On November 19, 1996, approximately 0810 Pacific standard time, N8005Q, a Cessna 421B, sustained substantial damage when it landed hard during an undershoot at Olympia, Washington. The airline transport pilot and his two pilot-rated passengers were uninjured. The aircraft had departed Tacoma Narrows airport, Tacoma, Washington, about 0730 on an IFR flight plan to Ontario, Oregon, before diverting to Olympia due to airframe icing conditions. Instrument meteorological conditions prevailed at the time of the accident. There was no report of the ELT actuating. During a telephone interview, the pilot stated that he encountered airframe icing and cycled the deice boots, but felt that the tail of the aircraft became "heavy," so he elected to divert after climbing to about 14,000 feet. On approach at 110 KIAS, he attempted to flare and the aircraft did not flare, and landed hard short of the runway. The airport was closed prior to the pilot's landing attempt due to snowplows on the runway, but this information was not disseminated to the pilot by ATC. The snowplow exited the runway prior to the pilot's landing attempt. In his written report, the pilot stated that he had frequently checked the wings for ice accumulation during climbout. At about 12,000 feet the rate of climb was decreasing and the airspeed had dropped to about 130 knots indicated. He continued to climb, noting what appeared to be a "mere" trace of ice. At 13,000, with almost no climb at 125 knots indicated, the pilot pulled the yoke back a little to climb and the aircraft began to shudder. The pilot then decided to divert, again checking the wings, seeing what he described as a trace of ice. He said he cycled the deice boots with no apparent change in wing appearance. While on approach at Olympia, he again cycled the boots between 3000 and 2000 feet MSL (mean sea level). The pilot stated that about 20-30 feet above the surface, he started a slight roundout, but when he eased back on the yoke, the airplane shuddered and the nose did not raise. At that point, he was ready to touch down, so he pulled back on the yoke while adding power. He stated that the airplane landed very hard. He did not notice any damage until he shut off the engines after taxiing in and noted that the propeller tips were bent. The airplane was inspected later by FAA inspectors, who also observed testing by A&P mechanics at Olympia. The surface deice system was checked in accordance with Cessna service manuals. It was determined that the electrical test functioned properly. During an air leakage test, the boots did not hold pressure due to multiple wing boot holes and a shuttle valve internal leak. Functional test showed both control valves did not direct proper pressure to the system, both shuttle valves did not direct pressure properly to the boots (leaking to the vacuum side of the valves), the indicator light did not operate during deice cycle. The pilot listed the right seat passenger as a copilot and dual student when he responded on his NTSB 6120.1/2 form. The right seat passenger was owner of the airplane, and was multi-engine rated, with 175 hours dual instruction recorded in this airplane. However, the flight was originally described as a business flight by the pilot.