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Spacepope
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Re: 737NG Pickle fork issue

Sun Nov 10, 2019 7:07 pm

So, have any actually been repaired and put back in service yet?
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767333ER
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Re: 737NG Pickle fork issue

Sun Nov 10, 2019 7:56 pm

mjoelnir wrote:
Aesma wrote:
lowbank wrote:
I did a bit of digging earlier today.
It appears that the pickle fork used to be made from made from aluminium billet. That material has good uniform properties and you are normally machining the component from a large over size piece of material.

They have changed to an aluminium close to size forging. In my experience the properties are inferior and inconsistent. Now I have no data on how much oversize the forging are, but I have properties to be inferior to billet.

It will be a cost reduction that’s going to bite them on the ar5e.

If they are lucky it’s a batch issue, if not it will be the whole fleet.


It's costing airlines, but does Boeing have to compensate them ?


One of the big claims of Boeing in regards to the 737NG was lower maintenance life cost than the A320. One or two pickle fork repairs and the cost of checking for it, with the associated down time, can have an influence on the cost of maintenance over the lifetime of a 737.

Another one of Boeing’s grand scams. Say their product is tougher ‘cause ‘merica and then at the same time cut costs and end up building it weaker or building it wrong.
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lowbank
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Re: 737NG Pickle fork issue

Mon Nov 11, 2019 6:23 pm

mjoelnir wrote:
lowbank wrote:
mjoelnir wrote:

The pickle fork was a component that was not supposed to crack.


No components are supposed to crack, but some do and it’s an accepted procedure to stop drill it.

Trying to think of a none engineers analogy for people to understand.

From a stress point of view the point of a crack is small and the stress is concentrated at that point. A stop drilled hole spreads the load.

So my analogy is trying to stick a sewing needle in your finger, how much pressure would that take? Then imagine how much pressure it would take to push a ball point pen into your finger.

Hope that helps understand how stop drilling reads the load and stops the crack propograting.


Saying it from an engineering standpoint. The pickle fork is designed as a life time part, that is not supposed to crack ever. That is why it was not checked upon. That is why cracks were found by accident, not at an regular inspection. Do I have to make it simpler for you as an engineer?



Right so as an Engineer, I know shit happens. Sometimes for reasons that become new reasons.
Also I will tell you that stress Engineers make lots of assumptions and their work is never exact even with the new fancy software we have.

So, every part we have has an acceptance criteria in the manual and it’s inspected every time it comes of the aircraft. That might be as basic as a visual inspection and any things spotted will be investigated further. Crack detection sprays are quick and easy to use.

If your saying that Boeing don’t have basic inspection of all parts that are on their aircraft when it’s in for maintenance, their profit above safety record is even more concerning.

If this has been found completely by accident by a guy spotting cracks when he is not supposed to be lucking for them, that person needs paying a million dollars as he saved the company from bankruptcy.
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iamlucky13
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Re: 737NG Pickle fork issue

Mon Nov 11, 2019 7:41 pm

mjoelnir wrote:
Saying it from an engineering standpoint. The pickle fork is designed as a life time part, that is not supposed to crack ever. That is why it was not checked upon. That is why cracks were found by accident, not at an regular inspection. Do I have to make it simpler for you as an engineer?


Speaking as an engineer, my take is you do not have to simplify it, but you do have to substantiate it.

If there has been corroboration provided for the assumption that these were found by accident, I missed seeing it.

The status as I understand it was the cracks were found during preparation for conversion work taking place at roughly 36,000 cycles, which is roughly when a semi-major inspection (in some maintenance plans, called a "heavy C check) also takes place.

I do not know if inspection of the pickle forks is specified in the maintenance plan for that interval, but it strikes me as more likely than inspecting that part for a cargo conversion. Would they have been inspecting the pickle forks during installation of a door and crash barrier a significant distance away, plus reinforcement of the floor beams?
 
benbeny
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Re: 737NG Pickle fork issue

Mon Nov 11, 2019 9:09 pm

767333ER wrote:
mjoelnir wrote:
Aesma wrote:

It's costing airlines, but does Boeing have to compensate them ?


One of the big claims of Boeing in regards to the 737NG was lower maintenance life cost than the A320. One or two pickle fork repairs and the cost of checking for it, with the associated down time, can have an influence on the cost of maintenance over the lifetime of a 737.

Another one of Boeing’s grand scams. Say their product is tougher ‘cause ‘merica and then at the same time cut costs and end up building it weaker or building it wrong.

They did well in 777, didn't they? Of course, mistakes happen all the time. A good question for this is why did the pickle fork start to fail at 22k/90k = 25% service life? It's apparently not related to winglet either because at least one that failed didn't even have winglets. A failure that early showed something inherently wrong.

Anyway, does anyone know whether if older NG (before manufacturing changes) impacted with this same crack and at what cycle?
 
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Revelation
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Re: 737NG Pickle fork issue

Mon Nov 11, 2019 9:35 pm

767333ER wrote:
mjoelnir wrote:
Aesma wrote:
It's costing airlines, but does Boeing have to compensate them ?

One of the big claims of Boeing in regards to the 737NG was lower maintenance life cost than the A320. One or two pickle fork repairs and the cost of checking for it, with the associated down time, can have an influence on the cost of maintenance over the lifetime of a 737.

Another one of Boeing’s grand scams. Say their product is tougher ‘cause ‘merica and then at the same time cut costs and end up building it weaker or building it wrong.

Maybe the EU took notice and did the same? https://news.aviation-safety.net/2012/0 ... -rib-feet/

In an ironic parallel, this was discovered not via routine inspection but because the EU made engine exploded and someone had to take the wing apart to fix it.
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morrisond
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Re: 737NG Pickle fork issue

Mon Nov 11, 2019 9:42 pm

Could the Pickle Fork issue be anything to do with excessively hard landings and a proper inspection not being done afterwards?
 
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Aesma
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Re: 737NG Pickle fork issue

Mon Nov 11, 2019 10:01 pm

mjoelnir wrote:
Aesma wrote:
lowbank wrote:
I did a bit of digging earlier today.
It appears that the pickle fork used to be made from made from aluminium billet. That material has good uniform properties and you are normally machining the component from a large over size piece of material.

