Re: A 777 with four engines.

Date:         26 Jul 98 23:57:18 
From:         "Richard Rea" <rrea@xmission.com>
Organization: ArosNet Inc.
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The Warden wrote in message ...
>Me who doesn't have much faith in new technology thinks that 4 engines are a
>greater safety factor, despite the extra cost. Also, if something happens
>and rudder control is lost, the two outboard engines could be pressed into
>providing sideways control (can't remember the technical term for it) and
>would do a better job than having two engines closer to the center line.
>For
>instance, if UAL 232 had been a 707, 747, A340, or even a DC-8, (first off,
>the problem wouldn't have happened, but that's another story), they may
>have
>been able to get a bit more directional movement, and may have been able to
>correct for that gust of wind that pushed them off of the runway and made
>the wing dig into the ground (if that had not happened, they would have
>landed safely). Personally, I think the 777 should be a trijet, at least...

If a gust of wind pushes you off course, having another engine isn't going
to help you much - the engines need time to spool up.
The greatest effect of having multiple engines is during takeoff, where an
engine failure is the most critical.  As for rudder control, the cases I
know of that resulted in loss of rudder control were cause by major failures
(e.g. Sioux City - DC10 - total loss of hydraulics, Japan - 747 - rear
pressure bulkhead failed and blew off part of the vertical tail).

Does anybody know of a case where a plane was controlled successfully using
asymmetric control of the engines?