A320, MD-80, 727

From:         David Lednicer <dave@amiwest.com>
Date:         01 Dec 93 03:16:29 PST
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	In reply to the question as to why MD-80s and 727s have their ventral
stairs down on the ground: it keeps them from tipping over (tail down)
should someone goof when loading them!  In the AIAA "Case Study in
Aircraft Design: The Boeing 727", Mark Gregoire relates a story about
when the first 727-200 was delivered to National Airlines.  "As it rolled
to a stop near the National hangar, amid the expectant dignitaries, the
pilot touched the brakes and the airplane nose went down and then recoiled
up and lifted the nose gear off the concrete approximately 6 to 8 inches. 
The gasps in the crowd were heard 3,000 miles away in Seattle.  Bill Clay
put a team together and, armed with weight and balance data, toured the
airlines outlining the entire spectrum of configuration control, ground
handling, ballasting, and precautionary measures from sloping ramps to
heavy snow loads on the tail.  As far as we know, no 727-200 has ever sat
on its tail and maybe we over reacted to the National incident, but that's
why, you will nearly always see a 727 with its rear airstairs down when
parked.  There are some rare cases where we attach lead to the radome
bulkhead for extreme loading conditions."

	As to why the Mercure looks so much like the A320 - yes it is
related and no, it isn't.  The Mercure was built by Dassault, which is a
(nominally) private French aero company, while Aerospatiale, which is part
of Airbus is the publicly held French aero company.  Back in the gestation
of the A320, Dassault was involved in one partnership which looked at a
growth Mercure with CFM-56s.  This partnership split, but begat other
partnerships that lead to the A320.  You might say that the growth Mercure
genetically led to the A320.  On the other hand, Dassault was not involved
(directly) in the design of the A320, so any relationship is distant.

David Lednicer             | "Applied Computational Fluid Dynamics"
Analytical Methods, Inc.   |   email:   dave@amiwest.com
2133 152nd Ave NE          |   tel:     (206) 643-9090
Redmond, WA  98052         |   fax:     (206) 746-1299