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Quality impeding Reliability. What are your stories?
2

Quality impeding Reliability. What are your stories?

Quality impeding Reliability. What are your stories?

(OP)
Without tainting the thread with my own views, let's look at a few responces first. Do you have a story about quality getting in the way of reliability in aerospace products?

RE: Quality impeding Reliability. What are your stories?

You better fully define what you mean by quality.

If you mean 'better made components' then, no I don't think I've experienced them causing a problem (I'm excluding possible situations where there was a design problem that poor quality may have been hiding).

If you mean 'QA systems' such as ISO-9001 then maybe.  I've heard the view espoused that because of the effort required to 'certify' design changes, or the like, that improvements sometimes aren't incorporated.

Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: Quality impeding Reliability. What are your stories?

2
hgldr,

   Many, many years ago, I was involved in a project for a European customer who insisted that we set up a  QA process.  The end result was that all the people who knew how to do the work wrote quality procedures, and we brought in contract people to do the actual work.  Quality suffered.

   If you are working with an organization controlled by rigid, procedure driven people, your QA process will be just another set of procedures to follow, and there will be no improvement in quality.

               JHG

RE: Quality impeding Reliability. What are your stories?

drawoh, well said.

RE: Quality impeding Reliability. What are your stories?

On the other hand what about the hundred years of experience suggesting that better quality leads to better reliability? Or do you buy Yugos in preference to Hondas?


 

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies  http://eng-tips.com/market.cfm?

RE: Quality impeding Reliability. What are your stories?

GregLocock,

   Better quality leads to better reliability.  A lot of QA processes (not all) lead to reduced quality, with all the attendant consequences.  

   I read the OP's use of "quality" as meaning QA.  A strict literal intepretation of his question does not make sense.

   During WWII, the Germans had problems controlling their Fritz_X glider bombs in combat.  The controls worked fine on the ground.  It was eventually found that a French slave worker had taken apart some coax cables, snipped the conductors inside, then reassembled everything.  The resulting electronics worked on the ground, but did not work in the air with the airplane vibrating.  One could argue that this was a quality program with the objective of reduced reliability.

   I cannot find any mention of this in Wikipedia. I got it from an aircraft history at home.  I will have to look it up.

               JHG

RE: Quality impeding Reliability. What are your stories?

Brazing job.

100,000 parts.

Didn't get full flow on maybe 1,300.  Still functional but appearance not suitable.   

Reran them and all looked good.  

What we missed was that the braze alloy had Zinc in it.  Every time it was heated it lost Zinc and the remelt temperature was maybe 50F higher.  

Customer went to use the parts in a machine set for the proper temperature which turned out to be too low for the reworked parts.  
 

Thomas J. Walz
Carbide Processors, Inc.
www.carbideprocessors.com

Good engineering starts with a Grainger Catalog.    

RE: Quality impeding Reliability. What are your stories?

(OP)
I wanted comments first before explaining the question more clearly. Quality in my industry is not the same as the word "quality" to most english speaking people. In street language, quality is synonymous with goodness, runs-forever, reliable, lasts-a-long-time, etc, etc. In Industry however, Quality basically means that every unit is built exactly the same. The epoxies are mixed exactly the same, at a controlled temperature, the oxide coatings are all controlled to within a few millionths of an inch, all the same.
 
If the original design and analysis is wrong, if a shaft is running beyond its torque rating, if a transistor is running too hot, then all of the units will be built exactly the same; with a transistor which is going to fail and a shaft which is going to break.   

KENAT's comment reminded me of what I see very often, "...because of the effort required to 'certify' design changes, or the like, that improvements sometimes aren't incorporated."
Sadly in aerospace, certification is so incredibly expensive, that faulty products are often sold even though the manufacturer knows that a simple fix will improve it. The FAA and ISO don't allow simple fixes though. I bet those O-rings on the Challenger had 20lb of paperwork with the word "Quality" stamped on each sheet.
 

RE: Quality impeding Reliability. What are your stories?

So what is your problem or question?

"The FAA and ISO don't allow simple fixes though"  Rubbish.  The FAA doesn't allow "fixes" based on wishful thinking, arm-waving and management BS.  While the cert process isn't perfect, its a lot better than not having any process.

 

RE: Quality impeding Reliability. What are your stories?

