From: rdd@cactus.org (Robert Dorsett)
Subject: Sources, and the applicability of the scientific method (747 crash)
Organization: Capital Area Central Texas UNIX Society, Austin, Tx
Date: Tue, 13 Oct 1992 08:33:58 GMT

In article <1992Oct13.003907.4353@athena.mit.edu> cid@athena.mit.edu (Derek H Cedillo) writes:
>I will not apologize for that kind of work ethic.  Some one who says
>"Only after persistent catastropic failures of a component should we
>"know to suspect".  I don't think that is good engineering.  
>Thats like saying you shouldnt worry amout something till something
>terrible happens (He said catastropic).  To me this sucks.  If there
>is even a slight cause for beleiving something may fail, it is good
>engineering practice to look at a fix for it as quickly as possible.

No, Derek, you don't seem to understand.  This is (for better or for worse)
a science group.  It is not a talk group, despite outward appearances (:-)).  
We therefore have to substantiate our claims.  

You've presented a fine collection of media excerpts.  I would add the
following observations, though, starting with the traditional debunking
of your sources (:-)):

1.  The mass media is a poor source of aviation-related information, even at
its best.  When you quote from AP or UPI, you're quoting the (usually)
anonymous contribution of a local staff reporter who may or may not know
what he's talking about (probably not), and who is almost certainly
incapable of prioritizing "technical" speculation.  I (and I suspect most 
others) on this group would tend to accept quotes from industry-standard 
periodicals (written for and by professionals) more seriously: Aviation Week, 
Flight International, Interavia, etc.  Not from an edited wire service report.
The wire services are marginal sources for "factual" information; skip any
piece that includes the word "analysis."

For instance, you quote excerpts from Nance.  Do you have any idea who this
guy is?  He was a Braniff 727 flight engineer, who retired before reaching
a flying position, to make a career on safety, in the early 80's.  He's
written a variety of books for the general market, dealing with air safety.
Now, while he's certainly researched his material, and his books are inter-
esting, he was never an airline *pilot*, and has never been employed in a 
"direct" technical safety capacity.  His interests are generally academic: 
he's about as much of a "safety expert" as I am (visits on Good Morning 
America notwithstanding :-)).  I enjoy his work, but I can't take him TOO
seriously.

The sad fact is, the mass media wants tidy answers.  A crash is only in
the news for three or four days, before it's dropped--a foreign crash even
earlier; a foreign crash not carrying Anglos almost instantly.  The pin issue
has given the media something to throw at the public, something which doesn't
make a terrible amount of sense, but which nicely "rationalizes" a 
horrendous event, something to let them move on to the next disaster. 

2.  The concept of "causality" is an important one in science.  It defines 
a *consequential relationship* between events.  Nothing can happen without
a cause.  If A causes B, and B causes C, then A led to C.  But if D or E 
also cause B, then we can't establish a direct factual link *based* upon the 
mere failure of C, even IF A *can* cause B (which can trigger C).  At least, 
not without a great deal more investigation, which is the point here.

It is irrational to make claims that "A caused C" without having access to 
the facts.  That's what MY point is, at least.  If you want to say "A may 
have caused C" then do so.  But do not say "A caused C," or base further 
arguments as if it did, until you (or, rather, others) complete the field
investigation and analysis.  It's a dead-end path, it wastes all of our 
time, and it's highly misleading.

The difference, again, is one between an "academic," conceptualized treatment 
of *possibilities*, and that of trying to represent such conclusions as fact.
The problem we have is not with the "facts" you have presented--which I'm sure 
we've all seen in our own daily papers.  It is the assertions you have made
based upon those facts.  I think you are making WAY too much of the pin
issue.  Maybe the pins were bad, maybe they weren't.  But they did NOT trigger
the two failures; we know that, nobody claims they did.  Maybe they were 
responsible for the detachment of the engines as a *secondary* effect, 
outside the design specs, maybe not.  But we really don't know, do we?  And 
there are so many other possibilities.

Yes, it's a REAL good idea for operators to check their pins.  Boeing,
operating from *real* facts (discovered problems), has a REAL problem, which
it's advising airlines to check for (one among dozens of items discovered
yearly).  As you say, that's good preventive maintenance.  

However, again, it's completely inappropriate to suggest that this crash was 
caused by that problem.  The evidence that WE have access to, at this point, 
is not conclusive enough to point to an answer, one way or the other.  

Am I getting through to you?  I don't want you to think everybody's 
beating up on you; we seem to have a simple failure to communicate.  In
your last couple of messages, you're accusing other posters of believing 
things that were never stated.


>>>>>very heavy, especially when filled with cargo.  Without much altitude
>>>>>its hard to recover, actually it is a 1/billion chance.
>>
>>where does this probability data come from?  the 747 is certificated to
>>continue climb following the failure of a single engine after V1.  [...]
>
>No data.  Just an estimate by a 747 pilot.

Well, I'm the offspring of a retired 747 pilot; he seems to think that there 
was a fighting chance.  It all depends on variables: the amount of altitude, 
the weight lost by the engines, the weight of the airplane, fuel dump rate, 
pilot technique and decision making, etc.  Evaluating these things can't be 
done on the fly: for a *conclusive* answer, find yourself a simulator and fly 
the profile.  And yes, this was in direct conversation; no, it was not a 
third-hand newspaper report, out of context (context?  How about a nice, 
definitive statement, with "I dunno, but I'd guess that..." nicely edited 
out).


Be careful when basing your arguments on the sanctity of unknown, 
unapproachable (to you) sources.  Just between you and me, there're a few 
airline pilots on the net, including a retired L-1011 captain and a 727 
captain.   And more than a few private pilots training for their F/E rating 
and/or type ratings in airliners.  Not to mention thousands of engineers and 
scientists at NASA, Boeing, McDonell Douglas, Honeywell, and the European 
Space Agency, among others.  MANY of whom have access to "real live ones" to 
cross-check their facts with.  If you discover that net.consensus is moving 
against you, there might be a reason...  *I've* certainly gotten stung, from 
time to time. :-)




---
Robert Dorsett
rdd@cactus.org
...cs.utexas.edu!cactus.org!rdd

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