#the titanium in the engine blades has a small impurity and it Breaks causing uncontained engine failure and severes the hydraulics

[whilomm]

these are claims from a different whistleblower than the one that was totally not murdered by boeing

(disclaimer, im not an expert and this article doesnt go into a ton of detail on the specific issues, so i could be a lil off, these are very much non-expert speculation rambles. anyone who understands better, feel free to correct me/add more deets).

if im reading it right these claims get into the way boeing has been outsourcing more and more manufacturing of parts to other companies, such as for the fuselage (the plane body as a whole, big tube u sit in). if those parts dont quite fit together right (and keep in mind the margins of error on these things can be VERY small in some cases, though im not sure exactly how much wiggle room they got here), that can lead to too much stress on certain parts.

like, for example, if one part of the fuselage is just baaaarely too big for the next part it connects to, it might all seem to fit together perfectly fine, but every time it takes off and lands or goes thru compression cycles (that is when they take off and land, going from low pressure-high pressure-low pressure), it just puts a BIT too much pressure on where they join. and over the years, that pressure just adds up until theres microscopic stress fractures, which become slightly larger stress fractures, until they get big enough that once a plane reaches a high enough altitude theres a midair disentegration, which is. exactly as bad as it sounds.

(sidenote: compression cycles can be more important for determining an airplanes lifespan than flight hours. the usual metaphor is bending a paperclip back and forth until it breaks, how many times can you bend it before metal fatigue sets in and it just snaps. holding it in a more bent position however will take a lot longer to snap it generally.)

now to be clear, every single plane has an intended service life, and its well known that planes can only take so many compression cycles before they start to get really hard to maintain without going kablooey. a plane may be rated for like, idk, 50k compression cycles (so, taking off and landing 50k times before its retired, because after that its no longer worth the maintenance vs just making a new plane). but if it turns out that plane has some flaw in its build that means itll develop fatal stress factures at only 20k cycles, well. thats bad. not sure exactly how the schedule on looking for stress factures looks like for maintenece crews (do they do it regularly for all planes on a set schedule? do they only do it occasionally for new planes, and start to ramp up checks as the plane gets older? dunno!) but well. generally speaking, a plane having a fatal flaw that gives it an explosive midlife crisis is Bad. i would hope theyd catch it! but i dont know enough about the deets of fuselage maintenence to know the specifics.

and OH YAY COMPOSITE MATERIALS. now, before anyone gets too freaked out thinking about the uh. submarine. use of composite materials is actually far more common on planes than on subs for a buncha reasons. one, planes just generally undergo a lot less in terms of pressure (that futurama joke, "this spaceship can handle between one and zero atmospheres", vs subs that have to deal with tens to potentially hundreds of atmospheres) but also because apparently, for complicated material engineering reasons, composite materials work much better under tension (high pressure INSIDE pushing OUT, like airplane) than under compression (high pressure OUTSIDE pushing IN, like submarine). heres a vid from someone who wrote their masters on composite materials under compression if you wanna hear from someone slightly smarter on the subject. im not gonna pretend like i understand the full deets, but "composites do OKAY with tension" is enough for me, go read the fancy scientific papers if you want more.

now, so that people do freak out at least a little bit: hm. dont like that they are using Way More Composite Than Usual on this plane. how much is the usual? idk, i assume composites are much more popular with low altitude small aircraft (bc well, weight and less pressure worries), dunno whats considered normal for high altitude longhaul crafts. but, apparently, the dreamliner is "more than usual". which, yeah cool, lighter weight airplanes use less fuel which is better for longhaul flights. is it. well tested enough though???

...anyway. im not an engineer, idk the full Deets, but well. havin lotsa fun hearing the engineers talk about how the parts of the giant metal skybirds dont fit together quite right and theyre using materials that fail more catastrophically than metal with less warning, experimentally, and we dont quiiiite have the data to know if. its a problem. thats really fun! LOVE hearing about how much theyre outsourcing parts, given how bad quality control of things as tiny as the titanium in some bolts or a little bit of the engine blades being not properly vacuum forged has lead to catastrophic failure in the past, and knowing how important sourcing of parts in airplanes is. all VERY yay!