Re: Superfan

Date:         24 Nov 97 03:27:48 
From: (H Andrew Chuang)
Organization: Concentric Internet Services
References:   1
Followups:    1
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In article <airliners.1997.2721@ohare.Chicago.COM>,
Marc Schaeffer  <> wrote:
>I would like to know what happens in the domain of the Superfan engines.
>A bit of history may be interesting. The Superfan -Ultra high bypass-
>engines were initially foreseen to be mounted on the A340. IAE intended
>to build a variant of the V2500 engine which incorporated a gearbox
>driven, variable pitch ducted fan added to the front of the 2500 core.
>Calculated fuel savings of 20% compared to classic engines were
>expected. The idea came up in Dec-86 and was cancelled in Apr-87 due to
>technical risks.
>- What's the status on UHB engines nowadays, is it under
>development/trials (PW/RR/GE/IAE/CFM ...) somewhere ?

I believe PW is probably the leader in this technology due to its past
experience developing a gearbox-driven propfan to compete with GE's
unducted fan (UDF).  PW was very interested in developing an Advance
Ducted Prop (ADP) engine.  However, I have not heard much about it,
lately.  I am not aware either GE or RR being actively pursuing this

>- Have similar/simplified techniques been adopted in the GE90 or Trent's

If you are referring to gearbox-driven and variable-pitch fan, then the
answer is no.

>- What about reliability, weight, costs, would they not reduce the
>expected cost advantage (-20% for fuel) ?

I don't think weight is an issue.  Even though you will have a much
larger fan, there will be less fan blades and you won't need a thrust
reverser because of the variable-pitch fan.  However, you can find out
about the reliability only when it's in the field.