I wonder on what basis Boeing thought that damage to a load-bearing part could be safely ignored? I hope it wasn't "nothing bad has happened for 50+ years, so it's unlikely to happen now"?
Boeing knew of flaw in part linked to UPS plane crash, NTSB report says
51–60 of 188 posts
Re: Boeing knew of flaw in part linked to UPS plane crash, NTSB report says
#52Earlier quoted context omitted.
> blaming the presumably foreign maintenance crew The same happened with MCAS, the pro-Boeing argument was that if those were American pilots it would have been fine.
As a matter of fact, the same issue did occur to US-based-airlines, and the pilots did catch it. That does not however answer the question of whether they just got lucky, or were more skilled, though there are some indications that it may have been skill.
Most likely just luck. These days US pilots can’t keep their planes separate from their helicopters so we're not exactly sending our best up there.
Re: Boeing knew of flaw in part linked to UPS plane crash, NTSB report says
#53Re: Boeing knew of flaw in part linked to UPS plane crash, NTSB report says
#54The headline is missing an important bit. Boeing knew of the flaw, and sent a letter to airlines about it. In 2011.
Well yes but Boeing also said it "would not result in a safety of flight condition." There's a lot of gray going on here.
What's gray? To me it looks like written proof of incompetence.
Re: Boeing knew of flaw in part linked to UPS plane crash, NTSB report says
#55Earlier quoted context omitted.
It's not really the same. Pilots need extensive training for how to handle emergency situations and maintenance crew don't. It's not super harsh to say that pilots in different regions are at different levels for those weird situations. It is super harsh to say that maintenance crews in some regions can't do their baseline job.
That's entirely false, the maintenance crew are highly trained people they don't figure out things on the go and when they have to figure out solution to an issue, it's based on what they know about the aircrafts from their training.
Totally agree. Maintenance staff often get ignored. It is worth pointing out how skilled these people are and, in general, how dedicated they are to their task. It is also worth pointing out that often maintenance do get involved in emergencies, especially those that work on the line. I had a guy catch a bleed air leak and signal fire in seconds, saving the engine and potentially a lot more. We like to think of the pilots, but maintainers deserve a lot of credit.
Re: Boeing knew of flaw in part linked to UPS plane crash, NTSB report says
#56Insane that we can have places like the skunk works create the sr71 and operate on shoe string budgets but the largest passenger plane company in the world can’t accurately assess risk on planes far under the former planes Mach 3 record
I don't see that as a valid comparison. SR-71s could operate with a much higher level of risk than commercial passenger planes. IIRC, SR-71s leaked fuel on the ground, and their wings dragged on the ground without special attachments. Pilots needed special pressure suits, etc. I also expect that they were much less complex than an aircraft that provides a comfortable, pressurized cabin; the high level of safety menti…
The SR-71 is pressurized. Not to sea level pressure, obviously, but it wasn't exactly unpressurized either. The main reason the crew wore pressure suits is for heat retention and oxygen delivery.
Re: Boeing knew of flaw in part linked to UPS plane crash, NTSB report says
#57Earlier quoted context omitted.
That's indeed a very naive conclusion. Once that bearing is gone the stress that it would normally allow to escape on account of rotation would be directly transferred to the metal around it and to the bolts holding the whole thing in place. Guess what broke first? So if that bearing went that's not quite a smoking gun yet but it would definitely be a step closer to a root cause.
After watching the below video, it's the excess bearing play and thus no-longer-constrained force directions that would seem to be the issue. With a proper tolerance bearing in place, the force is constrained so that other parts are only stressed in directions they're well suited to handle (because the bearing takes the load). Once the bearing develops excess tolerance, you've got a bucking engine that (to your point…
> The fact that Boeing supposedly modeled this and came up with non-safety critical in the event of bearing breakage... curious how that will turn out.
They'd have to show at least one plane with a bearing gone that still flies as intended. I suggest we break one on purpose, put the full complement of Boeing execs on that plane to prove its safety given the alternative of retracting that statement.
Re: Boeing knew of flaw in part linked to UPS plane crash, NTSB report says
#58I recall a lot of fingerpointing minutes after the crash by people blaming the presumably foreign maintenance crew. Even now there is a lot of uncertainty around this crash, maintenance - or lack thereof - or even wrong maintenance could still be a factor. But given the location of the part asking for a 'visual inspection' is a pretty strange move, the part is all but inaccessible when it is in its normal position an…
> blaming the presumably foreign maintenance crew The same happened with MCAS, the pro-Boeing argument was that if those were American pilots it would have been fine.
