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During 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
by alexanderstears 9y ago
During 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.