2 Ryanair 737s, EI-DAL and EI-DCL, is being reported by Skylines Aviation to be sent to VCV for pickle forks repairs

Boeing 737 -8AS 33718 1311 EI-DAL Ryanair ferried 26-27oct19 DUB-BGR-VCV for cracked wing forks repairs (+ 33806/1576 EI-DCL)

Anybody got total numbers at this point?

Qantas has grounded 1 738 after crack in pickle fork found, ramping up inspections on other jets

https://www.reuters.com/article/us-boei ... SKBN1X90R7

qf789 wrote:

Qantas has grounded 1 738 after crack in pickle fork found, ramping up inspections on other jets

https://www.reuters.com/article/us-boei ... SKBN1X90R7

I'm happy to see the repair cost is less than I estimated. The highest cost is the lost time. From the above link:

Repairing the cracks requires grounding the airplane, with remedial work costing an estimated $275,000 per aircraft, according to aviation consultancy IBA.

Lightsaber

[*]There are two follow up questions which are interesting:

The first is what would an airline during a heavy inspection after 25,000 cycles if there are no cracks at that time? Is it worth replacing it just in case or running the risk that cracks develop and then the plane is again out for a heavy and costly repair? Clearly and added expense which may be deemed not necessary but a repaired pickle fork would certainly add to the residual value of the aircraft.

The second is how often after the initial check will planes need to be rechecked? The checks are relatively straight forward so would it be something that is done after every 1,000 cycles? would it make sense to coincide these follow on pickle fork checks with the B-Checks in maintenance schedules?

Either Qantas 738 VXC or VXM is the aircraft affected by the cracked pickle fork. Qantas will also conduct inspections on 33 737-800's, all of which have more than 22,600 cycles, will be checked by the end of this week. The affected aircraft has 26,700 cycles. Meanwhile Virgin has inspected 19 737NG's over 22,600 cycles of which no cracks have been found

https://samchui.com/2019/10/30/qantas-t ... bnUZ3duLIV

djm18 wrote:

[*]There are two follow up questions which are interesting:

The first is what would an airline during a heavy inspection after 25,000 cycles if there are no cracks at that time? Is it worth replacing it just in case or running the risk that cracks develop and then the plane is again out for a heavy and costly repair? Clearly and added expense which may be deemed not necessary but a repaired pickle fork would certainly add to the residual value of the aircraft.

The second is how often after the initial check will planes need to be rechecked? The checks are relatively straight forward so would it be something that is done after every 1,000 cycles? would it make sense to coincide these follow on pickle fork checks with the B-Checks in maintenance schedules?

I think your second question answers the first. Inspecting the pickle forks on these aircraft will become a routine thing, so if a plane shows no sign of cracking on the initial inspection, any new cracking would be caught in a later inspection. I don't think they need to replace one preemptively, since the cracking doesn't happen suddenly but over a period of time.

2175301 wrote:

The real question is how fast Boeing can come up with the required spare Pickle Forks in order to replace them on the aircraft... I can see having a few in stock. But, not enough to repair more than 5 aircraft....

Of course, I suspect ramp-up by the part manufacturer could occur in less than a month... but, that's still a month or more for the aircraft to sit on the ground...

Have a great day,

They make 2 aircraft per day. Even with just-in-time efforts, if the part is the same between the NG and the MAX, I'd wager they have a decent number more than 5 pairs on hand in Witchita.

For the modest size and complexity of the part, I also suspect they can have more completed with machining and dimensional inspection of extra copies in less than a week, and then it's a matter of completing coating and paperwork.

I think part availability will be a lesser challenge than actually completing the replacements on several dozen aircraft.

djm18 wrote:

[*]There are two follow up questions which are interesting:

The first is what would an airline during a heavy inspection after 25,000 cycles if there are no cracks at that time? Is it worth replacing it just in case or running the risk that cracks develop and then the plane is again out for a heavy and costly repair? Clearly and added expense which may be deemed not necessary but a repaired pickle fork would certainly add to the residual value of the aircraft.

It would make sense to swap the forks while the plane is stripped for heavy checks. Even if no cracks are discovered. Otherwise, you’re facing a potential second invasive procedure soon after the heavy check.

Also, doing a prophylactic swap is better for preserving the value of the fleets - which is critical because airlines borrow against the equity in their planes, and a fleet that’s expected to crack in 5,000 flight cycles is worth a lot less than a fleet expected to crack in 25,000 FCs.

