WPR17LA075

The pilot's failure to detect the presence of water in the helicopter fuel system before the flight, which resulted in a total loss of engine power during cruise. Contributing to the accident was the pilot's delayed recognition of the power loss and late initiation of an autorotation, which resulted in a hard landing on the ocean.

The commercial pilot and the nonpilot-rated passenger/spotter were conducting an aerial fish-spotting mission in the turbine-powered helicopter, which was operating from a fishing boat in the south Pacific Ocean. According to the accident report filed by a representative of the parent company of the operator, about 30 minutes into the flight, at an altitude of about 1,000 ft above the ocean, the pilot noticed the GEN OUT annunciator light, indicating a generator problem. The pilot began the procedures to address the generator problem, which in part entails placing the generator switch in the OFF position, but then noticed that the helicopter was in an uncommanded descent, and that the main rotor rpm was below its normal cruise value. The pilot initiated an autorotation, but the float-equipped helicopter subsequently struck the water hard, and the main rotor blades severed the tail boom. The pilot was seriously injured, and the passenger/spotter was reported to have received minor injuries. The helicopter was recovered, and then examined by investigators about 3 weeks after the accident. No preimpact mechanical deficiencies of the airframe or engine that would have precluded continued flight were observed. The fuel system exhibited multiple signs of fuel contamination, primarily by water. The fuel in the engine fuel pump and in the line to the fuel spray nozzle was contaminated by water to a level that would not support engine operation. The fuel system design was such that the water in the pump and the fuel line could not have been introduced during or after the impact sequence, indicating that it was likely present in the fuel system before departure. The fishing boat's helicopter fuel storage and dispensing system was not available for examination, and therefore the investigation was unable to determine the source of the water contamination of the fuel. Because the pilot was not able to be interviewed for the investigation, his procedures regarding fuel contamination prevention and detection could not be determined. Regardless, the pilot's failure to detect the presence of water in the fuel system prior to flight was the proximate cause for the engine power loss. Although engine power loss in this model helicopter is typically signaled by multiple instrument, visual, tactile, and audio cues, the pilot did not detect the power loss until the helicopter was in an uncommanded descent. There was some evidence that the helicopter was equipped with an engine failure alerting system. The investigation was unable to determine whether the engine failure alerting system was installed and functioned properly, and if so, why the pilot failed to notice and respond to the alert in a timely manner. Because the engine failure alerting system is inoperative when the generator switch is in the OFF position, it is possible that, if the helicopter was equipped with a functional engine failure alerting system, the engine power loss occurred when the pilot was conducting the 'GENERATOR MALFUNCTION' procedures, and the engine power loss alerting system was thereby disabled. The investigation was unable to determine whether the generator problem occurred prior to the engine power loss, or the engine power loss precipitated the GEN OUT annunciation. The pilot's late detection of the engine power loss, and his consequent loss of altitude and delayed initiation of the autorotation, reduced the likelihood of a successful touchdown.

