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United finds loose bolts on plug doors during 737 Max 9 inspections

theaircurrent.com

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Re: United finds loose bolts on plug doors during 737 Max 9 inspections

#731

Post by drtgh »

drtgh wrote: post #682
SoftTalker wrote: post #548

Earlier quoted context omitted.

Pilots should (are supposed to) disable the auto-trim if it's doing something uncommanded/unexpected. Runaway trim can happen for reasons other than faulty software. MCAS was a new factor and they should have been told about it, I don't dispute that at all.

The manufacturer company put in larger engines than the aircraft is designed for. And they did it to avoid all the homologation licences and design costs involved in bringing a new aircraft to market with the appropriate tolerances, and to compete with another company's aircraft in time (Loss of sales). They introduced MCAS in the aircraft for to balance by software a hardware issue, a big design negligent issue whic…

Where I wrote,

> They introduced MCAS in the aircraft for to balance by software a hardware issue, a big design negligent issue which can lead to stalling.

> Every pilot flying that plane should have been warned that it was not a classic plane with a classic update.

I was mean,

> They introduced MCAS to use software to attempt to balance an aerodynamically unbalanced aircraft with a high stall tendency, in order to avoid designing a new aircraft.

> Any pilot flying that aircraft should have been warned that it was a plane that didn't want to fly aerodynamically, with software forcing it to fly without backed redundancy. It was not mere trimming.

Re: United finds loose bolts on plug doors during 737 Max 9 inspections

#732

Post by MarkMarine »

lobsterthief wrote: post #714
MarkMarine wrote: post #684

Earlier quoted context omitted.

safety wire and cotter pins are preferred methods on aircraft.

Yes. For mission-critical bolts and nuts, absolutely safety wire and cotter pins should be used.

The engineers at Bell also thought that blind bolts you couldn’t inspect in dailies should be wired.

Re: United finds loose bolts on plug doors during 737 Max 9 inspections

#733

Post by giardini »

RF_Savage wrote: post #576
MarkMarine wrote: post #573

I was responsible for safe for flight inspections on military aircraft and the photo included in that post is completely insane to me. Those bolts being loose (and they are BIG bolts) would mean multiple people in the installation process didn’t do their jobs, and signed their life on the line saying they did. When I did maintenance, there was someone (QA) there to witness every torqued bolt, inspect every safety wir…

The management imported from McDonnel-Douglas? The same management that drove it to ground? The fish rots from the head. And these constant problems sure do sound like a new company culture of cutting corners instead engineering first.

Wby the rush to judgement ("The fish rots from the head."). What was done and not done will be traced and the causes determined with good old engineering and detective work. Responsibility will be revealed and the proper parties punished.

Rushing to judgement merely obscures the true responsibilities.

Re: United finds loose bolts on plug doors during 737 Max 9 inspections

#734

Post by talldatethrow »

Dalewyn wrote: post #609
talldatethrow wrote: post #562

Earlier quoted context omitted.

Ive been working on cars and motorcycles and everything else other than airplanes for almost 25 years now, from motor swaps to transmission rebuild and custom suspension. The only time I ever use is a torque wrench is on engine internals, or smaller fancy areas into aluminum. Everything else, over the years, you learn by feel. You pay attention to the size of the bolt, the material it's going into, and it's overall j…

At the Costco where I get my car's tires swapped out (summer/winter tire swap) or rotated, the technician always tightens all the wheel nuts with a torque wrench. Then another, different technician comes by and checks all the nuts again with his own torque wrench. When all is done and I get the sign off paperwork, they strongly encourage me to stop by next time I'm there so they can quickly check the wheel nuts again…

I don't work at a mechanics shop.

Costco prior to probably 15 years ago used to just throw wheels on and hit them with air guns without a torque wrench in sight.

Mechanics shops snapping wheel studs was a common problem for years. A decent mechanic would know to never use a high torque impact gun on something with decently low torque threshold, as I said in my OP about experience. But that shows you how many years and millions of cars were/are on the road without caring about exact torque.

The reason Costco does this, and does it twice, is to make sure the lig nuts at tight on the first place... So you don't leave with one loose. The fact that they use a torque wrench is just because they got tired of replacing wheels studs.

Re: United finds loose bolts on plug doors during 737 Max 9 inspections

#735

Post by SoftTalker »

roelschroeven wrote: post #716
SoftTalker wrote: post #548

Earlier quoted context omitted.

Pilots should (are supposed to) disable the auto-trim if it's doing something uncommanded/unexpected. Runaway trim can happen for reasons other than faulty software. MCAS was a new factor and they should have been told about it, I don't dispute that at all.