That’s a lot of forks to swap if they’re gonna do every NG IN circulation. So they have to use a less efficient strategy if they’re parts limited.

The next question is whether airlines and the FAA are going to be content to swap in a part that’s known to fail in a critical structural junction.

2175301 wrote:

The real question is how fast Boeing can come up with the required spare Pickle Forks in order to replace them on the aircraft... I can see having a few in stock. But, not enough to repair more than 5 aircraft....

Of course, I suspect ramp-up by the part manufacturer could occur in less than a month... but, that's still a month or more for the aircraft to sit on the ground...

Have a great day,

Early in this thread I posted there were 25 sets of pickle forks available:
https://leehamnews.com/2019/10/08/boein ... le-part-2/

So far more than 5 were ready. But more than 25 have issues. This will take time to make spares.


Lightsaber

https://www.smh.com.au/business/compani ... 5360y.html

Second Qantas 737 with cracked pickle forks.

Agrajag wrote:

https://www.smh.com.au/business/companies/qantas-urged-to-ground-all-of-its-737s-after-second-aircraft-crack-discovered-20191031-p5360y.html

Second Qantas 737 with cracked pickle forks.

Qantas only has one 737 with cracked pickle fork, the news of the second one is just speculation at this stage, it has not been confirmed by the airline, the union representing QF's engineers is also putting out propaganda to make things sound a lot worse than they are

qf789 wrote:

Agrajag wrote:

https://www.smh.com.au/business/companies/qantas-urged-to-ground-all-of-its-737s-after-second-aircraft-crack-discovered-20191031-p5360y.html

Second Qantas 737 with cracked pickle forks.

Qantas only has one 737 with cracked pickle fork, the news of the second one is just speculation at this stage, it has not been confirmed by the airline, the union representing QF's engineers is also putting out propaganda to make things sound a lot worse than they are

So you are saying this story in the Herald is baseless?

iamlucky13 wrote:

2175301 wrote:

The real question is how fast Boeing can come up with the required spare Pickle Forks in order to replace them on the aircraft... I can see having a few in stock. But, not enough to repair more than 5 aircraft....

Of course, I suspect ramp-up by the part manufacturer could occur in less than a month... but, that's still a month or more for the aircraft to sit on the ground...

Have a great day,

They make 2 aircraft per day. Even with just-in-time efforts, if the part is the same between the NG and the MAX, I'd wager they have a decent number more than 5 pairs on hand in Witchita.

For the modest size and complexity of the part, I also suspect they can have more completed with machining and dimensional inspection of extra copies in less than a week, and then it's a matter of completing coating and paperwork.

I think part availability will be a lesser challenge than actually completing the replacements on several dozen aircraft.

Actually, part availability is a pretty big problem since the max uses completely different pickle forks and the remaining NG based aircraft that are being produced use different ones.

And if you think spares exist on a production line as fast as the 737 you're delusional.

Material availability for spares is a big problem. They'll have long lead times and will have to pay expedite fees.

My understanding is its just easier to replace the pickle fork once you've got it all torn down.

No need to replace ones that have been inspected and shown no cracking. That's the whole point of a damage tolerance inspection program.

Has anyone found out why this is happening? I understand the forks are designed and engineered to last the life of the aircraft.

I think the most interesting part of the Qantas bird is that it’s got less than 30,000 cycles but still has cracking. This makes one wonder if this is a common issue even on younger birds or just a one off.

trpmb6 wrote:

Actually, part availability is a pretty big problem since the max uses completely different pickle forks and the remaining NG based aircraft that are being produced use different ones.

I'm wondering if the MAX pickle forks can be used on the NG? Replacing cracked NG pickle forks with new ones means the same problem is likely to eventually happen again. Replacement with the new but the same OEM part sounds like a short term fix. The part probably needs a redesign, or substitution by a newer part already in production for the MAX.

Over a thousand inspected, less than 50 with issues:
https://www.bing.com/amp/s/amp.scmp.com ... acks-737ng


I'm searching for root cause. So far, nothing public.

Lightsaber

lightsaber wrote:

Over a thousand inspected, less than 50 with issues:
https://www.bing.com/amp/s/amp.scmp.com ... acks-737ng


I'm searching for root cause. So far, nothing public.

