On September 2, 1998, approximately 0810 mountain daylight time, a Long EZ, N5159P, built and being flown by a commercial pilot, incurred substantial damage when the aircraft touched down short of runway 30 at the Cascade airport, Cascade, Idaho. Federal Aviation Administration personnel, who were initially notified by the airport, reported that wing spar damage was incurred, and that all three landing gear had collapsed. The pilot and his passenger were uninjured. Visual meteorological conditions prevailed, and no flight plan had been filed. The flight, which was personal in nature, was to have been operated under 14CFR91 and originated from Cascade approximately 0740 on the morning of the accident. Winds at McCall, Idaho, located 24 nautical miles north, were reported as calm at 0750. The pilot, a Navy test pilot with approximately 1500 hours total flight time in the Long EZ, reported that on short final the aircraft began to settle rapidly and touched down hard approximately 250 feet short of the threshold. He indicated that there was no mechanical malfunction with the aircraft's power plant or systems. However, in his written report, he stated that on short final he "scanned the instrument panel and noticed the airspeed read 100 mph. (This is way too high to stop a Long EZ on a 4000' runway.) Aircraft attitude seemed normal, approach was at appropriate altitude/lineup, so I reduced power and deployed the speed brake. In my aircraft, the speed brake blows closed at 95 mph from aerodynamic forces - it stayed out. As I mentally started processing the fact that the speed brake did not blow back, I sensed an increase in the rate of descent. I retracted the speed brake, added full power, and eased the nose up - touching down 250' short of the runway." The pilot went on to add that the cause of the accident was "slow/failure to recognize and respond to airspeed reading high at critical point in landing." The pilot also reported that he believed the "airspeed indicator stuck at 100 mph during final approach." He stated that "I'm not sure this could have reasonably been foreseen or prevented; higher approach speed would have prevented the settle that developed on short final, but I would have had to instantly recognize the airspeed indicator error. By the time I recognized an excess rate of descent and initiated a wave-off, it was too late to avoid touching down."