LAX06FA104

The divergence of the main rotor from its normal plane of rotation for an undetermined reason, which resulted in main rotor/tail boom contact and loss of control.

During a short-distance positioning flight, the helicopter descended uncontrolled into terrain about 5 minutes after departure. There was evidence that the main rotor diverged from its normal plane of rotation and severed the tailboom. Review of the pilot's personal flight logbooks showed that he had over 500 hours of flight time in helicopters. Visual meteorological conditions prevailed at the time of the accident with light winds and clear sky conditions. Examination of the wreckage showed that the fuel control return fuel line B-nut was not threaded to the fuel control fitting assembly and was melted. Metallurgical examination could not ascertain whether or not the B-nut was secured to the fuel control prior to the accident.

1.1 History of the Flight On February 7, 2006, at 0802 Pacific standard time, a Robinson R44 II helicopter, N447SH, collided with terrain and burned approximately 3 miles west of the Minden-Tahoe Airport, Minden, Nevada. The pilot was operating the helicopter under the provisions of 14 CFR Part 91. The helicopter was registered to DRACOR. The private pilot, the sole occupant, sustained fatal injuries. The helicopter was destroyed in the post-impact fire. Visual meteorological conditions prevailed, and no flight plan had been filed. The pilot departed from Minden about 0755. According to the assistant manager of the Minden airport, the helicopter was based at Minden. The pilot also owned two airplanes, and used the helicopter to commute between his home and the airport. The helicopter was always stored overnight in a hangar at the airport, unless it had been repositioned to the pilot's house. The Federal Aviation Administration (FAA) accident coordinator interviewed a friend of the pilot following the accident. The pilot's friend indicated that they had flown from Minden to the Madera, California area in the days leading up to the accident, and had returned to Minden the previous day. Due to poor weather conditions, they were unable to land at the pilot's home so they landed at Minden. The pilot was repositioning the helicopter to his home when the accident occurred. Repeated attempts by the National Transportation Safety Board investigator to contact the pilot's friend were unsuccessful. 1.1.1 Witness Information A witness was standing in her home and watched the helicopter come up over the trees and descend downward. The helicopter then made a sharp left turn and hovered for about 20 seconds. At that point, the witness stated that the helicopter began moving backward for about 1,000 feet. As the helicopter was moving backward, both the engine and helicopter sounds seemed normal to the witness. The witness thought that the helicopter was about 60 feet above ground level but due to her position from her residence, it was difficult for her to judge. As she watched the helicopter continue to move backward, the witness turned away from the window. Shortly thereafter, she heard the main rotor blades and engine become really loud and make a "clunking and rattle noise." She looked in the direction of where the helicopter had been flying, and noted a smoke plume. An additional witness reported that he was outside working when he heard what he thought was a single-engine airplane "over rev" its engine, "...as if in a hard turn or pull out of a dive." He looked up and saw a fireball erupt, followed by a muffled impact sound, and then a louder explosion. 1.2 Personnel Information The pilot held a private pilot certificate and was rated to fly single-engine airplanes under both visual and instrument flight rules. The pilot also held a rating for rotorcraft-helicopters. The pilot's last third-class medical was issued on January 28, 2004. There were no restrictions or waivers. The pilot reported a total flight time of 900 hours on the medical certificate application. On June 14, 2004, the pilot attended the Robinson Helicopter Company Flight Instructor Safety and Refresher Clinic. On his application he reported 500 hours in airplanes, 493 hours in helicopters. Of the helicopter hours, 467 hours were in a Robinson R22, and 25 hours were in a Robinson R44, with an additional 1 hour flown in an unknown make and model helicopter. Two personal pilot logbooks were obtained from the pilot's family. The first logbook ended in January 2003. The second logbook contained a combination of airplane and helicopter time. The last entry listed for airplane flight hours was dated March 8, 2004, and a total time of 497.9 hours was recorded in the single engine airplane section. The entry dated June 7, 2004, contained a note that any further single engine airplane information would be recorded in another logbook and helicopter time would be recorded in this logbook. The last dated entry in the logbook was December 4, 2004, and the pilot's total time in helicopters was recorded as 537 hours. 1.3 Aircraft Information 1.3.1 General Aircraft History FAA aircraft records showed that the helicopter was sold to DRACOR by Silver State Helicopters on May 18, 2004, and registered by the accident pilot on May 28, 2004. No maintenance logbooks were recovered for the helicopter. A maintenance record was obtained from Silver State Helicopters dated October 24, 2005, which indicated that Robinson Helicopter Company (RHC) Service Bulletin 55 had been complied with. The total time on the helicopter was 122.4 hours. The logbook entry noted that the fuel control unit was removed and retrofitted with KI-178 (the RHC fuel control reorientation kit). The fuel control was reoriented and reinstalled. All ground and operational checks were successful and no discrepancies were noted. 1.3.2 Fueling The most recent fueling record of the helicopter at Minden was dated February 2, with the addition of 31.5 gallons of fuel. A fueling receipt obtained from Madera Municipal Airport, Madera, California, showed that a helicopter with a registration number of "447NNN" was fueled with 13.1 gallons of 100 low lead on February 5. It could not be confirmed if this was the accident helicopter. 1.4 Meteorological Information The closest official aviation routine weather report (METAR) was reported at Lake Tahoe Airport, South Lake Tahoe, California. At 0753 the following conditions were reported: wind from 300 degrees magnetic at 6 knots; sky conditions, clear; temperature, 50 degrees Fahrenheit; dewpoint, 19 degrees Fahrenheit; and altimeter, 30.40 inches of Mercury. 1.5 Medical Information The Douglas County Sheriff's Department-Coroner completed an autopsy on the pilot. The FAA Forensic Toxicology lab completed toxicological testing. The results were negative for carbon monoxide, cyanide, volatiles, and all tested drugs. 1.6 Wreckage and Impact Information The FAA accident coordinator responded to the accident scene. The debris path covered an area of approximately 100 yards. The first identified wreckage consisted of main rotor blade pieces and a cut section of tail rotor drive shaft. Forward from this point approximately 40 yards, was the tail rotor assembly with a portion of the tail boom still attached. Between the tail rotor assembly and the main wreckage, a distance of 60 yards, tail boom debris was identified. The main wreckage sustained extensive fire and impact damage, coming to rest on its left side on a magnetic heading of 262 degrees; the left skid was crushed and the right skid remained intact. The main rotor blades remained attached at the main rotor hub. 1.7 Tests and Research The wreckage was examined on February 17, 2006, at Plain Parts located in Pleasant Grove, California. The NTSB investigator, a Robinson Helicopter Company (RHC) representative, a Textron Lycoming representative, and an airworthiness inspector from the Sacramento Flight Standards District Office, were present. The fuselage structure of the helicopter was consumed by fire. The seat structures had burned away. The tailboom separated approximately 4 feet forward of the tail rotor gearbox assembly. The tail rotor spun freely and produced corresponding movement to the fractured tail rotor drive shaft. The tail rotor pitch change push pull tube remained attached to the tail rotor and the pitch of the tail rotor blades changed when the tube was manually activated by hand. A 9 by 4 inch section of the outboard, leading edge of the horizontal fin was separated from the structure and located loose within the wreckage. The tailboom was twisted to the right just forward of the vertical fin. The tail rotor drive shaft had fractured into 5 sections. According to the RHC representative, three of the separations e