WPR18LA010

A descent and subsequent impact with open ocean waters for reasons that could not be determined based on the available information.

During a night instructional flight in the helicopter, the commercial pilot receiving instruction and the flight instructor departed and flew uneventfully to an adjacent island, where they conducted a practice instrument approach to an airport before they initiated the published missed approach procedure. As the flight reestablished radio communication with air traffic control, the pilots obtained an instrument flight rules clearance for their return to the departure airport. Radar and radio contact with the helicopter were lost shortly thereafter. Air units from the United States Coast Guard and a local fire department located some floating debris in the ocean the night of the accident and the day following the accident, respectively. The wreckage was located about 12 months following the accident submerged in the Pacific Ocean at a reported depth of 298 ft. A portion of the located wreckage was recovered about 3 months later. A postaccident examination of the recovered wreckage revealed no evidence of any preexisting mechanical malfunctions that would have precluded normal operation of the airframe or engine. Weather radar depicted an area of moderate-to-heavy rain showers along the helicopter's flight path about the time radar and radio contact were lost. Although the pilots had access to sufficient weather information to properly plan their flight around the weather and could have asked for further assistance in avoiding the weather from air traffic control, they elected to fly into an environment favorable to unexpected changes in wind direction and speed due to heavy rain showers, which could result in localized instrument meteorological conditions; however, because only a portion of the wreckage was recovered, the reason for the helicopter's sudden descent and impact with open ocean waters could not be determined.

