On May 17, 1997, at 1610 eastern daylight time, N321JL, a Mooney M20M, was substantially damaged during a hard landing on runway 23 at the Madisonville Airport, Madisonville, Kentucky. The certificated commercial pilot/owner and a flight instructor were not injured. Visual meteorological conditions prevailed and a flight plan was not filed. The instructional flight was conducted under 14 CFR Part 91 and had originated from Owensboro, Kentucky. According to the pilot/owner, the purpose of the flight was to practice short field landings with a certificated flight instructor (CFI). He stated that the first landing was completed successfully; however, during the second landing, the airplane touched down hard 20-30 feet short of the runway, striking the tail of the airplane. The owner said, "...an attempt at recovery was made by applying full power, but the airplane would not climb, but instead traveled uncontrollably to the left, over the parallel taxiway and toward the FBO buildings... ." According to the owner, 75 knots was the airspeed he used for the first, successful, short field landing. He said the instructor told him to use the maximum performance landing speed as published in the Pilot Operating Handbook, revised in 1992, which called for a final approach speed of 70 knots. The owner said, on final approach, he slowed the airplane to 70 knots. When approximately 50 feet above the ground and 50-60 feet before the threshold of the runway, the airplane experienced a sudden uncontrolled descent without sufficient warning. The owner reported that there was no mechanical malfunction with the airplane.