Hughes 369 N81GG accident near Pukoo, Hawaii

Probable cause

The pilot's decision to continue visual flight into an area of instrument meteorological conditions at night in rain, which resulted in his geographic disorientation and controlled flight into terrain.

NTSB analysis

The airline transport pilot and passenger departed on an expected 30-minute visual flight rules flight that was destined for the pilot's private helipad and residence on the southeast side of a neighboring Hawaiian island. Before the flight, the pilot's mechanic asked the pilot not to fly due to the weather at the intended destination, but the pilot insisted on flying. The National Weather Service forecast products that were available before the flight indicated a trade wind pattern that would bring bands of rain, low visibility, and mountain obscurations to the eastern slopes of the islands, but it is unknown if the pilot reviewed these products or any other forecast of expected weather conditions along the flight route. One witness stated that the pilot routinely flew at night to his helipad and that she had previously seen the pilot's helicopter operating in dark adverse weather conditions. Several witnesses reported seeing the helicopter fly over their locations in dark conditions with wind and rain. Two witnesses reported that they saw the helicopter make an approach to a ridgeline near the pilot's helipad, but then the helicopter disappeared from view because of a cloud or terrain.

Meteorological data revealed that a line of rain showers moved over the accident site at the accident time. The reduced visibility and ceiling as the line of rain showers moved east to west over the rising mountain terrain likely resulted in instrument meteorological conditions and mountain obscuration conditions.

The helicopter wreckage was discovered 0.75 mile upslope of the intended destination. Tree and ground impact marks indicated a relatively level descent to the ground at an approach angle of about 18° on a 310° heading, which is indicative of impact with terrain in controlled forward flight. The helicopter was destroyed by impact forces and a postcrash fire. Examination of the wreckage revealed no evidence of any preimpact failures or malfunctions of the engine, drive train, main rotor, tail rotor, or structure of the helicopter. Damage to the mast support structure, main rotor hub, main rotor blades and upper flight controls is consistent with power-on main rotor blade impact damage.

Given the weather conditions and witness observations, the pilot encountered dark instrument meteorological conditions and rain while flying in an area of rising terrain as he likely searched for the helipad at his residence, which was outfitted with various lights that would have been difficult to see in reduced visibility. The pilot did not have the visual cues necessary to maintain clearance above the ground, resulting in geographic disorientation, which subsequently led to controlled flight into terrain.

Text from the NTSB. Open the NTSB docket for WPR17FA021 for the full record.