On September 11, 2003, about 1445 eastern daylight time, a Schweizer 269C-1, N6147Q, registered to Caribbean Helicopter Leasing, Inc., operated by Helicenter International Academy, was substantially damaged during a run-on landing at the Homestead General Aviation Airport, Homestead, Florida. Visual meteorological conditions prevailed at the time and no flight plan was filed for the 14 CFR Part 91 instructional flight from the Kendall-Tamiami Executive Airport, Miami, Florida, to the Homestead General Aviation Airport, Homestead, Florida. The certified flight instructor (CFI) and student sustained minor injuries. The flight originated at 1430, from the Kendall-Tamiami Executive Airport. The CFI stated that after departure the flight proceeded to the Homestead General Airport where he advised the student that the lesson would continue with "running landing" and "running take off" training from the previous day. The flight continued in the traffic pattern for runway 36, and when on short final approach to the runway at 5 feet above ground level, the helicopter was at 25 knots indicated airspeed. The helicopter contacted the runway with the skids parallel to the runway centerline, and the CFI allowed the helicopter to continue sliding. The CFI advised the student that the lesson would conclude with a "running takeoff", and upon lifting off the runway at an indicated airspeed of 35 knots, he noticed a vibration from the main rotor system. He noticed the rpm was decreasing and touched down again on the runway, at which time the helicopter began to "shake violently." He realized the flight had encountered ground resonance, and noticed that there was insufficient main rotor rpm to lift off the ground to stabilize the vibrating rotor blade system. He lowered the collective but felt a force when he attempted to reduce throttle input; he felt the force was the student pilot applying throttle input. At that point he was contacted in the head, lost consciousness, which he regained in the hospital. The student pilot advised a Federal Aviation Administration (FAA) inspector that when the flight was approximately 30 feet above ground level prior to performing a running landing, the CFI took the controls from him. The flight continued and while sliding on the runway, the CFI started screaming and froze on the controls. He (student pilot) then braced for impact. Following recovery of the helicopter, the landing gear and main rotor dampers were removed for further examination at the manufacturer's facility with FAA oversight. Examination of the main rotor blade dampers revealed all three exhibited damage associated from lead lag motions encountered in ground resonance. Examination of the four landing gear dampers which had been installed when the helicopter was manufactured revealed all tested out of limits for charge pressure (low). The helicopter was last inspected in accordance with a 100-Hour inspection on August 11, 2003; the helicopter had accumulated 87.9 hours since the inspection at the time of the accident. Review of the 100-Hour inspection guide revealed the landing gear dampers are required to be inspected for operation and condition, and for damper extension with a full fuel tank. Review of Section 12 of the Basic Handbook of Maintenance Instructions manual indicates the landing gear dampers will experience a decrease in pressure with subsequent use of the helicopter, and they should be extension checked during a 100-Hour inspection, or every 6 months, whichever occurs first. According to a memorandum from the Director of Flight Training to all flight instructors dated August 25, 2003, with respect to the Dominican Republic Flight Training Program, running landings were prohibited to be demonstrated and practiced until a new order was given. The helicopter minus the retained main rotor and landing gear dampers was released to the president and CEO of the owner of the helicopter on November 18, 2003. The retained main rotor and landing gear dampers were released to the president and CEO of the owner of the helicopter on March 23, 2004.