On January 12, 1999, at 1153 central standard time, a Gulfstream Commander 695A, N20GT, experienced a hard landing on runway 16 (5,001' X 100' dry/asphalt) near Wheeling, Illinois. The airplane sustained substantial damage. The pilot said that the airframe had some ice contamination and that at the time of the accident there was a 10 knot tailwind. The pilot and three passengers reported no injuries. The 14 CFR Part 91 corporate flight was operating in visual meteorological conditions. The flight departed Columbus, Ohio, at 0930, with an IFR flight plan on file. During an interview with the pilot-in-command, he stated that the airplane was being flown by the owner from the left seat that the time of the hard landing. He said that he was acting as pilot-in-command and giving instruction the other pilot. He said that the landing was hard, but he did not realize that there was any damage until he exited the airplane and saw the wrinkling in the tailcone section of the airplane. He said that the landing was downwind and that there was an accumulation of about 1/8 inch of ice on the leading edges of the wing and horizontal stabilizer. He said there was about 3/16" to 1/4" on the windshield wipers.