Artist's conception of N4522V, rolling through an inverted attitude, as the main body gear are forced down, seen through a break in the clouds during its rapid descent.
|Date||February 19, 1985|
|Type||No. 4 engine failure, crew error, crew fatigue, jet lag|
|Site||Over the Pacific Ocean near San Francisco, California U.S.A.|
|Aircraft type||Boeing 747SP-09|
|Flight origin||Taiwan Taoyuan International Airport|
|Destination||Los Angeles International Airport|
China Airlines Flight 006 (callsign "Dynasty 006") was a daily non-stop flight departing from Taipei at 4:15 pm and scheduled to arrive at Los Angeles International Airport at 7:00 am local time. On February 19, 1985, it was involved in a jet upset accident. The plane rolled over and plunged 30,000 ft (9,100 m), experiencing high speeds and G-forces (approaching 5 Gs) before the captain was finally able to recover from that rapid dive, and then to divert to San Francisco International Airport.
The accident occurred some ten hours into the regular service between Taipei and Los Angeles. The Boeing 747SP-09 was 350 miles (550 kilometers) to the northwest of San Francisco, cruising at an altitude of 41,000 ft (12,500 m). The flight crew consisted of captain Min-Yuan Ho, first officer Ju Yu Chang, flight engineer Kuo-Win Pei, relief captain Chien-Yuan Liao, and relief flight engineer Shih Lung Suwere. The accident sequence began when the No. 4 engine stalled at a low thrust setting, and then flamed out. That same engine had failed twice during previous flights (both while cruising at FL 410 & 430, respectively). In each of those cases, the engine was restarted, after descending to a lower altitude. The maintenance response to those logbook entries, was engine inspection, fuel filter drained and then replaced, vane controller inspected and then replaced, water drained from mach probes, and other filters replaced. None of those actions cured the recurrent stalling and flameout problem of the No. 4 engine..
The Captain instructed the flight engineer to attempt a restart of the No. 4 engine, while the plane remained at FL 410, with the autopilot still engaged. That was contrary to the flight manual procedure, which required the plane to be below 30,000 feet (9,100 m), before attempting to restart a flamed out engine. The restart attempt failed.
The airspeed continued to decrease, while the autopilot (AP) rolled the control wheel to the maximum left limit of 23 degrees. As the speed decreased even further, the plane began to roll to the right, even though the AP was maintaining the maximum left roll limit of 23 degrees. By the time the captain disconnected the AP, the plane had rolled over 60 degrees to the right and the nose began to drop. Aileron control was the only means available to the AP, to keep the wings level, as the AP does not connect to the rudder during normal cruise flight. To counteract the asymmetrical forces created by the loss of thrust from the No. 4 engine, it was essential for the pilot to manually push on the left rudder. However, the captain failed to use any rudder inputs at all, before or after disconnecting the AP. The resulting uncontrolled flight path is depicted in the diagram to the left.
The Captain's attention was drawn to the artificial horizon since it showed a vertical horizon which was also displayed by the First Officer's instrument, thus ruling out the possibility of an instrument failure. At this point the aeroplane was inside clouds, preventing visual cues for orientation. The aeroplane entered a steep dive at a high bank angle. Altitude decreased 10,000 ft (3,000 m) within only twenty seconds. The crew and passengers experienced g-forces reaching as much as 5g.
Only after breaking through the bottom of the clouds at 11,000 feet (3,400 m) could the captain orient himself and bring the plane under control, leveling out at 9,600 feet (2,900 m). They had descended 30,000 ft (9,100 m) in under two and a half minutes. The flight crew were under the impression that all four engines had flamed out, but the National Transportation Safety Board believes only engine No. 4 had failed. After leveling out the three good engines were giving normal power and a restart attempt brought No. 4 back into use. They began climbing and reported to air traffic control "condition normal now" and they were continuing on to Los Angeles. They then noticed that the inboard main landing gear were down and one of the plane's hydraulic systems was empty. Because they didn't have fuel to reach Los Angeles with the drag added by the landing gear, they diverted to San Francisco. Learning there were injured people on board, an emergency was declared and they flew straight in to the airport and landed without further incident to the plane and passengers.
There were two injuries. One was a fracture and laceration of a foot; the other acute back strain requiring two days of hospitalization. The aircraft was significantly damaged by the aerodynamic forces. The wings were permanently bent upwards by two inches, the inboard main landing gear lost two actuator doors, and the two inboard main gear struts were left dangling. Most affected was the tail, where large outer parts of both horizontal stabilizers had been ripped off. The entire left outboard elevator had been lost along with its actuator, which had been powered by the hydraulic system that ruptured and drained.
After substantial investigation, this accident brought to international attention the problem of jet lag as a contributing factor to pilot errors. The captain was considered to be highly experienced and had flown six international flights in the previous two weeks. Though he testified that he did not believe he was tired, NTSB investigators suggest that his inability to sleep during his rest period and the fact that the accident took place at 2 am Taipei time contributed to his inability to focus on and process important details about the aircraft's behavior that could have averted the accident.
After repairs were made to correct the significant damage to the plane, it returned to service on April 25, 1985. It continued in service for nearly 12 years until it was leased to China Airlines' sister company, Mandarin Airlines, on January 1, 1997. Later, it was owned and operated by Global Peace Initiative. As of February 1, 2007, the aircraft involved in this accident is reportedly for sale.