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Charles Murray
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Blogger
Re: Stupid Questions
Charles Murray   10/4/2012 9:07:54 PM
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Good point about asking dumb questions, MBlazer. For that to happen, a certain attitude is needed at the top -- one that welcomes all kinds of questions, not just those that sound intelligent but may, in fact, be worthless.

Tim
User Rank
Platinum
Almost right
Tim   10/4/2012 6:56:01 PM
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This story reminds me of a physics professor that refused to give partial credit on complex problems. His reasoning was that in real life even tiny mistakes like an errant punch slug can have disastrous consequences. We as engineering students had to learn that there is no almost wrong or almost right.

McG
User Rank
Iron
Re: Frightening
McG   10/4/2012 4:33:47 PM
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The problem described would have been in the autopilot system, not the primary flight controls.  As kenish correctly notes, C-130's have hydraulically-booseted manual controls, not fly-by-wire.  The Functionl Check Flight crew would not have the autopilot engaged during takeoff, but could have had an unexpected surprise when they engaged the autopilot in flight.  However, they could have quickly disengaged the autopilot, and most autopilots have clutches that will allow the crew to overpower the autopilot inputs with the cockpit controls.

TJ,  the metallic sliver was likely introduced by drilling of the structure near the harness, which introduced shavings into the harness that were not properly cleaned up.  Have seen this several times.  You would be shocked at the lack of QA at some of the military overhaul depots.  One major depot that one of my aircraft went through had no independant inspection.  They relied on the technician performing the work to inspect his own work (all in the interest of cost savings). 

SparkyWatt
User Rank
Platinum
Re: Frightening
SparkyWatt   10/4/2012 2:04:44 PM
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What surprises me is that a critical harness was checked for continuity, but not for isolation!

kenish
User Rank
Platinum
Re: Frightening
kenish   10/4/2012 11:58:14 AM
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I always preflight my plane, truck and motorcycle.  On the C-130 in the article a preflight probably would not have found the problem.  The elevator isn't visible from the cockpit, so "Flight Controls Free and Correct" would not help.  The first sign of trouble would have been at gear retraction as the author pointed out.

I do wonder a bit on the veracity....the flight controls in a C-130 "Herky Bird" are mechanical...pushrods, bellcranks, cables, and pulleys.  AFAIK even the latest "J" version is not fly-by-wire.

rv8iator
User Rank
Iron
Single point failure
rv8iator   10/4/2012 11:12:12 AM
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 After reading the story I don't believe that Lockheed designed a single point failure mode of the primary flight control system.   All aircraft are designed with redundancy based on risk.  Flight control failure though low in risk is high in severity and thus qualifies for redundancy.

benmlee2
User Rank
Gold
Re: Stupid Questions
benmlee2   10/4/2012 11:03:35 AM
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The longer I am in engineering, the longer I realize intuition is as important as math and numbers. Learning to listen to your intuition is as important as learning theories. There are so many interactions in a system, is impossible for anyone to systematically troubleshoot. Sometime when you are faced with a problem, is best to stand back and ask yourself what do you think. What does your little voice tell you.

mblazer
User Rank
Silver
Stupid Questions
mblazer   10/4/2012 10:11:16 AM
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It is always better to ask stupid questions before the accident than having to testify before the Accident Review Board.

If doesn't look right, investigate until you're certain there is no problem or there is one.  Is someone's word that "it's good enough" equal to an aircrews' life?

Johnathamilton
User Rank
Iron
Frightening - Show versus Tell
Johnathamilton   10/4/2012 9:20:15 AM
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Good points - I agree it is always more convincing to show than tell. We as engineers are often too busy to spend the time to figure out how to show - it's not always easy. But definitely worth it - especially when it comes to mission critical issues.

Rob Spiegel
User Rank
Blogger
Re: Frightening
Rob Spiegel   10/4/2012 12:25:58 AM
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Good point about show being better than tell, Dave. The story is also a good arguement for healthy skepticism.

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