On August 2, 1996, about 2000 Alaska daylight time, a wheel equipped Cessna 172K airplane, N78108, sustained substantial damage while landing at the McGann Industrial airstrip, Nikiski, Alaska. The solo private pilot was not injured. The 14 CFR Part 91 flight operated in visual meteorological conditions without a flight plan. The flight departed Merrill Field, Anchorage, Alaska, about 1900. During a telephone conversation with the NTSB investigator-in-charge (IIC) on August 5, the pilot stated he was landing to the west with a quartering headwind estimated at 10 to 15 knots. He said he had the appropriate airspeed for the landing approach, but the airplane suddenly dropped 50 to 75 feet and struck the runway. The airplane bounced, landed again hard, and nosed over. The pilot suspects that he encountered a windshear while on final approach. He also stated he believes that the nosegear collapsed during the first bounce, and on the second touchdown, the left main gear collapsed, which allowed the airplane to nose over.