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FAA issues emergency directive on 2,000 Boeing 737 NG, Classic planes

reuters.com

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Re: FAA issues emergency directive on 2,000 Boeing 737 NG, Classic planes

#51

Post by jcrawfordor »

wwv25 wrote: post #7

One of the inspection checklist items: Measure the clearance between the flapper bushings at both locations on each engine bleed air 5th stage check valve. If the clearance between the flapper bushings is a minimum of 0.004 inch (0.102 mm) at both locations, the engine bleed air 5th stage check valve at that location has passed this inspection. I knew that aviation engineering dealt with tight tolerances, but boy, it…

That's actually larger than the valve clearance specified for many automotive engines, which is commonly checked and adjusted by mechanics using feeler gauges or gap gauges. It's fairly straightforward.

Re: FAA issues emergency directive on 2,000 Boeing 737 NG, Classic planes

#52

Post by adenozine »

throwaway0a5e wrote: post #40
adenozine wrote: post #16

Earlier quoted context omitted.

They've had calipers for literally thousands of years. I used to be involved in some intermediate gunsmithing work, and we had these tools called 'dial calipers' which have a little gauge you read and you can measure extremely precise things. We used it for getting cylinder diameters or clearances that needed that degree of precision. I can only imagine that in aviation, there are even more advanced tools, especially…

This is basically the FAA putting everyone on notice by saying "yo, we found a few that were real bad so y'all gotta make sure you check yours real good." It's a bushing on a control surface, of course it wears over the course of normal use. If it sat for months and corroded slightly the corrosion would cause it to wear faster. This is all perfectly normal. These things are meant to fly so the engineering more often…

Suffice to say, nobody in my unit was rolling out with Hi-point.

Thanks for your post, you are clearly much more aware of aviation than I am, and what you've explained makes perfect sense.

I could've clarified that while I wasn't in control of ordinance, I had some level of trust in those who were, as I'd expect the engineers at Boeing have some level of trust in the designs and blueprints they are working on.

I'm curious to know more about the attitude that an engineer might have about their role in Boeing. It often seems that Boeing is being dragged through the mud, and rightfully so in some part due to the 737 MAX. However, I know enough to know that shit often rolls downhill, even onto those who never ate in the first place. I imagine there could be some disgruntled vibes going around in the shops, far from the boardrooms.

Re: FAA issues emergency directive on 2,000 Boeing 737 NG, Classic planes

#53

Post by lisper »

bewaretheirs wrote: post #44
linuxftw wrote: post #27

Earlier quoted context omitted.

The only person here that knows what they're talking about. Everyone's talking about calipers :/

Yep. To check tolerances, you'd need a go/no-go pair -- one that should fit, and a slightly bigger one which shouldn't.

This is a thing that non-aviators often don't realize about aviation in general: the hard part is designing the artifacts and processes so that by the time you get around to operations, everything is routine and nothing is hard. Flying, building and maintaining airplanes seems hard, but that's mainly because of the volume of stuff you need to know, not because any single item is particularly difficult. All aircraft are built, maintained, and flown by mere mortals. (The designers, on the other hand... ;-)

Re: FAA issues emergency directive on 2,000 Boeing 737 NG, Classic planes

#54

Post by throwaway0a5e »

FDSGSG wrote: post #42
0xffff2 wrote: post #35

Earlier quoted context omitted.

For small 4-6 seater general aviation aircraft it's hard (relative to a normal landing), but not at all unheard of. A modern 4 lane highway is more than wide enough, and very probably has a long enough straight section within range, to make for a relatively uneventful landing if you can get traffic to cooperate. You're absolutely correct though when it comes to larger aircraft. I rather doubt there are any examples o…

> I rather doubt there are any examples of an off airport landing of a 737 without significant damage to the aircraft. https://en.wikipedia.org/wiki/TACA_Flight_110

Looks like they had about 5000ft to work with. Not great, but not bad either.

https://www.google.com/maps/place/30%C2%B001'52.7%22N+89%C2%...

Re: FAA issues emergency directive on 2,000 Boeing 737 NG, Classic planes

#55

Post by redis_mlc »

mberning wrote: post #34
LittlePeter wrote: post #28

Earlier quoted context omitted.

