As the pilot was landing on runway 11, which was 2,600 feet long and 50 feet wide, the airplane touched down short of the runway lip, and the right main landing gear collapsed. The airplane then skidded off the right side of the runway onto the grass, and struck a fence. According to the pilot, 'just prior to normal touchdown, the airplane dropped from a downdraft or from wind shear.' The wind was reported to be from 120 degrees at 20, gusting 30 knots.