Re: Please answer - 757/767 Hydraulic Question (LONG!)

From:         woodhams@phoenix.princeton.edu (Michael Woodhams)
Organization: Princeton University Observatory
Date:         17 Feb 93 23:49:34 PST
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In article <airliners.1993.183@ohare.Chicago.COM> rdd@cactus.org (Robert Dorsett) writes:

[...]

>The important thing to note about this arrangement is that all these
>accessories require the engine blades to be spinning, NOT necessarily
>for the engine to be ON.  I.e., they aren't "steam-driven" from the

[...]

>When we start taking away engines, though, the RAT becomes an attractive 
>alternate power source.  If one loses all four engines on, say, a 747, 
>one is still developing a lot of independent power.  If one loses one or
>both engines on a twin, one has suddenly put a very large control burden 

So if a 747 (or other airplane with no RAT) has a loss of all engines
in such a way that they no longer spin, the airplane is without power,
and it is time to start dictating your will into the cockpit voice
recorder? The only single cause I can think of for this would be
flying into a volcanic ash cloud. Does this clog the engines
sufficiently to prevent generating power from windmilling? (I guess
not, as a 747 has survived this scenario.) If a 757, say, lost both
engines in ash, would the ash prevent the RAT from operating?

Michael W.