Re: Are "jets" really jets?

From:         Don Stokes <Don.Stokes@vuw.ac.nz>
Organization: Victoria University of Wellington
Date:         08 Sep 95 02:35:34 
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dpbsmith@world.std.com writes:
>Is a modern-day "jet" really a jet at all, or is it just a kind of turboprop
>where the propellor has lots of little blades and is concealed within
>a cowling?

A modern fanjet has a bypass ratio of about 5:1, that is five times as
much air goes through the fan and straight back out as goes through the
engine core.  But that doesn't mean five times the thrust comes from the
fan, since the core air comes out the tailpipe a *lot* faster.

A turboprop, on the other hand, dissipates most of the engine's energy
into the turbine to drive the propellor; very little thrust comes from
the tailpipe.

"Ducted fan" is the term used to describe an engine that looks like a
fanjet but behaves like a turboprop.

--
Don Stokes, Network Manager, Victoria University of Wellington, New Zealand.
don@vuw.ac.nz(work) don@zl2tnm.gen.nz(home) +64 4 495-5052 Fax+64 4 471-5386