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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

#31

Post by kube-system »

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…

This tool would be capable of performing that measurement with 0.001" accuracy. https://www.harborfreight.com/feeler-gauge-32-pc-63665.html

Someone performing maintenance in their garage on an internal combustion engine would encounter the need to measure the same tolerances, for example, adjusting valve clearances. This is a common and accessible measurement task.

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

#32

Post by letitbeirie »

Sebb767 wrote: post #25
rileyteige wrote: post #5

Earlier quoted context omitted.

Not necessarily. A "forced off-airport landing" could also be the result of an engine failure beyond gliding distance of an airport. Or engine fire, medical emergency in remote area, etc. There are many emergencies that could force an aircraft to the ground, off-field. Not all off-field landings result in an accident, or "crash". From our own regulations, NTSB 830 "NOTIFICATION AND REPORTING OF AIRCRAFT ACCIDENTS..."…

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

I was thinking that too, but ditching a plane into water doesn't really count as a crash. Not sure it counts as a "landing" either, but hey...

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

#33

Post by t0mas88 »

matt-attack wrote: post #30
JanSolo wrote: post #18

Interesting that the vast majority of 737s were flying so frequently that this was not found earlier. For their entire 20-ish year service life, those planes are never left idle long enough for this part to rust! Amazing. Goes to show how popular and successful the 737 line is.

And this may be obvious to some, but why does use inhibit rust?

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.

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

#34

Post by mberning »

LittlePeter wrote: post #28
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…

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.

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

#35

Post by 0xffff2 »

Sebb767 wrote: post #25
rileyteige wrote: post #5

Earlier quoted context omitted.

Not necessarily. A "forced off-airport landing" could also be the result of an engine failure beyond gliding distance of an airport. Or engine fire, medical emergency in remote area, etc. There are many emergencies that could force an aircraft to the ground, off-field. Not all off-field landings result in an accident, or "crash". From our own regulations, NTSB 830 "NOTIFICATION AND REPORTING OF AIRCRAFT ACCIDENTS..."…

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

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 of an off airport landing of a 737 without significant damage to the aircraft.

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

#36

Post by frakt0x90 »

leetrout wrote: post #3

I have been wondering how dangerous flying is going to be when when / if it comes back and all these planes come out of storage. Mechanical things just sitting around is some times far worse than them being in constant use.

You still have to keep the aircraft's normal maintenance schedule even when it's in storage.

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

#37

Post by JanSolo »

matt-attack wrote: post #30
JanSolo wrote: post #18

Interesting that the vast majority of 737s were flying so frequently that this was not found earlier. For their entire 20-ish year service life, those planes are never left idle long enough for this part to rust! Amazing. Goes to show how popular and successful the 737 line is.

And this may be obvious to some, but why does use inhibit rust?

From my cursory glance at the doc, the part in question is inside the bleed-air cutoff system. This is a flapper valve (a bit like in your toilet) that takes air from the engine and uses it for other systems in the plane (air conditioning, cooling, starting other engines, etc). When it's in use, the movement of the parts will prevent rust from building up in one spot. A little rust might accumulate, but it will be rubbed/wiped off when it's next used. The problem occurs when enough rust builds up that the flapper cannot move anymore.

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

#38

Post by richardwhiuk »

Sebb767 wrote: post #25
rileyteige wrote: post #5

Earlier quoted context omitted.

Not necessarily. A "forced off-airport landing" could also be the result of an engine failure beyond gliding distance of an airport. Or engine fire, medical emergency in remote area, etc. There are many emergencies that could force an aircraft to the ground, off-field. Not all off-field landings result in an accident, or "crash". From our own regulations, NTSB 830 "NOTIFICATION AND REPORTING OF AIRCRAFT ACCIDENTS..."…

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)

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

#39

Post by bamboozled »

linuxftw wrote: post #27
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.

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.

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

#40

Post by throwaway0a5e »

adenozine wrote: post #16
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…

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 favors dainty little parts that can barely do the job with maintenance tacked on over heavier overbuilt parts that you don't need to check as much.

>I can only imagine that in aviation, there are even more advanced tools, especially with a well-respected corp like Boeing.

Lol. "More advanced" often being something a long the lines of a $100000 dollar go-nogo gauge because you don't trust your employees to read a measuring tool.

>If these flapper bushings are bad consistently,

Bushings are probably (i.e. "almost certainly" but I wasn't in that engineering meeting so I don't know for sure) a wear item and of course they could build beefy ones but the OEM has to balance between weight and maintenance hours. Doesn't surprise me that a little extra corrosion grit in there makes them go out of spec fast.

>if guys are bringing me the same rifle with the same issue over and over, it makes me really uneasy because it's inefficient for my shop, and it points to carelessness from the vendor

The whole value proposition of a Hi-point or a Chinese pump shotgun is that the manufacturing tolerances are wide opens so that your wallet doesn't have to be.

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