Introduction
On February 5, 2018, at approximately 2348 local time, a UH-60M helicopter operated by the National Airborne Service Corps (NASC) departed Lanyu Airport on a medical evacuation mission to Taitung Fengnian Airport. The aircraft, registration NA-706, carried six occupants: a pilot, a co-pilot, a flight engineer, a patient, a patient's family member, and a nurse.
Sequence of Events
About 81 seconds after takeoff, the helicopter lost contact with air traffic control, and its radar blip disappeared from the radar screen. The aircraft was reported missing.
Wreckage Recovery
Underwater search efforts detected the flight recorder's underwater locator beacon signal on February 9. On March 5, the wreckage was located about 2 nautical miles west of Lanyu Airport at a depth of approximately 1,000 meters using a remotely operated vehicle. The wreckage was recovered on April 12. Examination of the wreckage revealed that the cockpit and tail section were missing. Two occupants were found dead, and four remain missing.
Findings and Probable Cause
The investigation identified that the flight crew's threat management, situational awareness, communication, and decision-making abilities were insufficient, and they lacked adequate understanding of the aircraft systems. During the night takeoff in variable wind conditions, they did not use the appropriate takeoff mode and failed to maintain a safe climb attitude and speed. When encountering turbulence, they did not promptly interpret changes in altitude and speed or take correct corrective actions, possibly experiencing spatial disorientation. At low altitude, while attempting to correct low airspeed by lowering the nose, they applied excessive power and pitch-down angle, causing the aircraft to impact the sea in a controllable state.
Safety Recommendations
The investigation issued multiple safety recommendations to the NASC, including improving crew training in threat management, situational awareness, and system knowledge; establishing instrument flight and night flight training requirements; reviewing training program completeness and resources; ensuring consistency and completeness of flight operations manuals; setting weather minimums for night medical evacuation flights; developing crew resource management training materials; and verifying the accuracy of certain flight data recorder parameters. A recommendation was also made to the Civil Aeronautics Administration to enhance runway lighting and guidance for nighttime emergency medical takeoffs and landings at Lanyu Airport.