> Thought this was interesting, given the discussions of ducted fans:
    >
    >
   http://www.aero-news.net/news/commair.cfm?ContentBlockID=1e59c2c5-8740-4f14-8ecd-20c5d5d37015&Dynamic=1
   <http://www.aero-news.net/news/commair.cfm?ContentBlockID=1e59c2c5-8740-4f14-8ecd-20c5d5d37015&Dynamic=1>
    >
   <http://www.aero-news.net/news/commair.cfm?ContentBlockID=1e59c2c5-8740-4f14-8ecd-20c5d5d37015&Dynamic=1
   <http://www.aero-news.net/news/commair.cfm?ContentBlockID=1e59c2c5-8740-4f14-8ecd-20c5d5d37015&Dynamic=1>>
    >
    > For fuel efficiency, the jets look more and more like
   turboprops.  Now
    > they're going to be gearing the bypass section..  If the customers
    > wouldn't complain, I'd think they'd just take the ducts off and
   go back
    > to propellers...
    >
    >
    > Regards,
    >
    > Matt-


   Matt,

   In the early 90's I was on the commercial side and they had a rig that
   per-dated this effort. I my memory is correct it was geared and had
   essentially a multi-bladed (something like 11 bladed) constant speed
   prop in
   the duct. It was made from a PW2000 core. I was told the thrust was much
   more than anticipated (no I won't say) and other numbers were good. The
   total package proof of concept was very heavy, but then again it was
   just
   for running in the test cells, not on a wing. I am going to assume
   they gave
   up on the CS-prop.

   At the time the V.P. of Engineering was  Dr. Ed Crow and he truly
   championed
   the concept (geared fan). I got to meet him via sessions thye would
   have to
   keep the employees up to date, and I liked him as leader and his take on
   things. I believe he retired and is doing something at the college
   arena. In
   my opinion it would be a tribute to him to get this on the wing and
   all the
   others that have been working on it behind the scenes all these years.
   Pratt has taken its lumps on the commercial side with not winning
   contracts
   to get on the wing of the most recent launches, at it is not do to
   lack of
   engineering prowess. The last time I had heard Boeing said they
   could make a
   business case for their entry in the 787 competition, perhaps this
   will be a
   home run for my old teammates back in East Hartford.

   On taking off the ducts, customer perception would not allow it, and
   I am
   not sure engineering wise it's a go. It has been a long time since I
   looked
   at a graph in PW's Jet Engine Familiarization Book, but turboprops
   have a
   sweet spot up to about 400mph (again if all the synapses are firin'
   ;-) ).

   My Best,
   Anthony

Very interesting insight, Anthony..  Thanks for the info.

I was talking about taking the duct off of the engines as a way to tweak
the noses of a few list members here, and was mostly kidding.  :)  I
agree that the data suggests that turboprops are appropriate for
airplanes slower than the current crop of airliners.

If customers weren't so fixated on speed (saving only a few minutes on
most shorter flights), straight winged turboprop powered airliners would
make more money than turbofans.  Horizon flies a variety of Dehaviland
DHC8 (dash8's) through Boise (where I am based).  The Q400's are
especially impressive (370kt max cruise) - I have to think the airlines
are making good money with them.


Regards,

Matt-


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