[nabilhat]

Who even uses calipers for critical precision? Calipers are for dimensions machinists append with -ish, as in four thousandths-ish. Important dimensions deserve a micrometer, especially the feeler guage that just said you need to tell your boss to scrap a 737. Decent machine shops even have different classes of micrometer; there's the one you carry in your pocket, and then there's the fancy set locked up in your boss's office that only comes out for special occasions, like when your boss has to tell their boss to scrap a 737.

[cartoonfoxes]

I see this in my own shop. Digital displays instill people with greater confidence in the measurement than is warranted. This is something of a UI fail, as the tool manufacturer (Mitutoyo) has very clearly defined measurement precision for all their metrology equipment (+- 0.001" and 0.0015" for the calipers).

[sgnelson]

That is a very interesting observation, thank you. I've never thought about the digital vs analog in terms of actual "oh, it's digital, it's better." measurement variation.

In my experience, I think you're probably right, it does seem like people may take them as "more accurate."

[kayfox]

You don't scrap a 737 for some worn out parts.

[doodlebugging]

This is why I still own most of the vehicles I've purchased over the last 30 years. It is much cheaper to replace worn parts, ideally before they fail, than it is to replace the entire vehicle. I have the skillsets needed to maintain my own equipment and the tools so I just monitor the operating condition of each and replace or repair things as needed.

These planes have regular maintenance checks and diagnostics to help identify issues before they become catastrophic failures. This whole thing is likely a normal maintenance issue, maybe unexpected due to the unusual nature of the scenario they face with so many idle jets, but not something that would have escaped their servicing routines. The system flagged a problem and now they can address it. If for some reason their diagnostics were not set up to detect this sort of issue then you have a problem.

[bluGill]

Airplanes worry about fatigue. They have to be replaced after so many years or the wings will fall off in the air. If the airplane is only a few weeks away from replacement when it fails an inspection you scrap it now, if it has years to go you replace parts.

[gonzo]

It’s not years, it’s “cycles” take-off/landing with pressurized passenger compartment in-between.

And it’s not often the wings fall off, but the tail does, or sometimes a huge hole opens in the “skin” of the airframe.

Example: Aloha Airlines Flight 243

[doodlebugging]

I don't disagree with this at all. That is how it should work and that is apparently how it is working.

[teh_klev]

Not that I want to be pedantic, but that's a rather sweeping statement. The decision to scrap would depend on things like the number of flight hours and takeoff/landing cycles on the air frame and the number of other worn parts, hitting meantime-before-failure on large numbers of parts/assemblies, such that it may be more economical to scrap.