Piper PA-28-140 N945RH accident near Dubois, Wyoming

Probable cause

The pilot's encounter with a windshear/downdraft that exceeded the climb performance capabilities of the airplane.

NTSB analysis

The pilot was following a highway to the northwest at 10,000 feet mean sea level. He crossed the mountain pass between 700 and 1,000 feet above ground level climbing slowly. Once on the west side of the pass, approaching the base of some cliffs, they encountered a strong down draft and the airspeed dropped rapidly and the airplane started to descend. The pilot reports that he attempted to keep the airspeed at 85 knots and climb but, that the airplane continued to lose altitude. He checked the engine instruments and did not note any degradation of engine performance. The airplane continued to descend. The pilot executed a forced landing in approximately the center of the valley ahead of them. The pilot reported that there were no preimpact mechanical malfunctions or failures. Based on the temperature and pressure readings from the closest weather reporting station, the density altitude at the accident site was about 9,200 feet.

Text from the NTSB. Open the NTSB docket for WPR09CA193 for the full record.