At about 1430 Mountain time, the helicopter was substantially damaged during a hard landing to Runway 17R at Centennial Airport in Englewood, Colo. The Private pilot and his passenger were uninjured. Visual conditions prevailed; the flight departed had Jefferson County Airport (BJC), Broomfield, Colo., at approximately 1400. During a takeoff, the pilot reported that after crossing the threshold at 40 knots and 40 feet agl, he felt like [he] was in a high rate of descent and the [helicopter] began to sink. The pilot suspected he was settling with power and decreased the collective and pushed the cyclic forward. The helicopter continued to sink, impacting the runway hard and sliding for approximately 6 feet. Examination revealed that the front and rear crossbar and the right tail boom support strut were bent. Density altitude was calculated at 8622 feet. The out-of-ground-effect hover ceiling was calculated at approximately 5600 feet and the in-ground-effect hover ceiling was calculated between 6200 and 7600 feet.