What happened
During a training flight at Homestead General Airport, a certified flight instructor (CFI) and a student pilot were practicing running landings and running takeoffs. While on short final approach for runway 3ob, the Bell 206 was at 25 knots indicated airspeed approximately 5 feet above ground level. The helicopter contacted the runway with its skids parallel to the centerline, and the instructor allowed the aircraft to continue sliding along the runway.
As the flight proceeded to a running takeoff, the helicopter lifted off at 35 knots indicated airspeed. At this point, the instructor noticed a vibration in the main rotor system accompanied by decreasing RPM. The helicopter touched down on the runway again, at which time it began to shake violently due to ground resonance. The instructor realized there was insufficient main rotor RPM to lift the aircraft and stabilize the vibrating blades. While attempting to manage the collective and throttle, the instructor was struck in the head and lost consciousness; he regained consciousness later at a hospital.
The student pilot reported that during the initial running landing approach, approximately 30 feet above ground level, the instructor took control of the aircraft. During the sliding portion of the landing, the student stated the instructor began screaming and froze on the controls, leading the student to brace for impact.
The investigation
Following the recovery of the helicopter, the landing gear and main rotor dampers were removed for examination at the manufacturer's facility under FAA oversight. Examination of the three main rotor blade dampers revealed damage associated with lead-lag motions caused by ground resonance. Additionally, all four landing gear dampers tested at low charge pressure, which was outside of acceptable limits.
The aircraft had completed a 100-hour inspection on August 11, 2003, and had flown 87.9 hours since that inspection. While the maintenance manual requires landing gear dampers to be checked for operation and extension, the investigation noted that pressure decreases with use. Furthermore, a memorandum dated August 25, 2003, had prohibited the practice of running landings within the Dominican Republic Flight Training Program until further notice.