Re: hydraulic problems with DC-10s??

From:         greg@octopus.dpsi.com (Gregory R. Travis)
Organization: Data Parallel Systems, Inc
Date:         08 Dec 92 15:50:51 PST
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Keith Barr <barrk@ucsu.Colorado.EDU> writes:

>The change in weight from a lost engine is minimal.  A fully loaded DC-10-30
>weighs 572,000 pounds.  A GE CF6-50C2B weighs only 8,731 pounds.  This means
>that in normal flight each wing needs to support 286,000 pounds.  If each
>wing supports the weight of its engine, now the left wing only needs to
>create 277,269 pounds of lift, a 3.05% decrease.  I would imagine that 
>ailerons easily can create a 3.05% increase in lift per side.

It seems to me that they each have to perform at only half this figure:
I.e. - the aileron on the wing that lost the engine needs to increase lift
by about 1.5% while the aileron on the "good" wing needs to go negative
and decrease that wing's lift by 1.5%.

This is quite muddled though, as other anti-lift devices (such as spoilers)
will deploy at a given amount of aileron deflection.  In fact, and I don't
have my DC-10 refs handy, I imagine that the ailerons on a -10 are locked
in place when the flaps are up (not the case in the Chicago crash, I know)
and that the loss of an engine AT CRUISE would have to be countered entirely by
lift spoiling devices (i.e. spoilers) on the opposite wing with a
suitable increase in the aircraft's overall AOA.

In any case, the ORIGINAL poster's position that the loss of an engine
from a wing, considering the engine's moment and weight, would render the plane
uncontrollable is not supported either by analysis or historic precedent.
Engines depart planes all the time...

BTW, just to be pedantic:  The wings do not each contribute exactly
50% of the total lift.  Remember that that fuselage itself contributes
a SUBSTANTIAL amount of lift at cruise as do the horizontal stabilizer
surfaces (in certain flight regimes!).

greg, the math bimbo
--
Gregory Reed Travis				D  P  S  I
Data Parallel Systems Incorporated   greg@dpsi.com (For MX mailers only!)
Bloomington, IN			     greg@indiana.edu (For the others)