From: cid@athena.mit.edu (Derek H Cedillo)
Subject: Crash causes and faults [Long] (was Re: El Al 747...)
Organization: Massachusetts Institute of Technology
Date: Fri, 9 Oct 1992 19:16:42 GMT

In article <1992Oct9.102012.21752@cactus.org> rdd@cactus.org (Robert Dorsett) writes:
>In article <1992Oct9.035126.14109@athena.mit.edu> cid@athena.mit.edu (Derek H Cedillo) writes:
>>In article <167@newave.newave.mn.org> john@newave.newave.mn.org (John A. Weeks III) writes:
>>>In <1992Oct7.005552.5844@athena.mit.edu> cid@athena.mit.edu (Derek H Cedillo):
>>>> I think boeing may have made a big boo-boo somewhere.
>>>
>>>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.  

>I can think of at least five common-cause-of-failure possibilities for a 
>double engine loss: sabotage, low oil, bird strike, poor preventive 
>maintenance, and pilot mismanagement of a bad situation.  One is an "act of 
>God," one's an act of malice, two are maintenance issues, and one's a 
>training/selection issue.    

Your bird strike has some possiblilites, but still good odds against it.
Although not any  engines are "bird-Proof" a large amount of them 
are made to be.  Engines are designed for bird strikes in mind, and
a great deal goes into making sure tragic loss of power doesnt arise
from a bird strike.  I worked for GE this summer and aided in some
testing.  If the engine is struck by a bird, or even multiple ones
it would still take a lot to make the engine break apart and fall off
the wing and affect the other engine.  

As far as sabatoge goes, this is unlikely.  A cargo plane is not
the likely target of a terrorist attack.  Who are they going to affect?
Unless they planned on doing this with the precise location of the crash
(the apartment complex)...maybe.  But how the hell could they have done that?

Preventative maintanence is a good possibility, especially when 
cracks were found in other pins.  If there were some, they should 
have been detected.  Good point.

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?


>The odds of a *structural* failure as the cause of a double engine loss (for 
>the *possible* reasons cited) is astronomical.

I am not saying that the engines just fell off and end of story.
There probably was an engine problem such as caused by a bird
strike or whatever the case may have been.  In fact the pilots did 
report engine problems shortly after take off and were planning on returning
to the airport.  My scenario is this, (lets say bird strike was the
problem for argument sake).
A flock of birds gets injested by both engines ( a little
far fetched, but put anything in this scenario for engine failure causes)
The enginesinjest the multiple aves and there is sever damage to the
Fan blades as well as the LPC (low Pressure Compressor)
You get severe unbalance loads due to these damaged rotors rotating
at 25K RPM.  The engines start to vibrate excessivly.  The pins break and
the engines fall.  Thing is, the pins shouldnt have broke, they are supposed
to reduce chances of other complications in emergency landing and crash
situations.  However, They shouldnt break due to excessive
vibrations in flight (which happens before engine can be shut down).
Now although this isnt a direct error by Boeing or anything, small cracks
in the pins as found in 15 others could lead to pre-mature breakage 
and thus disaster like this one.
Like I said before, It's not all boeing's fault or an inherent problem to 
747's in general, but rather it is just 
one of those things, that when you add in a manufacturing 
defect, shanty maintainence, and extraneous problems and flight 
things go wrong.  The only variable should be in flight problems and
maintainence and manufacturing should be foolproof or damn near.  

BTW boeing has changed the Pin design 3 times already.
That implies they havent quite got it right in my opinion.  
A pin is a (relatively) simple thing, so you cant really say the design got
changed out of superior tech. or simple improvements.  
Something like a pin or lets say "o-ring" re-design is usually
due to a problem with the existing one.  Just because
the design is pretty much "Easy"and to the point.
Challanger had the same situation.  A manufacturing defect
that in itself wasn't cause of disaster.  But when you couple that 
with failure to detect a leak and flight circumstances and disaster prevails.

>This type of armchair quarterbacking is always interesting: one always
>learns something new.  But before we translate this *speculation*--a 
>thought-exercise--into *fact,* and adjust our flying habits on it, let's 
>have at least a preliminary crash report (from the actual investigators--
>not the TV models) in our hands, eh?  :-)

I'm not armchair quarterbacking, Im using facts and quotes.  I am not 
basing my arguement on anyone elses.  I base all this on UPI articles
which give direct quotes from witnesses, 747 pilots, and figures by
athorities.  last I heard official death cound was 13.  Estimated
to be 250.  Cant get into rubble to find others.

>Me?  I'll fly on the 747, noooooo hesitation.  
>
Go ahead, I dont fly 747 anyway.  Usually DC-9, or 737 from 
Logan - Ohare

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

Derek H Cedillo
cid@athena.mit.edu