What happened
On April 13, 2017, a TransAsia Airways DHC-6-400 (registration B-55571) was operating a scheduled passenger flight from Taitung Airport to Lanyu Airport. The flight, designated DA7511, carried 16 passengers and three crew members.
At approximately 16:32 local time, the aircraft landed on Runway 13 at Lanyu Airport. During the landing roll, the aircraft began to veer to the left. In an attempt to correct the directional deviation, the pilot applied right rudder and attempted to use differential thrust. However, the pilot mistakenly increased the left engine' and reverse thrust to maximum. This unintended increase in left-side reverse thrust exacerbated the leftward drift, causing the aircraft to exit the runway and collide with the airport perimeter fence, resulting in substantial damage to the aircraft. There were no injuries to the 19 people on board.
The investigation
The Taiwan Transportation Safety Board (TTSB) examined the aircraft's flight data, engine performance records, and the pilot's training history. The investigation focused on the interaction between the wind conditions, the pilot's control inputs, and the airline's training protocols. Investigators reviewed the aircraft's maintenance logs, which showed no mechanical failures in the engine control or braking systems prior to the event. The investigation also scrutinized the airline's Safety Management System (SMS) and the regulatory oversight provided by the Civil Aviation Administration (CAA).
Findings
- The aircraft landed in a left crosswind, which initially caused the nose to point left.
- The pilot mistakenly increased left reverse thrust to maximum while attempting to use differential thrust to correct the leftward drift, which significantly worsened the excursion.
- The pilot was relatively new to the aircraft type, and both the pilot and the airline's crew lacked sufficient experience and standardized training regarding the effective use of differential thrust during landing rolls.
- TransAsia Airways lacked detailed guidance documents and standardized training for crew members regarding the timing and application of differential thrust during landings.
- The airline's Safety Management System (SMS) was found to be ineffective in identifying safety hazards, and there were deficiencies in the oversight of flight crew training and evaluation processes.
- The Civil Aviation Administration's oversight of the airline's self-inspection processes was insufficient to detect existing operational deficiencies.