I really struggle to understand how you could have used the term "well-respected" here. It ain't muscle memory, this was done deliberately. Could you explain how you can refer to Boeing being well-respected after the 737 MAX fiasco? Maybe I am missing something. [edit] remove a word

They are a respected company with many respected products, despite your personal feelings towards them. They did screw up big time with the 737 MAX, but they still have a huge portfolio of well engineered products and will surely launch more well respected products in the future.

> They are a respected company with many respected products, despite your personal feelings towards them. They did screw up big time with the 737 MAX, but they still have a huge portfolio of well engineered products and will surely launch more well respected products in the future.

No. All of their recent models have had serious issues. The 787 was also a death trap with Li battery fires and wing root cracking.

They outsourced fuselage construction to Spirit - a huge red flag for aerospace.

Re: FAA issues emergency directive on 2,000 Boeing 737 NG, Classic planes

#56

Post by WrtCdEvrydy »

bamboozled wrote: post #39
linuxftw wrote: post #27

Earlier quoted context omitted.

The only person here that knows what they're talking about. Everyone's talking about calipers :/

I love that out of all the more complex ideas about what may have been used, it turns out likely to be a solid piece of metal with of a given thickness, couldn't get more simple than that.

If you're into 3D Printing, feeler gauges are also a great way to level your bed... move the extruder 0.04 above the bed at four points, stick your 0.04 feeler under it and adjust the springs until it touches the feeler. Voila, one perfectly leveled 3D printer bed.

Re: FAA issues emergency directive on 2,000 Boeing 737 NG, Classic planes

#57

Post by enraged_camel »

MrBuddyCasino wrote: post #47

This may be a dumb question, but why use materials that can corrode on such an important part? Just use stainless steel (or AL or TI), problem solved?

Explain that to the MBAs and bean-counters who are in charge over at Boeing.

Re: FAA issues emergency directive on 2,000 Boeing 737 NG, Classic planes

#58

Post by bilbo0s »

bamboozled wrote: post #39
linuxftw wrote: post #27

Earlier quoted context omitted.

The only person here that knows what they're talking about. Everyone's talking about calipers :/

I love that out of all the more complex ideas about what may have been used, it turns out likely to be a solid piece of metal with of a given thickness, couldn't get more simple than that.

couldn't get more simple than that.

Believe it or not, that's actually a lot of the idea that drives commercial aviation design.

Or used to anyway.

Re: FAA issues emergency directive on 2,000 Boeing 737 NG, Classic planes

#59

Post by numpad0 »

rlpb wrote: post #19
wwv25 wrote: post #7

One of the inspection checklist items: Measure the clearance between the flapper bushings at both locations on each engine bleed air 5th stage check valve. If the clearance between the flapper bushings is a minimum of 0.004 inch (0.102 mm) at both locations, the engine bleed air 5th stage check valve at that location has passed this inspection. I knew that aviation engineering dealt with tight tolerances, but boy, it…

If it's a gap between two parts that they're measuring, that's as simple as a feeler gauge: https://en.wikipedia.org/wiki/Feeler_gauge . The set pictured there looks like it goes down to 0.05mm.

With that in mind the phrasing sound to me like “the bushing is supposed to be moving freely, if it’s stuck to the surface you have to replace it” in aviation lingo without using ambiguous words like “freely”

Re: FAA issues emergency directive on 2,000 Boeing 737 NG, Classic planes

#60

Post by rocqua »

richardwhiuk wrote: post #38
Sebb767 wrote: post #25

Earlier quoted context omitted.

I think it would be rather hard to land a plane off the airport without substantial damage, especially when talking about larger ones.

https://en.wikipedia.org/wiki/TACA_Flight_110 made a dead-stick landing on a grass levee with minor damage - it was later flown out (following an engine change which caused the landing in the first place)

For other confused readers:

A deadstick landing,is a type of forced landing when an aircraft loses all of its propulsive power and is forced to land. The "stick" does not refer to the flight controls, but to the traditional wooden propeller, which without power would just be a "dead stick".

https://en.wikipedia.org/wiki/Deadstick_landing

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