Lightsaber

What was discussed (as a possibility); the bigger up to date winglets do stress the wings more than prior and calculated. It is like as someone lengthens the wings by one or two meter. They are heavy and this weight is not neat the fuselages, this additional weight (and forces during flight) is at the outer edges at the wing tips. If than the B737 NG parts are applied with a little bit to rough force during construction (so cutting edges) to reduce the production times....slight damages and with time, you get cracks in the former slightly harmed Al alloys..

What is missing in all of the discussion here and elsewhere. After 30.000 around 5% of the B737 NG have already developed cracks...and all will be parked for several weeks to exchange and repair the forks. How many % will have developed cracks after 45.000, 60.000 and more cycles and hours?

kabq737 wrote:

I think the most interesting part of the Qantas bird is that it’s got less than 30,000 cycles but still has cracking. This makes one wonder if this is a common issue even on younger birds or just a one off.

If it's VXC or VXM as stated above, they're both 17 years old - not exactly spring chickens.

lightsaber wrote:

Over a thousand inspected, less than 50 with issues:
https://www.bing.com/amp/s/amp.scmp.com ... acks-737ng


I'm searching for root cause. So far, nothing public.

Lightsaber

The article is a bit ambiguous in that it says

A company spokesperson said that so far around 1,000 planes worldwide had “reached the inspection threshold”, with less than five per cent – or up to 50 jets globally – having “findings” that kept them grounded until repair."

To me, it is not clear whether "reached inspection threshold" = "inspected."

flyingclrs727 wrote:

trpmb6 wrote:

Actually, part availability is a pretty big problem since the max uses completely different pickle forks and the remaining NG based aircraft that are being produced use different ones.

I'm wondering if the MAX pickle forks can be used on the NG? Replacing cracked NG pickle forks with new ones means the same problem is likely to eventually happen again. Replacement with the new but the same OEM part sounds like a short term fix. The part probably needs a redesign, or substitution by a newer part already in production for the MAX.

Doesn't work that way.

The fit would necessitate changes to surrounding structure.

One can infer what type of issue it is based on how Boeing is responding to the issue. For instance, if it were a material lot issue they would have specific line unit #s to target. They aren't, they are telling anyone over so many cycles to inspect. So its not a material defect issue causing cracks. If Boeing is telling operators to just swap it out, its probably some process issue that went wrong and not something that needs to be redesigned. Much can be learned by paying attention to how the issue is solved. Operators won't accept a solution that requires follow on replacements unless it results in an advantage for them somehow.

qf789 wrote:

Agrajag wrote:

https://www.smh.com.au/business/companies/qantas-urged-to-ground-all-of-its-737s-after-second-aircraft-crack-discovered-20191031-p5360y.html

Second Qantas 737 with cracked pickle forks.

Qantas only has one 737 with cracked pickle fork, the news of the second one is just speculation at this stage, it has not been confirmed by the airline, the union representing QF's engineers is also putting out propaganda to make things sound a lot worse than they are

Do you have concrete evidence to say the SMH story is baseless?

There are too many posts here in this forum category that don’t cite sources.

T4thH wrote:

lightsaber wrote:

Over a thousand inspected, less than 50 with issues:
https://www.bing.com/amp/s/amp.scmp.com ... acks-737ng


I'm searching for root cause. So far, nothing public.

Lightsaber

What was discussed (as a possibility); the bigger up to date winglets do stress the wings more than prior and calculated. It is like as someone lengthens the wings by one or two meter. They are heavy and this weight is not neat the fuselages, this additional weight (and forces during flight) is at the outer edges at the wing tips. If than the B737 NG parts are applied with a little bit to rough force during construction (so cutting edges) to reduce the production times....slight damages and with time, you get cracks in the former slightly harmed Al alloys..

What is missing in all of the discussion here and elsewhere. After 30.000 around 5% of the B737 NG have already developed cracks...and all will be parked for several weeks to exchange and repair the forks. How many % will have developed cracks after 45.000, 60.000 and more cycles and hours?

Weren't there some aircraft without winglets that has cracks too?

cpd wrote:

qf789 wrote:

Agrajag wrote:

https://www.smh.com.au/business/companies/qantas-urged-to-ground-all-of-its-737s-after-second-aircraft-crack-discovered-20191031-p5360y.html

Second Qantas 737 with cracked pickle forks.

