NTSB Identification: LAX98FA007.
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Accident occurred Friday, October 10, 1997 in WARNER SPRINGS, CA
Probable Cause Approval Date: 07/31/1998
Aircraft: Schweizer 2-32, registration: N242DB
Injuries: 1 Fatal,1 Serious,1 Minor.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

The sailplane pilot departed on a 40-minute scenic flight. The sailplane was released from the airplane tow at 8,000 feet. According to passenger statements, they reached a height of 14,000 feet msl. They also stated that near the end of the flight time, the pilot descended through clouds. The sailplane collided with mountainous terrain about 6,000 feet msl. An ocean/atmosphere scientist glider pilot was flying the same area near the accident time. He stated that the day was dominated by powerful, yet rapidly changing lee wave systems, producing 10/20 knot updrafts and downdrafts in the coastal mountain ranges of the lower Southern California Bight. He stated that the lee wave structure is normally very steady and reliable. Based on about 1,800 hours of flying the wave, he believed that this unusual day was a 1 in 1,000 occurrence changing minute by minute. He stated that on three separate occasions, he encountered abrupt disintegration of a well ordered non-hydrostatic wave, which resulted in the immediate loss of 7,000 to 10,000 feet of altitude.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

the pilot's inadvertent flight into instrument meteorological conditions after inadvertently encountering mountain wave and associated downdraft conditions. The obscuration and high/mountainous terrain were related factors.

Full narrative available

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