Factory Info: Parts with Laser Cut Holes and Potential for Cracks

[N82VM]

The continued updates say these parts are fine.
Some will accept that some will not. I’m among the will not. Each update is more evidence of why the parts are fine (blue/green). Seems that Vans positioned is hardened. So is mine.

The swap from free replacement to TBD $$$ is Vans prerogative. The very least they could do is set a price.

1)Vans says the parts are fine (blue/green)
2) I disagree.
3) Vans study says they won’t, aren’t, and don’t have to replace them
4) Great! Since they’re fine I’d like to return them. (My preference even though they are super duper great parts and I’m just weird like that)
5) Vans can’t answer me about credit and shipping them back.

I’ve been given the run around for just shy of two weeks about returning unused LCP for credit. Talked to kits about returns Sept 26, they directed me to shipping because it was a large return. Contacted shipping Sep 26, email was forwarded to Ops Mgr and VP. Heard nothing, checked back Oct 2. Was told they are in meetings about it. Called Oct 6, Ops Mgr not available, called again at 3pm Pacific…everyone in shipping was gone.

Please please please take these unused “acceptable” LCPs back for credit and tell me how much punch parts are and get on with it.

 

[swift12]

Update: October 8, 2023

Engineering Assessment document updated - Added additional clarifying information and illustrative test sample photos to the "Accelerated Life Testing" section of the document:

Also, we realize that things are not moving as quickly as you or any of us here at Van’s would like. We are using all of our available resources to thoroughly identify and determine the full scope of potentially impacted customers and to plan accordingly. We are also assessing the time required to produce punched parts for those who want to go that route. At the same time, we are working to create instructions for the removal/replacement process to be used by our assembly teams and builders in the field. Of course, we remain engaged in extensive analysis, testing, and engineering reviews, examining which parts need to be removed/replaced and how to accomplish this in the fastest way possible.* We can assure you that our teams are working through this issue as quickly as we can. We expect to have more information to provide soon, but don’t want to make firm timeline commitments without sufficient confidence in those timelines. Please understand that this is a difficult, complex issue to resolve and plan for - and it’s very important to us to get it right for you. We will share more updates and plans as soon as we have them ready to go. Thank you.​

I have saved this yet again Greg...promises made by Vans. yes I want to go down the replacing these substandard parts. I'm extremely annoyed I have to pay again and always will be. Vans should not change from this....quote "We are also assessing the time required to produce punched parts for those who want to go that route."...unquote. I want these parts gone and no amount of engineering analysis will change my mind on that. quote..."and it’s very important to us to get it right for you....unquote. mmmm..i can only hope...I ordered june 2021 with a 6 month lead time.............................

 

[airguy]

The continued updates say these parts are fine.
Some will accept that some will not. I’m among the will not. Each update is more evidence of why the parts are fine (blue/green). Seems that Vans positioned is hardened. So is mine.

The swap from free replacement to TBD $$$ is Vans prerogative. The very least they could do is set a price.

1)Vans says the parts are fine (blue/green)
2) I disagree.
3) Vans study says they won’t, aren’t, and don’t have to replace them
4) Great! Since they’re fine I’d like to return them. (My preference even though they are super duper great parts and I’m just weird like that)
5) Vans can’t answer me about credit and shipping them back.

I’ve been given the run around for just shy of two weeks about returning unused LCP for credit. Talked to kits about returns Sept 26, they directed me to shipping because it was a large return. Contacted shipping Sep 26, email was forwarded to Ops Mgr and VP. Heard nothing, checked back Oct 2. Was told they are in meetings about it. Called Oct 6, Ops Mgr not available, called again at 3pm Pacific…everyone in shipping was gone.

Please please please take these unused “acceptable” LCPs back for credit and tell me how much punch parts are and get on with it.

I'm in the same boat here - I want to replace all the blue-label parts, I'll accept the green-label ones. If they are "just fine" then Vans shouldn't have any problem at all with me shipping them back to you for credit on non-LCP replacements. I'll even pay the shipping. What I will NOT do is install blue-label LCP's in my airplane. Vans has way too many SB's currently on the books for parts cracking that A) were not LCP and B) were not expected to crank in the first place, for me to accept that scenario.

 

[Derek.plough]

Please keep us updated on this!