They have changed to an aluminium close to size forging. In my experience the properties are inferior and inconsistent. Now I have no data on how much oversize the forging are, but I have properties to be inferior to billet.

It will be a cost reduction that’s going to bite them on the ar5e.

If they are lucky it’s a batch issue, if not it will be the whole fleet.


It's costing airlines, but does Boeing have to compensate them ?


One of the big claims of Boeing in regards to the 737NG was lower maintenance life cost than the A320. One or two pickle fork repairs and the cost of checking for it, with the associated down time, can have an influence on the cost of maintenance over the lifetime of a 737.


Sure but don't airlines get aircraft with the understanding that they will have to deal with future ADs ? At least that's what in the contract, then the manufacturer can always sweeten things if it wants more orders.
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smokeybandit
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Re: 737NG Pickle fork issue

Mon Nov 11, 2019 10:10 pm

Is there any evidence or conjecture as to when cracks would have happened? A gradual thing? Or did they happen early on, and just never got worse? Or with age?
 
mjoelnir
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Re: 737NG Pickle fork issue

Mon Nov 11, 2019 10:23 pm

Revelation wrote:
767333ER wrote:
mjoelnir wrote:
One of the big claims of Boeing in regards to the 737NG was lower maintenance life cost than the A320. One or two pickle fork repairs and the cost of checking for it, with the associated down time, can have an influence on the cost of maintenance over the lifetime of a 737.

Another one of Boeing’s grand scams. Say their product is tougher ‘cause ‘merica and then at the same time cut costs and end up building it weaker or building it wrong.

Maybe the EU took notice and did the same? https://news.aviation-safety.net/2012/0 ... -rib-feet/

In an ironic parallel, this was discovered not via routine inspection but because the EU made engine exploded and someone had to take the wing apart to fix it.


So what?
What has that post to do with the pickle fork issue?
Does that change anything on the pickle fork issue?
Does it change anything on that the pickle fork was a lifetime part?
Does it change that there was no inspection regime for the pickle fork?
 
kalvado
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Re: 737NG Pickle fork issue

Mon Nov 11, 2019 10:39 pm

smokeybandit wrote:
Is there any evidence or conjecture as to when cracks would have happened? A gradual thing? Or did they happen early on, and just never got worse? Or with age?

I don't think that is public (yet?), but if cracking is indeed cycle dependent - there can be a linear pattern along the crack showing propagation with cycles. It could be literally possible to count cycles since crack initiation and measure the propagation rate once those parts are in the lab.
 
tomcat
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Re: 737NG Pickle fork issue

Mon Nov 11, 2019 10:41 pm

Spacepope wrote:
So, have any actually been repaired and put back in service yet?


Some Belgian newspapers reported recently that LMI will supply to Boeing a batch of parts made of titanium as emergency replacement parts for the cracked pickle forks.
 
iamlucky13
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Re: 737NG Pickle fork issue

Mon Nov 11, 2019 11:47 pm

mjoelnir wrote:
Revelation wrote:
767333ER wrote:
Another one of Boeing’s grand scams. Say their product is tougher ‘cause ‘merica and then at the same time cut costs and end up building it weaker or building it wrong.

Maybe the EU took notice and did the same? https://news.aviation-safety.net/2012/0 ... -rib-feet/

In an ironic parallel, this was discovered not via routine inspection but because the EU made engine exploded and someone had to take the wing apart to fix it.


So what?
What has that post to do with the pickle fork issue?
Does that change anything on the pickle fork issue?
Does it change anything on that the pickle fork was a lifetime part?
Does it change that there was no inspection regime for the pickle fork?


The prior poster made a snarky, mock-nationalist, false claim (Boeing's basis for its claims about maintenance cost was the comparison of the actual in-service experience of the NG and CEO, not nationalism). It is relevant to that comment's implication that fatigue in lifetime parts that should not fatigue is a Boeing-specific issue.

Please substantiate your claim that the pickle fork is not covered by any current inspections.
 
mjoelnir
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Re: 737NG Pickle fork issue

Tue Nov 12, 2019 12:57 am

iamlucky13 wrote:
mjoelnir wrote:
Revelation wrote:
Maybe the EU took notice and did the same? https://news.aviation-safety.net/2012/0 ... -rib-feet/

In an ironic parallel, this was discovered not via routine inspection but because the EU made engine exploded and someone had to take the wing apart to fix it.


So what?
What has that post to do with the pickle fork issue?
Does that change anything on the pickle fork issue?
Does it change anything on that the pickle fork was a lifetime part?
Does it change that there was no inspection regime for the pickle fork?


The prior poster made a snarky, mock-nationalist, false claim (Boeing's basis for its claims about maintenance cost was the comparison of the actual in-service experience of the NG and CEO, not nationalism). It is relevant to that comment's implication that fatigue in lifetime parts that should not fatigue is a Boeing-specific issue.

Please substantiate your claim that the pickle fork is not covered by any current inspections.


It did not come up in any regulated check. It was found by accident on three frames being converted to freighters. If it checks on the pickle fork would have been done at regular checks, for example C check, it would be impossible that no frame would have been found with those cracks. There are just to many frames with this issue. Repairs would have been a regular occurrence a those checks and this thread would not exist.

Now you show me in what regular check the pickle fork is checked upon.

In regard to the snarky remark, that is from me. I actually assume that the lower service cost on the 737NG compared to the A320 is actual reversed today, I count as an advertising gimmick by Boeing and it was perhaps true in the first years of the A320, when Airbus was still collecting experience on that frame.

I assume that no fatigue testing was done on the 737NG fuselage or just the pickle forks and a lifetime of 90,000 cycle just grandfathered over from the classic.
 
iamlucky13
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Re: 737NG Pickle fork issue

Tue Nov 12, 2019 2:09 am

mjoelnir wrote:
iamlucky13 wrote:
Please substantiate your claim that the pickle fork is not covered by any current inspections.


It did not come up in any regulated check. It was found by accident on three frames being converted to freighters. If it checks on the pickle fork would have been done at regular checks, for example C check, it would be impossible that no frame would have been found with those cracks. There are just to many frames with this issue. Repairs would have been a regular occurrence a those checks and this thread would not exist.

Now you show me in what regular check the pickle fork is checked upon.

