NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
After the commercial pilot received an emergency medical services helicopter flight request, he quickly (in about 20 seconds) assessed the weather conditions and accepted the flight. No records were found indicating that the pilot obtained an official weather briefing before departing on the flight, and the investigation could not determine which weather resources the pilot used to assess the weather. About 8 minutes later, the pilot called the company's operations center to report that the flight was departing; this was the last communication received from the pilot. The helicopter was operating in an area that was known by company pilots, including the accident pilot, to have the potential for low visibility, even though there were no airport weather reporting facilities or Doppler radar coverage in the area.
A review of GPS data showed that, while en route to pick up the patient, the helicopter performed a slight descending 360° turn before continuing toward the hospital. Weather overlays with the GPS track indicated that the helicopter made the 360° turn about the same time that an outflow boundary wave, which could have increased the potential for windshear and strong updrafts and downdrafts and reduced ceilings and visibility. Following the 360° turn, the helicopter proceeded toward the destination. About 14 minutes later, the helicopter turned right and began flying toward a major highway. It is likely that, due to the reduced visibility in the area, the pilot was flying toward the highway to follow the lights toward the city. The helicopter then turned further right and began to climb. As the helicopter entered another outflow boundary wave, it turned left. The left turn tightened, and the helicopter began to rapidly descend into terrain. The helicopter impacted a mesa in a near-level attitude.
A review of a company communication recording showed that, about 17 minutes after the estimated accident time, the operations center attempted to contact the flight crew and was unsuccessful. The company sent three company helicopters to the accident helicopter's last known position; one helicopter pilot flew near the helicopter's site but was unable to see anything, and the two other pilots could not proceed close to the accident site due to clouds and low visibility. The wreckage was subsequently located by local law enforcement. A postaccident examination of the helicopter and engine did not reveal any anomalies that would have prevented normal operation.
Due to mid- and low-level cloud cover, it is likely that no lunar or celestial lighting was available for amplification by the pilot's night vision goggles (NVG). Since the helicopter was not equipped with an infrared spotlight, only cultural light would have been available for NVG amplification. However, the helicopter was operating in a remote, sparsely populated area with minimal cultural light. Although the pilot's recurrent training included recovery procedures from inadvertent entry into instrument meteorological conditions (IMC), and his training records showed that he satisfactorily completed this item on his most recent training flight about 8 months before the accident, the circumstances of the accident are consistent with the pilot's inadvertent visual flight into IMC, which resulted in a loss of helicopter control.