On September 20, 1996, about 1600 Alaska daylight time, a wheel equipped PZL-Mielec Wilga 104-80 airplane, N6630M, sustained substantial damage during an off airport landing approximately 52 miles east-southeast of Aniak, Alaska. The airline transport certificated pilot and the sole passenger aboard were not injured. The 14 CFR Part 91 flight operated in visual meteorological conditions. The purpose of the flight was to transport a hunting client to a hunting site. The flight last departed a local, rural hunting base camp, time unknown. The pilot reported he was making a landing approach to an off airport, unimproved site he routinely used to drop off a hunting client. The pilot said he was flying the airplane at 55 knots indicated airspeed on final approach, when a severe downdraft forced the airplane prematurely onto the landing surface. The airplane received substantial damage when it struck the runway. The pilot reported the wind to be about 18 to 20 knots from 220 degrees, with higher gusts. In his written report to the NTSB, the pilot noted his approach path to the landing site was slightly low, and the downdraft was caused by turbulence associated with the wind flowing over and down nearby terrain.