Investigation Summary
The aircraft, a Boeing 737-300, had a documented history of autothrottle issues in the days leading up to the accident. Maintenance records indicated that the right engine autothrottle had exhibited sluggish responses since November 20, 1992. During the descent towards Guilin, the crew engaged the autothrottle. As the captain attempted to level the aircraft at 7,000 feet by raising the nose, the autothrottle system attempted to increase power. However, the number 2 power lever failed to move from the idle position. To compensate for the lack of thrust from the right engine, the autothrottle advanced the number 1 engine further. The crew failed to recognize the asymmetrical thrust condition or the stationary number 2 throttle lever. The resulting yaw and roll forces caused the aircraft to bank nearly 90 degrees to the right. The crew was unable to recover from the upset at low altitude, and the aircraft impacted the mountain at high speed, resulting in total fragmentation of the airframe.
Final Conclusions
The investigation concluded that the primary cause was the crew's failure to monitor the engine instruments and power lever positions during a malfunction of the autothrottle system. The asymmetrical thrust created by the number 2 engine remaining at idle while the number 1 engine advanced led to a loss of control. Contributing factors included the known mechanical fault in the autothrottle system that had not been effectively repaired during previous maintenance actions.
Photographic Evidence (1)
Video Analysis
【歷史上的今天】1992.11.24_中國南方航空桂林空難機上有九名 ... — News report covering the crash of China Southern Airlines Flight 3943 near Guilin, which resulted in the deaths of all 141 people on board.
If playback is blocked, the owner has disabled embedding — use the link above.
Airframe & Maintenance
Systems & Failure Modes
Autothrottle
A system that automatically adjusts engine power levers to maintain a target airspeed or thrust setting. A malfunction caused the right lever to stick at idle during a critical phase of flight.
CFM56-3B-1 Engines
The twin turbofan engines produced asymmetrical thrust when one responded to autothrottle commands while the other remained at idle.
Interesting Facts
- 01The accident was the deadliest involving a Boeing 737-300 at the time of the occurrence.
- 02The aircraft was only 1.5 years old and had logged 4,165 flight hours.
- 03Maintenance logs from November 22 and 23 showed previous pilot reports of mechanical faults with the autothrottle.
- 04The impact was so severe that the aircraft was shattered into small fragments, and the flight data recorder was heavily damaged.
- 05The crash site was located approximately 20 kilometers south of Guilin Qifengling Airport.
Safety Actions & Advisories
Maintenance Procedures Review
The investigation highlighted the need for more effective resolution of recurring mechanical faults noted in pilot logs, specifically regarding the autothrottle system.
Location
ACCIDENT SITE · Coordinates taken from the wikidata coordinate.