HOME  |  NEWS  |  BLOGS  |  MESSAGES  |  FEATURES  |  VIDEOS  |  WEBINARS  |  INDUSTRIES  |  FOCUS ON FUNDAMENTALS
  |  REGISTER  |  LOGIN  |  HELP
Comments
View Comments: Newest First|Oldest First|Threaded View
Page 1/3  >  >>
dbues
User Rank
Gold
Re: JDLR
dbues   7/1/2013 11:49:49 AM
NO RATINGS
All,

I appreciate the interest that this article has drawn.  I am sorry to say that I no longer have access to the individual that related the story to me, so some questions will remain unanswered.  

What happens with refurbishment of complicated systems in an airplane can never be simulated, because there are too many "degrees of freedom" to explore.  You would have to be able to simulate Murphy's Law for each individual who had a hand in the work.

What I CAN say, after having assembled wiring harnesses like these over a few Summers during college, is that a Service Bulletin may have required a slightly larger whole to be punched (could be 1/16th inch larger) to accommodate a few more signal paths in the harness.  This would be punched out of the bulkhead panel and then, the new harness could be installed.  

Airmen usually think of FOD (Foreign Object Damage) OUTSIDE the aircraft, but this is an example of one INSIDE.  This is the reason that the Apollo spacecraft components were vibrated upside down to rid the spacecraft of FOD.  I can imagine that inhaling a rivet head in zero gee could ruin your whole day.

 

 

GuidoBee
User Rank
Iron
JDLR
GuidoBee   10/22/2012 5:09:07 PM
NO RATINGS
Before retiring in the Pengagon I had a USN Captain boss who firmly believed in the JDLR theory: just does'nt look right.  When planes were prepared to be "shot off the pointy end of the boat", there is a collection of maintenance people who are looking at the plane on the catapult and all are giving a "thumbs up" before the catapult officer "fires" the cat and launches the plane.  Any one of those "checkers" who may be very junior airmen, though highly trained, are given the authority to halt the launch if he / she sees something irregular.  It is a big deal to take a plane off the cat, as it has to be taken backwards to a position where the problem can be evaluated / resolved.  Making the call must be supported by the maintenance officers, as the consequence of a fault on launch can be catastrophic in terms of both costly material and lives.  Very often the "JDLR" is hard to define exactly, but when it is finally figured out, it may have been something very subtle and almost impossible to explain why it triggered a concern on the part of the guy who suspended the event.  Also, the system has to tolerate the occassional wrong guess: when there really is nothing wrong: the technician still has to be ready to do the same thing again the next time he sees something that JDLR.   Lots of the comments above bring familiar memories to mind from my 26 years of AC maintenance in the USN, USAF and aircraft manufacturer environment.  None are unbelievable to me.  Thanks for the memories. 

notarboca
User Rank
Gold
Re: Frightening
notarboca   10/18/2012 2:13:33 PM
NO RATINGS
Wow, the lack of good QA at the depot level is extremely scary.  I worked 12 years in the general/commercial avionics world, and EVERYTHING had to be checked by an in-house FAA approved inspector.  Techs certifying their own work is a recipe for disaster.

Tool_maker
User Rank
Platinum
Re: experience counts
Tool_maker   10/11/2012 3:59:54 PM
NO RATINGS
I take my hat off to anyone who is able to diagnose any electrical problem in an automobile. Perhaps with the right equipment and schematic, but to just be able to walk in and solve seems impossible.

oldpartsnrust
User Rank
Iron
Re: Frightening - Show versus Tell
oldpartsnrust   10/11/2012 3:34:32 PM
NO RATINGS
My wife relayed a story one of the tubing bender operators told her about a young "hot-shot" engineer that had designed a tube that he was convinced saved money, material, and maintenance cost by eliminating a few fittings.  He had spent days checking that the tube could be installed in one piece as opposed to being made in 3 pieces and assembled on the aircraft.  The tubing bender operator rejected the part several times, only to have it resubmitted without any changes.  This resulted in a "face to face" requested by the tubing bender operator.  He took the engineer, who was still adamantly defending the viability of the part, down to the bending machine and proceeded to "bend" the newly engineered part.  The tubing bender started whipping the tubing around wildly to make the multitude of small bends necessary resulting in large chuncks of tubing kinking, snapping off and flying around the shop.......  Obviously the engineer agreed to re-work the part......this time with fittings.

oldpartsnrust
User Rank
Iron
Re: experience counts
oldpartsnrust   10/11/2012 3:26:25 PM
NO RATINGS
Experience does count.  When I had my automotive electrical shop, I could "diagnose" a number of problems just from the customer's description...  Certain GM automobiles would have the radio shut off when the driver's door was opened.  This was a blown Cigarette lighter fuse, most likely caused by coins in the ashtray,,,, Certain Fords would trigger the intermittent wipers whenever the headlights were turned on, or the high beams activated.  This was a loose Driver side wiring harness body ground.  Imagine tracking those down the first time!

