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Old January 11th 04, 07:20 PM
Ed Rasimus
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On Sun, 11 Jan 2004 09:55:02 -0500, Air Force Jayhawk

An aircraft is only unstable if the aerodynamic center is forward of
the center of gravity. If the wing root is sufficiently aft and the
AC stays aft of the CG, stability remains.

Why? Well it was tried with the X-29 but I never have read why no one
has pursued it since. The advantage was supposed to be that the
boundary layer (the thick air right next to the surface caused by
friction and very annoying) builds up as the air moves aftward along
the wing. With a FSW, the thickest part of the BL is at the root
rather than near the control surfaces, enhancing control while at high
angles of attack. There are other advantages but it's been a while so
I can't recall them off the top of my head.

I knew the USAF pilot on the X-29 project...he said it flew fine and
had no issues with it.

As I recall the X-29 project, one of the objectives was evaluation of
the instability as a means of gaining agility for future highly
maneuverable aircraft. The "urban legend" was that the aircraft
required minimum of triple redundant FBW augmentation as loss of the
augmentation would result in immediate excursions from stable flight
and structural failure within seconds. The ultimate in "JC maneuvers".

Always thought it made for an extremely ugly airplane.

Wasn't the basic structure from an F-16A?

Ed Rasimus
Fighter Pilot (USAF-Ret)
"When Thunder Rolled"
Smithsonian Institution Press
ISBN #1-58834-103-8