Qantas only has one 737 with cracked pickle fork, the news of the second one is just speculation at this stage, it has not been confirmed by the airline, the union representing QF's engineers is also putting out propaganda to make things sound a lot worse than they are

Do you have concrete evidence to say the SMH story is baseless?

There are too many posts here in this forum category that don’t cite sources.

Qantas put out a press release 3 hours after the SMH was published stating

On Wednesday we advised that we had found one example of cracking in an aircraft with 27,000 cycles and this aircraft has been removed from service for repair. We’ll provide a further update when the checks are complete.
Qantas rejects the alarmist claims made by the licenced engineers’ union, which are irresponsible and completely inconsistent with advice from regulators and the manufacturer.

https://www.qantasnewsroom.com.au/qanta ... spections/

Furthermore my above comments include my own opinion on how the union is behaving, and if anyone who follows Australian aviation would know this is the way the union behaves when Qantas has an issue with an aircraft no matter how big or small the issue is, yet when it was announced a couple of weeks that Virgin needed to check 19 737's for pickle fork cracking it went practically unnoticed.

Mostly wrote:

djm18 wrote:

[*]There are two follow up questions which are interesting:

The first is what would an airline during a heavy inspection after 25,000 cycles if there are no cracks at that time? Is it worth replacing it just in case or running the risk that cracks develop and then the plane is again out for a heavy and costly repair? Clearly and added expense which may be deemed not necessary but a repaired pickle fork would certainly add to the residual value of the aircraft.

It would make sense to swap the forks while the plane is stripped for heavy checks. Even if no cracks are discovered. Otherwise, you’re facing a potential second invasive procedure soon after the heavy check.

Also, doing a prophylactic swap is better for preserving the value of the fleets - which is critical because airlines borrow against the equity in their planes, and a fleet that’s expected to crack in 5,000 flight cycles is worth a lot less than a fleet expected to crack in 25,000 FCs.

That’s a lot of forks to swap if they’re gonna do every NG IN circulation. So they have to use a less efficient strategy if they’re parts limited.

The next question is whether airlines and the FAA are going to be content to swap in a part that’s known to fail in a critical structural junction.

This is a really big job, so highly doubt they would just get changed at next heavy. Parts like these usually only get replaced when an issue is found. I would imagine the inspection cycle on this area will be of a shorter time between inspections.

Now if Boeing comes out with a Service Bulletin that installs a better part or a reinforcing repair then operators would likely replace the pickle forks. The failure rate is also pretty low.

Dalmd88 wrote:

This is a really big job, so highly doubt they would just get changed at next heavy. Parts like these usually only get replaced when an issue is found. I would imagine the inspection cycle on this area will be of a shorter time between inspections.

Now if Boeing comes out with a Service Bulletin that installs a better part or a reinforcing repair then operators would likely replace the pickle forks. The failure rate is also pretty low.

If you can reasonably expect most NGs to eventually crack by say, 50,000 FC, the fly it till it cracks mentality gets dicey.

It begs the question of whether it’s acceptable to knowingly fly an airplane until (and past, given the inspection interval) a structural element cracks.

If a wing comes off in heavy turbulence or on a hard landing, and someone can show that an operator’s protocol is to intentionally fly till it breaks, you’re asking for the lawyers to eat you alive.

Not to mention the ethics.

Qantas have confirmed three aircraft have cracks:

https://www.reuters.com/article/us-qant ... SKBN1XA2ON

Apparently the aircraft will be back online by the end of the year.

Mostly wrote:

If you can reasonably expect most NGs to eventually crack by say, 50,000 FC, the fly it till it cracks mentality gets dicey.

It begs the question of whether it’s acceptable to knowingly fly an airplane until (and past, given the inspection interval) a structural element cracks.

If a wing comes off in heavy turbulence or on a hard landing, and someone can show that an operator’s protocol is to intentionally fly till it breaks, you’re asking for the lawyers to eat you alive.

Not to mention the ethics.

To clarify, you are saying fly till the wing cracks or fly until the pickle fork cracks, because I can see airlines flying the a/c until the fork cracks, it would be no different from flying until a heavy check is due.

par13del wrote:

To clarify, you are saying fly till the wing cracks or fly until the pickle fork cracks, because I can see airlines flying the a/c until the fork cracks, it would be no different from flying until a heavy check is due.

Good point. An NG with an undiagnosed crack could lose a wing tomorrow. The strictly proper ethical maneuver is to recognize that there’s a structural design or manufacturing issue, ground the fleet, and swap in a properly engineered solution immediately.

