Re: Concorde's Engines

Date:         24 May 99 01:52:39 
From:         julian@gatwick.geco-prakla.slb.com (Julian Fitzherbert)
Organization: Schlumberger Geco-Prakla
References:   1
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In article <airliners.1999.498@ohare.Chicago.COM>, "Bill Herman" <hermanwc@fuse.net> writes:
>Do the Concorde's Olympus engines use some form of afterburner while flying
>supersonic?  A friend of mine doesn't think so, but I don't see how that
>plane can fly at Mach 2 without reheat.  I thought the F-22 was considered
>to be a great technological achievement because of its ability to fly beyond
>Mach 1 at military power (no afterburner).  It's hard to believe that a
>plane designed 20+ years prior to the F-22 already had that capability.

Somebody will probably give a better technical description but if not ..

Afterburners are used at takeoff and to go supersonic. However once at,
or near to, supersonic cruise they are not required. In supersonic
cruise a lot (I don't recall how much) of thrust comes not only from the
engine but also the intake and exhaust system. This means that the
increasing speed increases the thrust and Concorde actually wants to go
faster than the crews allow her to.  To prolong airframe life they limit
her to M2.0 but she could go faster. M2.2+ (a bit) so the SR-71 nothing
to worry about.

However, if an engine shuts down during supersonic cruise then the
flight becomes subsonic. Atlantic crossings sometimes have to divert to
the Azores in such a case as the fuel remaining may be insufficient to
complete the crossing subsonically.