The continued updates say these parts are fine.
Some will accept that some will not. I’m among the will not. Each update is more evidence of why the parts are fine (blue/green). Seems that Vans positioned is hardened. So is mine.

The swap from free replacement to TBD $$$ is Vans prerogative. The very least they could do is set a price.

1)Vans says the parts are fine (blue/green)
2) I disagree.
3) Vans study says they won’t, aren’t, and don’t have to replace them
4) Great! Since they’re fine I’d like to return them. (My preference even though they are super duper great parts and I’m just weird like that)
5) Vans can’t answer me about credit and shipping them back.

I’ve been given the run around for just shy of two weeks about returning unused LCP for credit. Talked to kits about returns Sept 26, they directed me to shipping because it was a large return. Contacted shipping Sep 26, email was forwarded to Ops Mgr and VP. Heard nothing, checked back Oct 2. Was told they are in meetings about it. Called Oct 6, Ops Mgr not available, called again at 3pm Pacific…everyone in shipping was gone.

Please please please take these unused “acceptable” LCPs back for credit and tell me how much punch parts are and get on with it.

Please keep us updated on this, I would also like credit for my “acceptable” parts. Thank you!

 

[swift12]

Please keep us updated on this, I would also like credit for my “acceptable” parts. Thank you!

add me to that list as well...ill take credit for ACCEPTABLE parts for punched replacements

 

[GrahamF]

Greg, thanks for the update on the testing methods - that is useful to know. A question around that - how was vibration worked into the testing?

Then a question on the engineering thinking behind the original decision to use laser-cut parts. As you know, conventional aviation practice is that if aluminium parts are cut with a laser then the heat-affected zone must subsequently be removed by mechanical means - thus making it an impractical technique for cutting small holes. What was the engineering reasoning by which Van's decided that it would be ok in this instance, and that conventional practice could be disregarded?

 

[Snowflake]

Since these have been “historically laser-cut parts” as Greg just stated, I wonder if this LCP process is the reason that engine baffles have been more prone to cracking in the past than other parts?

Do the engine baffles ever start cracking at rivet holes? On the baffles i've seen with cracks they always seem to start at points of obvious stress concentration... Folded corners, overlaps with adjacent baffles, etc.

 

[auburnaviator]

Do the engine baffles ever start cracking at rivet holes? On the baffles i've seen with cracks they always seem to start at points of obvious stress concentration... Folded corners, overlaps with adjacent baffles, etc.

Rob,
To be honest I don’t know and was merely commenting on the post that the other poster had made. Maybe there is no correlation at all between LCP and baffle cracking. But since Greg mentioned those parts have always been historically LCP and the previous post mentioned baffles having a known penchant to cracking I thought I’d make the connection and ask the question. There is a wealth of knowledge here, figured someone smarter than me might have more insight…

Regards,
Zach

 

[N82VM]

Please keep us updated on this, I would also like credit for my “acceptable” parts. Thank you!

Here’s the update,

Ops manger is not the right person for this question (ops mgr and vp were fwd’d my original question). I waited a week to find that out. From what I was told Greg H is the one that this falls to.

There is great sensitivity about returning LCPs, at least that is the vibe I get. I can’t help thinking that all this engineering data says these are “acceptable” parts. This should make it a no brainer for Vans to take them back (and stuff in another kit #newkitsales). They’re great right? Some new builder will be pleased as punch their kit came early because some cotton candy headed builder (me) rejected and returned perfectly good parts.

I’m waiting to hear back and I’m not holding my breath for obvious reasons.

Each update has been how great or even greater the parts are and not to worry. Maybe the next update will tell us they’re actually stronger than punched parts.

We are not getting substantial answers for the free of charge/“tbd” price reversal and/or shipping costs. That is the update people want. It’s not rocket surgery. Most of us would prefer an answer instead of this tippy toe hot potato dance that’s currently going on.

 

[Jonnyb]

The problem I see for Vans is that no one but you knows what’s happened to those parts while you have had them.

When a person buys a kit, those parts are manufactured and sent straight to the purchaser, Vans can vouch for each part. That would not be the case for parts that have sat in your workshop.

I don’t know how consumer law works in the US. Are you able to send back items that are good and demand a refund/credit?

 

[N82VM]

I received it Jan 2023, other than inventory they are untouched. With exception of the ones I put together.