Boeing themselves, including their CEOs, kept repeating that bullshit. Even after the FAA finally realised the issue, and refused Boeing's first attempted fix that relied on pilots being able to identify the situation and enact the procedure within 10 seconds (in various tests in a Southwest training center, it was around 30s on average). Then the FAA mandated a full redesign of the MCAS system to actually rely on two sensors and handle disagreements. And Calhoun kept repeating that "this wouldn't have happened with American pilots".
Re: Boeing knew of flaw in part linked to UPS plane crash, NTSB report says
#59Earlier quoted context omitted.
That's entirely false, the maintenance crew are highly trained people they don't figure out things on the go and when they have to figure out solution to an issue, it's based on what they know about the aircrafts from their training.
Maintenance crew are highly trained people that in strange situations can pause their work to figure out a fix and ask experts what to do. Very different from how a pilot has to handle strange situations. Being ready for anything in an airborne plane without a pause button is so much harder, impossibly hard, and not every air authority tries as hard to reach the impossible.
Stand outside an engine test cell for a while and tell me that maintenance crews don't deal with emergencies. I'll bet they do so more often than pilots, we just don't hear about it because there are no passengers at risk. Nobody is going to make a 'Sully' like movie about the maintenance mechanic that spotted an issue with a part under test before it led to one or more catastrophic failures. They're more likely to make a lawyer the lead than the mechanic.
This is not just filling out reports and looking at stuff, they're in no way comparable to your local garage mechanic (and not to dump on them either: they too have to deal with out of the ordinary situations).
The responsibility issues are the same as with the pilots as well, they fuck up people die.
Re: Boeing knew of flaw in part linked to UPS plane crash, NTSB report says
#60Earlier quoted context omitted.
That's indeed a very naive conclusion. Once that bearing is gone the stress that it would normally allow to escape on account of rotation would be directly transferred to the metal around it and to the bolts holding the whole thing in place. Guess what broke first? So if that bearing went that's not quite a smoking gun yet but it would definitely be a step closer to a root cause.
> Once that bearing is gone the stress that it would normally allow to escape on account of rotation would be directly transferred to the metal around it The bearing would have to sieze up and the bearing axle be locked to the race. There is some limit to rotational torque even with a siezed bearings. Metaphor: arthritic joints are not smooth, but they will rotate if given enough torque. From the images, it looks lik…
The forces on that mount are pretty extreme. Once the bearing seized it was really a matter of time before something gave and given the strength of the casing as well as the strength of the material and mount points it was a toss-up between the bolts and the casing. The previous evidence showed a clear order to the bolts breaking suggesting one bolt was heavier loaded than the remaining ones. The new evidence points to a much more extreme failure.
As for your 'limit to rotational torque': seized bearings do not 'rotate if given enough torque' they will break right out of their casings and whatever those casings are surrounded by. The reason is that unlike your cartilage the bearings are orders of magnitude harder than the materials around them. For a bearing to seize indicates that the material has already deformed, you either catch it before the race goes or it will crack and after that all bets are quite literally off. I'm not aware of any design that would spec a bearing in a situation with such forces that would still happily work with that bearing replaced by a bushing welded to the shaft and the surrounding material even if it is statically in exactly the same position.
What you describe is a worn bearing with an excess of play, not a seized one, which tends to exhibit roughly the same characteristics as a welded joint with dissimilar materials.
Bearings are wear items, bearings that are worn or seized are something that should never ever happen in an aircraft, there is no way that this particular design would continue to function with sufficient margin if that bearing would fail. If not caught before it breaks the next flight is going to be a disaster. Take off in a fully loaded aircraft of this size puts extreme stress on the engine mounts. They are designed with all of their parts in working order, this is not a case of 'oh, we'll fix that the next time this craft is in for maintenance'. All parts of a plane that is certified as airworthy are supposed to be operating as originally specified.
The default assumption is that it all looked good during the last inspection and that the time between the failure occurring and the plane going down was short. If it was not that would be highly unexpected. But again, until the final report is in that's speculative, and if anything the people at the NTSB are scary good at getting to root causes.