Moderators: jsumali2, richierich, ua900, PanAm_DC10, hOMSaR
Jacob2877 wrote:727Man wrote:trpmb6 wrote:
As has already been reported the -900 is a different design.
Two -900's and two -700's so far have had cracks found.
Not what I’ve read. I read it was 3 737-800
727Man wrote:Jacob2877 wrote:727Man wrote:
Two -900's and two -700's so far have had cracks found.
Not what I’ve read. I read it was 3 737-800
Sorry, I should have said in addition to the 7 -800’s (at that time).
lightsaber wrote:727Man wrote:Jacob2877 wrote:
Not what I’ve read. I read it was 3 737-800
Sorry, I should have said in addition to the 7 -800’s (at that time).
Do you have links? One reason we want tail numbers is double counting is a certainty. Your 7+2+2 are far higher than anything else I'm reading. Personally, I would be surprised at any -900 as the -700/-800 were released earlier.
Lightsaber
Palop wrote:I found the Leeham article interesting in that the winglets may be a contributing factor by changing the bending moment in the wing in an unexpected and unaccounted for way.
I know that the Max have a different pickle fork, but I was curious if this may have ramifications for the Maxes as well. Did Boeing do fatigue testing on the Max? And if so, how?
smokeybandit wrote:Any indication of which airlines are affected?
And what does "cracked" really mean here? Like, the pickle fork is about to fall apart? Or are these tiny cracks that really don't affect structural integrity, just they aren't parts that were ever intended to have cracks?
smokeybandit wrote:Any indication of which airlines are affected?
And what does "cracked" really mean here? Like, the pickle fork is about to fall apart? Or are these tiny cracks that really don't affect structural integrity, just they aren't parts that were ever intended to have cracks?
mjoelnir wrote:smokeybandit wrote:Any indication of which airlines are affected?
And what does "cracked" really mean here? Like, the pickle fork is about to fall apart? Or are these tiny cracks that really don't affect structural integrity, just they aren't parts that were ever intended to have cracks?
Cracked means that the aircraft gets grounded until it is repaired, so I assume it affects structural integrity.
IMO the FAA should remove the 90,000 cycle designation from the 737NG and install an inspect and repair regime instead. This first AD regarding inspection is in reality just to get an measure of the severity of this problem.
lightsaber wrote:mjoelnir wrote:smokeybandit wrote:Any indication of which airlines are affected?
And what does "cracked" really mean here? Like, the pickle fork is about to fall apart? Or are these tiny cracks that really don't affect structural integrity, just they aren't parts that were ever intended to have cracks?
Cracked means that the aircraft gets grounded until it is repaired, so I assume it affects structural integrity.
IMO the FAA should remove the 90,000 cycle designation from the 737NG and install an inspect and repair regime instead. This first AD regarding inspection is in reality just to get an measure of the severity of this problem.
There will be more ADs, the inspection intervals will shorten. But removing the 90,000 cycle life? Have we proven it isn't a manufacturing issue?
The A380 and A320 both were found to need wing reinforcement. The 60,000 cycle limit wasn't removed for the A320 or 36,000 for A380. Instead a repair was approved. New build aircraft are built to a certified modification. Or Embraer wing spars. Or...
There will be a temporary repair approved. There will be a permanent repair approved less than replacing the pickle forks. It will take a few years, but Boeing will get back to full duration on these.
mjoelnir wrote:lightsaber wrote:mjoelnir wrote:
Cracked means that the aircraft gets grounded until it is repaired, so I assume it affects structural integrity.
IMO the FAA should remove the 90,000 cycle designation from the 737NG and install an inspect and repair regime instead. This first AD regarding inspection is in reality just to get an measure of the severity of this problem.
There will be more ADs, the inspection intervals will shorten. But removing the 90,000 cycle life? Have we proven it isn't a manufacturing issue?
The A380 and A320 both were found to need wing reinforcement. The 60,000 cycle limit wasn't removed for the A320 or 36,000 for A380. Instead a repair was approved. New build aircraft are built to a certified modification. Or Embraer wing spars. Or...
