Re: hydraulic problems with DC-10's??

From:         drinkard@bcstec.ca.boeing.com (Terrell D. Drinkard)
Organization: Boeing
Date:         01 Dec 92 02:10:49 PST
References:   1 2 3
Followups:    1 2
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In article <airliners.1992.30@ohare.Chicago.COM> weiss@curtiss.SEAS.UCLA.EDU (Michael Weiss) writes:
>
>In article <airliners.1992.8@ohare.Chicago.COM> kls@ohare.Chicago.COM (Karl Swartz) writes:
>>In article <airliners.1992.6@ohare.Chicago.COM> sdl@linus.mitre.org writes:
>>>Some of my pilot friends have accused the DC-10 as having a
>>>particularly bad history of hydraulic problems (which have
>>>contributed to a few crashes).
>>Two, at least.  AA 191 at Chicago/O'Hare on May 25, 1979, and UA 232
>>at Sioux City, Iowa on July 19, 1989.
>
>I have a hard time believing that an intact hydraulic system would have
>prevented AA191 from crashing.  Let's face it, a wing-mounted engine falling
>off produces such a rediculous unbalance that even full aileron wouldn't be
>able to counter it.

Not true.  An engine departing the airplane is a planned for event, in
terms of stability and control.  An aileron would have no problem
countering just the imbalance of thrust (and it would actually be mostly
rudder), in fact, without the added drag of a windmilling engine, the
problem is a bit simplified.  Flight AA 191 lost the slats on the left hand
wing (if memory serves) because of Douglas' failure to include mechanical
lockouts on the slat actuators.  They were not required to certify the
airplane.  But then, why build a 'just barely good enough' airplane?  The
#1 engine departed the wing, taking the hydraulic lines that run along the
front spar with it.  This cause a major loss of pressure in the slat
actuators which were then pushed back into the wing by dynamic pressure.
The assymetrical loss of the leading edge high lift devices was a major 
contributing factor in this crash.

Interestingly enough, the DC-10 is often used as an illustration of how NOT
to design hydraulic systems.


-- 
Terry
drinkard@bcstec.boeing.com
"Anyone who thinks they can hold the company responsible for what I say has
more lawyers than sense."