On July 31, 2004, at 0950 mountain daylight time, a Piper PA-28-140, N4345J, collided with rough terrain when it overran the departure end of runway 08 (5,500 feet by 60 feet, dry asphalt) during an aborted takeoff, at the Custer County Airport (CUT), Custer, South Dakota. The certified flight instructor (CFI) and the student pilot were not injured. The airplane was substantially damaged. The 14 CFR Part 91 instructional flight was operating in visual meteorological conditions without a flight plan. The local flight was originating at the time of the accident. The CFI reported he was demonstrating a "ground effect acceleration takeoff" to his student when the accident occurred. The CFI reported the density altitude at the time of the accident was 7,800 feet. The CFI stated the airplane did not accelerate in ground effect to his target speed of 90 miles per hour (mph) so he initiated an aborted takeoff about 1,500 feet prior to the end of the runway. The CFI stated that upon touchdown, the braking action was poor. He stated, "I reduced back pressure for a more positive traction and applied brakes firmly, before applying back pressure again. It wasn't until this point that I was concerned as it became obvious that there was virtually no braking action. Moments later I asked the student to assist me in braking with her toe brakes." The CFI stated the airplane departed the end of the runway at a speed of about 70 mph. The student pilot reported the target speed was not achieved, so the takeoff was aborted. She stated the CFI "... cut power immediately, and began to flare. When it was evident that the aircraft was not slowing at a sufficient rate, the instructor dropped the nose and both instructor and student applied full brakes." The airport manager who witnessed the takeoff reported the airplane "... appeared to hit the runway from a height of approximately 10', two thirds of the way down runway eight. From which point, the 140 was still under full power all the remaining way to the white marks at the end of runway eight." He stated the engine power was then reduced and the airplane skidded between the runway end lights. The manager stated, "From the point of impact to the point where the throttle was fully retarded, there was a continuous cloud of blue smoke." The airplane came to rest in the grass approximately 250 feet from the departure end of the runway. Black skid marks and metallic scrape marks were visible on the runway. These marks began about 300 feet prior to the departure end of the runway and continued to the end of the runway. The airplane came to a stop with both main landing gear turned sideways. The scissors mechanisms on both main landing gear separated and the gear were turned sideways. The right wing was pulled away from the fuselage and the bottom of both wings were wrinkled near the landing gear attach points. The weather reporting station at CUT reported the conditions at 0953 were: wind 250 at 9 knots; 10 statute miles visibility; clear skies; temperature 26 degrees Celsius; dew point 5 degrees Celsius; and a barometric pressure of 30.04 inches of mercury. Using the current weather information along with a field elevation of 5,602 feet mean sea level (msl), the density altitude was calculated to be 8,110 feet. The takeoff was being made on runway 08 and the wind was from 250 degrees at 9 knots. The PA-28-140 Owner's Handbook provides a takeoff distance versus density altitude chart. The chart contains information for density altitudes up to 7,000 feet. The chart states "Extrapolation of chart above 7000 ft. is invalid." The landing distance versus density altitude chart indicates that at a density altitude of 7,000 feet, with 40 degrees of flaps, at gross weight with no wind, the landing distance would be 1,250 feet.