WPR12LA347

The commercial pilot of the turbine-powered helicopter was conducting his seventh agricultural application flight of the day. After completing a pass and while the helicopter was about 45 ft above ground level, the pilot entered a right course-reversal turn for another pass. While the helicopter was turning, the pilot felt it shudder, and shortly thereafter, he heard a loud "bang." The helicopter then began to shake, and the pilot had little to no control. The helicopter skidded right, started descending, struck the ground, and rolled onto its right side. Postaccident examination of the helicopter did not reveal any preimpact mechanical deficiencies or failures that would have precluded normal operation.

According to FAA information, the helicopter, serial number 1074, was manufactured in 1959, and equipped with a Lycoming VO-435 series piston engine. In 1985, it was equipped with an Allison 250-C20 series turboshaft engine, and re-registered with the FAA in the "restricted" category by Western Helicopter Services. According to information provided by the operator, at the time of its most recent annual inspection in June 2012, the helicopter had accumulated a total time in service of about 18,069 hours. The helicopter had departed from a heliport on private property that was located about 1/4 mile southeast of the accident site. On August 7, 2012, about 0715 Pacific daylight time, a Hiller UH-12D helicopter, N47035, sustained substantial damage subsequent to a hard landing in a clear-cut forest area in Deer Island, Oregon. The pilot received minor injuries, and the helicopter sustained substantial damage to the fuselage, main rotor blades, transmission, and tail boom. The helicopter was owned by Western Helicopter Services, Inc., and operated under contract to the United States Forest Service (USFS), under the provisions of 14 Code of Federal Regulations Part 137 as an aerial application flight. Visual meteorological conditions prevailed for the flight, and no flight plan had been filed. The pilot reported that he started spraying an herbicide about 0625, and had made six runs before stopping to refuel. He refueled with 35 gallons of Jet-A fuel for the turbine-powered helicopter, and took off for the seventh spray run. The pilot was making a right turn, at an altitude of about 45 feet above ground level (agl) for the next pass, when he felt the helicopter shudder. The pilot stated that the helicopter did not "feel right," and shortly thereafter he heard a loud "bang." The helicopter began to shake, and the pilot had little to no control; the helicopter was "skidding to the right" and descending. The helicopter struck the ground, and rolled onto its right side. The pilot shut down the engine, turned off the battery master switch, unbuckled his restraint harness, and exited the helicopter. According to the accident report filed by the operator, an on-site witness reported that there was a thin overcast layer at an altitude of about 2,000 feet agl, and that the visibility was "unlimited." The witness reported that the wind was from the northwest at 2 mph, and that there were no noticeable gusts or turbulence. Federal Aviation Administration (FAA) records indicated that the pilot held a commercial pilot certificate with a helicopter rating. According to information provided by the operator, the pilot had approximately 6,075 total hours of flight experience, all of which was in helicopters. His most recent flight review was completed in November 2011, and his most recent FAA second-class medical certificate was issued in July 2012. The wreckage was recovered from the accident site by the operator, before it could be examined on site by investigativepersonnel. A post wreckage-removal examination of the accident site by the FAA inspector did not yield any additional components of the helicopter, or any information that provided him with a better understanding of the accident sequence. According to information provided by the operator, the helicopter came to rest on its right side in a clearing in a forest. Information provided by the operator indicated that the helicopter was situated just off a road, and that an impact skid mark, and a portion of the tail boom were found on the road. The transmission and main rotor blade assembly was found lying adjacent to, and fracture-separated from, the engine and airframe. Both main rotor blades were substantially damaged. The right side of the cockpit/cabin was crushed and otherwise deformed. There was no post-crash fire. The tail rotor slip joint (normally situated just aft of the transmission), and the forward flange of the tail rotor drive shaft were removed and shipped to the National Transportation Safety Board (NTSB) Materials Laboratory in Washington, D.C., for detailed examination. Examination of those components did not detect any evidence of any pre-existing mechanical deficiencies such as corrosion or fatigue cracks. The operator reported that they considered the possibility of a compressor stall, and had removed and sent some unspecified engine components to an engine repair facility for examination. That examination did not detect any abnormalities with those components.