What happened
On a night flight departing from Hsinchu for Kaohsiung, the crew operated an aircraft following the discovery of a failure in the right-hand main bus during pre-flight checks. This electrical failure rendered several critical systems unavailable, including the autopilot, the yaw damper, and certain flight instruments such as the left-hand EFIS and flight director. Despite the fact that the Minimum Equipment List prohibited takeoff with an inoperative main bus, the decision was made to proceed with the flight under IMC conditions.
During the initial climb phase, the aircraft experienced significant aerodynamic issues. Following takeoff at 19:2-09, the pilot manually adjusted the right power lever angle to address an ITT temperature split between the engines. This adjustment caused a torque imbalance of over 13% between the engines, creating a force that induced a yaw and roll to the right. As the aircraft climbed, the crew's ability to monitor the flight was severely hampered by the lack of functional electronic displays.
The aircraft began to deviate from its assigned departure route, turning right while the crew reported a left heading. The pilot's workload increased significantly due to the necessity of manual flight without autopilot or yaw-damper assistance. As the flight progressed, the pitch and bank angles reached extreme, uncontrolled values. The aircraft entered a steep descent with increasing airspeed and sink rate, eventually impacting the sea.
Findings
- The crew failed to maintain situational awareness, leading to the loss of control.
- The failure of the right-hand main electrical bus caused malfunctions in navigation systems and flight instruments.
- The crew did not adhere to the Minimum Equipment List regarding the inoperative bus.
- The pilot operated the aircraft while suffering from fatigue and spatial disorientation.
- Flight operations were conducted in night-time IMC conditions with limited visual references.
- Standard operating procedures were not followed by the flight crew.