Re: A 777 with four engines.

Date:         29 Jul 98 00:29:27 
From:         C Fairburn <cf112@york.ac.uk>
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>
> This is like saying, "shouldn't we put build planes with titanium
> shielding to protect against small chunks of space debris re-entering
> out atmosphere."  Theoretically, that could bring a plane down, but the
> chances are sooooo small that it doesn't warrent the expense of trying
> to protect from it. Based on millions of flight hours, it is clear that
> a 4 engine aircraft does not have a significant safety advantage over a
> comparable twin.  If we were to spend an extra 5% of flight expenses in
> order to increase overall safety, adding extra engines to twins would
> not be the best investment of those safety dollars.

One could also come up with the statistical notion that, given engine
failures are (largely) independent events, having 4 engines as opposed to
2 actually increases the risk of engine malfunction on any given
airplane...

Of course, given that an engine failure has occurred, its effects on a
twin may indeed have a more significant implications due to impacts on
secondary systems (e.g.hydralics etc.). Also, as we see in cases like
Kegworth, here in England, shutting down an undamaged engine by mistake
doubtlessly has more impact in a twin !!

Chris fairburn (new eavesdropper to the list !)