There will be a temporary repair approved. There will be a permanent repair approved less than replacing the pickle forks. It will take a few years, but Boeing will get back to full duration on these.
The A320 did not start out with a 60,000 cycle limit. The original approved limit was 48,000 cycles and 60,000 hours. The limits were extended after further fatigue testing and checking of frames reaching the early lifetime limits. The wing cracks on the A380 were found due to the fatigue testing. It would be interesting to get a reference to wing cracks on the A320, as I have not heard of that.
The 737NG got its lifetime limits out of the box. The pickle forks are part of the lifetime parts, no limited lifetime expected. no checking regime, but the current AD, in place.. Cracking was not found through fatigue testing, but by chance at the conversion of older 737-800 to freighters.
ShamrockBoi330 wrote:5% of tested is a lot.I know its only 5% of airframes tested, but Is this compounding the MAX issue for anyone?
Any word or rumours who the 5% belong to?
sodbuster wrote:34 aircraft with cracks....3 -900's, but most -800's and -700's.
Jacob2877 wrote:Yes, it would be helpful if someone had a list. I would like to know where it was found that Southwest Airlines had two that were grounded because of the pickle fork issue.
mjoelnir wrote:lightsaber wrote:mjoelnir wrote:
Cracked means that the aircraft gets grounded until it is repaired, so I assume it affects structural integrity.
IMO the FAA should remove the 90,000 cycle designation from the 737NG and install an inspect and repair regime instead. This first AD regarding inspection is in reality just to get an measure of the severity of this problem.
There will be more ADs, the inspection intervals will shorten. But removing the 90,000 cycle life? Have we proven it isn't a manufacturing issue?
The A380 and A320 both were found to need wing reinforcement. The 60,000 cycle limit wasn't removed for the A320 or 36,000 for A380. Instead a repair was approved. New build aircraft are built to a certified modification. Or Embraer wing spars. Or...
There will be a temporary repair approved. There will be a permanent repair approved less than replacing the pickle forks. It will take a few years, but Boeing will get back to full duration on these.
The A320 did not start out with a 60,000 cycle limit. The original approved limit was 48,000 cycles and 60,000 hours. The limits were extended after further fatigue testing and checking of frames reaching the early lifetime limits. The wing cracks on the A380 were found due to the fatigue testing. It would be interesting to get a reference to wing cracks on the A320, as I have not heard of that.
The 737NG got its lifetime limits out of the box. The pickle forks are part of the lifetime parts, no limited lifetime expected. no checking regime, but the current AD, in place.. Cracking was not found through fatigue testing, but by chance at the conversion of older 737-800 to freighters.
bob75013 wrote:Jacob2877 wrote:Yes, it would be helpful if someone had a list. I would like to know where it was found that Southwest Airlines had two that were grounded because of the pickle fork issue.
https://www.wfaa.com/article/travel/sou ... eda5b84684
mjoelnir wrote:smokeybandit wrote:Any indication of which airlines are affected?
And what does "cracked" really mean here? Like, the pickle fork is about to fall apart? Or are these tiny cracks that really don't affect structural integrity, just they aren't parts that were ever intended to have cracks?
Cracked means that the aircraft gets grounded until it is repaired, so I assume it affects structural integrity.
IMO the FAA should remove the 90,000 cycle designation from the 737NG and install an inspect and repair regime instead. This first AD regarding inspection is in reality just to get an measure of the severity of this problem.
WayexTDI wrote:To be fair, the 737NG was an evolution of a mature airframe, that had been flying for decades, while the A320 was a brand new design. Not saying whether it was right or wrong to give the NG 90,000FC life limit "out of the box", but it was backed by decades of data.
lightsaber wrote:mjoelnir wrote:lightsaber wrote:There will be more ADs, the inspection intervals will shorten. But removing the 90,000 cycle life? Have we proven it isn't a manufacturing issue?
