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Old January 15th 04, 04:30 AM
Mary Shafer
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On Sun, 11 Jan 2004 18:20:34 GMT, Ed Rasimus

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".

Well, it didn't have to have all three computers working, just one,
which could have been the fourth, back-up one. But that wasn't a
long-term sort of thing.

However, it didn't hang around for seconds before it pitched up.
stalled, and departed controlled flight. Time to double amplitude was
a small fraction of a second, although I can't remember the number.
It was smaller than that of the F-16, but the F-16 isn't very unstable
(it's neutrally stable clean and full of fuel and could be flown,
albeit rather oddly, without augmentation until enough fuel burned
off, not that anyone except VISTA would try this).

The X-29 was statically unstable because the project was a technology
demonstrator for agile aircraft with forward-swept wings, aircraft
that were stall-resistant. It wasn't statically unstable because it
had a forward-swept wing.

Always thought it made for an extremely ugly airplane.

I thought it wasn't all that bad looking, myself. The X-31 was rather
plain, but the X-29 was OK.

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

No, that was the X-31, I think, at least for the gear and cockpit.
The X-29 used a couple of F-5s for the fuselages. I don't remember
how far aft the F-5 airframe went, but it definitely included the
cockpit and surrounding structure, as well as the gear, as I recall.


Mary Shafer Retired aerospace research engineer