N8648F

HISTORY OF FLIGHTOn July 5, 2018, about 0914 local time (coordinated universal time [UTC] + 12 hours), an MD Helicopters (Hughes) 369D helicopter, N8648F, impacted the Pacific Ocean near the Republic of Nauru in the Marshall Islands about 20 seconds after liftoff from a Taiwan-registered fishing ship. The commercial pilot and the non pilot-rated observer (who was the designated fish-spotter) received fatal injuries. The helicopter was destroyed by impact forces and salt water immersion. The helicopter was registered to Vertol Systems Company (VSC) of Hillsboro, Oregon, and operated as a Title 14 Code of Federal Regulations Part 91 aerial observation flight. Visual meteorological conditions prevailed at the time of the accident. No flight plan was filed for the flight, which was originating at the time of the accident.

There were no known recorded communications between the helicopter and the ship before or during the accident flight. A forward-facing surveillance video camera on the ship captured the helicopter's liftoff and water impact. The permanent-type float-equipped helicopter was positioned on the ship's landing platform, which was about 40 ft above the waterline. The sky was clear, the sea state was calm, and the water surface was glassy in appearance, with no waves and minimal swells. While on the platform, the helicopter faced about 45° to port (left). The left-side of the helicopter was visible and revealed that the left cockpit door was not installed. The helicopter lifted off and began an immediate descending right turn of about 90° heading change and disappeared off the right edge of the image frame. It then re-entered the image frame, traveling from right to left, well ahead of the ship's bow. The helicopter was sufficiently low that it left visible disturbances on the water surface behind it. While still flying forward, the helicopter contacted the surface of the water and immediately nosed over into an inverted position. The wreckage remained afloat, but the low resolution of the image prevented any determination of its condition.

The ship captain's statement indicated that two "skiff boats" were dispatched to "rescue" the helicopter occupants. Both occupants were recovered from inside the helicopter, but they were not able to be resuscitated. The wreckage was recovered and secured on the deck of the ship. No other significant details were provided in the ship captain's statement or accompanying incident report. Subsequent documentation showed that the helicopter was placed lying on its right side for transport to shore. About 4 days after the accident, the helicopter was delivered to the VSC facility on the atoll of Majuro in the Marshall Islands. VSC personnel righted and then partially disassembled the helicopter for storage in a temperature- and humidity-controlled shipping container, where it remained until examined by investigators a few months later. PERSONNEL INFORMATIONFederal Aviation Administration (FAA) records indicated that the US pilot held a commercial pilot certificate with rotorcraft-helicopter and instrument helicopter ratings and a flight instructor certificate with a rotorcraft-helicopter rating. Records and information provided by VSC were incomplete. As of November 2016, the pilot had accumulated about 650 hours of total flight experience, including about 428 hours in turbine-powered helicopters. According to information provided by VSC, the pilot began flying for VSC in 2017. VSC did not provide any information regarding the pilot's flight time at VSC. The pilot's most recent VSC "Annual Competency Check" flight review was completed in March 2018, and his most recent FAA second-class medical certificate was issued in October 2017. AIRCRAFT INFORMATIONFAA records indicated that the accident helicopter was manufactured in 1978 and was equipped with a Rolls-Royce (Allison) 250-C20B turboshaft engine. VSC records indicated that as of June 30, 2018, the helicopter had accrued a total time in service of about 17,560 hours, and the engine had a total time of about 15,645 hours. The records also indicated that the accident engine had been removed from another VSC helicopter and installed in the accident helicopter on that date. METEOROLOGICAL INFORMATIONMeteorological information provided by VSC included wind speed less than 10 knots, visibility 10 miles, clear skies, and temperature 31°C. AIRPORT INFORMATIONFAA records indicated that the accident helicopter was manufactured in 1978 and was equipped with a Rolls-Royce (Allison) 250-C20B turboshaft engine. VSC records indicated that as of June 30, 2018, the helicopter had accrued a total time in service of about 17,560 hours, and the engine had a total time of about 15,645 hours. The records also indicated that the accident engine had been removed from another VSC helicopter and installed in the accident helicopter on that date. WRECKAGE AND IMPACT INFORMATIONThe wreckage was examined in Majuro about 2 months after the accident. The fuselage was mostly intact, but most of the tailboom was absent. All four landing gear struts and braces were attached to the fuselage. Crush and skin deformation were observed along the upper portions of the aft fuselage, tailboom fairing, and the upper aft left side of the cockpit. Both aft (cabin) doors were present and attached. Both front (cockpit) doors were absent, and damage patterns were consistent with those doors not being installed for the accident flight. Most windscreen and cabin Plexiglas were absent.

