On July 2, 2001, about 0850 Alaska daylight time, a Lockheed L-382G airplane, N401LC, sustained substantial damage during landing at the Lake Minchumina Airport, Lake Minchumina, Alaska. The airplane was being operated as an instrument (IFR) cross-country cargo flight under Title 14 CFR Part 121, when the accident occurred. The airplane was registered to, and operated by Lynden Air Cargo LLC. The crew of the airplane, consisting of the captain, first officer, flight engineer, and a load master, were not injured. Visual meteorological conditions prevailed, and an IFR flight plan was filed. The flight originated at the Ted Stevens International Airport, Anchorage, Alaska, about 0800. During a telephone conversation with the National Transportation Safety Board investigator-in-charge on July 2, the director of operations for the operator reported the airport has a gravel runway that is oriented on a 020/200 degree heading. He added that the captain flew over the airport to inspect the runway conditions, and subsequently elected to use runway 20. He said that the runway is 4,200 feet long, 90 feet wide, and that the gravel runway had a number of frost-heaves that have developed during the past winter. The director of operations said that the captain was making an approach to runway 20, and on initial touchdown the airplane "skipped" as the main wheels touched down on the crest of one of the frost-heaves. He said that the airplane became airborne, floated slightly, and then touched down about 750 feet beyond the approach end of the runway. During the second landing flare, the main landing gear wheels touched on the downhill side of a second frost-heave, which allowed the tail of the airplane to contact the gravel runway. The captain characterized the second touchdown as within acceptable limits, but with a slightly nose high attitude. After touchdown, the captain lowered the nose of the airplane, brought the engines into reverse, and completed the landing. After landing rollout, the airplane was taxied to parking. A postflight inspection by the crew discovered a 4 feet by 2 feet puncture on the belly of the airplane, just forward of the main cargo door.