Re: Interresting thread in comp.lang.eiffel

["Robert I. Eachus" <rieachus@earthlink.net>]

(I'm replying directly because it has been a few days, and this is
getting
pretty far from Ada and or Eiffel.  But feel free to quote elsewhere...

Ken Garlington wrote:
> 
> "Robert I. Eachus" <rieachus@earthlink.net> wrote in message
> news:396CA5AD.EE955F7A@earthlink.net...
> >    As I remember it, there was planned to be a relationship as part of the full-up
> > simulation of the flight control system.  When the decision was made not
> > to use the SRIs in the simulation, that part of the contract was cut back or
> > cancelled.  I think they still had the SRI hardware supplier on contract, but not the
> > software developers.
 
> Actually, I posted the AW&ST articles on my website. They indicate that
> Sextant was a full partner in Ariane 5, and in fact that the Ariane 4 SRI
> was *not* used "as is". See

    First, there is a bit of confusion above.  If the software
developers in England
had been involved in the SIMULATION contract, they could have, and
probably would
have noticed the problem.  But they were not on contract for the Ariane
5, they were
contracted to develop a new IRS for the Ariane 4!

    This game playing was AFAIK the idea of CNES. The IRS was upgraded
for Ariane 5,
but--and here the game playing begins.  It was decided to use the "new"
IRS in the
Ariane 4.  To keep the cost overruns on the Ariane 5 down, the
development costs
were moved to the Ariane 4.  So far, no problem.  But then, and I'll
quote the report
on this:

 "It is even more important to note it was jointly agreed [by CNES and
its contractors]
not to include Ariane 5 trajectory data in the IRS' requirements and
specifications."

    There is the disaster in one sentence.  The new IRS for the Ariane
5, was designed
for, and only for, the Ariane 4. And since EASAMS Ltd. was a major
contractor on the
Ariane 4, but a sub to Aerospatiale on the Ariane 5, they were not
directly involved
in the decision not to get the Ariane 5 data, and according to my
sources, the decision
was directly due to the unwillingness by the French to release the data
to a British
firm--even though most of the work was done in Germany.  (I heard the
later after two
German beers.  So while some of this is very well documented, I can't
vouch for that.
I can vouch for the fact that EASAMS never got the Ariane 5 specs.  Not
they were told
not to use them, but they were not permitted to see them.)  And I also
know, and it is
very well recorded, that the issue of horizontal position post launch
was NOT decided
by the programmers.  They objected, and it went to a multi-contractor
review where it
was decided not to protect it.  But this was at an ARIANE 4 meeting, not
an Ariane 5
meeting, because the development of the new IRS was officially part of
the Ariane 4
project.

    I'm sorry to keep harping on this, but system engineering and system
integration
is what MITRE does, and at MITRE I worked on several multi-national
projects.  I was
in a position to gather some of this information first-hand, but MITRE
as such put a
lot of effort into figuring out where the failure occurred, even before
the official
report came out.  We wanted to make sure that we didn't repeat the same
errors, and I
was able to use the Ariane 5 as an object lesson on one project.

    By the way, I am now, as of last week, on long term disability. :-( 
I'm better
than I was in January, but I still haven't been into the office since
then.  Hopefully,
I'll get to finish some books and article while they are trying to
figure out just what
is wrong.
 
> The gains changed abruptly when the aircraft transitioned from
> takeoff-and-landing to up-and-away mode. This produced a sudden transient,
> triggering the start of the PIO. The transition now occurs more gradually.

   That fixes the primary cause, but not the actual failure mode.  Does
the stick now
have tactile feedback?  Or has the rate limit on the stabilator been
changed?  (Yes,
avoiding sudden non-pilot-induced control inputs is a very good thing. 
But tactile
feedback, such as stick shakers for stall warnings have the great
advantage of
focusing the pilot on where the action is needed.

-- RIE