Re: 2 engines vs 4 engines planes

From:         drinkard@bcstec.ca.boeing.com (Terrell D. Drinkard)
Organization: Boeing Commercial Airplane Group
Date:         30 Oct 93 22:33:43 PDT
References:   1
Followups:    1 2
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In article <airliners.1993.673@ohare.chicago.com>,
Dietmar Hanke <acm@SkyNet.GUN.de> wrote:
>
>I have recognized that more and more aircrafts used for transatlantic 
>flights just have 2 engines, like the B-767, B-757, A300 ...
>What happens if one of the 2 engines of a B-767 fails somewhere over the 
>atlantic? Which distance can this jet still fly by just using one engine.

This is a slightly more complex question that you might first guess.
Currently, the 767 (with all the appropriate engines and auxilliary
equipment and crew/maintenance training & certification) is certified to
fly 180 minutes away from the nearest "suitable" airport.  Distance is
velocity multiplied by time, and the 767 is certified to fly at MMO
(maximum operating mach number) on one engine.  Interestingly, it can
actually do that.  :-)  Some folks opt for the Maximum L/D speed which
is somewhat slower.  So, basically, find a speed you like, and multiply it
by three.  That would be your answer.  

Now.  Not all operators are certified for 180 minute ETOPS (the above example).
Some are allowed 120 minutes, some 90, some only 75.  Some aren't allowed
to fly ETOPS at all under any circumstances.  :-)  (Typically this is an
economic decision made by the airline - not a reflection of relative
safety - because of the onerous bookkeeping requirements.)

>Is it possible to fly a B-747 when 2 of the 4 engines failed? Was it even 
>possible when both engines on one wing woudn't work anymore?

Yes.  (I just happen to have a 747 configurator right beside me.)

>I allways prefer a flight on a B-747 when I have to get from Frankfurt to 
>New York if there were also 2 engine jets on that route. Would you think 
>the same way?

No.  :-)  I'd go with the 767 because of the nicer seating arrangements.
Or maybe an MD-11 so that I can check out the competition's stuff.
Unless I could afford one of those cool upper deck seats.  :-)

>Thanx for a response to my questions.

No charge.



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