In regard to the snarky remark, that is from me. I actually assume that the lower service cost on the 737NG compared to the A320 is actual reversed today, I count as an advertising gimmick by Boeing and it was perhaps true in the first years of the A320, when Airbus was still collecting experience on that frame.

I assume that no fatigue testing was done on the 737NG fuselage or just the pickle forks and a lifetime of 90,000 cycle just grandfathered over from the classic.


If there are very few occurring before 24,000 cycles, but a non-trivial number (over 5%?) happening before 36,000 cycles (which it sounds like very few aircraft have reached), and there are inspections at both of those intervals, then it is most certainly possible that they are being inspected, but no cracks found because they typically develop in between those checks.

I do not know for certain whether the pickle fork is inspected. All I know is I have seen photos of heavy checks where aircraft are stripped down to such an extent that the pickle forks could be inspected, along with most of the rest of the structure. I would certainly appreciate authoritative knowledge on this from anyone who knows.

I would also appreciate speculation, even when there is a basis for it, being identified in some manner as speculation (eg - "It seems to me unlikely that...).

Your comment was not the snarky one. I agree that this finding undermine's Boeing's service cost advantage. I was referring to 767333ER's comment as being snarky.

I'm also looking for an answer about fatigue testing. I found some references to fatigue testing of the fuselage, to well beyond 90,000 cycles, but without the wings, and it sounds like only under pressurization cycles for the sake of understanding how the skin performs. I do not know if that was the sole NG fatigue test done, or if a full airframe fatigue test was also done, but might be difficult to find information about because the volume of information published on the internet was far lower at the time.
 
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Re: 737NG Pickle fork issue

Tue Nov 12, 2019 2:30 am

I don't believe this has previously been linked to in the thread, but here is more information about the issue in the official record of the Airworthiness Directive, which includes in the supporting documents a technical bulletin to airlines about the cracks and the inspection procedure:
https://www.regulations.gov/docket?D=FAA-2019-0711

It includes photographs of both cracked and intact pickle forks, and of the inspection location. Summary:

  • The first 737-800, which was being inspected during conversion, had 1 inch long cracks in both rear spar pickle forks
  • This prompted 4 more 737-800 to be inspected. 2 had no cracks, 1 had a single pickle fork cracked, the other had both forks cracked.
  • 13 x 737-700's were also inspected at this time with no cracks.
  • These first 18 aircraft inspected ranged from 20,000 to 41,000 cycles.
  • The area of cracking is in the wheel well, but access is difficult due to systems mounted in the wheel well. See the photo on page 11.
  • Pictures of the cracks are on pages 18 and 19
 
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CALTECH
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Re: 737NG Pickle fork issue

Tue Nov 12, 2019 7:36 am

iamlucky13 wrote:
The prior poster made a snarky, mock-nationalist, false claim (Boeing's basis for its claims about maintenance cost was the comparison of the actual in-service experience of the NG and CEO, not nationalism). It is relevant to that comment's implication that fatigue in lifetime parts that should not fatigue is a Boeing-specific issue.

Please substantiate your claim that the pickle fork is not covered by any current inspections.


When the wing to body fairings are removed, usually there is a Zonal Inspection performed. But those making snarky and false claims wouldn't know that.....

What airlines reported costs were in 2014.....
https://www.planestats.com/bhsn_2014dec
You are here.
 
mjoelnir
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Re: 737NG Pickle fork issue

Tue Nov 12, 2019 8:51 am

CALTECH wrote:
iamlucky13 wrote:
The prior poster made a snarky, mock-nationalist, false claim (Boeing's basis for its claims about maintenance cost was the comparison of the actual in-service experience of the NG and CEO, not nationalism). It is relevant to that comment's implication that fatigue in lifetime parts that should not fatigue is a Boeing-specific issue.

Please substantiate your claim that the pickle fork is not covered by any current inspections.


When the wing to body fairings are removed, usually there is a Zonal Inspection performed. But those making snarky and false claims wouldn't know that.....

What airlines reported costs were in 2014.....
https://www.planestats.com/bhsn_2014dec


Could you point to frames where the pickle fort cracks were found through your taunted zonal inspection and repaired, rather than now through the inspections mandated by the AD?

What does your data set show beside that MX cost are widely varying and actually no use without reference to the actual average age of the relevant fleets?
 
Dalmd88
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Re: 737NG Pickle fork issue

Tue Nov 12, 2019 10:09 am

mjoelnir wrote:
CALTECH wrote:
iamlucky13 wrote:
The prior poster made a snarky, mock-nationalist, false claim (Boeing's basis for its claims about maintenance cost was the comparison of the actual in-service experience of the NG and CEO, not nationalism). It is relevant to that comment's implication that fatigue in lifetime parts that should not fatigue is a Boeing-specific issue.

Please substantiate your claim that the pickle fork is not covered by any current inspections.


When the wing to body fairings are removed, usually there is a Zonal Inspection performed. But those making snarky and false claims wouldn't know that.....

What airlines reported costs were in 2014.....
https://www.planestats.com/bhsn_2014dec


Could you point to frames where the pickle fort cracks were found through your taunted zonal inspection and repaired, rather than now through the inspections mandated by the AD?

What does your data set show beside that MX cost are widely varying and actually no use without reference to the actual average age of the relevant fleets?

I can't on the 737, but we did find one with a Zonal inspection on a 757 during a C Check.
 
mjoelnir
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Re: 737NG Pickle fork issue

Tue Nov 12, 2019 10:26 am

Dalmd88 wrote:
mjoelnir wrote:
CALTECH wrote:

When the wing to body fairings are removed, usually there is a Zonal Inspection performed. But those making snarky and false claims wouldn't know that.....

What airlines reported costs were in 2014.....
https://www.planestats.com/bhsn_2014dec


Could you point to frames where the pickle fort cracks were found through your taunted zonal inspection and repaired, rather than now through the inspections mandated by the AD?

What does your data set show beside that MX cost are widely varying and actually no use without reference to the actual average age of the relevant fleets?

I can't on the 737, but we did find one with a Zonal inspection on a 757 during a C Check.


Is the pickle fork on the 757 defined as a lifetime part or a limited life part?

We have to look at what happened and the timeline.

