Fred Gilham <gilham@snapdragon.csl.sri.com> wrote:
+---------------
| rpw3@rpw3.org (Rob Warnock) writes:
| > Paolo Amoroso <amoroso@mclink.it> wrote:
| > +---------------
| > | Paul Wallich <pw@panix.com> writes:
| > | > Well, there were the stories about fly-by-wire aircraft flipping
| > | > upsidedown when they crossed the equator...
| > |
| > | I heard a similar story, but the aircraft flipped upside down *in a
| > | simulation*.
| > +---------------
| >
| > These may all be urban legend variations of a different story
| > altogether: What is certainly true is that very-low-altitude
| > terrain-following autopilots have code in them to, in certain cases,
| > roll the plane upside down when going over the top of a large hill...
...
| > The [possibly urban legend] story is that an early version of the
| > software would, when flying across a completely flat prairie, roll
| > the plane inverted then immediately upright again when it passed
| > over a cow. ;-}
|
| Well, since I sit a couple doors down from the person (Peter Neumann)
| who moderates the Computer Risks forum, I naturally looked this up in
| the computer risks archive. Here's the article:
| ----------------------------------------
| F-16 Problems (from Usenet net.aviation)
| Bill Janssen <janssen@mcc.com>
| Wed, 27 Aug 86 14:31:45 CDT
...
| o Since the F-16 is a fly-by-wire aircraft, the computer keeps the
| pilot from doing dumb things to himself. So if the pilot jerks hard
| over on the joystick, the computer will instruct the flight surfaces
| to make a nice and easy 4 or 5 G flip. But the plane can withstand a
| much higher flip than that. So when they were 'flying' the F-16 in
| simulation over the equator, the computer got confused and instantly
| flipped the plane over, killing the pilot [in simulation]. And since
| it can fly forever upside down, it would do so until it ran out of
| fuel.
+---------------
O.k., so that validates the "crossing the equator...in simulation" story,
but says nothing about nap-of-the-earth terrain-following autopilots
[and "flip...over cow" stories"], which I believe came much later.
Maybe even as late as the F-111?
-Rob
-----
Rob Warnock <rpw3@rpw3.org>
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