Their policy says I have 2 years

 

[mburch]

The problem I see for Vans is that no one but you knows what’s happened to those parts while you have had them.

For what it's worth, in years past I have received parts from Vans that were obviously scratched up and used, and even one part that had already been completely rattle-can primed! So it's not like they have historically always been real sticklers for the quality of returned parts, apparently. (I decided to replace the aforementioned parts on my own dime as they were comparatively low-cost)

 

[spatsch]

Do the engine baffles ever start cracking at rivet holes? On the baffles i've seen with cracks they always seem to start at points of obvious stress concentration... Folded corners, overlaps with adjacent baffles, etc.

Same here. Mine cracked at a folded corner.

Oliver

 

[dmattmul]

Baffles are LCP's?

Since these have been “historically laser-cut parts” as Greg just stated, I wonder if this LCP process is the reason that engine baffles have been more prone to cracking in the past than other parts? Purely speculation and more just asking the question…. It could also be that since they are in such close proximity to the motor that they get a lot more vibrations compared to other parts and thus are more prone to cracking?

My baffles were received before the LCP issue came up but looking at my pics (RV-10) almost all my baffles had blue film. Don't have or remember what the 14 contained. Maybe over the years some baffles were LCP and some punched on different models.

 

[cwilkins]

Return Policy

I received it Jan 2023, other than inventory they are untouched. With exception of the ones I put together.

Their policy says I have 2 years

Once people like Vic Syracuse and Doug Reeves started posting about shutting down the thread because of the “vender bashing” of Van’s Aircraft over the LCP disaster I made the decision that I was no longer willing to wait patiently for this issue to be resolved.

In fact, there were at least a few posts from people saying if we weren’t satisfied we could go with another company. I haven’t decided if I’m going to go with another kit manufacturer or just go back to certified aircraft, but I did decide to abandon my RV-14 project and return it to Van’s. I have an empennage kit that was opened, inventoried, and organized in my shop. I also have a wing kit in the original crate that hasn’t even been opened for inventory. On September 28th, I emailed Van’s Aircraft for directions on how to return my kits. I sent the email to [email protected], [email protected], and [email protected], and CCd [email protected]. The only response I have received thus far was an email from Anne Bobbitt stating she would forward my refund request to Greg Hughes. Good to know we have 2 years to return the kits.

[ed. I’m sorry to read you are leaving the RV community. I wish you the very best. Kindest, Doug]

 

[ccarlson]

Once people like Vic Syracuse and Doug Reeves started posting about shutting down the thread because of the “vender bashing” of Van’s Aircraft over the LCP disaster I made the decision that I was no longer willing to wait patiently for this issue to be resolved.

In fact, there were at least a few posts from people saying if we weren’t satisfied we could go with another company. I haven’t decided if I’m going to go with another kit manufacturer or just go back to certified aircraft, but I did decide to abandon my RV-14 project and return it to Van’s. I have an empennage kit that was opened, inventoried, and organized in my shop. I also have a wing kit in the original crate that hasn’t even been opened for inventory. On September 28th, I emailed Van’s Aircraft for directions on how to return my kits. I sent the email to [email protected], [email protected], and [email protected], and CCd [email protected]. The only response I have received thus far was an email from Anne Bobbitt stating she would forward my refund request to Greg Hughes. Good to know we have 2 years to return the kits.

I am very sorry to hear you have decided to abandon your project, but I understand and respect the decision. I wrestle with the same decision whenever I check my inbox or walk past my boxes of empennage, wing, and fuselage parts to get to other items in my garage. I have a threshold, of course, but I have not reached it - yet. I've wanted to build an RV for 27 years, and despite all of this, I mostly still do.

On a positive note, you received a response. I sent an email on Sep 26 and have not received any response at all. Nothing. Zero. Bupkis. At this point, I cannot help but wonder if I am being patient or gullible.

 

[N8DAV8R]

When a person buys a kit, those parts are manufactured and sent straight to the purchaser, Vans can vouch for each part.

Wait...I can't tell. Are you 'saying' that with a straight face?

 

[Jonnyb]

Wait...I can't tell. Are you 'saying' that with a straight face?

Mostly!!

 

[MIKE JG]

Not that it matters much but I finally got around to my standard RV-8 wing kit.