- No information about pickle fork cracks on the 737.
- Than there are found cracks on three 737-800 to be converted to freighters. The frames have around 37,000 cycles.
- That gets reported and an AD is done by the FAA. Immediate check on frames 30,000 cycles and over. Check on frames between 22,600 cycles and 30,000 cycles inside of 1,000 cycles. 5% of checked frames show cracks in the pickle forks.
- Now they found cracks on frames below 22,600 cycles.

How does that fit with regular inspection of pickle forks and finding cracks through zonal inspections?
 
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Re: 737NG Pickle fork issue

Tue Nov 12, 2019 10:42 am

mjoelnir wrote:
How does that fit with regular inspection of pickle forks and finding cracks through zonal inspections?


Since we can completely rule out that the excellent mechanics teams of the US first world premium airlines did not carry out an important inspection of the shell during the C-checks for many years, we can assume that this part will not be seen as a part of wear and was originally designed for the life of the aircraft

But that is not a boeing thing I think.
That was just bad luck.
That could happen to Airbus technicians just as well.
 
bgm
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Re: 737NG Pickle fork issue

Tue Nov 12, 2019 10:50 am

CALTECH wrote:
iamlucky13 wrote:
The prior poster made a snarky, mock-nationalist, false claim (Boeing's basis for its claims about maintenance cost was the comparison of the actual in-service experience of the NG and CEO, not nationalism). It is relevant to that comment's implication that fatigue in lifetime parts that should not fatigue is a Boeing-specific issue.

Please substantiate your claim that the pickle fork is not covered by any current inspections.


When the wing to body fairings are removed, usually there is a Zonal Inspection performed. But those making snarky and false claims wouldn't know that.....

What airlines reported costs were in 2014.....
https://www.planestats.com/bhsn_2014dec


"Usually"?

It's either part of the inspection or it isn't. And if it was, how come the cracks weren't found on previous inspections?
 
mjoelnir
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Re: 737NG Pickle fork issue

Tue Nov 12, 2019 11:00 am

South Korea is the latest country to ground a number of Boeing 737NG found to have structural cracks, following worldwide inspections of the popular narrowbody.

https://www.flightglobal.com/news/artic ... ks-462155/

That is the situation in South Korea. 13 frames with cracks. 9 above 30,000 cycles, 4 below 30,000 cycles. Frames will be repaired by January 2020.

It seems that most users do not wait to make the inspection for 22,600 to 29,999 cycle frames, but do it in the short term.
 
morrisond
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Re: 737NG Pickle fork issue

Tue Nov 12, 2019 11:55 am

iamlucky13 wrote:
[*]The area of cracking is in the wheel well, but access is difficult due to systems mounted in the wheel well. See the photo on page 11.
[*]Pictures of the cracks are on pages 18 and 19[/list]


Huh - Interesting. That may feed into my speculation from above.

"Could the Pickle Fork issue be anything to do with excessively hard landings and a proper inspection not being done afterwards?"

Worldwide maintenance issues? Not doing proper inspections upon an hard landing in an hard to see place? No - that would never happen in todays non-competitive highly profitable Airline industry.....

But to be clear I am speculating.
 
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Revelation
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Re: 737NG Pickle fork issue

Tue Nov 12, 2019 12:57 pm

iamlucky13 wrote:
The prior poster made a snarky, mock-nationalist, false claim (Boeing's basis for its claims about maintenance cost was the comparison of the actual in-service experience of the NG and CEO, not nationalism). It is relevant to that comment's implication that fatigue in lifetime parts that should not fatigue is a Boeing-specific issue.

Right, 767333ER said it was a Boeing/murica thing so it was totally appropriate to point out that Airbus/EU had a problem with rib feet cracking on A380 which was of a similar scale in terms of expense and loss of revenue service time, and ironically was also not found during routine inspection but was found because the RR engine on the QF A380 exploded and the relevant area of the aircraft was being disassembled for repair.
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Wake now, discover that you are the song that the morning brings
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zoom321
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Re: 737NG Pickle fork issue

Tue Nov 12, 2019 1:05 pm

With Max having heavier more powerful engines under the wing & other stuffs mostly 'grandfathered' from NG, does that mean it will crack even earlier than NG ? That is IF it ever flies again.
 
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trpmb6
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Re: 737NG Pickle fork issue

Tue Nov 12, 2019 2:05 pm

zoom321 wrote:
With Max having heavier more powerful engines under the wing & other stuffs mostly 'grandfathered' from NG, does that mean it will crack even earlier than NG ? That is IF it ever flies again.


No.

The max, despite what the media will claim about being "grandfathered" was reevaluated for the new loads. All structure is reevaluated for new loading whenever a change happens. Much of the structure of the max is actually different from the NG which was different than the Classic. The NG had a fatigue test done because of that.

What people don't realize is when we talk about "grandfathering" we are referring to the change product rule. It doesn't let us just slap new engines on a plane and say, well they're not really that much bigger so it's fine we're grandfathered in. You have to reanalyze everything.. I mean everything.. for the new loading.

This applies to everything from your A380 down to the smallest of Cessna planes.
 
mjoelnir
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Re: 737NG Pickle fork issue

Tue Nov 12, 2019 3:09 pm

Revelation wrote:
iamlucky13 wrote:
The prior poster made a snarky, mock-nationalist, false claim (Boeing's basis for its claims about maintenance cost was the comparison of the actual in-service experience of the NG and CEO, not nationalism). It is relevant to that comment's implication that fatigue in lifetime parts that should not fatigue is a Boeing-specific issue.

Right, 767333ER said it was a Boeing/murica thing so it was totally appropriate to point out that Airbus/EU had a problem with rib feet cracking on A380 which was of a similar scale in terms of expense and loss of revenue service time, and ironically was also not found during routine inspection but was found because the RR engine on the QF A380 exploded and the relevant area of the aircraft was being disassembled for repair.


Yes routine inspection did not catch it, because the frame it was detected on was that young. The material for the rips were changed. In the end it was not actually the material, but problems in the wing manufacture, that put the rips under stress.

The point with Boeing murica, was the actual the very high and optimistic 90,000 cycle that the fuselage should be able live and that included the pickle fork.
 
smokeybandit
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Re: 737NG Pickle fork issue

Tue Nov 12, 2019 4:40 pm

I still think it's quite important to find out when the cracks would have appeared. There's a big difference between the cracks appearing early on in the life of the airplane and not getting worse vs. a gradual worsening through each cycle.

