LAX05FA264

The pinion to turbine shaft coupling failed in fatigue due to a misaligned turbine shaft, which resulted in a loss of engine power.

Following a loss of engine power, the helicopter impacted the ground during the application of chemicals to an agricultural field. Post accident examination of the engine showed that the power turbine to pinion gear coupling had fractured. Metallurgical examination of the affected components showed that the coupling failed in fatigue, which effectively separated the engine from the main rotor gearbox. The fatigue was the result of a misaligned power turbine outer shaft, where the axis of the turbine shaft was angled slightly relative to the coupling and pinion axes. The turbine section had been removed from another engine due to metal contamination. The turbine section was repaired and subsequently installed on the accident helicopter on August 11, 2004, where it operated for 770.3 hours prior to the accident. Weight and balance calculations showed that the helicopter was in excess of its certificated maximum gross weight by 174 pounds.

HISTORY OF FLIGHT On August 10, 2005, at 0600 Pacific daylight time, a San Joaquin Helicopters OH-58A+ restricted category helicopter, N177SJ, impacted terrain while performing aerial pesticide application to onion crops in Lancaster, California. San Joaquin Helicopters, who was also the registered owner of the helicopter, was operating it under the provisions of 14 CFR Part 137. The commercial pilot sustained fatal injuries; the helicopter was destroyed. Visual meteorological conditions prevailed and no flight plan had been filed. The pilot departed about 3 minutes prior to the accident and was completing the first pesticide application of the day when the accident occurred. According to a local farmer who was assisting in the ground portion of the aerial application, the pilot departed from a fuel and chemical loading truck about 1/2-mile south of the accident site. He estimated that the pilot flew the helicopter about 60 to 65 miles per hour and 20 feet above ground level. He maneuvered the helicopter upward to clear a house surrounded by 40-foot tall trees. The helicopter then started downward toward the field and went out of the view of the witness. The witness then drove around a corner and saw the helicopter continue downward toward the field until the nose of the helicopter impacted the ground. Upon impact, the helicopter tumbled down the field before coming to rest. As the helicopter descended toward the field, the witness did not hear any unusual noises coming from the engine, and the approach path to the field appeared normal. PERSONNEL INFORMATION The pilot held a commercial pilot certificate for single engine airplanes and helicopters. A second-class medical was issued in March of 2005, and held the restriction that the pilot must wear corrective lenses. The medical was issued on the condition of a waiver for color blindness. The operator reported that the pilot had a total flight time of 4,089 hours in helicopters with 50 hours in the last 90 days. A copy of the pilot's personal flight logbook was obtained from his family and recorded a total of 4,481.2 flight hours in helicopters. The pilot entered the last 6 entries by monthly flight hour totals, with the last entry dated July 2005. AIRCRAFT INFORMATION The helicopter was maintained in accordance with the Federal Aviation Administrations (FAA) approved San Joaquin Helicopters instructions for continued airworthiness report (Report SJH 97-001). The last annual inspection was completed on March 23, 2005, at a total airframe time of 4,894.3 hours. The last inspection (for continued airworthiness) was completed on June 22, 2005, at a total airframe time of 5,211.00 hours, and a total engine time of 2,446.9 hours. The helicopter had accrued 99 hours since the last inspection. At the time of the accident, the engine had approximately 2,540.8 hours. On August 31, 2004, the turbine was installed on the engine at a total engine time of 1,770.5 hours. The turbine section had been removed from another engine for "metal contamination." The turbine was inspected and subsequently installed on the helicopter where it operated for 770.3 hours prior to the accident. San Joaquin Helicopters modified the accident helicopter from a Bell OH-58A to a Bell OH-58A+, and a new type certificate was issued on February 4, 1998. The modification from the original type design included the installation of the four following items: 1. Lead-acid battery installation 2. Ag-Air systems installation 3. ISOLAIR Model 3900-OH58 spray system installation 4. Flight hour recording meter The helicopter was restricted to agricultural operations in accordance with 14 CFR Part 21.25. WRECKAGE AND IMPACT INFORMATION The National Transportation Safety Board investigator-in-charge (IIC), the FAA accident coordinator, and representatives from Bell Helicopter Textron, and Rolls Royce, all parties to the investigation, responded to the accident site on August 11, 2005. The main wreckage came to rest at these approximate global positioning coordinates: N 34 degrees, 42.437 minutes W 118 degrees, 01.952 minutes, at an elevation of about 2,400 mean sea level (msl). The helicopter impacted a field of onion crops that ran from south to north. The wreckage area covered approximately 80 yards, spanned a width of 40 feet, and the debris field was in a northerly direction. On the southeast corner of the property was a house surrounded by 40-foot tall trees. The crops began about 200 feet from the house. Powerlines were located on the eastern edge of the field. The first identified point of contact (FIPC) was one of the nozzles from the chemical spray system, located about 75 feet from the start of the field's southern side. North from FIPC was the toe portion of the right skid tube. The toe of the skid was buried approximately 2 feet in the soft agricultural soil, and positioned vertically from the ground. Forward and to the right of the skid was a rectangular imprint, similar in size and shape to a main rotor blade. The top portions of the onion stalks in the area of the rectangular imprint were cut at 45-degree angles. Branching outward and to the right from this area were additional rectangular imprints. The main rotor blades and hub assembly were just forward of the imprints and about mid-debris field. One of the tail rotor blades, and the right anti-torque pedal were located 50 feet to the left of the perpendicular imprints. The crops between the main rotor assembly and the tail rotor blades were noticeably disrupted and contained various helicopter debris leading up to the main wreckage. Scattered throughout the debris path were the left door, Plexiglass shards, chemical spray nozzles, the seat back, and cockpit paperwork. The main structure of the helicopter was resting on its right side along a northerly heading. The cockpit structure and instrument panel were crushed and separated from the cabin portion and just forward of the main structure. The cabin area remained intact. Forward 30 feet and 15 feet to the left of the main structure, was the center section of the tailboom that was separated from the main structure one foot aft on the tailboom. Approximately 20 feet forward and 10 feet right of the main structure, was the tail rotor assembly still connected to the aft portion of the tailboom. Portions of the chemical spray system on the helicopter were found throughout the debris field. The majority of the system had separated from the fuselage, as well as from the spray system attachment frame. MEDICAL INFORMATION The Los Angeles County Coroner completed an autopsy on the pilot. The FAA Bioaeronautical Research Laboratory completed toxicological testing on specimens of the pilot. The results were negative for all tested drugs, volatiles, cyanide, and carbon monoxide. TESTS AND RESEARCH The recovered wreckage was examined at Aircraft Recovery Services, Inc., on August 12, 2005, by the NTSB investigator and representatives from Bell Helicopter Textron and Rolls Royce. Airframe The cockpit structure of the helicopter was crushed and torn away from the remaining cabin structure during the accident sequence. The right side appeared more damaged than the left side. The left seat pan remained intact and the cockpit floor containing the anti-torque pedals was torn away. The right seat (pilot's seat) pan and cabin structure were separated from the seat frame. Three of the four pilot's seat belt attachments were fractured. On the left side of the seat belt, both attach points were fractured. The top right attach point was fractured, but the lower right attach point was intact. The right shoulder harness webbing had separated. The pilot's restraint system was removed from the helicopter and sent to the NTSB Materials laboratory for further examination. The flight controls, or portions of them, were traced thro