3 ms·
> But maintenance people in aviation aren't really ever exercising those creative problem solving skills This is the opposite of what happened. The engineers w
by bambax 4y ago
> But maintenance people in aviation aren't really ever exercising those creative problem solving skills
This is the opposite of what happened. The engineers were confronted with a novel and unexpected problem, and instead of following procedure (which they lacked access to) they applied "creative problem solving skills". From TFA:
> Although it was possible to install the post-SB fuel lines and hydraulic pump with a pre-SB hydraulic tube, the tube would rest against one of the fuel lines at a point where it rounded a 90-degree bend close to the pump. Aware that the plane could not be dispatched unless there was clearance between the tubes, the technicians torqued a nut on the end of the hydraulic tube until it rose approximately 0.635 mm off the face of the fuel line.
Torquing a nut so that the hydraulic tube isn't technically rubbing against the fuel line is pretty creative and seems to solve the problem. But it didn't take into account pressure and vibration while in flight, and almost caused the death of 306 people.
- iso1631 4y agoI'm amazed they can measure the distance between two real non-fixed components down to a few micrometers (they wrote 0.635mm, implying somewhere between 630um and 640um) If 0.635mm (an odd number itself which happens to be exactly 1/40th of an inch, or "25 thous" in American sizes) and they let it go that sounds really odd. That's literally the size of a grain of sand. If the concern is rubbing, sure that implies it will move during flight.
- bambax 4y ago0.635 mm is indeed an odd number. The thickness of a piece of 80gsm paper is 0.065 mm, so maybe what is meant is "about the thickness of ten sheets of paper"...?
- jamincan 4y agoIt's precisely 0.025 inches.
- intrasight 4y agoWho else thinks that if a tolerance of the thickness of a sheet of paper, in a mechanic/maintenance setting, could cause the death of over 300 people, that there's a striking lack of fault-tolerance in the design.
- plasticchris 4y agoIt sounds to me like they stuck a machinists shim in there, effectively a bit of precisely measured metal.
- nick889996544 4y agoShim feeler gauges would be readily available in most shops checking wear on moving parts. 0.0025 inches (0.635mm) was included in the first high quality (gearwrench brand) set that I looked up online.
- mrguyorama 4y agoPlane maintenance involves a lot of precise and specially designed tools.
- mannykannot 4y agoI wonder if this nut, if not every nut on an ETOPS airliner (or in general), has a specific torque value. If adjusting the torque can open up a gap, presumably doing so could close one as well.