The Hansen-provided accident report stated that the weather at the time of the event included winds from 350 degrees at 5 knots, visibility 20 miles, clear skies, temperature 26° C, and daylight conditions. The pilot was a US citizen who held FAA Commercial and Flight Instructor certificates. The filed report indicated that the pilot had about 2,936 total hours of flight experience, all of which were in helicopters, and 1,350 hours of which were in the accident helicopter make and model. The pilot's most recent flight review was completed in July 2015, and his most recent FAA second-class medical certificate was issued in January 2016. The medical certificate status reverted to third-class status after 12 months, and per FAA regulations, the pilot could not exercise his commercial privileges for compensation. NTSB attempts to interview the pilot were unsuccessful; he was still hospitalized and could not be reached telephonically. FAA attempts to interview the pilot in person on March 13 were also unsuccessful; he refused to speak to the FAA without counsel, but was unable or unwilling to provide the name of, or any other contact information for, his counsel. Two days later, the pilot was transferred by air ambulance to the Philippines for surgery related to his accident injuries. The pilot made no subsequent contact with the NTSB. The observer was a Japanese citizen, and according to a representative of Hansen Helicopters, he had no pilot experience. The observer was evacuated to Japan shortly after the accident, and no NTSB attempts were made to interview him. The helicopter, an OH-6A (Manufacturer's Model 369A, SN 101355) was delivered new to the US Army on February 24, 1970 as US Army SN 69-15985. Hughes Tool Company (HTC), Aircraft Division was the original manufacturer of the helicopter. HTC underwent several ownership (and name) changes subsequent to the production of this helicopter. FAA registration and airworthiness documentation indicated that the helicopter was powered by a Rolls-Royce (Allison) C250 series turboshaft engine. FAA records indicated that the helicopter was first registered to Jim's Air Repair in August 2009. Jim's Air Repair is based in the country of Vanuatu. Hansen-provided information stated that the airframe had 7,374.8 total hours of service, that the engine had 2,702.4 total hours of service, and that the engine had accumulated 393.7 hours in service since its most recent overhaul. Airframe The investigation team's first contact with the helicopter was about 3 weeks after the accident. The helicopter was examined inside a Hansen Helicopters building, where it was reported to have been stored since shortly after the accident. It was upright, resting on the left utility float, fuselage lower structure, and the right forward and aft struts. The right utility float had been removed from the helicopter during recovery. The four fuselage attach points for the landing gear struts/dampers were severely damaged, with torn skins and fractured structure. The fuselage sustained extensive impact damage, with the left side more damaged than the right side. The tailboom was separated into at least two sections. According to the Hansen Helicopters report, one portion of the tail boom assembly that was severed by the main rotor blades during the ocean impact was lost at sea. The recovered section was fracture-separated from the fuselage near fuselage station (FS) 197.78, and extended to approximately FS 258.0. The recovered section showed evidence of main rotor blade contact. The tailboom aft of FS 258.0, including the vertical and horizontal stabilizers, tail rotor transmission, and the tail rotor system, was not recovered from the ocean. The canopy windscreens and overhead transparencies, doors, and doorframe structures were all damaged from impact. The cockpit instrument panel and center console assembly, and its associated components, showed little damage. Two hour meters were located in the helicopter. One displayed a reading of 937.8 hours, and the other one displayed a reading of 1,245.9 hours. Hansen personnel did not provide any information regarding the functions of these two hour meters. Both the left and right cockpit seat pans were significantly deformed downward, and their box structures were crushed. The seat restraint systems were intact and functional. The helicopter was equipped with single pilot, left hand controls. Cyclic and collective control system continuity was confirmed. The cyclic stick balance was consistent with the trim actuators being neutral. Anti-torque control continuity was confirmed from the pilot's pedals to the fractured tail rotor control rod at the tailboom separation point. The main rotor system hub assembly and components, strap assemblies, pitch housings, feather bearings, and pitch change links were relatively undamaged. The rotor system exhibited hub damage that was consistent with excessive blade lead/lag excursions and high flapping angles. All four main rotor blades were unbroken, with varying degrees of bends and skin damage. The damage to the main rotor system components was consistent with low rotor rpm, power-off, main rotor blade strikes. Drivetrain continuity was established from the engine, through the main transmission, to the main rotor. Rotation of the main rotor hub by hand resulted in rotation of both the engine-to-transmission drive shaft and the tail rotor driveshaft. The over-running clutch assembly was functional. The transmission cooler blower assembly appeared undamaged. The main transmission appeared undamaged. One transmission magnetic chip plug had a small amount of unidentified paste-like material on it, and the other chip plug was clean. The tail rotor driveshaft separation locations matched the locations of the tailboom separations. The shaft fracture signatures were consistent with lower-than-flight-normal rpm. Engine The engine is a two-spool design. In the direction of airflow, the first spool is referred to as "N1," and includes all 7 compressor stages and the first 2 turbine stages. The N1 turbine section, which drives the compressor, is also referred to as the "gas generator" turbine. The second spool includes the last two turbine stages and the mechanical accommodations to drive the rotor system. This section is also referred to as the "N2" or "power turbine" section. The engine mounting structure was properly secured and generally intact. All engine mounts exhibited deformation consistent with a hard landing. Inspection of the engine exterior revealed no evidence of fire or uncontained failure. The N1 section was able to rotate freely, and had no indications of foreign object damage or housing rubbing. The N2 section showed no visible damage. Its rotation was stiff, but this appeared consistent with saltwater corrosion damage to the accessory gearbox, and not with impact damage. All fuel, lubrication, and pneumatic lines, and their associated fittings, were found to be at least finger tight. No evidence of oil leakage was observed in the engine bay or surrounding area. The helicopter was positioned at an angle which precluded an accurate oil level determination, and no indications of oil underfill were noted. No obstruction of the intake was noted, and no evidence of any mechanical failures or deficiencies that would have prevented normal engine operation was observed. Fuel System No information regarding the fuel on board, either at the time of departure or at the time of the accident, was provided to the investigation. No fuel was observed in the fuel tank during the examination. The fuel pump power wire was not wrapped around the start pump fuel line, as it was required to be; this condition can result in an erroneous fuel quantity indication. In addition, the in-tank quantity sensor exhibited visible corrosion. A vacuum check of the engine fuel system indicated that there was a slow leak wit