Seems unlikely though - but props to the Qantas engineers union for trying to do the right thing.

benjjk wrote:

Qantas have confirmed three aircraft have cracks:

https://www.reuters.com/article/us-qant ... SKBN1XA2ON

Apparently the aircraft will be back online by the end of the year.

So the union was right.

zkojq wrote:

So the union was right.

No.
As called out by management Purvinas was irresponsible in his comments.

The US FAA recommended
- immediate (within 7 days) inspection of 737s with 30k+ cycles - QF had none in this category
- medium term (within 1000 cycles, or 6-7 months for QF) for 22.6k-30k cycles - QF had 33 in this category.

So QF has completed something required by 6-7 months within a month, and found 3 of 33 aircraft with issues - all with approx 27k cycles, so presumably the 2002/03 delivered VH-VX* series.

At the time Purvinas made the statement to ground all 75 737s the mechanics would have already completed about 30 inspections.

If I was a union mechanic, I'd be angry. Either
- the union leader doesn't trust the inspection work already conducted; or
- doesn't have a clue what his members are doing


So there are now a few airlines with rates seemingly above 5%
Korean - 9 of 42 (though airfleets only shows 32 and only 20 that are 10+ years old ) - all issues with 30k+ cycles.
Qantas - 3 of 33 - all issues with 27k cycles.
GOL - 11 of ?? (Got 119 NGs but I'd think only 20 with 22+k cycles)

-

Best quote I've read on this was from a pilot who basically said the only aircraft without a crack is the one that isn't built yet.

zkojq wrote:

benjjk wrote:

Qantas have confirmed three aircraft have cracks:

https://www.reuters.com/article/us-qant ... SKBN1XA2ON

Apparently the aircraft will be back online by the end of the year.

So the union was right.

About grounding the entire fleet? Disagree. In any case the union only said they should be grounded until they've been inspected. Qantas have finished the inspections now so even if the union were in charge they would be back in the air today.

Mostly wrote:

par13del wrote:

To clarify, you are saying fly till the wing cracks or fly until the pickle fork cracks, because I can see airlines flying the a/c until the fork cracks, it would be no different from flying until a heavy check is due.

Good point. An NG with an undiagnosed crack could lose a wing tomorrow.

This is just not true. These cracks cannot bring down an otherwise serviceable aircraft unless they are allowed to develop much into much more than the inch or so that these ones are - which takes many thousands more cycles.

benjjk wrote:

This is just not true. These cracks cannot bring down an otherwise serviceable aircraft unless they are allowed to develop much into much more than the inch or so that these ones are - which takes many thousands more cycles.

I’m not saying it’s likely. You’re right that it hasn’t happened yet. But I doubt you’d argue that a wing connected to a cracked fork can cope with less load before it fails. So the question is how much less. And you and I don’t know the answer to that.

Could bad turbulence cause a failure? Probably not. But maybe. Could a hard landing cause a failure, probably not. But maybe. The point is that we don’t know.

We do know that cracks in parts that weren’t engineered to crack can transmit stress to areas that may not have been engineered to handle that stress, so runway failures can happen.

Don’t get me wrong, I’m not suggesting that failure is likely, what I’m saying is that we don’t have enough data to make an assessment. And the track record isn’t great so far with the manufacturing consistency of the part, so that adds to overall uncertainty.



Quick edit: the accepted safety factor for commercial aviation is 1.5 to 2.5. Boeing’s corporate culture probably means they’re on the left side of that range. So figure we’re a 1/3 drop in structural integrity away from being at a safety factory of 1.0. That’s not outside the realm of possibility

qf789 wrote:

cpd wrote:

qf789 wrote:

Qantas only has one 737 with cracked pickle fork, the news of the second one is just speculation at this stage, it has not been confirmed by the airline, the union representing QF's engineers is also putting out propaganda to make things sound a lot worse than they are

Do you have concrete evidence to say the SMH story is baseless?

There are too many posts here in this forum category that don’t cite sources.

