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Priming Drilled Holes - An Electrical Issue

David Paule

Well Known Member
Every once in a while something in Wall Street Journal directly pertains to our airplanes. As you might know, Boeing is working through a new issue with the 737 MAX. This time it's a simple electrical issue. Here's the gist of it:

"The Federal Aviation Administration on Thursday said it is investigating why Boeing missed that a minor production change involving drilled holes wound up as the root of potential electrical problems.....

"...Previously, factory workers first drilled initial so-called pilot holes, primed and then drilled a second set of holes. The second set of holes stripped away the primer, allowing metal to touch metal and thus providing a protective “grounding path” for electrical current. By only drilling a single set of holes, the primer got in the way of that safeguard. The aim was to make the manufacturing process more efficient, some of the people said.

"...The 737 MAX’s electrical issue first surfaced in early February when a newly produced jet wouldn’t start for Boeing pilots after it rolled out of the factory, according to people familiar with the matter."

Dave
 
Understanding the electron flow path is extremely important, no matter what the application - 737 or RV7.

I can confess that in the late 1980s I had a very small part in a project that will remain nameless that used carbon fiber for the first time replacing fiberglass and metal. Apparently the guys that were working on the electric parts had assumed that carbon fiber was an insulator like fiberglass. The entire "device" was powered by electricity. I was too dumb and inexperienced to know the difference, but I did know that when the sparks and smoke started flying, something bad was happening. I stood there with my chin on my chest while another kid that knew what was happening started cutting wires and yanking out components. He probably saved some lives that day. Quite exciting.
 
Every once in a while something in Wall Street Journal directly pertains to our airplanes. As you might know, Boeing is working through a new issue with the 737 MAX. This time it's a simple electrical issue. Here's the gist of it:

"The Federal Aviation Administration on Thursday said it is investigating why Boeing missed that a minor production change involving drilled holes wound up as the root of potential electrical problems.....

"...Previously, factory workers first drilled initial so-called pilot holes, primed and then drilled a second set of holes. The second set of holes stripped away the primer, allowing metal to touch metal and thus providing a protective “grounding path” for electrical current. By only drilling a single set of holes, the primer got in the way of that safeguard. The aim was to make the manufacturing process more efficient, some of the people said.

"...The 737 MAX’s electrical issue first surfaced in early February when a newly produced jet wouldn’t start for Boeing pilots after it rolled out of the factory, according to people familiar with the matter."

Dave

a very interesting study in organizational management. I suspect that the original design team was quite large and designed the two step drilling process for just this reason. Years later, a small team focused only on cost reduction comes by and changes things without the same depth of knowledge and without significant design oversight and introduces new problems. The designers created a specific process for a specific reason and the bean counters come by and see it only as an un-necessary inefficiency that must have been missed by the designers lack of expertise in operational efficiency / cost management.

Watch the movie / series about the space shuttle - Challenger. Small, post flight testing team kept finding indications of premature failure in the large o-ring. Yet management wouldn't authorize a re-design. Unsure how accurately this series reflects reality, but an interesting view into how bureaucratic organizations operate when outside of the design phase.
 
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