Some team will have fun researching that.
 
StTim
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Re: 737NG Pickle fork issue

Tue Nov 12, 2019 4:47 pm

Revelation wrote:
iamlucky13 wrote:
The prior poster made a snarky, mock-nationalist, false claim (Boeing's basis for its claims about maintenance cost was the comparison of the actual in-service experience of the NG and CEO, not nationalism). It is relevant to that comment's implication that fatigue in lifetime parts that should not fatigue is a Boeing-specific issue.

Right, 767333ER said it was a Boeing/murica thing so it was totally appropriate to point out that Airbus/EU had a problem with rib feet cracking on A380 which was of a similar scale in terms of expense and loss of revenue service time, and ironically was also not found during routine inspection but was found because the RR engine on the QF A380 exploded and the relevant area of the aircraft was being disassembled for repair.


It would be better for a.net if the original had been reported rather than a similarly poor post.

The people who find a constant need to snipe or indulge in fanboyism are really dragging down the site.
 
iamlucky13
Posts: 1263
Joined: Wed Aug 08, 2007 12:35 pm

Re: 737NG Pickle fork issue

Tue Nov 12, 2019 10:51 pm

bgm wrote:
CALTECH wrote:
When the wing to body fairings are removed, usually there is a Zonal Inspection performed. But those making snarky and false claims wouldn't know that.....


"Usually"?

It's either part of the inspection or it isn't. And if it was, how come the cracks weren't found on previous inspections?


"Usually" depends on if it is in the maintenance plan for the aircraft, which has to be approved by the regulators and subsequently is mandatory.

The only concrete answer to the question asked is that so far is that we in this thread don't know.

Two possible answers:

1) There were no cracks present during any of the previous inspections. More specifically, all frames with cracks would have developed them after their last heavy check, and the 737-800 undergoing conversion was the first aircraft to reach a check with cracks. Assuming 24,000 cycles* is a heavy check interval, then this also assumes that the handful developing cracks before that interval either had not happened to reach that interval yet, or they were missed.

2) No inspection of the pickle forks is done. This assumes the Maintenance Review Board determined that this part of the aircraft does not require checks.

* I'm unclear on this. It sounds like the 737 maintenance intervals may be primarily flight hours based. This is one of those details determined by the Maintenance Review Board.
 
iamlucky13
Posts: 1263
Joined: Wed Aug 08, 2007 12:35 pm

Re: 737NG Pickle fork issue

Tue Nov 12, 2019 10:55 pm

morrisond wrote:
iamlucky13 wrote:
[*]The area of cracking is in the wheel well, but access is difficult due to systems mounted in the wheel well. See the photo on page 11.
[*]Pictures of the cracks are on pages 18 and 19[/list]


Huh - Interesting. That may feed into my speculation from above.

"Could the Pickle Fork issue be anything to do with excessively hard landings and a proper inspection not being done afterwards?"


I don't think it tells us much one way or the other. I wouldn't rule it out, but given the variety of airlines finding cracks, I'm skeptical there are shortcuts being taken after hard landings.
 
acechip
Posts: 50
Joined: Fri Nov 30, 2018 12:22 am

Re: 737NG Pickle fork issue

Tue Nov 12, 2019 11:41 pm

mjoelnir wrote:
Revelation wrote:
iamlucky13 wrote:
The prior poster made a snarky, mock-nationalist, false claim (Boeing's basis for its claims about maintenance cost was the comparison of the actual in-service experience of the NG and CEO, not nationalism). It is relevant to that comment's implication that fatigue in lifetime parts that should not fatigue is a Boeing-specific issue.

Right, 767333ER said it was a Boeing/murica thing so it was totally appropriate to point out that Airbus/EU had a problem with rib feet cracking on A380 which was of a similar scale in terms of expense and loss of revenue service time, and ironically was also not found during routine inspection but was found because the RR engine on the QF A380 exploded and the relevant area of the aircraft was being disassembled for repair.


Yes routine inspection did not catch it, because the frame it was detected on was that young. The material for the rips were changed. In the end it was not actually the material, but problems in the wing manufacture, that put the rips under stress.

The point with Boeing murica, was the actual the very high and optimistic 90,000 cycle that the fuselage should be able live and that included the pickle fork.

This would have been believable with zero doubt may be ten years ago. In the wake of the Max crisis, anything that the company states as part of good engineering practice, could (should?) be viewed with a bit of a skepticism. Now, this is not to absolve Airbus either. It could just as well apply to any company that claims to make " safe planes safer" while grossly underestimating the design deficiences.
 
Mostly
Posts: 14
Joined: Wed Oct 09, 2019 10:35 pm

Re: 737NG Pickle fork issue

Wed Nov 13, 2019 1:17 am

mjoelnir wrote:
South Korea is the latest country to ground a number of Boeing 737NG found to have structural cracks, following worldwide inspections of the popular narrowbody.

https://www.flightglobal.com/news/artic ... ks-462155/

That is the situation in South Korea. 13 frames with cracks. 9 above 30,000 cycles, 4 below 30,000 cycles. Frames will be repaired by January 2020.

It seems that most users do not wait to make the inspection for 22,600 to 29,999 cycle frames, but do it in the short term.


13% of the ones they inspected. They keep stacking up. I’m very interested to hear when China weighs in - thousands of short hop NGs there.
 
foxtrotbravo21
Posts: 49
Joined: Fri Jan 01, 2016 2:52 am

Re: 737NG Pickle fork issue

Wed Nov 13, 2019 2:50 am

still believed that the pickle fork cracks' issue is still either from the assemly of the plane and or from the manufacturing process of the pickle fork. Doubt it is a design fault.
 