Tool_maker
User Rank
Platinum
Re: experience counts
Tool_maker   10/9/2012 12:51:33 PM
NO RATINGS
  I have been in manufacturing since 1964 and I love to hear a younger voice admit that there are occasions when experience counts for something. As another poster on this thread has said, sometimes things just did not sound right. It is amazing to me how much seat-of-the-pants knowledge is rejected by people new to the field because it does not appear in a textbook nor is there an algorithm written to which it can be tested.

  It goes without saying that a dinosaur like me also needs to be receptive to innovation. It is called teamwork.

William K.
User Rank
Platinum
Preventing the nasty crash
William K.   10/5/2012 9:11:45 PM
NO RATINGS
"Intuition" is not just wild hunches popping out of the air! Most often it is built on both experience and understanding of a system, or systems. A complete ubderstanding does not need to come from experience, and experience alone does not bring understanding. But some few people develope both, and hence become quite valuable.

What I wonde is just what kind of test would have spotted that problem, and how often are tests like that done? A short circuit between circuits on a harness plug is not something that one person would check for with a multimeter alone. Finding the problem by dignostics would have meant looking at the circuits and finding what wires could have a problem that would cause the symptom, , and then tracing that circuit to find the problem. Not a simple task by any means.

TunaFish#5
User Rank
Gold
missing facet of the story
TunaFish#5   10/5/2012 10:14:30 AM
NO RATINGS
Explained neither in the story nor in the comments I've seen is what moved the quality guy to hit the gear limit switch when the elevator motion showed a transient behavior.

OK, somebody mentioned intuition -- fine; I'll buy that.

Another mentioned autopilot system.  Well, OK, but how does that get you into the wheel well when autopilot's off?

Still a great story, but this omission leaves this engineer a bit dissatisfied the inspector's "whimsical" reach into the wheel well.

GlennA
User Rank
Gold
experience counts
GlennA   10/4/2012 10:19:12 PM
NO RATINGS
The story doesn't say how many years of experience the mechanic had.  After spending several years working on stone machines I could diagnose many problems by a slight difference in the noise the machine made.  A new operator couldn't distinguish the difference.  So the twitch that was of no concern to a less experienced mechanic, obviously caught the attention of the more experienced mechanic.

Page 1/3  >  >>


Partner Zone
Latest Analysis
A bold, gold, open-air coupe may not be the ticket to automotive nirvana for every consumer, but Lexus’ LF-C2 concept car certainly turned heads at the recent Los Angeles Auto Show. What’s more, it may provide a glimpse of the luxury automaker’s future.
Perhaps you didn't know that there are a variety of classes, both live and archived, offered via the Design News Continuing Education Center (CEC) sponsored by Digi-Key? The best part – they are free!
Engineer comic Don McMillan explains the fun engineers have with team-building exercises. Can you relate?
The complexity of diesel engines means optimizing their performance requires a large amount of experimentation. Computational fluid dynamics (CFD) is a very useful and intuitive tool in this, and cold flow analysis using CFD is an ideal approach to study the flow characteristics without going into the details of chemical reactions occurring during the combustion.
The damage to Sony from the cyber attack seems to have been heightened by failure to follow two basic security rules.
More:Blogs|News
Design News Webinar Series
12/11/2014 8:00 a.m. California / 11:00 a.m. New York
12/10/2014 8:00 a.m. California / 11:00 a.m. New York
11/19/2014 11:00 a.m. California / 2:00 p.m. New York
11/6/2014 11:00 a.m. California / 2:00 p.m. New York
Quick Poll
The Continuing Education Center offers engineers an entirely new way to get the education they need to formulate next-generation solutions.
Jan 12 - 16, Programmable Logic - How do they do that?
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  67


Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.
Learn More   |   Login   |   Archived Classes
Twitter Feed
Design News Twitter Feed
Like Us on Facebook

Sponsored Content

Technology Marketplace

Copyright © 2014 UBM Canon, A UBM company, All rights reserved. Privacy Policy | Terms of Service