NTSB Identification: FTW98LA352.
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Accident occurred Saturday, August 08, 1998 in HUNTSVILLE, UT
Probable Cause Approval Date: 12/01/1999
Aircraft: Piper PA-28-161, registration: N54TM
Injuries: 2 Serious.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
The flight instructor and his student were from Fort Worth, Texas, and they were crossing a mountain ridge eastbound at 9,500 feet msl when the flight instructor reported that they 'encountered a serious downdraft.' He immediately began a 180 degree turn and then reversed direction again back eastbound. The flight instructor stated that the 'airplane was descending about 2,500 feet per minute with full power.' The student stated that 'just as we hit some trees, I remember hearing the stall horn.' The forecast wind aloft was approximately 10 knots at 9,000 feet msl. The density altitude for 10,000 feet was calculated to have been 13,061 feet. Using the airplane's manufacturer Climb Performance charts, N54TM had approximately 210 feet per minute climb capability. The degree of bank that the flight instructor utilized for his turns was not documented, but, the book 'Flight Theory For Pilots' states that as the turning bank angle increases, the energy demands to maintain level flight asymptotically increases. The flight instructor reported that he acquired most of his flight training in Colorado Springs, Colorado, before moving to Fort Worth, Texas.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The flight instructor's failure to ensure adequate altitude/clearance with terrain, resulting in an encounter with a downdraft, loss of airspeed, onset of a stall/mush, and collision with high terrain.. Contributing factors were high density altitude, downdrafts, mountainous terrain, and trees. Full narrative available
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