Taiwan´s Aviation Safety Council has concluded its investigation into the fatal TransAir Airways ATR 72-600 crash into the Keelung river in February last year, concluding that the accident was a result of many contributing factors, but ultimately attributes the disaster to the crew´s actions, the council said.
In its final report, the council says that during the aircraft´s initial climb after takeoff from Taipei Songshan airport, an intermittent discontinuity in the right-hand engine´s auto feather unit (AFU) may have initiated the automatic take-off power control system (ATPCS) sequence, resulting in the autofeather of the right-side engine.
The crew, however, failed to perform the necessary abnormal and emergency procedures to identify and correct the failure. This led the pilot flying to retard the power of the left-hand engine, ultimately shutting it down.
The loss of power and inappropriate flight control inputs generated a series of stall warnings, including the activation of the stick shaker and pusher. Still, the crew failed to immediately recognise the loss of power in both engines, and respond to warnings in-time.
Transcripts derived from the cockpit voice recorder suggest the crew, speaking in a mixture of English and Mandarin, failed to grasp the nature of the situation. There were three people in the cockpit: two captains and a first officer in the jump seat as an observer pilot.
Besides crew error, investigations also identified other contributing factors such as the airline´s flight operations processes and regulatory oversight of TransAsia by the Civil Aeronautics Administration.
The report adds that the intermittent signal discontinuity in the right engine´s AFU may have caused the ATPCS to not be armed during take-off roll, or was activated during the initial climb, which resulted in a complete ATPCS sequence including autofeathering. Evidence indicated that the discontinuity was likely caused by compromised soldering joints inside the AFU.