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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

#161

Post by dingaling »

CaptainZapp wrote: post #24
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…

Boeing used to be a well respected company. At least until the merger with McDonnell Douglas, which turned it from an engineering driven company to a financial engineering company.

And in turn the same had happened with Douglas; McDonnell's investment was reluctantly accepted in order to save the company but utterly changed the culture from engineering to finance.

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

#162

Post by dingaling »

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 still have a huge portfolio of well engineered products

Mostly obtained by acquisitions.

In current production only the 737, 747, 777 and 787 and T-7 originate solely from Boeing.

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

#163

Post by dingaling »

Contax wrote: post #91
jefftk wrote: post #50

The title here should have "737 NG, Classic" not "737 NG Classic". As in "Boeing 737 NG and Classic aircraft", not "Boeing 737 NG Classic aircraft".

And why not just "NG and Classic"? Really curious, I see this replacement of "and" for a comma in a lot on headlines, and I don't know why or where it comes from (English is not my first language). Is there a name for this?

It confused me too when I first started working in the USA where it is common in headlines.

Using an ampersand requires only one more space than a comma but is unambiguous.

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

#164

Post by _trampeltier »

elliekelly wrote: post #73
rlpb wrote: post #19

Earlier quoted context omitted.

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.

Perhaps an odd question from someone who only just found out that feeler gauges exist - do they periodically calibrate or confirm the measurements of the gauges? If someone is sticking the same gauge into tight spaces all day wouldn't it wear down, even slightly, and alter the reliability of the measurement?

For things to measure, where a person finally have to sign for an OK, tools allways have to be calibrated and tested (not just in aerospace industrie). Thats also the reason, why there is not just the persons name but also the toolnumber on the test protocol.

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

#165

Post by benhurmarcel »

aunty_helen wrote: post #152
t0mas88 wrote: post #33

Earlier quoted context omitted.

In normal use these valves take air out of the turbine stage, so they see very very hot air with almost zero moisture in it in normal use. If you park them long enough I can imagine they get wet from rain or even just condensation.

According to the AD this is the 5th stage bleed air valve, so on the compressor side and cold air. >Bleed air is tapped at the 5th and 9th stages of the HP compressor and from the fan. https://hursts.org.uk/airbus-technical/html/ar01s19.html#idm... (Airbus doc but the engines are CFM56 on the 737 models listed) Also according to this page the CFM56 doesn't have a turbine bleed air takeoff.

When you say "cold air" I guess you mean that it's bled before the combustion stage. It's not cold at all after the compression.

And bleed air is indeed always taken in the compressor, never in the turbine. First there's no point taking it later than the compressor, you just want compressed air. And it's ultimately used to ventilate the cabin, you don't want fuel vapors or smell.

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

#166

Post by benhurmarcel »

perardi wrote: post #68
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?

I’m guessing some other parameter was more important. Thermal expansion characteristics, ease of tooling, interactions with the materials around it, resistance to some other non-oxidative chemical corrosion…

This particular valve sees temperatures above 600°C. You basically need to use steel or inconel.

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

#167

Post by refurb »

teh_klev wrote: post #107
refurb wrote: post #74

Earlier quoted context omitted.

They are typically harden steel, so wear minimally and when you test a gap, you’re not really applying much force. If the feeler gauge doesn’t slip in with minimal force, then that tells you the gaps is smaller than the gauge.

> If the feeler gauge doesn’t slip in with minimal force, then that tells you the gaps is smaller than the gauge. The numbers of sets of comically bent out of shape feeler gauges I've encountered in my life demonstrates that there's a bunch of folks out there who don't understand how they're supposed to be used. As in "maybe if I just push harder this'll fit" :)

It’s a combination feeler gauge/pry bar!

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

#168

Post by aunty_helen »

benhurmarcel wrote: post #165
aunty_helen wrote: post #152

Earlier quoted context omitted.

According to the AD this is the 5th stage bleed air valve, so on the compressor side and cold air. >Bleed air is tapped at the 5th and 9th stages of the HP compressor and from the fan. https://hursts.org.uk/airbus-technical/html/ar01s19.html#idm... (Airbus doc but the engines are CFM56 on the 737 models listed) Also according to this page the CFM56 doesn't have a turbine bleed air takeoff.

When you say "cold air" I guess you mean that it's bled before the combustion stage. It's not cold at all after the compression. And bleed air is indeed always taken in the compressor, never in the turbine. First there's no point taking it later than the compressor, you just want compressed air. And it's ultimately used to ventilate the cabin, you don't want fuel vapors or smell.

Stage 5 would be pretty early on. However generally when talking about the HPC you're talking about cold air. At this stage, cold air that's sprayed on the turbine housing when engine power is reduced to thermally shrink the metal to keep the turbine blades and casing within tolerance for efficiency's sake.

All is explained in the link I posted, would recommend it as good introductory reading on the subject.

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

#170

Post by deeblering4 »

At the beginning of lockdowns I was wondering what might break down on the fleets of planes that have been grounded, or under utilized.

I wonder what other bugs will be uncovered from not exercising machines that are designed to be used on a very regular basis.

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