At 1854, the recorded weather conditions at PHMK, located 6.3 miles southeast of the last radar target, included wind from 030° at 8 knots gusting to 21 knots, 10 statute miles visibility, light rain, few clouds at 3,300 ft above ground level (agl), a broken cloud ceiling at 6,000 ft agl, a broken cloud layer at 7,000 ft agl, temperature 24°C, dew point 20°C, and an altimeter setting of 30.04 inches of mercury. The closest National Weather Service (NWS) Weather Surveillance Radar-1988, Doppler (WSR-88D) to the accident site was the Molokai, Hawaii, radar (PHMO), which was located 6 nm south-southwest of the accident site at an elevation of 1,363 ft. The WSR-88D captured base reflectivity imagery at 1917 and 1918 (shown in figures 1 and 2, respectively; the black line shows the helicopter's flight path). The imagery depicts moderate-to-heavy values of reflectivity within the vicinity of the last radar target. Rain showers and convective clouds produce outflow boundaries and gust fronts throughout their life cycle. An outflow boundary or gust front can create an environment favorable for unexpected changes in wind direction and speed. There were no lightning strikes in the vicinity of the last radar target around the time of the accident. Figure 1: WSR-88D base reflectivity imagery at 1917 Figure 2: WSR-88D base reflectivity imagery at 1918. The NWS office in Honolulu, Hawaii, issued an Area Forecast Discussion (AFD) at 1600, which was the closest AFD to the accident time. The aviation section of the AFD discussed that the trade winds would bring strong gusty northeast winds; AIRMET Tango was valid for temporary moderate turbulence. Scattered rain showers were forecast to continue through the day with reduced ceilings and visibility in the showers. A search of official weather briefing sources revealed that neither pilot requested an official weather briefing from Leidos or DUATS; however, one of the pilots requested ForeFlight weather information at 1803. The weather information from ForeFlight contained the most recent METARs, AIRMETs, PIREPs, Area Forecast, TAFs, and Winds Aloft Forecast. It is unknown if either pilot checked any additional weather information before or during the accident flight. For further meteorological information, see the weather study in the public docket for this investigation. Flight Instructor The flight instructor, age 24, held a commercial pilot certificate with rotorcraft-helicopter and instrument helicopter ratings. In addition, he held a flight instructor certificate with rotorcraft-helicopter and instrument-helicopter ratings. The flight instructor was issued a second-class FAA medical certificate on January 5, 2017, with the limitation, "must wear corrective lenses." On the application for that medical certificate, the flight instructor reported a total flight experience of 630 hours, of which 300 hours were in the previous 6 months. Pilot Receiving Instruction The pilot receiving instruction, age 27, held a commercial pilot certificate with a rotorcraft-helicopter rating. He held a second-class FAA airman medical certificate that was issued on June 2, 2017, with the limitation, "must wear corrective lenses." On the application for that medical certificate, the pilot reported a total flight experience of 139 hours. Review of the pilot's flight training records revealed that, as of the most recent entry, dated October 12, 2017, he had accumulated a total of 186.9 hours of flight experience, of which 18.5 hours were in the previous 30 days. A private company hired by an individual to locate the helicopter reported that, in October 2018, they initially located the wreckage submerged about 2 miles offshore of Molokai at a depth of 298 ft. A representative from the company reported that they recovered a portion of the wreckage on January 24, 2019. Review of video recordings from an underwater remotely-operated vehicle showed that the fuselage was severely fragmented and partially embedded within the ocean floor. Both main rotor blades remained attached to the hub, which remained attached to the drive shaft. Both main rotor blades appeared to be straight with visible damage to the tip of one blade. The main rotor pitch link on one blade remained attached to the blade and swashplate, the other was not visible. The main rotor drive shaft was bowed on the lower end. The tailboom was impact damaged and the tail rotor gearbox was separated. The tail rotor drive shaft remained inside the tailcone. The tail rotor drive shaft was disconnected about 10 inches aft of the intermediate flex coupling and appeared angular and jagged. The intermediate flex coupling was not bent or distorted. No visible damage to the grooves of the upper sheave were observed. The forward flex coupling was disconnected/fractured from the clutch shaft. The skid assemblies were separated. Portions of the fuel system, cyclic, and collective controls were not observed. The recovered airframe components included the tail rotor gearbox, tail rotor blades, main rotor flight control jack shaft, tail rotor pedals including one removable pedal, several sections of interior panels, one section of aft left door frame (including a seatbelt), one forward seatbelt shoulder harness, all three main rotor flight control servos, hydraulic reservoir housing, several small sections of frame tubing, a small section of tail rotor flight control tubes, several small sections of main rotor gearbox housing, main rotor gearbox driveshaft bearing race, several instruments (one unidentified, compass housing, portion of the directional gyro), the warning light control box, a short section of fuel line with a portion of the fuel valve attached, a portion of the fuel cross-over fuel line, two landing light housings, a short section of a wire bundle, a section of the tail rotor guard, one V belt, and one life vest. One forward hydraulic servo was separated from its mount. The other forward servo remained attached to the mount; however, the mount was separated from the airframe. The aft servo was separated from the airframe and was severely bent (in excess of 120°). None of the servos could be actuated by hand. The jackshaft was separated from its mount. The tail rotor assembly was recovered separately from the airframe. The pilot's side right pedal was fractured at the bearing block. The pedal was recovered separately. The pilot's side left pedal pip/quick release pin was found displaced from the adjustable pedal assembly and exhibited no damage or bending. No damage was observed to the pedal pin holes. The tail rotor gearbox was separated from the tailcone. The mounting flanges on the gearbox, along with a portion of bulkhead, were fractured and exhibited signatures consistent with overload. No additional damage was noted to the gearbox. The input and output shafts rotated more than 360° by hand with no anomalies noted. Blue oil was observed in the gearbox sight gauge. The chip detector revealed no evidence of any metallic chips. The output shaft was straight. The tail rotor pitch control would not move by hand. Both tail rotor blades were bent outward 90° near the blade root, with overload fractures in the area of the bends. One blade exhibited leading edge impact damage and the tip cap was missing. The aft flex coupling was disconnected at the flex plate ears. The remaining yoke ears on the input shaft were bent 45°. The mounting hardware remained secure. The main rotor gearbox housing exhibited angular and jagged fracture surfaces. There was no evidence of any mechanical damage to the recovered inside areas of the main rotor gearbox housing. The airframe tube sections exhibited overload signatures on all the fracture surfaces and were bent/distorted. The section of the aft rear doorframe exhibited severe wrinkling along with overload signatures on all fracture surfaces. Portions of the airframe that r