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Date: Fri, 27 Jun 2003 15:00:03 -0400
From: Hyman Rosen <hyrosen@mail.com>
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Subject: Re: Boeing and Dreamliner
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Date: 2003-06-27T15:00:03-04:00
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Robert I. Eachus wrote:
> Were you involved in the actual decision?
 >  Do you know something that we don't?

That's what the report says.
<http://www.dcs.ed.ac.uk/home/pxs/Book/ariane5rep.html>
     "No reference to justification of this decision
      was found directly in the source code. Given the
      large amount of documentation associated with any
      industrial application, the assumption, although
      agreed, was essentially obscured, though not
      deliberately, from any external review."

> I find it hard to keep from laughing at someone documenting this as a 
> "limitation" of the Ariane 4 code:  "Caution moving Ariane 4 more than 3 
>  kilometers during gyroscope alignment may have serious consequences."

There was an unprotected conversion in the code,
with nothing to explain why it was unprotected.
The review team seems to think that this is a
problem. It's their conclusion, not mine.

> The details were all well documented.  Including the Ariane 4 
> REQUIREMENT for the alignment software to run for 40 seconds after 
> launch, and why it was required.  This requirement did not apply to the 
> Ariane 5, and anyone looking at the Ariane 4 documentation would see 
> potential serious consequences associated with not fixing this 
> requirements.

Well, apparently not. In any case, leaving the alignment function
on triggered the problem, but the actual problem was the shortcut
in the code and the lack of warning for when that code would be
invalid.