The A380 and A320 both were found to need wing reinforcement. The 60,000 cycle limit wasn't removed for the A320 or 36,000 for A380. Instead a repair was approved. New build aircraft are built to a certified modification. Or Embraer wing spars. Or...
There will be a temporary repair approved. There will be a permanent repair approved less than replacing the pickle forks. It will take a few years, but Boeing will get back to full duration on these.
The A320 did not start out with a 60,000 cycle limit. The original approved limit was 48,000 cycles and 60,000 hours. The limits were extended after further fatigue testing and checking of frames reaching the early lifetime limits. The wing cracks on the A380 were found due to the fatigue testing. It would be interesting to get a reference to wing cracks on the A320, as I have not heard of that.
The 737NG got its lifetime limits out of the box. The pickle forks are part of the lifetime parts, no limited lifetime expected. no checking regime, but the current AD, in place.. Cracking was not found through fatigue testing, but by chance at the conversion of older 737-800 to freighters.
It was played down as A320 corrosion.
http://i.stuff.co.nz/business/3402061/C ... rbus-wings
This was found after the 60k extension.
Airbus didn't find their issue in fatigue testing either and far earlier than 48,000 cycles. The Airbus finding was a surprise. It turned out island hopping was brutal on A319/A320 family wings.
My point is that there will be a repair. The regulations do not specify how a problem is found. The first finding was at about 36,000 cycles. The pickle forks with a life of 90,000 cycles must be inspected every 30,000 cycles.
The fact there are so many found after 35,000 tells us these passed. Now the low cycle incident is of concern.
So for now, ground if cracks found and increase inspections. 25 findings out of 500 is bad, but not unprecedented.
There will be shorter inspection intervals until a standard repair is found that returns the life to design.
That repair cannot happen until a new stress analysis is performed. Just as a temporary repair will be found.
There is a process. The cycle test was with a maximum allowed stress (it is well known for aluminum vs. cycles for life). Just knowing the youngest happened at 20,600 cycles and many later tells us the actual stress level. Boeing has good stress engineers that will find a permanent and temporary repair.
The A380 wing cracks are an example. They happened incredibly early. Well before the inspection. Only found because of a RR uncontained engine failure.
The process is intentionally non-punititive to have self disclosure. The was a 738BCF where that self disclosure found the problem and created the AD.
There is a checking regimen. Every HMC. If you cannot inspect visually, x-ray. I assume the HMV required inspection might be altered/improved.
I'm not sure what you are trying to imply.
Legally, there was a self reported finding. The FAA issued an AD on inspections. The data from those inspections will result in a new AD on modified inspection intervals.
Rework is always an approved repair (return to drawing) or pickle fork replacement.
Permanent repairs take time.
Lightsaber
acechip wrote:A question would be, why was this not discovered during a regular heavy check at say, 20k cycles? Why did it have to be discovered accidentally during a freighter conversion? Is that because of the 90k cycle safe life limit?
iamlucky13 wrote:Leeham reported one frame had cracking found at 23,600 cycles. Other aircraft showing cracking are apparently in the general ballpark of 30,000 cycles. If Leeham is correct that heavy checks are done every 6 years, then that would mean very roughly 12,000, 24,000, and 36,000 cycles.
It is a reasonable guess that none of these aircraft had the cracks present at the time of their last heavy check.
lightsaber wrote:mjoelnir wrote:lightsaber wrote:There will be more ADs, the inspection intervals will shorten. But removing the 90,000 cycle life? Have we proven it isn't a manufacturing issue?
The A380 and A320 both were found to need wing reinforcement. The 60,000 cycle limit wasn't removed for the A320 or 36,000 for A380. Instead a repair was approved. New build aircraft are built to a certified modification. Or Embraer wing spars. Or...
There will be a temporary repair approved. There will be a permanent repair approved less than replacing the pickle forks. It will take a few years, but Boeing will get back to full duration on these.
