Cessna U206F N206KL accident near Donnelly, Idaho

Probable cause

The pilot's failure to maintain clearance from terrain while maneuvering in likely low-ceiling and low-visibility conditions in mountainous terrain.

NTSB analysis

Before departing on the cross-country flight over mountainous terrain, the accident pilot and two other pilots going to the same remote airstrip discussed the weather and checked webcams positioned throughout the passes. The accident pilot took off first and flew south before turning east to cross the mountains, while the other two pilots chose to fly north before crossing the mountains. Inflight radio communications from the accident pilot indicated that when he first turned east to cross the mountains, he encountered weather that required him to turn around and fly further south before turning east again. No further radio communications from the accident pilot were heard. The other two pilots reported encountering marginal weather with low clouds during their flights to the destination, which they completed without incident. Flight track data downloaded from the accident airplane's onboard GPS unit indicated that, during the final 40 seconds of the flight, the airplane made a left turn of about 90 degrees followed by a right turn of about 180 degrees while maintaining an altitude of about 8,150 ft. This flightpath suggests that the pilot was following the contour of the horseshoe-shaped ridgeline at that location. However, the ridgeline varied in elevation between about 8,000 and 8,200 ft, and the airplane impacted steep, heavily wooded terrain about 100 ft below the top of the ridgeline.

A postaccident examination of the airframe and engine did not reveal any anomalies that would have precluded normal operation. Due to the location of the accident site, weather reporting stations and weather products were limited. Satellite imagery did not show low-level clouds because of a mid-level cloud layer at 15,000 ft. A weather model run to simulate relative humidity over the accident site revealed that the lower altitudes above terrain likely had a much lower visibility with relative humidity greater than 98%. Thus, it is likely that the pilot was maneuvering the airplane in or near low clouds when he lost visual contact with the ground resulting in controlled flight into terrain.

Text from the NTSB. Open the NTSB docket for WPR14FA044 for the full record.