On September 17, 2002, about 0845 Alaska daylight time, a Cessna 206 airplane, N8515Q, sustained substantial damage when it nosed over during landing at the Circle City Airport, Circle, Alaska. The airplane was being operated as a visual flight rules (VFR) cross-country positioning flight under Title 14, CFR Part 91, when the accident occurred. The airplane was operated by 40 Mile Air Ltd., Tok, Alaska. The commercial certificated pilot, the sole occupant, was not injured. Visual meteorological conditions prevailed, and a VFR flight plan was filed. The flight originated at the Tok Airport, about 0730. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), on September 17, the director of maintenance for the operator reported that the pilot landed the airplane on the gravel-surfaced runway at Circle. During the landing roll, one side of the nose wheel flange partially separated from the wheel hub. The nose wheel flange dug into the runway surface, and the airplane nosed over. The airplane received damage to the wings, fuselage, and empennage. The airplane is equipped with a McCauley nose wheel assembly, and a 600 X 6 tire. The two halves of the wheel flange are bolted together on either side of the wheel hub assembly with six hex-head bolts per side. The bolts are threaded into the hub, and are required to be torqued to 200 inch-pounds. The bolts are not equipped with any lock-washers. On September 18, a Federal Aviation Administration (FAA) inspector, Fairbanks Flight Standards District Office (FSDO), reported he traveled to the Tok Airport, and to the Circle City Airport. The inspector said that he located one wheel flange bolt at the Tok Airport, along the accident airplane's departure taxi path to the runway. The bolt, and bolt threads, were undamaged. The inspector located another wheel flange bolt at the destination, Circle City Airport. The bolt was sheared.