The A320 did not start out with a 60,000 cycle limit. The original approved limit was 48,000 cycles and 60,000 hours. The limits were extended after further fatigue testing and checking of frames reaching the early lifetime limits. The wing cracks on the A380 were found due to the fatigue testing. It would be interesting to get a reference to wing cracks on the A320, as I have not heard of that.
The 737NG got its lifetime limits out of the box. The pickle forks are part of the lifetime parts, no limited lifetime expected. no checking regime, but the current AD, in place.. Cracking was not found through fatigue testing, but by chance at the conversion of older 737-800 to freighters.
It was played down as A320 corrosion.
http://i.stuff.co.nz/business/3402061/C ... rbus-wings
This was found after the 60k extension.
Airbus didn't find their issue in fatigue testing either and far earlier than 48,000 cycles. The Airbus finding was a surprise. It turned out island hopping was brutal on A319/A320 family wings.
My point is that there will be a repair. The regulations do not specify how a problem is found. The first finding was at about 36,000 cycles. The pickle forks with a life of 90,000 cycles must be inspected every 30,000 cycles.
The fact there are so many found after 35,000 tells us these passed. Now the low cycle incident is of concern.
So for now, ground if cracks found and increase inspections. 25 findings out of 500 is bad, but not unprecedented.
There will be shorter inspection intervals until a standard repair is found that returns the life to design.
That repair cannot happen until a new stress analysis is performed. Just as a temporary repair will be found.
There is a process. The cycle test was with a maximum allowed stress (it is well known for aluminum vs. cycles for life). Just knowing the youngest happened at 20,600 cycles and many later tells us the actual stress level. Boeing has good stress engineers that will find a permanent and temporary repair.
The A380 wing cracks are an example. They happened incredibly early. Well before the inspection. Only found because of a RR uncontained engine failure.
The process is intentionally non-punititive to have self disclosure. The was a 738BCF where that self disclosure found the problem and created the AD.
There is a checking regimen. Every HMC. If you cannot inspect visually, x-ray. I assume the HMV required inspection might be altered/improved.
I'm not sure what you are trying to imply.
Legally, there was a self reported finding. The FAA issued an AD on inspections. The data from those inspections will result in a new AD on modified inspection intervals.
Rework is always an approved repair (return to drawing) or pickle fork replacement.
Permanent repairs take time.
Lightsaber
mjoelnir wrote:What I am trying to imply is, that it would perhaps had been prudent, after the big changes from the classic to the NG, to run a NG frame through fatigue testing.
If you do not realize the difference to find things by fatigue testing, rather than by accident...
iamlucky13 wrote:acechip wrote:A question would be, why was this not discovered during a regular heavy check at say, 20k cycles? Why did it have to be discovered accidentally during a freighter conversion? Is that because of the 90k cycle safe life limit?
I'm not sure the "accidentally" is quite an accurate description.
Leeham reported one frame had cracking found at 23,600 cycles. Other aircraft showing cracking are apparently in the general ballpark of 30,000 cycles. If Leeham is correct that heavy checks are done every 6 years, then that would mean very roughly 12,000, 24,000, and 36,000 cycles.
It is a reasonable guess that none of these aircraft had the cracks present at the time of their last heavy check.
Speaking of which, don't cargo conversions tend to happen when a frame is coming up on a heavy check, because the check can be done more cost effectively then, and the air frame price is lower?
As an additional note, the AD estimated the inspections currently being done at only 1 hour work time (and if I remember right, 1 hour paperwork time). While it's unfortunate to have to add additional maintenance cost, it won't be onerous if a relatively frequent inspection interval is mandated due to this.
FluidFlow wrote:According to the Seattle Times there are now 36 aircraft grounded out of 686 tested. A repair station is now being set up in Victorville.
FluidFlow wrote:According to the Seattle Times there are now 36 aircraft grounded out of 686 tested. A repair station is now being set up in Victorville.