Qantas put out a press release 3 hours after the SMH was published stating

On Wednesday we advised that we had found one example of cracking in an aircraft with 27,000 cycles and this aircraft has been removed from service for repair. We’ll provide a further update when the checks are complete.
Qantas rejects the alarmist claims made by the licenced engineers’ union, which are irresponsible and completely inconsistent with advice from regulators and the manufacturer.

https://www.qantasnewsroom.com.au/qanta ... spections/

Furthermore my above comments include my own opinion on how the union is behaving, and if anyone who follows Australian aviation would know this is the way the union behaves when Qantas has an issue with an aircraft no matter how big or small the issue is, yet when it was announced a couple of weeks that Virgin needed to check 19 737's for pickle fork cracking it went practically unnoticed.

Qantas has now contradicted you:

https://www.smh.com.au/business/compani ... 536fe.html

"Of the 33 of Qantas’ 737 aircraft that required inspection, three were found to have a hairline crack in the pickle fork structure. These aircraft have been removed from service for repair," a statement from the airline read.

This directly contradicts your post which is quoted for reference. More so, here is the exact Qantas media release, direct from the airline:

https://www.qantasnewsroom.com.au/media ... eet-check/

Mostly wrote:

benjjk wrote:

This is just not true. These cracks cannot bring down an otherwise serviceable aircraft unless they are allowed to develop much into much more than the inch or so that these ones are - which takes many thousands more cycles.

I’m not saying it’s likely. You’re right that it hasn’t happened yet. But I doubt you’d argue that a wing connected to a cracked fork can cope with less load before it fails. So the question is how much less. And you and I don’t know the answer to that.

Could bad turbulence cause a failure? Probably not. But maybe. Could a hard landing cause a failure, probably not. But maybe. The point is that we don’t know.

We do know that cracks in parts that weren’t engineered to crack can transmit stress to areas that may not have been engineered to handle that stress, so runway failures can happen.

Don’t get me wrong, I’m not suggesting that failure is likely, what I’m saying is that we don’t have enough data to make an assessment. And the track record isn’t great so far with the manufacturing consistency of the part, so that adds to overall uncertainty.



Quick edit: the accepted safety factor for commercial aviation is 1.5 to 2.5. Boeing’s corporate culture probably means they’re on the left side of that range. So figure we’re a 1/3 drop in structural integrity away from being at a safety factory of 1.0. That’s not outside the realm of possibility

The crack does reduce the margin of safety, which is why these particular aircraft are grounded - though ferry flights are permitted. But to suggest that means a wing could fall off tomorrow is, to borrow the Qantas press release, alarmist. Put it this way: after the MAX debacle I would expect the FAA to be taking a very conservative approach to this. But even they have said the inspections can wait until a convenient time (within limits obviously), and don't need to happen right away.

One more thing: I have been told that replacement of the pickle forks takes about 3000 man-hours. With a fix that expensive, "fly until it cracks" is the only realistic avenue here, unless it's a very high-time aircraft likely to see imminent cracking.

benjjk wrote:

Mostly wrote:

benjjk wrote:

This is just not true. These cracks cannot bring down an otherwise serviceable aircraft unless they are allowed to develop much into much more than the inch or so that these ones are - which takes many thousands more cycles.

I’m not saying it’s likely. You’re right that it hasn’t happened yet. But I doubt you’d argue that a wing connected to a cracked fork can cope with less load before it fails. So the question is how much less. And you and I don’t know the answer to that.

Could bad turbulence cause a failure? Probably not. But maybe. Could a hard landing cause a failure, probably not. But maybe. The point is that we don’t know.

We do know that cracks in parts that weren’t engineered to crack can transmit stress to areas that may not have been engineered to handle that stress, so runway failures can happen.

Don’t get me wrong, I’m not suggesting that failure is likely, what I’m saying is that we don’t have enough data to make an assessment. And the track record isn’t great so far with the manufacturing consistency of the part, so that adds to overall uncertainty.



Quick edit: the accepted safety factor for commercial aviation is 1.5 to 2.5. Boeing’s corporate culture probably means they’re on the left side of that range. So figure we’re a 1/3 drop in structural integrity away from being at a safety factory of 1.0. That’s not outside the realm of possibility

The crack does reduce the margin of safety, which is why these particular aircraft are grounded - though ferry flights are permitted. But to suggest that means a wing could fall off tomorrow is, to borrow the Qantas press release, alarmist. Put it this way: after the MAX debacle I would expect the FAA to be taking a very conservative approach to this. But even they have said the inspections can wait until a convenient time (within limits obviously), and don't need to happen right away.

One more thing: I have been told that replacement of the pickle forks takes about 3000 man-hours. With a fix that expensive, "fly until it cracks" is the only realistic avenue here, unless it's a very high-time aircraft likely to see imminent cracking.

