Re: Boeing naming convention for 777

Date:         03 Oct 99 17:38:42 
From:         "robert wright" <>
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>If by PW4077 you mean the engine used on United's sixteen original
>(non-ER) 777s, it's a PW4084 run at lower thrust -- I checked out the
>model / serial number plate on one of them after seeing a number of

    Yes, they are physically identical from a component standpoint.  That is
what I discovered this week.  How, may I ask, did you manage to look at the

>debates over the matter.  The PW4090 (also used by United, on the
>777-200(ER)) is different, though all AW&ST's Source Book reveals is
>a higher dry weight (15,740 lbs vs 14,995 lbs) and higher pressure

    The 4090 is basically a "throttle bend", designed to be run with more
fuel, which translates to more power from the turbine and a higher
rotational speed, hence a higher pressure ratio in the compressor.
Materials are a bit different due to higher temperatures and I would assume
the cases are designed heavier to withstand greater loads in the event of
damage, and that would account for the higher weight.

    They also introduced some new compressor airfoil design methods into the
later PW4000 models, but I think these just missed the 4090 and got picked
up by the 4098.  These new techniques led to differently shaped stator and
rotor airfoils which are supposed to reduce separation and increase the
compressor efficiency.  Some initial growing pains on the 4164/68, but they
worked fairly well on the 4098.