Re: B757 "Heavy Jet"?

From: (C. Marin Faure)
Organization: Northwest Nexus Inc.
Date:         24 Jun 96 00:42:03 
References:   1
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In article <airliners.1996.946@ohare.Chicago.COM>, wrote:

>     Hello I was wondering if someone can help me understanding why the
> FAA decreed the 757 as a Heavy Jet.
> I know it fits the Cat. just by using its weight, but if I'm not
> mistaken that was not the reason behind the ruling.
> Thank you ...... Mooney1

I believe its category was changed because of its wingspan and wingtip
vortex characteristics.  The 757, like the 767, was given very long wings
to maximize its efficiency.  These wings can generate fairly strong tip
vortices (sp?).  However, the 757's lower weight plus the fact that
everyone thought of it simply as a 727 "replacement" suggested it could be
in a lower category, which meant the spacing between it and a following
plane could be less than the spacing between a heavy jet and the plane
behind.  After a few well-publicized incidents in which the media managed
to give the 757 wing a bad rep (it's actually an excellent wing, and the
757 still has the lowest seat-mile cost of any commercial jetliner), the
FAA simply moved the 757 into the higher category, which was more accurate
as far as its wing characteristics are concerned anyway, thus increasing
the spacing between the 757 and a following airplane.  End of wake vortex

C. Marin Faure
   author, Flying a Floatplane