N6168E
Posts: 37
Joined: Sun Sep 16, 2007 5:57 am

Re: 737NG Pickle fork issue

Wed Nov 13, 2019 4:07 pm

Aviation Week is reporting that cracks have been found in other locations on the Pickle Forks and planes will have to be re-inspected. This is behind a paywall. https://aviationweek.com/commercial-avi ... 9387403cd1
Fair use extract:
"Checks of frame fittings and failsafe straps, or pickle forks, turned up cracks in four aircraft near fasteners that were not covered in the original inspection order issued Oct 3. As a result, Boeing on Nov. 5 recommended that operators expand the checks to include eight fasteners, up from two in the previous order. FAA will mandate the checks in an airworthiness directive (AD) slated to be published Nov. 13 and effective immediately."
"The new directive, which is expected to be adopted by other regulators, calls for aircraft in the high-cycle category to be re-inspected within 60 days. Aircraft in the lower cycle category must re-inspect the entire area within 1,000 cycles."
 
macc
Posts: 928
Joined: Tue Nov 09, 2004 8:11 pm

Re: 737NG Pickle fork issue

Wed Nov 13, 2019 5:13 pm

N6168E wrote:
Aviation Week is reporting that cracks have been found in other locations on the Pickle Forks and planes will have to be re-inspected. This is behind a paywall. https://aviationweek.com/commercial-avi ... 9387403cd1
Fair use extract:
"Checks of frame fittings and failsafe straps, or pickle forks, turned up cracks in four aircraft near fasteners that were not covered in the original inspection order issued Oct 3. As a result, Boeing on Nov. 5 recommended that operators expand the checks to include eight fasteners, up from two in the previous order. FAA will mandate the checks in an airworthiness directive (AD) slated to be published Nov. 13 and effective immediately."
"The new directive, which is expected to be adopted by other regulators, calls for aircraft in the high-cycle category to be re-inspected within 60 days. Aircraft in the lower cycle category must re-inspect the entire area within 1,000 cycles."


Does that mean that already inspected planes have to be rechecked again? That must be truly annoying, and costly.
I exchanged political frustration with sexual boredom. better spoil a girl than the world
 
kalvado
Posts: 2931
Joined: Wed Mar 01, 2006 4:29 am

Re: 737NG Pickle fork issue

Wed Nov 13, 2019 5:41 pm

macc wrote:
N6168E wrote:
Aviation Week is reporting that cracks have been found in other locations on the Pickle Forks and planes will have to be re-inspected. This is behind a paywall. https://aviationweek.com/commercial-avi ... 9387403cd1
Fair use extract:
"Checks of frame fittings and failsafe straps, or pickle forks, turned up cracks in four aircraft near fasteners that were not covered in the original inspection order issued Oct 3. As a result, Boeing on Nov. 5 recommended that operators expand the checks to include eight fasteners, up from two in the previous order. FAA will mandate the checks in an airworthiness directive (AD) slated to be published Nov. 13 and effective immediately."
"The new directive, which is expected to be adopted by other regulators, calls for aircraft in the high-cycle category to be re-inspected within 60 days. Aircraft in the lower cycle category must re-inspect the entire area within 1,000 cycles."


Does that mean that already inspected planes have to be rechecked again? That must be truly annoying, and costly.

Looks like yes for re-inspection, and looks like not too costly: procedure is to slide boroscope in and visually check parts....
 
iamlucky13
Posts: 1263
Joined: Wed Aug 08, 2007 12:35 pm

Re: 737NG Pickle fork issue

Wed Nov 13, 2019 6:59 pm

macc wrote:
Does that mean that already inspected planes have to be rechecked again? That must be truly annoying, and costly.


Annoying yes, but fortunately the cost of inspection is small. The AD estimated 1 hour to do the check, and 1 hour to do the paperwork. As far as I can see, no panels need to be removed. It's a matter of going out to the plane with a borescope, ducking into the wheel well, and manuevering the borescope over and behind some hydraulic lines, etc to see the suspect areas of the fittings.

Cracks in different locations is making my suspicion lean slightly toward a manufacturing defect rather than an under-designed part. I would normally expect a specific area of the fitting to be consistently the highest loaded and point of initiation. This is very speculative on my part, however.
 
kalvado
Posts: 2931
Joined: Wed Mar 01, 2006 4:29 am

Re: 737NG Pickle fork issue

Wed Nov 13, 2019 7:13 pm

iamlucky13 wrote:
Cracks in different locations is making my suspicion lean slightly toward a manufacturing defect rather than an under-designed part. I would normally expect a specific area of the fitting to be consistently the highest loaded and point of initiation. This is very speculative on my part, however.

Seems consistent with the speculation that change in manufacturing process changed part strength. That is some borderline between design and manufacturing thing...
 
lowbank
Posts: 511
Joined: Wed Mar 25, 2009 9:10 pm

Re: 737NG Pickle fork issue

Wed Nov 13, 2019 7:16 pm

iamlucky13 wrote:
macc wrote:
Does that mean that already inspected planes have to be rechecked again? That must be truly annoying, and costly.


Annoying yes, but fortunately the cost of inspection is small. The AD estimated 1 hour to do the check, and 1 hour to do the paperwork. As far as I can see, no panels need to be removed. It's a matter of going out to the plane with a borescope, ducking into the wheel well, and manuevering the borescope over and behind some hydraulic lines, etc to see the suspect areas of the fittings.

Cracks in different locations is making my suspicion lean slightly toward a manufacturing defect rather than an under-designed part. I would normally expect a specific area of the fitting to be consistently the highest loaded and point of initiation. This is very speculative on my part, however.



Always remember, visual inspection is only 97% effective.
Every days a school day.
 
User avatar
PW100
Posts: 4123
Joined: Mon Jan 28, 2002 9:17 pm

Re: 737NG Pickle fork issue

Wed Nov 13, 2019 9:03 pm

morrisond wrote:
iamlucky13 wrote:
[*]The area of cracking is in the wheel well, but access is difficult due to systems mounted in the wheel well. See the photo on page 11.
[*]Pictures of the cracks are on pages 18 and 19[/list]


Huh - Interesting. That may feed into my speculation from above.

"Could the Pickle Fork issue be anything to do with excessively hard landings and a proper inspection not being done afterwards?"

Worldwide maintenance issues? Not doing proper inspections upon an hard landing in an hard to see place? No - that would never happen in todays non-competitive highly profitable Airline industry.....

But to be clear I am speculating.


If so, proper inspections would not stop cracking, just perhaps identify them earlier.

