On April 26, 2005, about 1900 Alaska daylight time, a wheel equipped Cessna 180 airplane, N4685A, sustained substantial damage while landing at an off airport site, about 12 miles northwest of Anchorage, Alaska. The solo private pilot was not injured. The airplane was being operated as a visual flight rules (VFR) personal flight under Title 14, CFR Part 91, when the accident occurred. Visual meteorological conditions prevailed, and no flight plan was filed. The flight originated about 1730, from the Lake Hood Airstrip, Anchorage, Alaska. During a telephone conversation with the National Transportation Safety Board investigator-in-charge on April 28, the pilot reported that during the landing roll on a grass-covered site, the main landing gear wheels encountered soft terrain, and the airplane nosed down. The airplane sustained substantial damage to the wings and fuselage. The pilot reported there were no preaccident mechanical problems with the airplane.