26-Jan-96 10:37 ab…@qnx.com (Andrew Boyd) wrote

>John Yesberg <j…@tcs28.itd.dsto.gov.au> wrote:
>>However, I’m also sure that there are some pilots who would
>>appreciate the "expertise" built into the system by engineers
>>who weren’t in a panic.

Then again, there are some of us pilots that appreciate the fact
that human experts are falible !

>heh.  I’m a graduate engineer.  Took a weird triple-major of
>math, cs and ee.  Graduate-level courses in determinisitic
>and non-deterministic control theory and filtering.

BS Electrical Engineering + grad courses in Stochastic Processes,
DSP, Vector Analysis, Complex Variable Analysis…

>Been designing and coding real-time os code for ten years now.
>I also hold a commercial pilot’s license, with current multi-ifr
>and flight instructor ratings.  Flew 300 hrs last year.

Have been doing real-time embedded systems software for 14 years;
F16 radar, electronic warfare systems, Ballistic fire control
software.  PP/ASEL/IA.

>One thing that a little experience in the software biz will
>teach you is that there are two kinds of bugs in software:
>  1) the software does not perform as specified
>  2) the specification was incomplete [or simply wrong]
>(1) is easy.  (2) is hard.  Anyone that claims that they
>have a complete spec for a fly-by-wire system is a fool
>or a liar, or both.  Life is too complex, esp for an
>engineer who isn’t a pilot.

A*B*S*O*L*U*T*E*L*Y (although, (1) can be hard too)

Also, you have to remember that the hardware engineers and
system engineers are also humans, and can’t think of
everything !

An old crusty systems engineer told me that there were two classes of
unknown problems in the world — Unks and Unk-Unks.

The Unks were the unknowns that you *knew* were going to
occur

The Unks-Unks were the unknowns that you had no idea
about, but were sure to occur.  Unk-Unks ALWAYS occur when
you are dealing with any type of system, complex or not.  Why ?
because we’re human !

Personally, the day I step into an airliner that has no pilots
in the front office is the day I start flying AMTRAK airlines !

Regards
Mark S. Bell                           412-268-7925 (Voice)
Software Engineering Institute         412-268-5758 (Fax)
Carnegie Mellon University             ** These are my opinions,
4500 Fifth Ave, Pittsburgh PA.,15213      not those of the SEI or CMU **