Re: Jet vs Prop (eg EMB135)

Date:         07 Oct 97 14:10:17 
From: (Mr. Daniel H. O'neill)
Organization: Prodigy Services Company 1-800-PRODIGY
References:   1
View raw article
  or MIME structure

It helps if you remember that a turboprop is an ultra high bypass
unducted fan.  The reason for ducting the fan is that props get
wasteful when the tips hit supersonic velocities, and you must paddle
faster than Mach 1 to approach Mach 1.   Turbofan C-1 disk blade
sections are biconvex at their outer spans and the duct keeps the shock
waves from propagating all over the place.  (all the noise is energy
that isn't propelling the airplane).   Propellers do a fine job of
subsonic propulsion, and the difference between .5 Mach and .8 Mach
doesn't mean much on a short flight, most of your travel time is spent
in the car and walking around the airport anyway!