Our British cousins have a saying, "horses for courses".  There is a common misconception that piston or rotary driven ducted fans are a cheap alternative to turbo-fans or turbo-jets.  They are not and aviation history is littered with projects that reinforce this fact.  On the other hand, they do have their uses, particularly in agricultural aircraft.  Had Dowty not withdrawn from the market, we might have quite a number of very efficient utility aircraft operating in speeds of 0-150 mph.  One of the points that is often missed is that a properly designed ducted fan could be the basis for a really fun series of slower sport planes with the appearance of jets, the advantage of great low speed thrust (take-offs and landings), relatively low noise level (but only if designed properly) and enhanced ground safety.
I actually did a pretty in depth cut at a wooden semi-scale Panther a la
5151 mustang, et al.  It's quite possible to build a decent little plane and be the first boy on your block to pretend to have a jet.  As long as you're willing to settle for putzing around the airport and don't demand cross-country efficiency.  Up to about 400 mph you can't beat a decently designed prop job.

George W

A friend built a dandy sportplane with a ducted fan.  'Course, he's an
aerodynamicist for Raytheon Aircraft.  He knows this stuff.  Darned good
Engineer all around.

Jet-like, yes.
Nice performer, yup.
Still around?  Nope.

Ducted fans have a HORRIBLE power-out condition.  It's like having an
umbrella or dragchute thrown out.  Funny thing about sportplanes, sooner
or later you have a power-out situation.  Then alla sudden, that ducted
fan is not your friend and you WISH you had a prop.

If you can deadstick an F-4 fighter, you could probably deadstick a
ducted fan sportplane.  Anything less need not apply ;-)

Larry Schurr



The Rotary Engine NewsLetter. Powered by Linux.
ACRE NL web site. http://www.rotaryeng.net
Copyright 1998-2006 All world wide rights reserved.