contributing factor was the unsuitable vegetation-covered mountainous terrain.
Investigator assessment
Analysis narrative
After encountering downdrafts, the glider was damaged when the pilot landed on unsuitable brush-covered mountainous terrain. The commercial pilot had planned to take the fare-paying passenger on a 45-minute-long sightseeing ride. Downdrafts were encountered after soaring for nearly 30 minutes. The pilot was unable to cross over a mountain ridge and to get to the airport. The pilot landed on the brush covered mountainside in an uphill direction and at minimum speed.
Source record
Factual narrative
On December 3, 2005, about 1500 Pacific standard time, a Burkhart Grob, G 103 Twin II, N4601M, landed on a mountainside near Llano, California. The glider was substantially damaged upon impacting bushes. Neither the commercial certificated pilot nor passenger was injured during the revenue sightseeing introductory flight. The Great Western Soaring School, in Llano, operated the glider. The flight was performed under the provisions of 14 CFR Part 91. Visual meteorological conditions prevailed, and no flight plan was filed. The flight originated from Llano about 1430. The pilot reported that the planned 45-minute-long ride for the passenger had been uneventful until encountering strong downdrafts. The glider lost altitude while the pilot searched for an area where less sink was evident. The pilot reported that she was unable to cross back over a mountain ridge and glide to a suitable landing site. The pilot landed in an uphill direction, touching down at a minimum airspeed. The glider appeared undamaged when the pilot initially viewed it. Substantial structural airframe damage was noted following the glider's recovery from the brush-covered mountainside, and the National Transportation Safety Board was notified of the accident.