So, in your situation, how is "Quality impeding Reliability"?  I can see how it would affect production, but if product of consistant "quality" is being produced I don't understand how it affects "reliability".  Or are you referring to "Poor Quality" as opposed to customer requirements?

"Good to know you got shoes to wear when you find the floor." - Robert Hunter
 

RE: Quality impeding Reliability. What are your stories?

Personally I use Dr. Deming's definition that quality is exactly what the customer says it is.  

We differentiate quality, reliability, consistency and many forms of each as distinct attributes of the same process.   Remember the story of the blind men and the elephant.  One felt it and determined it was a wall, another felt a tree trunk, a third felt a rope and a fourth felt a snake while the fifth felt a huge leaf.   

Your question seems like playing with words.    Much as in high school we devised elaborate math formulas to prove that 1+1 =0 and other nonsense.  

Personally I am really impressed by the aircraft certification process.   Many tens of thousands of parts all interacting and the planes rarely fall out of the sky.  It is still a very safe method of transportation.        
 

Thomas J. Walz
Carbide Processors, Inc.
www.carbideprocessors.com

Good engineering starts with a Grainger Catalog.    

RE: Quality impeding Reliability. What are your stories?

Seems like the OP hasn't used 'reliability' in his Demming definition of 'quality'.  Anyway looks like a classic thread where anecdote will be presented as data.



 

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies  http://eng-tips.com/market.cfm?

RE: Quality impeding Reliability. What are your stories?

(OP)
SWComposites, your comment that it's "Rubbish" that the FAA doesn't allow simple fixes shows me that you really have not seen how expensive re-certification is. Your bias that simple fixes are defined as "arm waving" may point to an actual problem of what goes on in your particular office.
 
In the orignal question of this thread I was looking for actual examples from actual projects, and there ARE many stories.



 

RE: Quality impeding Reliability. What are your stories?

(OP)
12 posts already and only one example. Engineers I know who actually work in aerospace have many examples. If you are in that industry, I know you've seen similar stories. Here's a few from three different companies:

Inductor core cracking on an aircraft battery charger due to excessive core loss. Engineering found a simple alteration of the inductor was necessary. QA sais can't do. Re-certification would cost over $20k though. Fix was never implemented.

Diodes within a rocket thruster subject to voltages beyond their rating. Fortunately, this would only occur during a worse case condition not seen with typical conditions yet. QA would require expensive recertification of the entire unit if the fix were installed. Simple change to a different diode never took place.

Unstable oscillations from a voltage supply to software unit in a satellite. Engineering found a simple chip capacitor added solves it. Change was tested in lab over temperature extremes and CAD analysis. QA sais no. Change would require vibration tests, certified thermal chamber tests, re-writing documents like build procedures, certification compliance, etc...too expensive and time-consuming. Units were shipped with unstable supply lines. They were all built the same. QA was satisfied.

If you are an engineer in aerospace, I know you've seen similar stories.   

RE: Quality impeding Reliability. What are your stories?

Phil Crosby is considered "Old hat " by some QA gurus these days, but a comment he made in the 70's still resonates among some QA people.

"Tip:
Be very careful about where you apply zero defects. If what you're doing contributes towards a mission critical or complex goal, you'd better adopt a zero defects approach, or things could quickly unravel.
 

However, if you fanatically follow a zero defects approach in areas which don't need it, you'll most likely be wasting resources. One of the most important of these resources is time, and this is where people are accused of time-destroying "perfectionism.""
B.E.

 

RE: Quality impeding Reliability. What are your stories?

Dear hgldr,

Originally it looked like you were after a philosophical discussion about the relationship between quality and reliability.  Now it looks like you are talking about quality specifications that are not perfect.    To me those are two entirely different topics.  
 

Thomas J. Walz
Carbide Processors, Inc.
www.carbideprocessors.com

Good engineering starts with a Grainger Catalog.    

RE: Quality impeding Reliability. What are your stories?

Seems part of the problem is your QA departments operating outside their field of responsibility/expertise.

In my time in Aerospace/Defense it was up to Engineering and the Customer Desk officer to decide the types of decisions you're talking about.

It was Engineering's Names that went on the Certificates of Design, not QA.

It was up to QA to ensure units built actually met the data pack referenced by the Certificate Of Design.

Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: Quality impeding Reliability. What are your stories?

hgldr,

   I have worked with people who have aggressively demanded consistency, in my opinion, frustrating efforts to improve processes.

   You need to distinguish between QA procedures, and actually achieving quality.  QA is just like any other job.  It is futile if you do it badly.   

               JHG

RE: Quality impeding Reliability. What are your stories?

Quote (hgldr):

...

Inductor core cracking ...

Diodes within a rocket thruster ...

Unstable oscillations from a voltage supply ...

   Are these conflicts with your QA department, or are they conflicts with management?  QA requires you to follow procedures and submit documentation.  It is management that decides that it is not worth the effort.
 

               JHG

RE: Quality impeding Reliability. What are your stories?

This thread should be retitled to "Does management greed impede reliability?"  Sadly the answer is yes in too many cases.

As KENAT stated, QA should have nothing to do with certification; that is an engineering responsibility.  Engineering should discuss the certification requirements with the customer/FAA and determine the required data/testing/etc.  

Sounds like in the cases quoted, insufficient testing was originally done, and now management doesn't want to pay to fix the problem.  Hard to have sympathy.

Perhaps the real question should be "why wasn't the customer/FAA informed about the defective conditions?"


 

RE: Quality impeding Reliability. What are your stories?

(OP)
To avoid confusion I shouldn't have used the word "quality" in the first paragraph. Most of the engineers at the companies I have worked with throw this term around loosely to mean, "quality control procedures" or, "government paperwork requirements" or similar. In some instances the problem could be attributed to "management greed" as SWcomposties wrote because indeed, it all boils down to cost. My opinion is that the management of aerospace firms didn't make the expensive paperwork requirements in the first place. We're just stuck with them.  

Mainly it's the high cost of re-certification which is demanded by the certification agencies which I am attempting to aim this discussion at.  

Again, the question was, What are your stories. . . ?"

Surely some of you have seen cases of product improvements and corrections which weren't made because of the high cost of certification.

 

RE: Quality impeding Reliability. What are your stories?

One of my first tasks as an Engineer was to look at a certain 'aircraft accessory' that my company made, compare it to similar more modern items and see where we could share parts/techniques or otherwise save money.  This item was essentially expendable & made by the thousand so there was a real drive on cost.

Well I looked at the prints, talked to manufacturing and came up with a list of something like 30 items.

A lot of these looked like simple changes - swapping custom parts for similar off the shelf parts.  Changing materials/treatments to lower cost ones etc.

However, when you looked at what testing would have been required to certify many of these changes, be it vibration tests, ultimate strength tests, salt spray or similar tests, drop tests, flight tests... almost none of them were viable.

Now my guess is a lot of them probably would have been fine.  So you could argue that this is one of the examples you're asking for.  However, when you're talking about parts that not only get flown around over our heads, but in my case also go 'bang', then I'm OK with erring on the side of caution.  

Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: Quality impeding Reliability. What are your stories?

I think it's important to have some moderatly high bar to pass before an aircraft part is considered airworthy.  Without that we will end up with crappy airplanes.  Once that is passed we ask ourselves what hurdles must be jumped to make a change to an already acceptable design.  The FAA usually want's the same hurdles to be jumped, but in some cases they will accept an argument from similarity that most of the tests can be skipped.  If you were changing one diode for another, and both diodes were structurally similar why recertify the vibration test.  You probably do need to recert any electrical functional test.

Of course if you say these simple changes need no recert at all you now are on that slippery slope that ends at "We just exchanged the main aluminum structural spar for an equivalent design in fiberlass.  So no retest is needed."  Of course this is a ridiculous extreme, but defining that line is difficult, and the damage that could be caused by making an unacceptable but apparantly minor change severe for example the KC hyatt disaster.

The problem could be greedy management.  The problem could also be clueless management who don't know how to argue effectivly with the FAA that a specific test is not needed, or that an alternate test is acceptable.  For the diode I would have suggested the diode be mounted in a similar maner in a test board and vibration tested.  If the individual compontent passes, then the swap is accpetable. QED.  

Sometimes the FAA makes you go through the hoops of comeing up with a test plan and then saying you can skip the test.  

-Kirby

Kirby Wilkerson

Remember, first define the problem, then solve it.

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