On May 21, 1998, at 1518 central daylight time, a Bell 206BIII helicopter, N206TA, owned and operated by Bell Helicopter Textron, was substantially damaged during a hard landing near Hurst, Texas. Visual meteorological conditions prevailed, and a company flight plan was filed for the Title 14 CFR Part 91 instructional flight. The flight instructor and the commercial pilot receiving instruction were not injured. The flight instructor reported that he was demonstrating an autorotation with a 180 degree turn to Lane 4, at the Bell Helicopter Hurst Heliport. At approximately 100 feet AGL, the flight instructor determined a power recovery was necessary due to low rotor RPM and a high rate of descent. At about 50 to 70 feet the flight instructor increased the throttle to full on; however, the engine did not respond, and the autorotation was continued. The instructor reported that prior to touchdown, he verified that the throttle was full on. The helicopter touched down on the departure end of Lane 4, bounced and veered off of the lane 45 degrees to the right. The helicopter then touched down in the grass bouncing two more times before coming to a stop upright about 70 feet from the end of the lane. The instructor also reported that as the aircraft bounced and ran through the grass he "felt [the] engine begin to spool and [he] closed the throttle to idle." The 3,200 hour pilot receiving instruction reported that as the helicopter "rolled out of the turn," at 100 feet, the flight instructor elected to initiate a power recovery and execute a go-around. At approximately 50 to 70 feet the instructor attempted to "add throttle," but the engine did not respond. The instructor "continued to try and get the throttle and engine to respond," then he "leveled the aircraft and we hit the runway straight ahead." Examination of the helicopter revealed that the aft structural panel on the right side of the fuselage was wrinkled. The spike plate under the main transmission was damaged, the main drive shaft contacted the isolation mount, and one main rotor blade struck the tail rotor drive shaft cover. The aircraft's engine was inspected and returned to service.