From: lmiller@aero.org (Lawrence H. Miller)
Subject: Re: CAL 747 (Re: Coffee cups in the cockpit (Re: A320 yarns))
Organization: The Aerospace Corporation, El Segundo, CA
Date: Tue, 28 Jul 1992 17:34:39 GMT


Just to set the record straight, from the NTSB accident report
NTSB/AAR-86/03
China Airlines Boeing 747-SP, N4522V
300 Nautical Miles Northwest of
San Francisco, California
February 19, 1985


In article <168324152.M21208@mwvm.mitre.org> M21208@mwvm.mitre.org writes:
>>
>Center at the time, and knew the controller involved.  As I recall, the
>aircraft was at FL410 with the autopilot in speed hold mode.

	Actually, Performance Management System (PMS) mode.
	More importantly, as we shall see, lateral guidance
	is controlled only through ailerons, not through rudder.

>Due to turbulence
>the autothrottles were jockeying the power around to try to hold a constant
>Mach, and the #4 engine failed to reaccelerate ("hung") as the power was
>increased after a reduction.  The FE (incorrectly) announced a flameout, and
>the crew began restart procedures even though Boeing stated that the maximum
>restart altitude was something like FL300.  In the meantime, nobody was minding
>the store while the autopilot diligently tried to hold M0.85 and heading on
>three engines at FL410.  (Not for long!)  Eventually the captain decided
>to get with it, but the aircraft stalled and rolled into the dead engine
>almost simultaneously.

	Actually, the pilot was concentrating on the airspeed, which
	was fluctuating substantially.  Eventually (after about 3 minutes)
	the pilot turned off the autopilot in order to disengage the
	speed hold mode.  Here's where the control problems started: the
	autopilot had been holding about a 23 degree left wing down
	wheel deflection.  Correct manual engine-out control input is
	to counter with rudder away from the failed engine, and also with
	a very small wheel deflection away from the failed engine.

	Once the autopilot was disconnected, and with the pilot's attention
	still on the airspeed, the aircraft continued to roll out of
	control.  The pilots now believed the attitude indicators had failed.
	The aircraft never did stall, but it ended up in a pitch down
	as much as -67 degrees, and completely rolled vertically.

	The pilot regained control when the aircraft emerged from 
	the clouds at about 9500' and he could see the horizon.

>Definitely a CRM problem, along with some (literally) incredible airmanship.
>What interface problems were brought out?  (I don't have the report at hand...)

	Here are the conclusions from the NTSB report:

				3. CONCLUSIONS
	3.1	Findings
		1.  The flightcrew was properly certificated and qualified.

		2.  The changing airspeeds encountered by Flight 006 and the
		    resultant compensating throttle adjustments were caused
		    by wind speed variations.

		3.  The No. 4 engine did not flame out, but "hung" at about
		    1.0 EPR.

		4.  During his attempt to recover the No. 4 engine, the
		    flight engineer did not close the bleed air valve switch
		    before advancing the No. 4 throttle.
		
		5.  The other three engines did not lose thrust nor did they
		    flame out.


		6.  The captain did not disengage the autopilot in a timely
		    manner after thrust was lost on the No. 4 engine.  The
		    autopilot effectively masked the approaching onset of the
		    loss of control of the airplane.
		
		7.  The captain was distracted from his flight monitoring
		    duties by his participation with the flight engineer in
		    the evaluation of the No. 4 engine's malfunction.

		8.  With the exception of the loss of thrust on the No. 4
		    engine, no other airplane malfunction affected the
		    performance of the airplane; the loss of thrust on the
		    No. 4 engine did not contribute to the accident.

		9.  The captain was also distracted by his attempts to arrest
		    the airplane's decreasing airspeed, and this also
		    contributed to his failure to detect the airplane's
		    increasing bank angle.

		10. The lateral control deflections required to maintain
		    level flight under conditions of thrust asymmetry and
		    decreasing airspeed exceeded the limits of the autopilot's 
		    lateral control authority, causing the airplane to roll
		    and yaw to the right.  The captain lost control of the
		    airplane when, after disengaging the autopilot, he failed
		    to make the proper flight control corrections to recover
		    the airplane.

		11. The damage to the airplane was a result of the acceleration 
		    forces and high airspeed that occurred during the upset and
		    recovery maneuvers.

	3.2	Probable Cause

		The [NTSB] determines that the probably cause of this
	accident was 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.

-- 
Larry Miller		The Aerospace Corporation
PO Box 92957		LA, CA 90009-2957
lmiller@aero.org	310-336-5597
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