737NGs have cracked 'pickle forks' after finding several in the jets.
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"Boeing 737 Next Generation (737NG) is the overarching name given to a fleet of aircraft that began production in 1991. It includes the Boeing 737-600, Boeing 737-700, Boeing 737-800 and Boeing 737-900 — variations with different seating capacity. The 737NG featured improved fuel capacity, a 25 percent larger wing capacity, and an ability to fly 900 more nautical miles than earlier 737 models. Southwest Airlines was the world's first airline to take delivery in 1997, and by April 2012, 4,000 Boeing 737NGs had been delivered around the world.
Two decades after the debut of the 737NG, Boeing announced plans for a new model: the Boeing 737 Max 8."
"
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https://airlinesfleet.com/american-a...-and-pictures/
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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
If cracks are found, then do you know what steps need to be taken (interior stripped around the wing box area for example) to get to the problem area?
Appreciate your accurate information in many of your posts.
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My 737-900ER flight this morning was switched to a 757-200OW flown up from Salt Lake to Boise over night - gate agent announced it was the largest plane they had ever used at Boise. Wouldn't surprise me if the airlines are acting aggressively on this one.
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I have not seen any information yet about proposed repair schemes other than replacing the entire cracked fitting with a new one. That obviously is a not a quick repair, but I don't know exactly what steps would be involved.
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Thanks for the response.
Seems this may be quite a lengthy repair job so I will be interested in seeing the details of the repair procedure when published.
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Boeing Floorboard Tape.
https://www.e-aircraftsupply.com/pro.../GSC2195813022
Last edited by B727223Fan; 6th Oct 2019 at 04:47. Reason: incomplete Link
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YIKES ! significant issue re cracks from another site if true
50 percent of those > 25000 cycles in one airline checked with cracks
First 10 acft checked 5 cracked
By Jetson on Saturday, Oct 5th 2019 19:41Z
My company started the AD checks two days ago.
By the A.D. Aircrafts with 25.000 or more cycles have 7 days to have the pickles checked otherwise will be grounded.
Aircrafts with less than 25.000 cycles have longer schedules.
In 5 of 10 first aircrafts checked (all with more than 25.000 cycles) the cracks were found and are grounded. They don’t have any idea for how long since there is no definitive bulletin to repair it (the A.D. only states which aircrafts will be checked first and to have all aircrafts with cracks grounded until further instruction)
They are guessing they will be grounded for more than 40 days.
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https://www.avherald.com/h?article=4cd92d2a&opt=0
50 percent of those > 25000 cycles in one airline checked with cracks
First 10 acft checked 5 cracked
By Jetson on Saturday, Oct 5th 2019 19:41Z
My company started the AD checks two days ago.
By the A.D. Aircrafts with 25.000 or more cycles have 7 days to have the pickles checked otherwise will be grounded.
Aircrafts with less than 25.000 cycles have longer schedules.
In 5 of 10 first aircrafts checked (all with more than 25.000 cycles) the cracks were found and are grounded. They don’t have any idea for how long since there is no definitive bulletin to repair it (the A.D. only states which aircrafts will be checked first and to have all aircrafts with cracks grounded until further instruction)
They are guessing they will be grounded for more than 40 days.
=========
https://www.avherald.com/h?article=4cd92d2a&opt=0
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This is the problem with an Airline buying and operating too many of one type of aircraft. I remember reading a story where it stated that American Airlines owns 300 737-800's. Imagine if 50 percent of them require the 7 day inspection and 50 % of them are cracked. That would wreak havoc on Airline schedules and available seats. In my 45 years in aviation I do not ever remember a commercial airliner being grounded as long as the 737 MAX.
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YIKES ! significant issue re cracks from another site if true
50 percent of those > 25000 cycles in one airline checked with cracks
First 10 acft checked 5 cracked
By Jetson on Saturday, Oct 5th 2019 19:41Z
My company started the AD checks two days ago.
By the A.D. Aircrafts with 25.000 or more cycles have 7 days to have the pickles checked otherwise will be grounded.
Aircrafts with less than 25.000 cycles have longer schedules.
In 5 of 10 first aircrafts checked (all with more than 25.000 cycles) the cracks were found and are grounded. They don’t have any idea for how long since there is no definitive bulletin to repair it (the A.D. only states which aircrafts will be checked first and to have all aircrafts with cracks grounded until further instruction)
They are guessing they will be grounded for more than 40 days.
=========
50 percent of those > 25000 cycles in one airline checked with cracks
First 10 acft checked 5 cracked
By Jetson on Saturday, Oct 5th 2019 19:41Z
My company started the AD checks two days ago.
By the A.D. Aircrafts with 25.000 or more cycles have 7 days to have the pickles checked otherwise will be grounded.
Aircrafts with less than 25.000 cycles have longer schedules.
In 5 of 10 first aircrafts checked (all with more than 25.000 cycles) the cracks were found and are grounded. They don’t have any idea for how long since there is no definitive bulletin to repair it (the A.D. only states which aircrafts will be checked first and to have all aircrafts with cracks grounded until further instruction)
They are guessing they will be grounded for more than 40 days.
=========
Think this is fixed below but I can only be sure once actually posted. I will test it once posted. Sometimes the links work when that have been put in a quote box as above.
https://www.pprune.org/rumours-news/...l#post10581584
From what I can see, the MOM just talks of reporting all findings but then states in the penultimate Para, “Depending on findings, a ferry flight may be permitted”.
