Re: Unducted fans?

From: (Nickolas E. Hein)
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Date:         07 Jan 94 02:44:48 PST
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In article <airliners.1994.828@ohare.Chicago.COM>, kls@ohare.Chicago.COM (Karl Swartz) writes:
> >what happened to unducted fans?
> The biggest appeal to the UDF was fuel economy.  When fuel prices
> retreated a bit, so did the appeal of the UDF.  Compounding this
> was the risk/cost of the new technology, noise and vibation problems,
> and potential image problems of what some might view as a "prop"
> plane.
> Delta's MD-90 launch order actually included the option to convert
> some of the orders to a UDF version, but everyone else lost interest.
> >I seem to recall that somebody even bolted a prototype onto one side
> >of a DC-9 and flew it around.
> The prototype MD-80, actually.  I once saw it at Mojave, with an
> extra-long pylon but no #1 engine at that point.  Boeing did the
> same thing with a 727.  Seems to me the MD-80 had a GE engine while
> the 727 had a Pratt, but I wouldn't bet on it.
I worked for Douglas Aircraft in Long Beach on the MD80 Propfan program
from 1985 to 1987.  GE built and flew the only working prototype engine
and flew it first on a Boeing 727-100 flight test airplane, then a
modified MD83 several months later.  I led a team to develop the flight
simulator for the MD but left the company a few weeks before first flight
for something even more interesting.

The fuel consumption was reduced such a huge amount (60%) that the airlines
would have bought it even with today's fuel prices, if the engine manu-
facturers had been willing or able to make the investment.  They weren't
and when they asked the airframers to share the risk that killed it 
quickly.  It did have some problems remaining to be solved (noise, 
wing anti-ice without engine bleed air, limited growth potential) but
nothing worse than what was overcome in the development of turbofan

Although the project was abandoned completely around 1989 the results
of some of the experiments have led to higher-speed propellers for
general aviation turbo-prop aircraft and larger bypass ratios on the
new generation of commercial transport engines for the 777 and the like.

It was without question the most exciting engine program ever to come
about in peacetime and I wish someone had followed through with it on

Hope this is of interest.  Let me know if you'd like to hear more.

I take responsibility for everything I say but I could still be wrong. 
Check all calculations.
Nickolas Hein                    | Voice: (206) 662-4980