The fix takes less than 2 weeks - 12 days I heard. And that is for the first airplane. Unless they have a huge team working 24-7, the estimate of 3,000 hours seems high.

I’ve also heard it is not a full replacement of the picklefork, but a patch with structural reinforcement. For context, sometimes you can fix a crack by drilling holes at each end...

sxf24 wrote:

benjjk wrote:

Mostly wrote:

The fix takes less than 2 weeks - 12 days I heard. And that is for the first airplane. Unless they have a huge team working 24-7, the estimate of 3,000 hours seems high.

I’ve also heard it is not a full replacement of the picklefork, but a patch with structural reinforcement. For context, sometimes you can fix a crack by drilling holes at each end...

It's currently a team of around 15 or so Boeing AOG support techs working 24x7. There are no part issues anymore. It's just available labor now that is the issue.

It is indeed a picklefork replacement (actually dual replacement now since parts are available). Watch the video that was posted earlier in this thread.

727Man wrote:

sxf24 wrote:

benjjk wrote:

It's currently a team of around 15 or so Boeing AOG support techs working 24x7. There are no part issues anymore. It's just available labor now that is the issue.

It is indeed a picklefork replacement (actually dual replacement now since parts are available). Watch the video that was posted earlier in this thread.

If those 15 guys are averaging $64/hr, that gets you to the $275,000 estimate for the job that we’ve been hearing. Doesn’t account for parts costs and aircraft downtime (we’ll see if Boeing can avoid having to pay for that).

Overtime makes that $64/hr seem impossibly low.

Anybody got the per day lost revenue of a NG down for maintenance?

trpmb6 wrote:

And if you think spares exist on a production line as fast as the 737 you're delusional.

While I don't know specifics about how the 737 program manages their machined parts inventory, I'm not speculating from a position of ignorance about aerospace part supply.

Even when posters do make ignorant comments, calling them delusional is hardly an exemplary display of character on your part.

https://finance.yahoo.com/news/boeing-s ... 00893.html

Confirms the 50 number, although Reuters makes it sound like a big number rather than a tiny fraction of those inspected.

Interesting comment about WN. Seems consistent with the above reporting that the second wave of inspections of less-urgent frames did find some cracks.

qf789 wrote:

cpd wrote:

qf789 wrote:

Qantas only has one 737 with cracked pickle fork, the news of the second one is just speculation at this stage, it has not been confirmed by the airline, the union representing QF's engineers is also putting out propaganda to make things sound a lot worse than they are

Do you have concrete evidence to say the SMH story is baseless?

There are too many posts here in this forum category that don’t cite sources.

Qantas put out a press release 3 hours after the SMH was published stating

On Wednesday we advised that we had found one example of cracking in an aircraft with 27,000 cycles and this aircraft has been removed from service for repair. We’ll provide a further update when the checks are complete.
Qantas rejects the alarmist claims made by the licenced engineers’ union, which are irresponsible and completely inconsistent with advice from regulators and the manufacturer.

https://www.qantasnewsroom.com.au/qanta ... spections/

Furthermore my above comments include my own opinion on how the union is behaving, and if anyone who follows Australian aviation would know this is the way the union behaves when Qantas has an issue with an aircraft no matter how big or small the issue is, yet when it was announced a couple of weeks that Virgin needed to check 19 737's for pickle fork cracking it went practically unnoticed.

https://www.theguardian.com/business/20 ... om-service

Three? Still baseless?

lightsaber wrote:

Over a thousand inspected, less than 50 with issues:
https://www.bing.com/amp/s/amp.scmp.com ... acks-737ng


I'm searching for root cause. So far, nothing public.

Lightsaber

Scaled up to the whole NG fleet, this means about the same number of grounded NGs as there are MAXs grounded.

Also, if they just replace the broken fork by another fork, the same procedure will have to be repeated again and again after about the same time?

Is there also a permanent fix in sight?

Over time almost all metal cracks. That's why you have inspections.

benjjk wrote:

Mostly wrote:

benjjk wrote:

This is just not true. These cracks cannot bring down an otherwise serviceable aircraft unless they are allowed to develop much into much more than the inch or so that these ones are - which takes many thousands more cycles.

I’m not saying it’s likely. You’re right that it hasn’t happened yet. But I doubt you’d argue that a wing connected to a cracked fork can cope with less load before it fails. So the question is how much less. And you and I don’t know the answer to that.

