For 4 years I worked in the Quality Assurance department for a major manufacturer that supplied switch assemblies and readout displays for commercial aircraft control panels. The title of this article might make you believe this story is about some magically wonderful machine that never fails. You might feel justified in asking, “What’s wrong with that?”
But THAT was the problem!
This was no ordinary piece of equipment. This was TEST equipment! It’ s purpose is to fail – or more precisely to let us know when there is a problem, much like the purpose of a circuit breaker to fail, to prevent something worse from happening, like overheating wires in the walls of our house setting our home on fire.
In the case of this tester, possibly to prevent a commercial airplane from crashing. Specifically the purpose of this particular machine was to let us know when a bad switch assembly was being tested – to “fail” that switch assembly. If a malfunctioning switch assembly was inserted in the machine, the machine should light up red to indicate a failed switch assembly.
However, the manufacturer’s test procedure read something like, “if the machine passes a known good switch assembly, the machine is working.” Note: the manufacturer who wrote that was the same guy who had designed, and built the tester, and who also worked at the bench next to mine.
I happened to be filling in for the Customer Returned Materials (CRM) processor on the day that one particular switch assembly was returned to us from the aircraft manufacturer.
Since, all of these switches must meet stringent military standards for quality assurance, it was easy to trace the failure back to the piece of test equipment about which this article was written, which is the reason I called this article, “The Test Equipment that Failed to Fail”.
This machine worked so well (according to the manufacturer) that it not only passed good switch assemblies, it passed most bad switch assemblies too, as long as they weren’t more than 75% bad.
In other words, the test equipment failed to fail!
If you ever flew on commercial airlines in the 1980s, you’ll be happy to know that each of these switch assemblies had quadruple redundancy built in – there were 4 individual switches working together in each switch assembly – in case one of the 4 switches failed, the other 3 could take the load.
Naturally, as these stories often go, that which is designed to protect us, is also the reason that bad components would get past the inspection process.
I took the switch assembly that was returned as bad, and retraced it’s route. I plugged it into the switch tester that had passed it. Green lights. I once again checked each of the 4 individual switches with an ohm meter. The first failed to do anything, the other 3 worked fine. When I put 4 individual switches into the tester and actuated each one separately, all 4 lights lit up green – not just the green light for the particular switch I was activating, but also for each of the other switches, whether I activated them or not.
I soon figured out that when the pins of a switch were inserted, the contacts on the tester would spread out and short against the contacts for the adjacent switch. Basically, if at least one of the four switches worked, that would satisfy the test equipment!
The switch tester, due to a design flaw, failed to fail assemblies that weren’t at least 75% bad. If any one of the four individual switches worked, the test equipment lit up green, indicating, falsely, that the switch was 100% good!
The more important failure, for this story, is that the switch tester passed it’s own test, due to a faulty assumption on the part of the manufacturer – the guy that worked at the bench next to mine.
If the switch tester didn’t complain when the switches worked, it was assumed everything was fine!
So, what does any of this have to do with Running Barefoot?
Practically everything!
Our bare soles are saturated with sensitive nerve endings – any of you who have siblings that you tortured by tickling their bare soles, or who tortured you by tickling your bare soles. know what I’m talking about!
These nerve endings are part of our own personal quality assurance test equipment. Their very important task is to let us know immediately, emphatically,and with each and every step, among other more subtle issues – which we’ll discuss later, how hard our feet are pounding into the ground while we are running.
Shoe manufacturers test the design of their shoes before they start production. The problem is, their test is similar to that of the test equipment above, “if we don’t perceive significant impact in our soles while running, the shoes are fine”.
Sadly, shoe manufacturers actually take this a step further. Their goal is actually to eliminate the feedback from our soles, even when we are pounding too hard – when we are manufacturing bad steps!
Much like my co-worker thought he was doing our employer a favor, by insuring that nearly every switch was shipped, whether they were 100% good or not, running shoe manufacturers are mistakenly trying to eliminate the sensation of impact, no matter how badly we are running.
“That’s wonderful!” you might be thinking, “I don’t want to feel impact while I’m running.”
But, again, the problem is that we really should be feeling impact, among other things! That’s why we have so many nerve endings, of all places, in the soles of our feet. This information, is vitally important if we want to improve our running technique, to learn to eliminate pounding (not just the sensation of pounding), sheer forces, and excess strain on the rest of our body. These messages ultimately can teach us to run more gently, more gracefully, hopefully, reducing the risk of serious injury!
Just like the test equipment I wrote about above should be letting us know when assemblies are bad, so that we don’t ship them to our customers, that information can also be fed back to the assembly line to improve the quality of future products.
Without this information, who knows how sloppy our running technique might become, and how many bad steps we have shipped to your customers?
Our customers know!
At least eventually, when their airplane is crashing … or our knees are damaged and in chronic pain, as a result of years of senseless pounding – literally senseless, because, by wearing shoes that protect us from these sensations, we have blocked our first line of defense against long-term damage. We are, literally, running without some of our senses – with any footwear we are running to some degree, “senselessly!”
So let’s take off our shoes, even those so-called “barefoot” shoes and allow our quality control inspectors – the nerves in our bare soles – to send the necessary feedback to our brains so we can insure that we are, or begin, running gently and gracefully!
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