Here we are again, this misconception just won't die. In the 737 MAX, the only way to disable auto-trim also disables powered trim (the thumb buttons). As grand parent says, at a certain step in the sequence it was not physically possible for a pilot to trim the plain back to stability manually. It simply can't be done. In the 737 ng, there was a button to do just that. That would have been useful. And that's even ig…

The thumb buttons would override MCAS. But then you'd have to disable the trim motors and trim manually (by hand-cranking a wheel). That part was not clearly understood by the pilots, because they were not told about MCAS.

Re: United finds loose bolts on plug doors during 737 Max 9 inspections

#736

Post by joquarky »

rvba wrote: post #583
RF_Savage wrote: post #576

Earlier quoted context omitted.

The management imported from McDonnel-Douglas? The same management that drove it to ground? The fish rots from the head. And these constant problems sure do sound like a new company culture of cutting corners instead engineering first.

Looks like the installer did their job poorly and the QA rubber stamped it without checking. Are the QAs required to make photos to prove that they did their job? Like those food delivery people. Alternative is wrong bolts, or sabotage. But more possible - one lazy QA ghosting.

Perhaps the installer and/or QA person should be required to be a passenger on the plane after their inspection and before they can mark the task complete.

Re: United finds loose bolts on plug doors during 737 Max 9 inspections

#737

Post by tremon »

psunavy03 wrote: post #104
fullshark wrote: post #30

Earlier quoted context omitted.

I think it would require a fatal air crash of an American flight with a major celebrity on board.

. . . and the US airline industry has still not had a fatal crash in just under 25 years.

Kobe Bryant's death in 2020 doesn't count? I guess because it was a private charter (and a helicopter, but that's still air travel)?

Re: United finds loose bolts on plug doors during 737 Max 9 inspections

#738

Post by bb88 »

MattPalmer1086 wrote: post #723
mangodrunk wrote: post #709

Earlier quoted context omitted.

I disagree with you. You are stating it, but you are not giving reasons. Managers who weren’t developers tend to not be able to manage the team. They can’t help with or understand the technical decisions made. The non-technical managers tend to be project managers just focused on dates.

We may be talking about different levels of management here. A manager should not be making technical decisions, they should have team leads and architects who do that. It's their job to manage the team, interface with the business, prioritise work and give cover to the team so they can get on with it. I guess if you have a manager who is making technical decisions, they are really a hybrid manager/contributor role.…

Then what exactly is the non technical manager's added value?

He has no experience to lead the team in high pressure situations. Like production being down.

He can't truly have a first person understanding of the work of the people who he manages. He has to rely upon others to tell him who's good and who's bad. That sets up a pecking order.

He can't help or mentor engineers with design decisions, or provide a historical context.

He doesn't understand the technology so there's an immediate communication and knowledge barrier that has to be overcome between him and his directs.

He doesn't feel the pain of a bad decision, because he's not coding it, and he can't emphasize with them since he doesn't code.

He tends to push feature development without fixing technical debt. Again that's pain he personally doesn't feel.

Re: United finds loose bolts on plug doors during 737 Max 9 inspections

#739

Post by cyanydeez »

giardini wrote: post #733
RF_Savage wrote: post #576

Earlier quoted context omitted.

The management imported from McDonnel-Douglas? The same management that drove it to ground? The fish rots from the head. And these constant problems sure do sound like a new company culture of cutting corners instead engineering first.

Wby the rush to judgement ("The fish rots from the head."). What was done and not done will be traced and the causes determined with good old engineering and detective work. Responsibility will be revealed and the proper parties punished. Rushing to judgement merely obscures the true responsibilities.

the point is maintenance personnel might be directly signing off but that doesn't mean they're directly responsible if their management set unrealistic timetables. that's the point, systems are as accountable as individuals but often individuals are easier to indict and scapegoat.

Re: United finds loose bolts on plug doors during 737 Max 9 inspections

#740

Post by [deleted] »

jacquesm wrote: post #489
johnwalkr wrote: post #486

Earlier quoted context omitted.

It's a complex topic. Depending on the design, lubrication may be required or forbidden. And if it's required, it should normally be on the threads only, under the head is usually forbidden. And it's very important to understand that in most mechanical design with fasteners, the fasteners provide tension, and friction between 2 faces actually carries the load. Too little tension then fasteners can be sheared off. Too…

Lots of good stuff in this comment but I'm confused about the +/- 30% accuracy quote, in my experience it is relatively easy to reach sub 10% accuracy based on comparing different (good quality) torque wrenches against each other and against a calibrated one. Is there something I am missing here?

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