The cockpit retained most of its original volume. The "OFF/ON" key, battery switch, and start pump switch were all set to their respective "ON" positions, and the fuel valve handle was found in its open, fuel on position. No seat pan deformation of either forward seat was observed. Both seats were equipped with four-point harnesses. Both lap belts had been cut, presumably by ship personnel during rescue/recovery efforts. The harness webbing remained connected to the inertia reels, which operated normally.

Flight controls were installed only at the left cockpit station. Collective control continuity was verified to the top of the tunnel-routed control tube. The cyclic stick was connected to the lateral lower control tube and the lower bell crank, but the upper ends of the control tubes were fractured. The antitorque pedals remained attached and free to move. Continuity was established from the pedals to the upper end of the control tube.

Most of the tailboom, including the tail rotor, tail rotor transmission, and vertical and horizontal stabilizers, had separated from the helicopter and were not recovered. Both the tail rotor drive shaft and the tail rotor pitch control tube were truncated at the location of the tailboom separation.

The main rotor hub remained attached to the main rotor drive shaft, which remained splined into the main transmission. The helicopter had five main rotor blades. The red and white main rotor blades were wrapped around the rotor head multiple times. A 32-inch section of the yellow main rotor blade remained attached to the hub; the remaining section of the blade was absent. The blue and green main rotor blades were absent.

The main transmission was securely attached to the airframe, but was damaged by saltwater corrosion, and mechanically seized. No metal particles were observed on the transmission chip detectors. The engine-to-transmission drive shaft remained connected at both ends. The tail rotor drive shaft remained connected to the main transmission. No distortion or other abnormalities of the KAflex couplings were found. The freewheel unit was removed, and it manually rotated smoothly in one direction and locked in the other direction, consistent with the unit's design.

The engine remained securely mounted to the airframe with evidence of some external impact damage. The oil reservoir was overfilled, consistent with oil migration due to the helicopter being on its side while in transit to Majuro. The scavenge oil filter was clean, and a minor amount of sludge and a black plastic-like fragment were observed on the pressure oil filter element. Both engine chip detectors were free of ferrous material. Separately, the engine oil system was equipped with a check valve that could occasionally become stuck open, and permit oil to enter the engine gearbox. That oil would then be ejected or burned during engine start-up, but this condition would not have any adverse effect on normal engine operation.

Throttle and power turbine governor linkages were both continuous from the collective control to their respective engine components and moved freely. The compressor inlet and first-stage wheel showed no foreign object damage. The N1 rotor did not rotate in either direction. The N2 rotor did not rotate in the drive direction but rotated in the opposite direction. The 4th stage turbine wheel was undamaged. After the turbine module was separated from the gearbox, both the N1 and N2 rotors rotated freely.

All engine fuel line connections were secure, and all fuel lines contained fuel. A vacuum check of the fuel system did not reveal any air leaks. A leak check of the pneumatic system that controls engine power was attempted, but an obstruction in the power turbine governor Pc air input tee prevented a full test. According to the Rolls-Royce representative, this clogging was consistent with saltwater immersion. The engine fuel system components were removed, and the lines were inspected; no cracks or abnormalities were observed. The airframe and engine-mounted fuel filters had no contaminants. A total of 23 gallons of fuel was drained from the helicopter. A fuel sample was clear and straw colored, with no contamination or water visible.

All observed damage was consistent with water impact and immersion, and/or severing of the tailboom. The airframe and engine examinations did not reveal any pre-impact abnormalities

that would have precluded normal operation. ADD...