Subject: Re: ILC2005: McCarthy denounces Common Lisp, "Lisp", XML, and Rahul
From: rpw3@rpw3.org (Rob Warnock)
Date: Tue, 28 Jun 2005 22:09:43 -0500
Newsgroups: comp.lang.lisp
Message-ID: <DdKdnSRKm4dqjV_fRVn-oA@speakeasy.net>
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>
627 26th Avenue			<URL:http://rpw3.org/>
San Mateo, CA 94403		(650)572-2607