From: rdd@cactus.org (Robert Dorsett)
Subject: Re: Crash causes and faults [Long] (was Re: El Al 747...)
Organization: Capital Area Central Texas UNIX Society, Austin, Tx
Date: Sat, 10 Oct 1992 02:18:18 GMT

In article <1992Oct9.191642.23055@athena.mit.edu> cid@athena.mit.edu (Derek H Cedillo) writes:
>>>>I don't think so.  The 747 is an extremely safe aircraft.  With all of the
>>>>miles and flights that 747's complete each day, there would be many more
>>>>crashes if there were any "big boo-boos" in the aircraft.
>>>
>>>To me, 2 aircaft that lose 2 engines on the same wing shortly
>>>after take-off within 10 months of eachother is a boo-boo.
>>>Especially when both ended so fatally.  
>>
>>To me, uninformed conclusions before they even have a death count is a 
>>"boo-boo."  I call your boo-boo "coincidence," until the forensic evidence
>>suggests otherwise.  
>
>Does the idea of a service bulletin put out by boeing and the FAA 
>about engine mount pins failing have any impact?
>15 such pins have been found recently to have cracks in them that could
>lead to thier failure.  

Let's define the word "boo-boo."  Which I assume to mean "mistake."  Before
you can make that claim, you must establish (a) that there was evidence of
an *error* in the original design process, *based* upon then-current
industry-design knowledge, and even that (b) using *current* design, the
same CCF can't kill two engines.  

Are we talking about a mistake in design, or a mistake in the maintenance
spec?

What I'm looking for is causality.  There are people on rec.travel.air that
are acting like the 747 has turned into some kind of DC-10 overnight, for 
instance, which is clearly *not* the case.  I suggest that there cannot be 
any claims of relationships at this point, and that media-intercepted service 
bulletins are being used for effect.  Literally *hundreds* of service 
bulletins go out each year, on *every* airplane.  Dozens of airworthiness
directives from the FAA.  The media does not report any of these: only
highlights them when there are crashes, which raises the issue of priorit-
ization, and, again, responsibility.  Even if the bulletin DID exist, it's
one thing if it's one among dozens of equal priority, quite another if 
it's a singular "high-priority" maintenance item.

The more airplanes out there, the more experience the manufacturer obtains, 
and the more it learns about faults in design, produced by ongoing flight 
operations.  When it detects them, it seeks to correct them: this is how the 
system works.  If the customer doesn't correct them, the "boo-boo" claim is 
especially tenuous, and nonproductive.  It's when manufacturers don't properly
correct known faults, such as in the case of the early DC-10 cargo door, 
that we should go for the jugular.


>Pilot error is a real tough call.  Like I mentioned earlier, 747's are
>very heavy, especially when filled with cargo.  Without much altitude
>its hard to recover, actually it is a 1/billion chance.
>As far as a pilot error causing engines to fail and fall off,
>this is obviously ludicrous. But I dont think this is what you meant right?

Why not?  If there was a sustained compressor stall/surge and associated
heavy vibration, and the captain continued to use the engine *despite* 
that vibration, it could cause an uncontained engine failure, no?  Similarly,
if overtemp or oil indications for that engine were ignored, it could also
cause catastrophic failure.

Besides, I have the utmost faith in the capability of the authorities to 
implicate the pilots of any crash. :-(



>Derek H Cedillo
>cid@athena.mit.edu


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

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