The AD, however, has an instruction to “…. repair if any cracking is found” (Para 1 of the AD and subsequently the last Para of P2 of the AD) and also talks of Ferry Flights to move the [affected] aircraft “….. to a location where the airplane can be repaired if any crack is found.” (at Para (I) on the penultimate page of the AD). It also states that repairs should be made ".... using a method approved by the FAA or [Boeing].".
There seems to be no “….. carry out repairs within…...” statement – it looks like a case of “if cracked – repair iaw Instruction XXXX and you may be given an exception for a ferry flight if needed to get the repair done elsewhere” - not that the AD quotes any "instructions" - it's all a bit vague! Maybe there is something in the Boeing Manuals (ie an Instruction XXXX) re size/nature of cracks before repair is needed as as often the case but I don’t have that sort of info to hand. From my experience, in Primary Structure, often there is little if no leeway before a repair is needed - but that should all be laid down in the Maint Manuals.
Again, I may be missing something but that’s how I read it FWIW. Not sure what you think. Cheers, H ‘n’ H
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Here are the US 737 NG Numbers from a web page story.
"In the United States, Boeing 737NGs are operated by the following US-based airlines:"
"In the United States, Boeing 737NGs are operated by the following US-based airlines:"
- Alaska Airlines (138 in fleet)
- American Airlines (304)
- Delta Air Lines (217)
- Southwest Airlines (695)
- Sun Country (18)
- Swift Air (4)
- United Airlines (329)
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Though I'm not involved with B737 maintenance, I am involved in a "cracked forging" inspection program with another type. In my opinion, in terms of a primary structure forging the only "repair" which might be approved could be dressing out of a very tiny crack, otherwise it will be repair of the airplane by replacement of the cracked part. I'll be surprised of a crack so small to be permitted to be dressed out could be detected before getting too long to require part replacement. It is generally otherwise not possible to "repair" a primary structure forged part (as by adding an element to share the load across the crack). A reference to "repair" [of the airplane] will likely be by part replacement. Letting alone the magnitude of the task to replace the pickle fork, another concern will be the availability of replacement parts. Industry can hope that Boeing had a large run of forgings made, and they sit either partly or fully completed. As forgings are a long lead time & and special process part, that are commonly made in batches, rather than as needed.
A forged part may be incorporated in a primary structure design, because that single part is a very efficient means to carry the load. If that part cannot carry the load (because it has become cracked), there typically is not a parallel load path available within that space or attachment to carry the load via an alternate path, so putting a strap across the cracked area is not a likely repair. By the time you did that, you'd have to bypass the entire design load into the same fastener holes, so you may as well replace the defective part.
The reference to an FAA or Boeing approved repair is a subtle reference to the fact that there is no other approved repair scheme to be found - you must request an approval for the proposed repair from either the FAA or Boeing. Otherwise there would be a "repair in accordance with...." statement in the AD. Perhaps in the future there may be, as suggested, but not yet. And, cunningly, the AD wording requires a defect found to be reported, because it serves industry well to have the data about defects. This because I expect that the Boeing maintenance manual might already describe or allow repair of the airplane by replacement of a defective part. So if an operator found a crack, and had a replacement part in stock, they might be able to simply replace the defective part in accordance with existing Boeing instructions. That's fine, but the initial defect must still be reported for statistical reasons.
A forged part may be incorporated in a primary structure design, because that single part is a very efficient means to carry the load. If that part cannot carry the load (because it has become cracked), there typically is not a parallel load path available within that space or attachment to carry the load via an alternate path, so putting a strap across the cracked area is not a likely repair. By the time you did that, you'd have to bypass the entire design load into the same fastener holes, so you may as well replace the defective part.
The reference to an FAA or Boeing approved repair is a subtle reference to the fact that there is no other approved repair scheme to be found - you must request an approval for the proposed repair from either the FAA or Boeing. Otherwise there would be a "repair in accordance with...." statement in the AD. Perhaps in the future there may be, as suggested, but not yet. And, cunningly, the AD wording requires a defect found to be reported, because it serves industry well to have the data about defects. This because I expect that the Boeing maintenance manual might already describe or allow repair of the airplane by replacement of a defective part. So if an operator found a crack, and had a replacement part in stock, they might be able to simply replace the defective part in accordance with existing Boeing instructions. That's fine, but the initial defect must still be reported for statistical reasons.
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Replacing cracked 'pickle forks' with new, but identical, forgings just kicks the problem down the road. Presumably, the replacement forgings have the same weakness, and will have a tendency to crack in the same way, so the part will need to be re-designed and re-manufactured, to stop the problem for the longer term. Those aircraft that have the forging replaced now may have to do it all again when better forgings are available.
If the pickle forks are supposed to be good for the design life of the air frame it is very unlikely there will be a lot of spares on a shelf. Lead time on forgings can be months.
In such areas, usually you are talking of limited scratches/nicks being blended out from my memory. Usually a crack was a "here we go" moment and leads to a world of pain and grief as you suggest (replacement and all that entails). However, I have come across main lift frames in the RW world having repairs but my memory is such that I can't remember how the original frames were produced - they were fairly robust tho! Do recall a good cue to inspect the frame "out of phase" was when the aircrew started saying how smoothly the aircraft was now flying all of a sudden!
A whole new meaning of "stress relief"!!!!I just got the feeling, given no repair details have been quoted yet (that we know of), that Boeing/the FAA are still getting to grips with exactly what they have on their plates here - as will the poor operators! As pettinger93 and SLF3 observe, a permenant solution would require a redesign - unless you just "life" the forging and accept an ongoing cost in the interim/future. Whatever it is, sounds like it's not going to be fun.
