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

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

#531

Post by thsksbd »

WheatMillington wrote: post #31
chatmasta wrote: post #14

This is reassuring news to me, as someone who has opted for Airbus over Boeing (and even paid extra for it) whenever given the choice since the first 737-MAX crashes in 2017.

How is this reassuring?! Are you sure you don't mean "vindicating" or similar? Hard to understand how anyone could feel reassured by this.

Id feel mostly vindicated (which is worse - no one likes that guy), but also reassured. Reassured that I'm not crazy!

The decision OP took might have been extreme and costly (time wise and effort mostly). People around him might have lightly whispered to him to be reasonable, or "trust the experts". This wears on you eventually and you start to doubt your own reasonableness.

Boeing starts leaving bolts unfastened and all of a sudden you remember the almost weekly stream of pre-pandemic HN articles with new material on Boeing's fall from excellence.

Boeing's marketing dept. was capitalizing that everyone had forgotten about the MAX. The few of us who remembered it maybe weirdos, but we're nut nuts!

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

#532

Post by WalterBright »

SAI_Peregrinus wrote: post #500
9659 wrote: post #464

Earlier quoted context omitted.

"Runaway stab trim". It is a memory item, every pilot should be able to perform it from memory. Turn off the motor, and the trim is manual. There is a crank right there in the cockpit. If it is too hard to turn, change aircraft configuration to reduce the forces required to. Pilot know how to do this. This pilot stuff, they understand the forces on the flight controls and what impacts them. Boeing made an engineering…

Boeing also reduced the size of the manual trim wheels , which let them become impossible to turn sooner than on previous 737s.

The electric trim switches override MCAS. This was explained in the Emergency Airworthiness Directive sent to all MAX pilots after the first crash.

Also, overspeeding the airplane makes it much harder to turn the manual trim wheel. The cockpit voice recorder on the EA flight recorded the overspeed warning horn, which the crew did nothing about (they were at full power, should have pulled the throttles back).

The LA crew restored normal trim twenty-five times before crashing. What they never did was turn it off after restoring normal trim.

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

#533

Post by someonehere »

Are airlines still saving money by “servicing” their airplanes overseas with cheaper labor like my friend told me a few years ago?

After 9/11 a friend who I’m close with was laid off as well as many other maintenance people. United began the process of moving their plane maintenance people to southeast Asian locations to cut down on labor.

Race to the bottom to save money and now loose bolts?

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

#534

Post by dilyevsky »

bb88 wrote: post #496
dilyevsky wrote: post #448

Earlier quoted context omitted.

Would you pay at least 2x for your software to have couple more nines of reliability? I’m gonna guess that “no”. At places where it costs $$$ to have bugs shipped to the end customer (e.g phones) or where there’re regulatory requirements they still have dedicated qa.

It depends. 1% of 10000 is 100. .01% is 1. If someone came up to me and said, "Hey I can save you 99% of expected costs with 1% of your profit.", I might go for it.

Which is what i said in second part of my comment. For most software businesses the cost of shipping a bug is trivial and/or poorly measured so due to McNamara fallacy it is readily exchanged for well measured cost of having a functioning qa team

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

#535

Post by johnwalkr »

trebligdivad wrote: post #154

https://www.youtube.com/watch?v=maLBGFYl9_o is a good video explaining how the bolts/doors etc are supposed to go together.

Oh wow. I made another comment about how important tension in fasteners is, to provide a clamping load and therefore friction between two faces. I was thinking that there must have been a process failure. Fasteners often shear off if there is not enough tension and therefore friction. But in this case it looks like there is not any clamping load between parts for at least some of the fasteners, so those fasteners basically act only as pins. There are other "stop pad" parts that constrain movement of the plug but as far as I can tell they must be compliant/flexible parts. The video mentions "roller pins" which for a door would be used with a cam mechanism. I think that stop pads plus roller pins/door/cam mechanism holds the door securely, but stop pads plus plug/pins does not.

