This July 2009 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
Aircraft: Cessna 172. Injuries: 1 Serious, 1 Minor. Location: Thermopolis, Wyo. Aircraft damage: Substantial.
What reportedly happened: The student pilot and his instructor were on a night flight in VFR conditions. There was no moon. The Cessna was descending some nine miles from the home airport when the airplane’s wheels hit a ridge. The elevation of the ridge was approximately 1,650 higher than field elevation. Although the airplane initially rolled across the terrain at a high rate of speed, it soon encountered the elevated edge of a dirt road. The contact with the road edge resulted in a loss of control. Although the instructor did not specifically remember an unusual rate of descent or any sense of the airplane sinking, it was his opinion that a “mountain wave downwash” may have contributed to the accident.
Probable cause: The instructor’s failure to ensure that his dual student maintained clearance from the terrain during a dark night visual flight rules descent.
For more information: NTSB.gov NTSB Identification: WPR09CA348