737NGs have cracked 'pickle forks' after finding several in the jets.
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The first article I read on the pickle forks (sorry, can't find it now) said that originally, the part was cut from billet aluminum, creating a lot of waste. It also had to then be shipped to a subcontractor on California for 'normalization'. The new forks are forged, (not cast), and 'don't need to be normalized', or shipped to California. (I suspect that maybe they still do.)
Aha! From Waterpilot's comment (#10) above: "To increase materials efficiency, the main component of the pickle fork is now produced out of forged, restrike aluminum. Previously the part was produced from block aluminum, which generated a significant amount of scrap because the pickle fork component was cut and shaped from the block. The pickle fork forgings now arrive in the approximate shape of the component so less aluminum is scrapped. In addition, the type of aluminum previously used for the pickle fork required shipping to California for stress relieving and return back to Auburn for continued production. The current aluminum forgings do not require stress treatment."
Aha! From Waterpilot's comment (#10) above: "To increase materials efficiency, the main component of the pickle fork is now produced out of forged, restrike aluminum. Previously the part was produced from block aluminum, which generated a significant amount of scrap because the pickle fork component was cut and shaped from the block. The pickle fork forgings now arrive in the approximate shape of the component so less aluminum is scrapped. In addition, the type of aluminum previously used for the pickle fork required shipping to California for stress relieving and return back to Auburn for continued production. The current aluminum forgings do not require stress treatment."
The restrike die operation is, fundamentally, a solid forming operation. The main difference is that a restrike die is used after most of the major forming already has been performed suggesting that the components may still start life as block aluminium / aluminum.
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The AD that calls for repetitive inspections on a large lot of 737 is out and can be read here
http://rgl.faa.gov/Regulatory_and_Gu...2019-20-02.pdf
http://rgl.faa.gov/Regulatory_and_Gu...2019-20-02.pdf
The patent for pickle forks as aircraft wing-to-fuselage joint dates to 2013: https://patents.google.com/patent/US20150097076A1/en
The pickle fork diagram is included as a description of prior art. And probably predates this patent by some years.
Interesting that, restrike.
The restrike die operation is, fundamentally, a solid forming operation. The main difference is that a restrike die is used after most of the major forming already has been performed suggesting that the components may still start life as block aluminium / aluminum.
The restrike die operation is, fundamentally, a solid forming operation. The main difference is that a restrike die is used after most of the major forming already has been performed suggesting that the components may still start life as block aluminium / aluminum.
aluminum.
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The pickle fork diagram is included as a description of prior art. And probably predates this patent by some years.
It's all of the 373NGs.
The immediate action for 30k cycles, and the rest within 1000 cycles.
Then there the repeat inspection every 3500 cycles.
would be interesting to see the Boeing Multi-Operator Message MOM-MOM-19-0536-01B.
I'm assuming that's not public.
The immediate action for 30k cycles, and the rest within 1000 cycles.
Then there the repeat inspection every 3500 cycles.
would be interesting to see the Boeing Multi-Operator Message MOM-MOM-19-0536-01B.
I'm assuming that's not public.
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Regarding the Boeing MOM:
From the FAA AD itself:
"This service information also provides procedures for reporting inspection results to Boeing. This service information is reasonably available because the interested parties have access to it through their normal course of business or by the means identified in the ADDRESSES section".
Companies have access to the MOM (which is sent to the relevant operators) and actions for reporting back to Boeing when the inspections have been made.
This information isn't normally shared to the public.
From the FAA AD itself:
"This service information also provides procedures for reporting inspection results to Boeing. This service information is reasonably available because the interested parties have access to it through their normal course of business or by the means identified in the ADDRESSES section".
Companies have access to the MOM (which is sent to the relevant operators) and actions for reporting back to Boeing when the inspections have been made.
This information isn't normally shared to the public.
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The AD requires eventual inspection of all aircraft with more than 22,600 flight cycles. The FAA in the AD preamble estimated that to currently be about 1900 of the NG airplanes.
The part of the pickle fork fitting that is required to be inspected is exposed in the top forward corners of the wheel wells. With all the equipment installed near that location, it is not possible to get your head into positions that allow an adequate direct visual inspection of each of the fittings. Photos of that area that are adequate to detect the cracks have been taken by holding a cell phone up in that area. The AD requires an inspection using a borescope. There is no work required to gain access for the inspection. You just need a ladder and a borescope. It can be done in less than one hour. If you find a crack you are grounded until an approved repair is made.
The part of the pickle fork fitting that is required to be inspected is exposed in the top forward corners of the wheel wells. With all the equipment installed near that location, it is not possible to get your head into positions that allow an adequate direct visual inspection of each of the fittings. Photos of that area that are adequate to detect the cracks have been taken by holding a cell phone up in that area. The AD requires an inspection using a borescope. There is no work required to gain access for the inspection. You just need a ladder and a borescope. It can be done in less than one hour. If you find a crack you are grounded until an approved repair is made.
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The Boeing MOM referenced in the AD is available to the public in the public rule making docket, which can be viewed at:
https://www.regulations.gov/document...2019-0711-0002
https://www.regulations.gov/document...2019-0711-0002
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The Boeing MOM referenced in the AD is available to the public in the public rule making docket, which can be viewed at:
https://www.regulations.gov/document...2019-0711-0002
https://www.regulations.gov/document...2019-0711-0002
Just my opinion based on a fair amount of background re fasteners, holes, coldworking, tooling, and a very very small bit of repair issues
First- thanks to dave for the document complete with pics
second - I will draw your attention to the FACT that it was/is the Fail safe strap portion of the PF - not the PF- as the scare press would infer-
third- note that most - many NG will need nothing done/inspected till the next check - and an estimate of 1 hour for inspection is not unreasonable- which does not count time to possibly clean area, maybe take photos and complete paperwork.
Fourth - Even assuming the crack went to both holes and to both edges, the ' wings' will not fall off since the larger bolts ABOVE the smaller ones take the load. Under that event, then a major rework of some type might well be needed.
Fifth - the obvious cure to prevent such happening would be during production to ensure at time of assembly, the holes in that area be drilled, coldworked, reamed, and interference fit bolts installed. A few extra steps- relatively easy to do during assembly at wichita. It is possible that such coldworking was supposed to be done- but was missed since it involves an extra drill and ream operation during assembly. No easy way to ensure it was done.
I'll refer you to my post number 11 in this thread for more details
28th Sep 2019, 07:45
#11 (permalink)
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Grebe - regarding your second point: Some of the initially inspected airplanes had both the pickle fork fitting outer chord AND the fail safe strap cracked in a given location. This is mentioned in the AD discussion section. It's shown in the first page of pictures in the Boeing document as well.
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Grebe - regarding your second point: Some of the initially inspected airplanes had both the pickle fork fitting outer chord AND the fail safe strap cracked in a given location. This is mentioned in the AD discussion section. It's shown in the first page of pictures in the Boeing document as well.
True but my point in #4 I believe still applies
Fourth - Even assuming the crack went to both holes and to both edges, the ' wings' will not fall off since the larger bolts ABOVE the smaller ones take the load. Under that event, then a major rework of some type might well be needed.
Could someone tell me the difference between a 737NG and a 737-800. Also I see there are different varients of the 800 version. For example Egyptair fly the 866 varient. Is it to do with range?
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866 is a Customer Code which identifies an 800 Series for Egyptair. A United Airlines 800 would be an 824 for example. It’s a method Boeing uses to sort out and customise technical manuals etc.