Re: Rear Engined Aircraft

From:         shevell@leland.stanford.edu (Richard Shevell)
Organization: Stanford University, Dept. of Aero/Astro
Date:         02 Dec 94 02:48:59 
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In article <airliners.1994.1738@ohare.Chicago.COM>, David Lednicer
<dave@amiwest.com> wrote:

> 	The nacelles on 727s, DC-9s, etc. are canted nose up because of 
> the downwash created by the wing.  You want the inlet highlight plane to 
> be at right angles to the local flowfield, which behind the wing is 
> deflected downwards.  DC-9 nacelles are canted up 3 degrees and I believe 
> that the 727 nacelles are canted 3.5 degrees nose up.  The nacelles also 
> have a toe angle.  On the DC-9, the highlight plane is toed 2 degrees in, 
> but the engine thrust line is toed 2 degrees out.  Wing mounted engines 
> also have non-zero cant and toe, to match the local flow field.

I think we said this earlier but here it is again.  In addition to the
above, an upward inclination of the thrust line provides a little free
lift.  The loss of thrust is trivial since the cosine of 3 degrees is
.99863, and lift is increasd by 5% of the thrust since sine of 3 degrees is
.05234.  
-- 
Richard Shevell
Email: shevell@leland.stanford.edu