Thursday, March 3, 2022

MIL-Spec

No, Kenny. Not MIL-Fer.

Military Specifications. Some sound a little bit crazy, like the adhesive bonded, composite helicopter blade with the specification that every blade had to be 200% tested to destruction.

Say what? What did they have left after testing to put on helicopters. And how do you test the same part to destruction twice?

Some bright-eyed and bushy-tailed engineer noticed that all composite blades started to fail from the ends while they did durability testing. Blades were cut apart and it was verified that the ends were most vulnerable to poor wet-out and entrained air-bubbles which squished out to pancake-shaped voids when the assembly was clamped together and the adhesive cured.

Two, may three, birds were killed with one stone when they decided to make the blades one meter longer than required and to saw 1/2 meter off each end. Those ends were then destructively tested. If both ends met the spec the blade was a "good" one and used. The test also had the advantage of removing the two portions of the blade most likely to start to fail, a failure which could then propagate to the rest of the blade.

For shits-and-giggles, the bright-eyed, bushy-tailed engineer decided to label that form of process validation "200% Test-to-Failure" and the name stuck.

6 comments:

  1. That was creative engineering at its finest!

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  2. yuk-yuk!

    Kind of like the "Write Only Memory"....

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  3. Sometime Mil Spec means it's awesome. Sometimes it just means it meets the lowest and cheapest standard imaginable.

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    1. No. It means it's more expensive.
      My equipment was down and not war ready.
      I could go to Radio Shack and by the transistor I needed for a dime.
      Except I couldn't.
      I had to wait three days for the approved transistor.

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  4. Dan, you are so right. I do not miss doing QA for a DoD contractor. Sometimes the level of stupidity, especially in some of the younger engineers at Picatinny was mind boggling.

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  5. Mil-Spec does not necessarily mean 'the best'. It just means the item met the specific standard specified in the Bid for Contract put out by DOD.

    I do not remember which Apollo astronaut said the following. It might have been Buzz Aldrin. But when asked by a reporter what it felt like just before being launched into space by a Saturn V, he said that all he could think about was the fact that he was sitting atop a rocket with over 100,000 parts, each one of them built by the lowest bidder. Mil-Spec.

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