On September 13, 2003, about 1150 mountain daylight time, a tail-wheel equipped 1956 Cessna 182, N5547B, was destroyed after colliding with forested terrain near Upper Loon Creek Airstrip, approximately 27 miles west of Challis, Idaho. The airplane was owned by the pilot, and was being operated as a visual flight rules (VFR) cross-country flight under the provisions of Title 14, CFR Part 91. The airline transport pilot-in-command and passenger sustained fatal injuries. Visual meteorological conditions prevailed and no flight plan had been filed for the flight. The flight originated from Indian Creek Airstrip, approximately 20 minutes prior to the accident. The pilot's planned destination was Upper Loon Creek Airstrip (U72). A witness reported that the accident airplane was the lead aircraft of a flight of two that departed Johnson Creek (3U2) about 1030 local. The pilot planned an intermediate stop at Indian Creek (S81) with a final destination of Upper Loon Creek. Following the intermediate stop, the accident aircraft departed Indian Creek for its final destination (U72) approximately 15 nautical miles to the east, southeast. The witness, who was piloting the number two airplane, stated that the accident aircraft climbed to approximately 8,000 feet (MSL) while flying down the river from Indian Creek. He stated that about four miles south of Thomas Creek (2U8), the pilot of the accident airplane turned south "up the first drainage" and began a descent into the canyon. The witness communicated to the accident pilot that he was in the wrong canyon, stating over the radio "get out of there now". Shortly after the radio call, the witness observed the accident pilot initiate a turn to the left. Approximately 170 degrees into the turn, the airplane impacted a large tree near the canyon's edge. After colliding with the tree, the airplane caught fire and subsequently impacted terrain in a nose low attitude. Reference attached map for additional information. Search and rescue personnel located the wreckage in a heavily wooded drainage valley approximately seven miles northwest of Upper Loon Creek. The narrow valley is bordered by steep rising terrain. Post-accident inspection and teardown of the airplane's engine revealed no evidence of a pre impact mechanical malfunction or failure. See attached report for additional information.