WPR14TA149 · Bell OH-58A

The intent of the public aircraft flight was to transport an injured dog from the Sheriff Department's K-9 division to an urgent care facility after it had been shot while on duty. After arriving at the Sheriff's Air Support Unit (ASU) headquarters about 0100, the pilot discussed the weather conditions with the on-duty command pilot and confirmed that visual meteorological conditions prevailed at both the departure and arrival airports. He was aware that a weather front was moving through the area and that he would likely encounter instrument meteorological conditions while en route. Therefore, he planned to use an airport about halfway along the route as a backup landing site if the weather conditions deteriorated. The pilot's decision to attempt the flight with known deteriorating weather conditions was likely due to self-induced pressure to complete the flight because of the dog's injury.

The departure was uneventful, but, as the helicopter approached the alternate airport, it encountered light rain, strong wind, low clouds, and fog. The pilot decided to proceed and see if the helicopter could traverse a pass east of the airport. However, once the flight got beyond the lights of the city, the pilot lost all visual reference after flying into clouds; the helicopter was about 500 ft above ground level at this time. He decided to slow the helicopter and initiate a gradual descent to exit the clouds. Unknown to the pilot, the windshield had misted up due to a water leak, which limited the effectiveness of the night vision goggles (NVG) that he and the tactical flight officer (TFO) were using for the flight. During the descent, the TFO realized that the windshield had fogged up because he could still see out of the side window, and the pilot turned on the de-mister. Shortly after, a highway came into view, and the helicopter struck its surface about 5 miles past the alternate airport. The helicopter bounced and then rotated about 180 degrees. It appeared to be handling normally, so the pilot chose to return to the alternate airport. Upon landing, he discovered that the helicopter had sustained substantial damage.

The weather conditions at the alternate airport were below the ASU minimums both before takeoff and during the flight. However, the ASU did not have formal risk assessment procedures in effect. The weather conditions at night and the misted windshield would have been conducive to the pilot's experiencing spatial disorientation.

Although the helicopter was equipped with a radar altimeter, its audible and visual alert functions were turned off at the time of the accident. If the pilot had used the radar altimeter, it would have given him an opportunity to react when the helicopter reached or descended below a predetermined altitude. The pilot, who was also the ASU's chief flight instructor, admitted that the typical effectiveness of the NVGs likely led to complacency on his part.

The pilot had been working the day leading up to the accident and had been awake for about 16 hours. He reported that he was about 2 hours into restful sleep when he was woken to perform the mission. Therefore, he attained minimal rest for the mission, which was performed during a time when he would otherwise be asleep and likely degraded his performance and decision-making ability.

Verbatim NTSB analysis and probable cause from the NTSB dataset