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China Airlines 006

Accident Case Study

The NTSB report touches on all the issues but dances around them when it comes to finding causation. Perhaps a list by topics would help:

  • Engine failure procedures. When a turbulence-induced airspeed excursion in cruise flight caused the autothrottles to bring all four engines to a lower setting and then a high setting, engines 1, 2, and 3 accelerated normally while #4 struggled to keep up. As a result, the first three engines achieved maximum EPR to make up for the lagging #4. The #4 engine was "hung" at near idle. Since the other three engines were looking for maximum EPR, they shed some of their bleed air loading which #4 assumed, further degrading its performance. The flight engineer attempted a relight at altitude, FL 410, but the correct procedure would have been to descend to FL 300 or below. The flight engineer also forgot to shut off the #4 engine bleeds as required by procedure, which would have made the start that much more difficult.
  • Aircraft control. As engines #1, #2, and #3 went to full power and the #4 to sub idle, the aircraft banked to the right, as would be expected. The captain did not add corrective rudder and instead kept the autopilot engaged and focussed on the decaying airspeed. They requested and were cleared to a lower altitude, which the pilot selected on the autopilot, keeping it in control with no rudder input. When he finally disengages the autopilot, still with no rudder input, the aircraft snaps right and steepens its dive into the clouds.
  • Unusual attitude recognition and recovery. Before departing controlled flight, the aircraft control wheel was deflected 22° left while the aircraft was in a 23° right bank. In just 33 seconds the aircraft rolled 64° and pitched to 68 degrees down to lose over 10,000 feet. The airplane then rolled on its back. Throughout this, the crew became convinced that all three attitude indicators were faulty. (They were not.) The airplane lost another 10,000; while pulling as much as 5 Gs. The captain was not able to recover until they popped out of the clouds at 10,000'.
  • Crew Resource Management. The captain did not assign any duties to the first officer other than to make a radio call during the build up to and moments during the aircraft upset. Nobody was focussed on flying the aircraft.

The crew were hailed as heroes for getting the airplane on the ground without killing anyone. It would soon become apparent that they took an event that should have been nearly routine, an engine relight, and almost lost the airplane with everyone on board. But how could this be? Once again the NTSB report doesn't say, but reading the report objectively leads to a few conclusions:

  • Training. China Airlines did not require unusual attitude recognition and recovery training for its crews, nor did it emphasize cockpit duties delegation during an abnormal situation.
  • Fatigue. The captain had crossed eighteen time zones during six flights in six days and the mishap occurred during his circadian low.

 

images

Figure: Photograph of Empennage, from NTSB Report, Figure 8

Accident Report

  • Date: 19 FEB 1985
  • Time:
  • Type: Boeing 747SP-09
  • Operator: China Airlines
  • Registration: N4522V
  • Fatalities:0 of 23 crew, 0 of 251 passengers
  • Aircraft Fate: Repaired
  • Phase: En route
  • Airports: (Departure) Taipei-Chiang Kai Shek International Airport (TPE/RCTP), Taiwan; (Destination) Los Angeles International Airport, CA (LAX/KLAX), United States of America

Narrative

The flight from Taipei to about 300 nmi northwest of San Francisco was uneventful and the airplane was flying at about 41,000 feet mean sea level when the No. 4 engine lost power. During the attempt to recover and restore normal power on the No. 4 engine, the airplane rolled to the right, nosed over, and entered an uncontrollable descent. The captain was unable to restore the airplane to stable flight until it had descended to 9,500 feet. After the captain stabilized the airplane, he elected to divert to San Francisco International Airport, where a safe landing was made. Although the airplane suffered major structural damage during the upset, descent, and subsequent recovery, only two persons among the 274 passengers and crew on board were injured seriously.

The maximum vertical acceleration forces recorded during the descent were 4.8Gs and 5.1Gs as the airplane descended through 30,552 feet and 19,083 feet, respectively.

Probable Cause

"The captain’s preoccupation with an inflight malfunction and his failure to monitor properly the airplane’s flight instruments which resulted in his losing control of the airplane. Contributing to the accident was the captain’s over-reliance on the autopilot after the loss of thrust on the no. 4 engine."

See Also:

Crew Resource Management

Desynchronosis

Unusual Attitudes

References

Aviation Safety Network

Air Crash Investigations: Panic Over the Pacific, Cineflix, Episode 31, Season 4, No. 6, 20 May 2007

NTSB Aircraft Accident Report, AAR-86/03, China Airlines Boeing 747-SP, N4522V, 300 Nautical Miles Northwest of San Francisco, California, February 19, 1985

Revision: 20140326
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