On June 17, 2014, about 1500 central daylight time, a Bell 206B helicopter, N536T, made a hard landing at the Decatur Municipal Airport (KLUD), Decatur, Texas. The flight instructor and pilot rated student received minor injuries, and the helicopter was substantially damaged. The helicopter was registered to MBM Aviation Consultants, Inc., and operated by the Federal Aviation Administration (FAA) under the provisions of 14 Code of Federal Regulations Part 91 as a training flight. Visual meteorological conditions prevailed for the flight, which operated without a flight plan. The flight originated from the Fort Worth Alliance airport (KAFW), Fort Worth, Texas.
The flight was planned as part of the agency's quarterly proficiency program for inspectors. The contract flight instructor, who was initially scheduled to fly, was not available to perform the flight. An FAA flight instructor was then scheduled, and flew in the morning with another FAA employee. The accident flight was the student's first flight with the FAA instructor, and the instructor's second flight of the day. The afternoon flight had a similar flight profile as the morning's flight and was estimated to last about 2.5 hours.
The instructor and pilot rated student reported that they were about 2 hours into the proficiency flight, and had completed a series of maneuvers, which included straight-in and 180-degee auto rotations. To complete the flight objectives before proceeding back to KAFW, the instructor planned to demonstrate another 180-degree auto rotation. The instructor reported, the rotor speed was in the mid to low section of the green band, at 200 feet at the start of the approach. At the beginning of the flare, he tried to roll in full throttle, but felt resistance, and he didn't get the power restored in time. He then elected to level the helicopter, so the tail wouldn't hit first and roll the helicopter over. The helicopter touched down on the asphalt 100 feet short of the fix distance markers on runway 17.
The pilot rated student, reported that on the last 180-degree auto rotation, the instructor was at the controls. At 100 feet on the approach, he noticed that the rotor speed was at a minimum and the rate of closure was slow. He felt they were going to be short, so he called for power and reached for the throttle to confirm it was full on.
Another helicopter, which was in the airport traffic pattern, made a radio call to determine the position of the accident helicopter; the radio call, was not answered. They then noticed the helicopter on the ground, upright, just east of runway 17. The main rotor blades were not turning, the tail boom was missing just aft of the horizontal stabilizer and that there was a debris path, beginning about 400 feet before the 1,000 foot fixed distance markers.
The NTSB, FAA, and technical representatives from the engine and airframe manufacturers responded to the accident site. Examination of the runway revealed a scar consistent with the tail boom impacting the runway first. The helicopter came to rest upright, partially off the runway, approximately 207 feet, from the first impact point. Numerous marks, consistent with the helicopter's landing skids were noted between the first scar and the helicopter. The helicopter was sitting on its landing skids, but leaning to the left. The tail boom had separated just aft of the stabilizer, the tail rotor gear box was torn from the tail boom. The transmission was tilted aft and had broken free of the driveshaft. Both main rotor blades had impact damage, consistent with striking the tail boom and horizontal stabilizer. The NTSB investigator demonstrated free movement of the throttle while the corresponding pointer movement at the FCU (Fuel Control Unit) was witnessed by the engine technical representative.
An examination of the throttle system was conducted on June 19, 2014, by FAA maintenance inspectors. The inspection was conducted in accordance with Bell helicopter maintenance manual (BHT206 MM-1, chapter 76-00-00). No abnormalities were noted the throttle system and it met the manufacturer's instructions for continued airworthiness.