Investigation Summary
Before departure, the crew identified a failure in the Right Hand (RH) Main Bus. According to the aircraft's Minimum Equipment List (MEL), takeoff is prohibited with an inoperative main bus, yet the captain elected to proceed to reach a maintenance base. The failure disabled the autopilot, yaw damper, and several flight instruments including the right-hand EFIS and both the LH/RH Flight Directors, leaving the crew with severely degraded attitude references. Additionally, the failure caused the No. 2 engine anti-ice start bleed valve to remain open, creating a temperature split between the engines. During the climb, the crew attempted to equalize engine temperatures by reducing the right power lever, which created a significant torque asymmetry. Without the yaw damper or active rudder input, the aircraft began a slow roll to the right. The captain, who had been on duty for over 11 hours and completed nine previous flights that day, suffered from fatigue and spatial disorientation. In the darkness and IMC, he failed to recognize the developing bank and eventually exacerbated the roll with incorrect aileron inputs. The aircraft reached a bank angle of 161 degrees and a pitch of 65 degrees nose-down before impacting the water at high speed.
Final Conclusions
The Republic of China Civil Aeronautics Administration (CAA) released the final accident report on June 5, 2001. The investigation concluded that the primary cause was the flight crew's failure to maintain situational awareness, resulting in the loss of aircraft control. Contributing factors included the failure of the RH main electrical bus, the crew's non-compliance with the MEL and standard operating procedures, and the captain's fatigue and spatial disorientation while operating in night IMC conditions.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Crew Experience
Captain
Former Air Force veteran; line instructor.
First Officer
In line training at the time of the accident.
Observer First Officer
Promoted to captain training; familiarization flight.
Systems & Failure Modes
RH Main Bus
The primary electrical distribution point for the right side of the aircraft; its failure disabled the autopilot, yaw damper, RH EFIS, and both Flight Directors.
Yaw Damper
A system that automatically provides rudder inputs to dampen oscillations; its failure required the pilot to manually coordinate turns, which was not performed.
Electronic Flight Instrument System (EFIS)
The digital cockpit display system; the failure of the RH Main Bus caused the RH EFIS to go black or flag, depriving the First Officer of primary attitude information.
Anti-ice Start Bleed Valve
The No. 2 engine valve failed to the open position due to the electrical loss, causing a 15 degree C ITT increase and leading the crew to create a torque asymmetry while trying to compensate.
Interesting Facts
- 01The captain had been on duty for over 11 hours and was on his tenth flight of the day.
- 02The aircraft was operated in violation of the Minimum Equipment List (MEL) which required the main electrical buses to be functional.
- 03The First Officer was in line training and had only 44 hours of experience on the Saab 340.
- 04The failure of the RH Main Bus caused the right-side EFIS to go black, depriving the First Officer of attitude information.
- 05The aircraft impacted the water with a bank angle of 161 degrees right and a pitch of 65 degrees nose down.
Safety Actions & Advisories
MEL Compliance Reinforcement
The investigation emphasized the critical importance of adhering to the Minimum Equipment List, particularly regarding primary electrical systems.