Could bad turbulence cause a failure? Probably not. But maybe. Could a hard landing cause a failure, probably not. But maybe. The point is that we don’t know.

We do know that cracks in parts that weren’t engineered to crack can transmit stress to areas that may not have been engineered to handle that stress, so runway failures can happen.

Don’t get me wrong, I’m not suggesting that failure is likely, what I’m saying is that we don’t have enough data to make an assessment. And the track record isn’t great so far with the manufacturing consistency of the part, so that adds to overall uncertainty.



Quick edit: the accepted safety factor for commercial aviation is 1.5 to 2.5. Boeing’s corporate culture probably means they’re on the left side of that range. So figure we’re a 1/3 drop in structural integrity away from being at a safety factory of 1.0. That’s not outside the realm of possibility

The crack does reduce the margin of safety, which is why these particular aircraft are grounded - though ferry flights are permitted. But to suggest that means a wing could fall off tomorrow is, to borrow the Qantas press release, alarmist. Put it this way: after the MAX debacle I would expect the FAA to be taking a very conservative approach to this. But even they have said the inspections can wait until a convenient time (within limits obviously), and don't need to happen right away.

One more thing: I have been told that replacement of the pickle forks takes about 3000 man-hours. With a fix that expensive, "fly until it cracks" is the only realistic avenue here, unless it's a very high-time aircraft likely to see imminent cracking.

So how much time industry had before an accident if problem wasn't noticed? My impression is not that much.
Of course, we don't know how fast crack propagates and how bad consequencies can really be. Possibly - not very likely - this is a self-limiting process to begin with. From Boeing-FAA responce, though, this seems to be a bad case of propagating crack and possible bad outcome.
As far as I understand, once the crack is initiated - a countdown timer is started, and it is a matter of time before part is weakened to the point it cannot handle the load. AD assumes few thousand cycles before that happens; lets guess 5k - that is 3 years at 5 cycles a day.
Now there are 50 planes with cracking at various stages; no data on how badly or mildly cracked different frames are. Assuming more or less uniform distribution of crack progress, the worst case could be within 5000/50=100 cycles until a failure, that is about a month of flying, and expected crash rate would be on the order of 10/year.
Maybe I am missing something, but grounding older fleet doesn't sound that crazy with such probabilities. Apparently, FAA and Boeing decided that expedite inspections is a safe enough bet. One has to remember that those are just that - estimates and bets. Boeing just lost big time on "10 months before next event" one.

kalvado wrote:

So how much time industry had before an accident if problem wasn't noticed? My impression is not that much.
Of course, we don't know how fast crack propagates and how bad consequencies can really be. Possibly - not very likely - this is a self-limiting process to begin with. From Boeing-FAA responce, though, this seems to be a bad case of propagating crack and possible bad outcome.

Wild guess would be that given 50+ 15-20+ year old aircraft have cracks is that not all of them appeared in the last month, and some have probably been there for many years without major consequences.

Of course we're all a lot safer now that this has been detected without a fatality, and the pickled fork will now be one of many areas of potential metal fatigue that are investigated during maintenance.

Just like say lap joints
https://en.m.wikipedia.org/wiki/Aloha_A ... Flight_243

moa999 wrote:

Over time almost all metal cracks. That's why you have inspections.

The cracks were discovered by accident.

This part had a lifetime design, no regular inspections scheduled. The lifetime of the picleforks were included in the 90,000 cycle lifetime of the 737NG. IMO the 90,000 cycle lifetime for the 737NG should be scrapped, or a different lifetime limit on the pickle forks set.

Boeing should look at still younger frames before the 22,600 cycle limit, to be sure that cracks do not show up on still younger frames.

moa999 wrote:

Over time almost all metal cracks. That's why you have inspections.

Correct me if I am mistaken, but the pickle forks are designed as a "safe life" component. They are supposed to last the entire service life of the aircraft (80000 flight cycles?) without needing a replacement or repair. To have the pickle forks develop cracks at less than 30000 cycles is not reassuring for a "safe life" component.

I understand that these cracks were only discovered by chance in a freighter conversion and the pickle forks are not usually inspected. I don't think there is disagreement that metals can fatigue or crack, but in this case the concern is why this component seems to be failing much earlier than anticipated. Does anyone know when the pickle forks are usually inspected?