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WTF? I thought aircraft maintenance stipulated that all parts have to be inspected, some often, others seldom, but none never.
by Arnt 9y ago
WTF? I thought aircraft maintenance stipulated that all parts have to be inspected, some often, others seldom, but none never.
- foldr 9y agoA 747-400 has 6 million parts (according to Google). Good luck inspecting all of those.
- icebraining 9y agoOn each plane it would not be reasonable, but on a few planes it could be done, and would detect defects like the one described above.
- Arnt 9y agoAircraft procedures aren't reasonable. Go and read an accident post-mortem sometime, they're gorgeous. They describe debugging with all the dials turned to eleven. Inspirational.
- Parcissons 9y agoIf at least there where crawlspaces for inspection robots planned into the design.
- colechristensen 9y agoThe reasons planes are so safe is because there are several "unreasonable" things about designing and maintaining aircraft that most engineers would think somewhere between unnecessary and ridiculous. A lot can be learned from aerospace engineering and the systems engineering used to design air and space vehicles.
- tyingq 9y agoAlso, a fair amount of the safety of civilian aircraft is because the aircraft owners don't get to skip critical processes, maintenance, etc. They have to answer to regulatory agencies, inspections, etc. 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.
- alexanderstears 9y agoDuring the D maintenance, every part should be inspected. Things like fuel lines should be inspected much more regularly, ideally more often than it would take to rub through a fuel line. 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.
- foldr 9y agoIf the 6 million parts figure is correct, it's obvious that it is not possible to inspect every part of a 747. Suppose we allow 1 minute per part inspection. Then that's still about 11 years of inspection time (without taking any breaks!)
- dozzie 9y ago> that's still about 11 years of inspection time 11 person-years. You don't need the same person to conduct all the inspection.
- foldr 9y agoSure, but you'd need thousands of people to get it down to anything reasonable, even with the highly optimistic 1 minute per part inspection estimate. 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.
- alexanderstears 9y ago6 million parts is probably misleading. Bolts, screws, and washers are replaced perfunctory and with aerospace-grade parts that are presumed to be in compliance - half the parts on a plane might be things that are replaced that way. Also, that part count is probably inclusive of the engines and avionics and those are inspected on separate schedules by separate technicians. Lord knows how many parts are on a 747 circuit board, but as long as the board is working correctly, do you need to check every capacitor on the board? The D service also takes tens of thousands of hours and months - each panel is removed and every inch of the aircraft is inspected by master technicians and factory representatives. IT can only happen at special factories that have the space for the plane to come apart and come back together like it should.
- cm2187 9y agoI believe that B747 do get regularly tear down. They basically remove all the cabins, lots of the conduits and wires, remove the instruments in the cockpit, inspect hidden areas, and reassemble the whole thing. https://en.wikipedia.org/wiki/Aircraft_maintenance_checks#D_check https://en.wikipedia.org/wiki/Aircraft_maintenance_checks#D_...
- foldr 9y agoA tear down doesn't necessarily involve inspecting every part.
- chiph 9y agoThey inspect pretty near every part on a 747 during a D check. Including the toilets. https://youtu.be/x_yHtfGH0nI?t=36m55s 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.
- foldr 9y agoI'm sure they do a thorough inspection, but there is nothing in the video to suggest that they inspect literally every part, or anything close to it. Note that by "every part" I mean every component, not every area of the plane. Your remark about the toilets suggests that you may have assumed the latter interpretation.
- dmoy 9y agoI'm looking this up now from a sibling comment, I think that yes every N years a civilian aircraft goes through a complete teardown and inspection, taking >50,000 person-hours of time or something depending on the complexity of the aircraft. However the military apparently doesn't do this.