Introduction
On April 7, 2020, at approximately 1530 hours, a National Airborne Service Corps (NASC) AS-365 N2 helicopter, registration NA-103, crashed at Kaohsiung International Airport after losing control during a simulated tail rotor failure procedure. The aircraft sustained damage to the main rotor and overturned on the runway, but no occupants were injured. The five-person crew comprised a pilot-in-command (left seat, monitoring pilot), a copilot (right seat, flying pilot), a flight engineer, and two additional crew members.
Accident Sequence
The helicopter departed Kaohsiung at 1405 hours and flew to the Liugui area for routine training maneuvers between 4,000 and 1,000 feet. At approximately 1501, the crew began their return to the airport. At 1516, they contacted Kaohsiung Tower, requesting permission to perform simulated governor failure and tail rotor failure exercises after landing. The tower cleared the request, advising that Runway 09 was active with wind from 290 degrees at 9 knots. The aircraft was in a downwind condition as it approached for the simulated tail rotor failure procedure.
At about 1530, after entering the runway at low altitude and low speed, the helicopter experienced an uncontrolled right yaw and loss of attitude. The main rotor struck the ground, and the aircraft rolled left before coming to rest inverted on the runway.
Investigation Findings
The Taiwan Transportation Safety Board (TTSB) investigation concluded that the pilot-in-command lacked sufficient understanding of the characteristics and correct procedures for tail rotor failure. During the exercise, he failed to keep both feet on the directional control pedals, which prevented timely correction of the right yaw. This resulted in the helicopter losing level flight and striking the main rotor on the ground.
Additional findings included inadequate briefing for the training exercise, lack of detailed procedures for such briefings, deficiencies in training and checking programs, and gaps in safety management and crew resource management (CRM) training.
Probable Cause
The pilot-in-command had insufficient knowledge of tail rotor failure characteristics and complete operating procedures. During the simulated tail rotor failure, he did not follow the procedures and failed to keep both feet on the directional control pedals, leading to an uncontrolled right yaw and main rotor strike.