Live data from Hacker News

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

reuters.com

101–110 of 170 posts

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

#101

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?

bearings and bushings need to be hard to resist wear and maintain their dimensions. Stainless steels hard enough for the job are too brittle and those other metals (Al, Ti) aren't even close to the hardness of any category of steel.

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

#102
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…

While machining down to thousands of an inch is a bit tricky, actually measuring that small isn't that hard. Vernier calipers are cheap (Typically the issue isn't the ability to measure to such tight tolerances, the problem is physically getting the calipers into position to do the measurement. Airplanes are full of tight spaces with weird angles, which makes measuring parts without extensive disassembly kind of hard.

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

#104

Earlier quoted context omitted.

Most english speakers also wouldn't be familiar with the term, but it is called 'Headlinese'. https://en.wikipedia.org/wiki/Headline#Headlinese

And it's dumb. We're not setting hot lead into column inches anymore.

But we are trying to fit summaries into a limited screen real estate

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

#105
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…

I know someone who used to be in the business of installing high precision machining equipment. I relay the following anecdote: When he came on site once, the workers who put the machine down on its bedding told him, he didn't need to level it, since they already levelled it "to a thou" (Indian workers). He laughed and said: "Good, someone already did the coarse work for me!".

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

#106

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

Your post seems to imply that a bad product negates the respect earned by leading an industry, nay, multiple industries, for several decades. Do you really truly think that just because the MAX is a POS, that everything that comes out of Boeing can be evaluated under that same lens? Surely you aren't so blind to the reality that engineers do occasionally produce quality work. To your credit, I wouldn't fly myself or…

> Do you really truly think that just because the MAX is a POS, that everything that comes out of Boeing can be evaluated under that same lens?

No I do not. I still wouldn't ever refer to Boeing as well-respected nowadays. Granted, it may be irrational quirk of mine.

To clarify, do I respect Boeing? Yes. But I would not make a post on the Internet and write out "well-respected". I understand Boeing's cultural shift from being an engineering-first company and its MAX fiasco would not warrant "well-respected" in many people's eyes nowadays.

Was Boeing well-respected in the past? Yes. Is Boeing well-respected nowadays? Yes. But to deliberately write it out to me feels like trolling and stoking fire. You surely must understand that a lot of people lost a bit of respect for Boeing in recent years.

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

#107
post #74

Earlier quoted context omitted.

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?

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" :)

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

#108

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.

In my opinion, a big screw up at least warrants that you lose respect, at least temporarily.

They can regain respect by building new good products. Or by admitting mistakes, surely not by laying blame on the pilots.

I am less forgiving. If you want to forgive them, that's your choice.

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

#109
post #87

Earlier quoted context omitted.

You don't scrap a 737 for some worn out parts.

This is why I still own most of the vehicles I've purchased over the last 30 years. It is much cheaper to replace worn parts, ideally before they fail, than it is to replace the entire vehicle. I have the skillsets needed to maintain my own equipment and the tools so I just monitor the operating condition of each and replace or repair things as needed. These planes have regular maintenance checks and diagnostics to h…

Airplanes worry about fatigue. They have to be replaced after so many years or the wings will fall off in the air. If the airplane is only a few weeks away from replacement when it fails an inspection you scrap it now, if it has years to go you replace parts.

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

#110
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…

4 thou isn't a particularly high degree of precision. For about five bucks you can get feeler gauges more accurate than that, and for about thirty you can get a micrometer that's accurate to 0.0005" over a whole inch. (I checked mine against a set of grade 2 gauge blocks at their calibrated temperature.) Normal CNC machines, not designed for extreme precision but the sort of thing an exceptionally serious hobbyist or…

There's a "high tech" (i.e. they mostly don't use cutting tools) machining shop nearby; their proprietary machines (designed & built in-house, never sold or leased externally, only used for contract manufacturing) are repeatable within a few µm (they offer tolerancing below 5 µm on finished parts) and move about as quick as the rapid traverse on a more standard CNC milling machine.
Post reply on HN