If so, then the "worldwide maintenance issues" seems to concentrate mainly on NGs . . . do I see a pattern here? :scratchchin:
Immigration officer: "What's the purpose of your visit to the USA?" Spotter: "Shooting airliners with my Canon!"
 
morrisond
Posts: 2858
Joined: Thu Jan 07, 2010 12:22 am

Re: 737NG Pickle fork issue

Wed Nov 13, 2019 9:33 pm

PW100 wrote:
morrisond wrote:
iamlucky13 wrote:
[*]The area of cracking is in the wheel well, but access is difficult due to systems mounted in the wheel well. See the photo on page 11.
[*]Pictures of the cracks are on pages 18 and 19[/list]


Huh - Interesting. That may feed into my speculation from above.

"Could the Pickle Fork issue be anything to do with excessively hard landings and a proper inspection not being done afterwards?"

Worldwide maintenance issues? Not doing proper inspections upon an hard landing in an hard to see place? No - that would never happen in todays non-competitive highly profitable Airline industry.....

But to be clear I am speculating.


If so, proper inspections would not stop cracking, just perhaps identify them earlier.

If so, then the "worldwide maintenance issues" seems to concentrate mainly on NGs . . . do I see a pattern here? :scratchchin:


Yes Mechanics possibly not inspecting NG's properly after landing or the procedure needs to be rewritten to remove the parts necessary to see in there after a hard landing - if that is possibly a contributing factor to the cracking..

At least they can't argue it's too high above the ground to see in there....
 
kalvado
Posts: 2931
Joined: Wed Mar 01, 2006 4:29 am

Re: 737NG Pickle fork issue

Wed Nov 13, 2019 9:50 pm

morrisond wrote:
PW100 wrote:
morrisond wrote:

Huh - Interesting. That may feed into my speculation from above.

"Could the Pickle Fork issue be anything to do with excessively hard landings and a proper inspection not being done afterwards?"

Worldwide maintenance issues? Not doing proper inspections upon an hard landing in an hard to see place? No - that would never happen in todays non-competitive highly profitable Airline industry.....

But to be clear I am speculating.


If so, proper inspections would not stop cracking, just perhaps identify them earlier.

If so, then the "worldwide maintenance issues" seems to concentrate mainly on NGs . . . do I see a pattern here? :scratchchin:


Yes Mechanics possibly not inspecting NG's properly after landing or the procedure needs to be rewritten to remove the parts necessary to see in there after a hard landing - if that is possibly a contributing factor to the cracking..

At least they can't argue it's too high above the ground to see in there....

If crack is initiated on hard landing, there may be hundreds more cycles before it is visible.
But that again boils down to training of Boeing engineers - it is their job to identify potential weak spots and develop maintenance procedures. Bottom line - Boeing failed again, and that is because of lack of employee's professional skills....
 
JayinKitsap
Posts: 2288
Joined: Sat Nov 26, 2005 9:55 am

Re: 737NG Pickle fork issue

Thu Nov 14, 2019 3:40 am

kalvado wrote:
If crack is initiated on hard landing, there may be hundreds more cycles before it is visible.
But that again boils down to training of Boeing engineers - it is their job to identify potential weak spots and develop maintenance procedures. Bottom line - Boeing failed again, and that is because of lack of employee's professional skills....


Well, if it is visible immediately after a hard landing, it was just moments away from a collapse.
 
User avatar
CALTECH
Posts: 3428
Joined: Thu May 17, 2007 4:21 am

Re: 737NG Pickle fork issue

Thu Nov 14, 2019 4:00 am

bgm wrote:
CALTECH wrote:
iamlucky13 wrote:
The prior poster made a snarky, mock-nationalist, false claim (Boeing's basis for its claims about maintenance cost was the comparison of the actual in-service experience of the NG and CEO, not nationalism). It is relevant to that comment's implication that fatigue in lifetime parts that should not fatigue is a Boeing-specific issue.

Please substantiate your claim that the pickle fork is not covered by any current inspections.


When the wing to body fairings are removed, usually there is a Zonal Inspection performed. But those making snarky and false claims wouldn't know that.....

What airlines reported costs were in 2014.....
https://www.planestats.com/bhsn_2014dec


"Usually"?

It's either part of the inspection or it isn't. And if it was, how come the cracks weren't found on previous inspections?


'Ususally' WTB fairing(s) removed for nutplate repair, or composite repair. Usually Sheet Metal takes it off repairs it and reinstalls the WTB fairing(s). A quick look, no inspection, is usually done to make sure everything looks good inside there. That's one example of no inspection.

If there is a detailed visual or zonal inspection in the area with the WTB fairings removed, then it does get a inspection.

So the statement " It's either part of the inspection or it isn't." is not valid.

And the statement " And if it was, how come the cracks weren't found on previous inspections? " may have many answers.
Crack had not propagated enough to be identified.
Crack had began after the last inspection.
Some cracks are hard to see, especially with the corrosion preventative compounds placed over many areas of a aircraft, such as Cor-Ban. Cor-Ban has a tint to it such as in this wheel well, one can see the Cor-Ban on the Keel Beam and other parts. I believe the wheel well area is actually painted a bright white gloss paint....

Image

And believe that this is a close up photo of one of the cracks.

Image

Cracks in metal aircraft happen, that's why aircraft are under inspection programs. Sure that Airbus didn't expect Fuselage cracks in the A-320, but they have happened. Usually either inspections and or newly designed parts resolve these issues.

https://www.mro-network.com/safety-regu ... oposed-ads
'Mar 22, 2017
The European Aviation Safety Agency (EASA) issued four proposed airworthiness directives (PAD) for the Airbus A320 family.
EASA issued PAD 17-034 due to cracks found on the aircraft body at frame 36 during center fuselage certificate full-scale fatigue tests. The cracks can lead to crack propagation and deterioration of the structural integrity of the airplane.

The cracking issue has been addressed since 1997 by Airbus Service Bulletin A320-57-1016 and DGAC France AD 97-311-105. This PAD provides updated special inspection requirements.'

This is why inspections on aircraft never stop.
You are here.
 
User avatar
CALTECH
Posts: 3428
Joined: Thu May 17, 2007 4:21 am

Re: 737NG Pickle fork issue

Thu Nov 14, 2019 4:04 am

mjoelnir wrote:
CALTECH wrote:
iamlucky13 wrote:
The prior poster made a snarky, mock-nationalist, false claim (Boeing's basis for its claims about maintenance cost was the comparison of the actual in-service experience of the NG and CEO, not nationalism). It is relevant to that comment's implication that fatigue in lifetime parts that should not fatigue is a Boeing-specific issue.

