NTSB Report on Forest Service Plane Crash

From the NTSB probable cause report: "The National Transportation Safety Board determines the probable cause(s) of this accident as follows.
The pilot's misidentification of the airplane's location, which resulted in his improper decision to fly into the wrong drainage, and his failure to maintain terrain clearance while executing a turn to reverse course after he realized his navigational error. Contributing factors were the low visibility due to mist, obscuration of the mountainous terrain, and the pilot's lack of experience in back country flying."

You can read the full probable cause report, the report synopsis, the factual report, and the full narrative on the NTSB website.

Source: "Report blames pilot for Bob Marshall crash." Missoulian September 15, 2005. B1.