What happened
On December 5, 2018, an Airbus AS365N3 helicopter, registration NA-106, operated by the National Police Agency National Airborne Service, was conducting an emergency medical evacuation mission approximately 11 nautical miles west of Pengjia Islet. The crew, consisting of a pilot, co-pilot, and flight engineer, was accompanied by two Coast Guard personnel for a joint maritime patrol mission.
During the recovery of a Coast Guard crew member via hoist, the hoist cable began to swing and became jammed against the right landing gear, preventing further retrieval. To resolve the jam, the crew decided to descend and attempt to hover near the water's surface, intending to use the tension of the person in the water to release the cable from the landing gear.
As the operation progressed into the night, the loss of ambient light and the absence of visual references made stable hovering difficult. During the descent, the aircraft's ground speed fluctuated significantly, and the rescue worker was struck by the sea surface twice. Upon being recovered into the cabin, the crew member was found unconscious with severe internal injuries and fractures. Despite performing CPR during the flight back to Songshan Airport, the individual later succumbed to their injuries.
The investigation
The Taiwan Transportation Safety Board (TTSB) examined flight data, GPS records, and onboard video to reconstruct the sequence of events. The investigation focused on the aircraft's ability to maintain a stable hover in darkness and the lack of specific operational limitations for nighttime maritime hoisting using the AS365N3 model. The investigation also reviewed the communication between the flight crew, the ground command center, and the vessel involved in the medical evacuation.
Findings
- The primary cause of the injuries was the failure to maintain a stable hover during the cable release attempt, which resulted in the rescue worker impacting the water surface with significant force.
- The aircraft lacked an automatic hovering function, and the crew had not received specific training for nighttime maritime hoisting under these exact failure conditions.
- The loss of visual references after sunset made it impossible for the pilot to accurately judge altitude and ground speed, leading to uncontrolled vertical and horizontal movements.
- There were no clear organizational regulations within the National Airborne Service prohibiting the use of the AS365N3 for nighttime maritime hoisting or requiring mission termination after dusk.
- Inadequate communication and preparation on the target vessel delayed the initial hoisting process, pushing the operation into the high-risk period of darkness.