Calling this particular problem maintenance debt is a bit disingenuous. PMCS/PMI could have been performed perfectly for decades and not caught this problem. Peculiar dichotomy in this story; the conflation of design flaw and lack of spare parts and improper maintenance.

It's not like the manufacturer can't schedule a full disassembly of a unit 10 years into its lifetime. Car magazines do it.

Wait hang on, I was under the impression that a D check (?) did exactly this, every 6-7 years. This is second hand knowledge from a pilot buddy so maybe I'm forgetting something. Also it's on the civvy side of things, maybe the military does stuff differently?

If it's as simple as the military has shittier maintenance checks, then that's a solvable problem.

Edit: ok looked it up, it is a civilian vs military thing.

How much time do you spend performing exhaustive checks for problems that don't exist?

Also, I like to be the first to know I'm wrong. If I make 100 aircraft and dedicate one to disassembly for study after a quarter of its estimated life, I'll be a .75% investment on better understanding my product. If De Havilland had done that, the stress on the square windows of the Comet would have been discovered before they started falling from the skies and we'd all be flying more beautiful planes.

I was shocked when I found out that, in more than 100 flights, nobody inspected the underside or the leading edges of the shuttle in orbit to check for damage incurred on lift off. They were pretty sure the only dangerous part of the flight was the re-entry.

You say a problem does not exist. You may have good reason to think it doesn't, and, yet, people die because it does.

You absolutely should spend time looking for things you expect not to find, because sometimes you will be wrong.

When you're maintaining an aircraft, a nuclear plant, or anything sufficiently complex or life critical, you should spend a certain amount of time looking for ghosts. You _will_ find them. Your model of an engineered system should include a finite rate of unknown bugs.

https://www.militarytimes.com/news/your-navy/2017/08/27/navy...

https://news.ycombinator.com/item?id=15118141

However the military apparently doesn't do this.

https://en.wikipedia.org/wiki/Aircraft_maintenance_checks#D_...

https://youtu.be/x_yHtfGH0nI?t=36m55s

So far as the HH-53 (the USAF version), when I rode one in the 80's, the saying was that if it wasn't dripping hydraulic fluid, there was something wrong.

A lot can be learned from aerospace engineering and the systems engineering used to design air and space vehicles.

The US military polices itself, so important things can be made optional. They don't have to answer to the FAA on maintenance issues, for example.

But a visual inspection on a fuel line can be really difficult. I had a motorcycle with a leaky fuel line once, luckily it sprung a leak while warming up in my driveway and I turned off the bike before anything bad happened but it was almost impossible to tell where the leak was without pressurized fuel, the hose looked pristine without positive pressure to highlight the crack.

In race cars, they sometimes 'overpressure' the fuel line (above operating pressure but below max pressure) to check for leaks, I wonder if they ever do that routinely for aircraft.

11 person-years. You don't need the same person to conduct all the inspection.

I'm open to being corrected on this, but no-one has yet posted any evidence that there is any extant procedure for inspecting every part of a 747.

That is disingenuous.