On paper all 6 degrees of freedom may be constrained with the plug but in principle compliant pads may allow shear forces and/or rattling on the fasteners and they eventually fail.

I will eat my hat if the eventual required solution doesn't involve some kind of mating cup/cone or wedge shaped parts to more positively constrain the plug.

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

#536

Post by xtracto »

0cf8612b2e1e wrote: post #202
rconti wrote: post #160

So, about that Max 10 on which you were hoping to get fast-track approval...

Airbus must be having a fantastic week.

Airlines should stop buying Boeing airplanes. At this point they are catastrophes waiting to happen.

Fortunately, most airlines in my country use Airbus planes.

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

#537

Post by WalterBright »

ethbr1 wrote: post #495
9659 wrote: post #464

Earlier quoted context omitted.

"Runaway stab trim". It is a memory item, every pilot should be able to perform it from memory. Turn off the motor, and the trim is manual. There is a crank right there in the cockpit. If it is too hard to turn, change aircraft configuration to reduce the forces required to. Pilot know how to do this. This pilot stuff, they understand the forces on the flight controls and what impacts them. Boeing made an engineering…

> And that is how aviation becomes safer every year; at a significant cost of customers lives. "Significant" might be inaccurate. It looks like FAA Part 121 accidents over the last 10 years with fatalities have been... 4. [0] For a total of 6 fatalities. [0] https://www.ntsb.gov/Pages/AviationQueryV2.aspx ; 2018 (1 passenger fatality) https://www.ntsb.gov/investigations/Pages/DCA18MA142.aspx ; 2019 (3 crew fatalities…

That low accident rate is nigh inconceivable. It's an incredible achievement.

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

#538

Post by ShadowBanThis01 »

WalterBright wrote: post #427
actionfromafar wrote: post #412

Earlier quoted context omitted.

The problem was not really the software in isolation, but that pilots expected the 737 NG to behave exactly like the old version - because Boeing decided it was too expensive to retrain pilots.

The expense for retraining pilots falls on the airline. Retraining has its own problems. No matter how well retraining is done, pilots still make mistakes from doing the right thing for the previous plane that is the wrong thing for the one they are currently flying. Adjusting airplanes to fly the same way is a major safety advantage.

If a pilot can't be expected to maintain the pitch of a plane on takeoff, he has no business flying ANYTHING.

What Boeing did (and is STILL doing) is expect pilots to know or remember obscure NON-PILOTAGE (and in the case of MCAS, BURIED) trivia to prevent disaster.

Now... what's the more-responsible approach? Expect pilots to pilot, or expect them to recall an ever-growing list of workarounds to incompetent system design?

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

#539

Post by xtracto »

avalys wrote: post #362
chippiewill wrote: post #129

Earlier quoted context omitted.

Only the max-9 has the door plug, the smaller airframes don't have that door, and the larger airframes always have the door fitted

It's not really about the door plug per se, it's about how Boeing's entire manufacturing, design and QA process could allow such an elementary mistake to escape notice in the first place. If they got this wrong, what other bolts didn't they tighten properly? This question is especially relevant since just a few weeks ago, Boeing issued an airworthiness directive about loose bolts in the rudder system. In any reasonab…

The crazy thing is that since the old Max fiasco several of us believed that the priorities of the Boeing company were completely wrong: they had decided to cut so many corners to increase profit to the point of negligence. Doing That, in an airplane is just crazy.

Their manufacturing process is just kaput. And there is no force that will make them fix it until their planes start falling mid flight in pieces.

I find it unfathomable that the FAA is basically sitting watching with their arms crossed. They should fine the heck out of Boeing and ground all their planes. But american protectionism is strong in this one.

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

#540

Post by ShadowBanThis01 »

actionfromafar wrote: post #412
ShadowBanThis01 wrote: post #386

Earlier quoted context omitted.

Except, of course, from Boeing's aircraft-software QA... which killed hundreds of people already.

The problem was not really the software in isolation, but that pilots expected the 737 NG to behave exactly like the old version - because Boeing decided it was too expensive to retrain pilots.

Wrong.
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