If the pickle fork is really affected on every single 737NG then this is a problem for Boeing because the pickle fork should last for the whole life time of the aircraft. I guess the repair costs and the compensation for the 3 weeks of grounding will probably be paid for by Boeing (product liability). As the NG is at the end of its production cycle, every single NG could be and probably will be over time affected. Thats over 6700 repairs over the next 10-20 years, which would be 1-2 aircraft per day, with a duration of 21 days for the repair, thats between 20-40 aircraft affected at the same time. So lets hope it is an isolated case only affecting a limited amount of pickle forks due to a bad delivery and not a construction fault effecting all of them.
Here is the source: https://www.seattletimes.com/business/boeing-aerospace/cracks-found-on-more-than-5-of-older-boeing-737s-in-pickle-fork-inspections/
Armadillo1 wrote:how old ex-Ryanair planes now?
seahawk wrote:It was done, but it is still testing. In that case it seems like winglets and use of short runways are both indicators.
planecane wrote:FluidFlow wrote:According to the Seattle Times there are now 36 aircraft grounded out of 686 tested. A repair station is now being set up in Victorville.
If the pickle fork is really affected on every single 737NG then this is a problem for Boeing because the pickle fork should last for the whole life time of the aircraft. I guess the repair costs and the compensation for the 3 weeks of grounding will probably be paid for by Boeing (product liability). As the NG is at the end of its production cycle, every single NG could be and probably will be over time affected. Thats over 6700 repairs over the next 10-20 years, which would be 1-2 aircraft per day, with a duration of 21 days for the repair, thats between 20-40 aircraft affected at the same time. So lets hope it is an isolated case only affecting a limited amount of pickle forks due to a bad delivery and not a construction fault effecting all of them.
Here is the source: https://www.seattletimes.com/business/boeing-aerospace/cracks-found-on-more-than-5-of-older-boeing-737s-in-pickle-fork-inspections/
The 21 day repair is to replace the pickle forks with new ones. As lightsaber said, a reinforcement modification will be developed and installed on all aircraft BEFORE the cracks develop. This modification will certainly be far less expensive and time consuming. As lightsaber also said, once a repair is certified, a repair and reinforcement will be able to be done on aircraft with cracks that doesn't involve replacing the pickle forks with new ones. This will also be a less costly and time consuming repair.
They aren't just going to inspect and replace pickle forks when cracks are found for the rest of the 737NG service life.
FluidFlow wrote:planecane wrote:FluidFlow wrote:According to the Seattle Times there are now 36 aircraft grounded out of 686 tested. A repair station is now being set up in Victorville.
If the pickle fork is really affected on every single 737NG then this is a problem for Boeing because the pickle fork should last for the whole life time of the aircraft. I guess the repair costs and the compensation for the 3 weeks of grounding will probably be paid for by Boeing (product liability). As the NG is at the end of its production cycle, every single NG could be and probably will be over time affected. Thats over 6700 repairs over the next 10-20 years, which would be 1-2 aircraft per day, with a duration of 21 days for the repair, thats between 20-40 aircraft affected at the same time. So lets hope it is an isolated case only affecting a limited amount of pickle forks due to a bad delivery and not a construction fault effecting all of them.
Here is the source: https://www.seattletimes.com/business/boeing-aerospace/cracks-found-on-more-than-5-of-older-boeing-737s-in-pickle-fork-inspections/
The 21 day repair is to replace the pickle forks with new ones. As lightsaber said, a reinforcement modification will be developed and installed on all aircraft BEFORE the cracks develop. This modification will certainly be far less expensive and time consuming. As lightsaber also said, once a repair is certified, a repair and reinforcement will be able to be done on aircraft with cracks that doesn't involve replacing the pickle forks with new ones. This will also be a less costly and time consuming repair.
They aren't just going to inspect and replace pickle forks when cracks are found for the rest of the 737NG service life.
Alright, that's good news.
Does anyone here has a rough estimation what a fix like this would cost? The development, testing and certification will probably cost a bit. Afterwards when it can be done on premise from the airline maintenance it should be rather cheap, a few hours of work.
