On August 18, 1994, at 2030 Alaska daylight time, a wheel equipped Cessna 182 airplane, N2791G, owned and operated by the pilot-in-command, collided with the visual approach slope indicator (VASI) on runway 29 at the Ketchikan Airport, Ketchikan, Alaska during landing. The private certificated pilot and his two passengers, the sole occupants, were not injured and the airplane sustained substantial damage. The pleasure flight, conducted under 14 CFR Part 91, last departed Wrangle, Alaska at 1945 and the intended destination was the site on which the accident occurred. No flight plan was in effect and visual meteorological conditions prevailed. Confirmation of substantial damage to the plane's right wing and aileron assembly was completed on September 16, 1994. The pilot reported that during the approach for landing, he encountered a downdraft and the airplane dropped to the runway surface and then became airborne again while drifting to the left. The pilot indicated that he applied right rudder and when the aircraft touched down again, he cut the engine power and dropped two notches of flaps. The pilot was not aware that the airplane struck the VASI indicator housing until he was notified by airport personnel the following day. Airport personnel reported that the VASI indicator housing is mounted on 4 frangible posts. The top of the housing is about 4 feet above the ground. The housing is located 54 feet to the left of the left edge of runway 29.