Please substantiate your claim that the pickle fork is not covered by any current inspections.


When the wing to body fairings are removed, usually there is a Zonal Inspection performed. But those making snarky and false claims wouldn't know that.....

What airlines reported costs were in 2014.....
https://www.planestats.com/bhsn_2014dec


Could you point to frames where the pickle fort cracks were found through your taunted zonal inspection and repaired, rather than now through the inspections mandated by the AD?

What does your data set show beside that MX cost are widely varying and actually no use without reference to the actual average age of the relevant fleets?


Obviously trying to explain this to someone with no maintenance background and a biased fanboy view would be a waste of time. Now factual numbers are Trumped by fanboyism.
You are here.
 
mjoelnir
Posts: 9411
Joined: Sun Feb 03, 2013 11:06 pm

Re: 737NG Pickle fork issue

Thu Nov 14, 2019 4:59 am

CALTECH wrote:
bgm wrote:
CALTECH wrote:

When the wing to body fairings are removed, usually there is a Zonal Inspection performed. But those making snarky and false claims wouldn't know that.....

What airlines reported costs were in 2014.....
https://www.planestats.com/bhsn_2014dec


"Usually"?

It's either part of the inspection or it isn't. And if it was, how come the cracks weren't found on previous inspections?


'Ususally' WTB fairing(s) removed for nutplate repair, or composite repair. Usually Sheet Metal takes it off repairs it and reinstalls the WTB fairing(s). A quick look, no inspection, is usually done to make sure everything looks good inside there. That's one example of no inspection.

If there is a detailed visual or zonal inspection in the area with the WTB fairings removed, then it does get a inspection.

So the statement " It's either part of the inspection or it isn't." is not valid.

And the statement " And if it was, how come the cracks weren't found on previous inspections? " may have many answers.
Crack had not propagated enough to be identified.
Crack had began after the last inspection.
Some cracks are hard to see, especially with the corrosion preventative compounds placed over many areas of a aircraft, such as Cor-Ban. Cor-Ban has a tint to it such as in this wheel well, one can see the Cor-Ban on the Keel Beam and other parts. I believe the wheel well area is actually painted a bright white gloss paint....

Image

And believe that this is a close up photo of one of the cracks.

Image

Cracks in metal aircraft happen, that's why aircraft are under inspection programs. Sure that Airbus didn't expect Fuselage cracks in the A-320, but they have happened. Usually either inspections and or newly designed parts resolve these issues.

https://www.mro-network.com/safety-regu ... oposed-ads
'Mar 22, 2017
The European Aviation Safety Agency (EASA) issued four proposed airworthiness directives (PAD) for the Airbus A320 family.
EASA issued PAD 17-034 due to cracks found on the aircraft body at frame 36 during center fuselage certificate full-scale fatigue tests. The cracks can lead to crack propagation and deterioration of the structural integrity of the airplane.

The cracking issue has been addressed since 1997 by Airbus Service Bulletin A320-57-1016 and DGAC France AD 97-311-105. This PAD provides updated special inspection requirements.'

This is why inspections on aircraft never stop.


I call BS. Either you are looking for cracks in the pickle fork or you do not. Either it is on the program for a check or it is not. If it is in the program, than there is a method to find them in the program and you have to sign off on they are there or are not.

What do you want to say with the example of the AD for the A320?
Cracks were found at the fatigue testing. Exactly as it should be. That is what fatigue testing is about, that why you do fatigue testing. You find something, you put out an AD how to handle it.

This cracking in the 737NG comes in a part, where cracks were not expected. If in some of the heavy maintenance somebody would have been looking for cracks there, they would have been found, because the maintenance crews are not all idiots. That tells me there was no mandate to check for this cracks.

This pickle fork cracks were not found through fatigue testing, but by accident. If you do not understand the difference, that is your problem.

When the maintenance engineers or technicians wer told by the AD to look for them, they were found and they were found in numbers.
 
benbeny
Posts: 240
Joined: Thu Nov 03, 2016 1:44 pm

Re: 737NG Pickle fork issue

Thu Nov 14, 2019 1:20 pm

iamlucky13 wrote:
macc wrote:
Does that mean that already inspected planes have to be rechecked again? That must be truly annoying, and costly.


Annoying yes, but fortunately the cost of inspection is small. The AD estimated 1 hour to do the check, and 1 hour to do the paperwork. As far as I can see, no panels need to be removed. It's a matter of going out to the plane with a borescope, ducking into the wheel well, and manuevering the borescope over and behind some hydraulic lines, etc to see the suspect areas of the fittings.

Cracks in different locations is making my suspicion lean slightly toward a manufacturing defect rather than an under-designed part. I would normally expect a specific area of the fitting to be consistently the highest loaded and point of initiation. This is very speculative on my part, however.

Still, if you multiply it to cover 50+ planes needing inspections from AD, you have 100 hours extra to pay.

Have we seen any issues on older 737 NG?
 
mjoelnir
Posts: 9411
Joined: Sun Feb 03, 2013 11:06 pm

Re: 737NG Pickle fork issue

Thu Nov 14, 2019 3:11 pm

benbeny wrote:
iamlucky13 wrote:
macc wrote:
Does that mean that already inspected planes have to be rechecked again? That must be truly annoying, and costly.


Annoying yes, but fortunately the cost of inspection is small. The AD estimated 1 hour to do the check, and 1 hour to do the paperwork. As far as I can see, no panels need to be removed. It's a matter of going out to the plane with a borescope, ducking into the wheel well, and manuevering the borescope over and behind some hydraulic lines, etc to see the suspect areas of the fittings.

Cracks in different locations is making my suspicion lean slightly toward a manufacturing defect rather than an under-designed part. I would normally expect a specific area of the fitting to be consistently the highest loaded and point of initiation. This is very speculative on my part, however.

Still, if you multiply it to cover 50+ planes needing inspections from AD, you have 100 hours extra to pay.

Have we seen any issues on older 737 NG?


We are talking about the older and oldest 737NG.

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