Of the 93 parts affected, 18 are listed as red or yellow. Of those I got lucky, I only need Vans to replace 6 of those as the other 12 were ok by manufacture date.

Of the remaining parts, I am electing not to use 69 of those listed as acceptable for use, the blue colored parts. Fair enough as that is my choice. Unfortunately these are mostly wing rib sections at $20 a piece.

The total for replacement of all the parts I want replaced is going to be over $1300 with S/H factored in if forced to pay full price.

Not complaining, just throwing this out there for reference for others and really hoping for a good discount on these parts.

 

[andrepew]

I'm in the same boat here - I want to replace all the blue-label parts, I'll accept the green-label ones. If they are "just fine" then Vans shouldn't have any problem at all with me shipping them back to you for credit on non-LCP replacements. I'll even pay the shipping. What I will NOT do is install blue-label LCP's in my airplane. Vans has way too many SB's currently on the books for parts cracking that A) were not LCP and B) were not expected to crank in the first place, for me to accept that scenario.

I was thinking about accepting a green-label part but decided against it.

My reasoning is, eventually the plane will be sold -- either by me or by a relative. A prospective buyer will do their homework and ask the big question about LCPs in the plane. I want to be able to say to that buyer flat out "There are no LCPs in this plane."

 

[rocketman1988]

...and

I was thinking about accepting a green-label part but decided against it.

My reasoning is, eventually the plane will be sold -- either by me or by a relative. A prospective buyer will do their homework and ask the big question about LCPs in the plane. I want to be able to say to that buyer flat out "There are no LCPs in this plane."

...and you would be wrong.

There a other parts, outside of the parts affected by the current issue, that have been LC, and are perfectly fine...

 

[Bullpup]

...and you would be wrong.

There a other parts, outside of the parts affected by the current issue, that have been LC, and are perfectly fine...

The parts outside/before this issue aren't even listed on the LCP list. Green parts, on the other hand, are being returned to CNC punch, and are well within a buyer's prerogative to ask.

Regardless, giving them your reply is unlikely to help purchase negotiations...

 

[ncardella]

Update: October 8, 2023

Engineering Assessment document updated - Added additional clarifying information and illustrative test sample photos to the "Accelerated Life Testing" section of the document:

Also, we realize that things are not moving as quickly as you or any of us here at Van’s would like. We are using all of our available resources to thoroughly identify and determine the full scope of potentially impacted customers and to plan accordingly. We are also assessing the time required to produce punched parts for those who want to go that route. At the same time, we are working to create instructions for the removal/replacement process to be used by our assembly teams and builders in the field. Of course, we remain engaged in extensive analysis, testing, and engineering reviews, examining which parts need to be removed/replaced and how to accomplish this in the fastest way possible.* We can assure you that our teams are working through this issue as quickly as we can. We expect to have more information to provide soon, but don’t want to make firm timeline commitments without sufficient confidence in those timelines. Please understand that this is a difficult, complex issue to resolve and plan for - and it’s very important to us to get it right for you. We will share more updates and plans as soon as we have them ready to go. Thank you.​

Greg - We can all agree things are not moving as fast or efficient as we all like.

Question: What is Van's plan for the QB kits? We need answers on how to proceed.

 

[Jack_G_S]

I have to admit I was wrong when saying Van’s would never say that cracks are ok while referencing AC 23-13a in the same document.

As others have pointed out that would open up another can of worms. What are the limits? How many cracks are allowed? What are the size limits? Ect.

My impression is the new angle is to redefine what the primary structure is.

AC 23-13a: “Primary Structure. Primary structure is that structure which carries flight, ground, or pressurization loads, and whose failure would reduce the structural integrity of the airplane.”

Van’s definition: “Primary Structure (typically the skins and spars of the airframe). This stabilizing structure is used to maintain shape and prevent buckling of another part, which increases that primary component’s ability to resist compression or shear loads.”

 

[scrollF4]

I want to be able to say to that buyer flat out "There are no LCPs in this plane."

...and yet you'd be telling the buyer a falsehood. As Vans has already stated, laser-cut parts have been included in RV kits for many years. The engine baffle kit is one aforementioned example. Those parts have simply not been an issue.

Now, if you want to guarantee to the buyer that there are no LCPs with the holes improperly edge-cut (the REAL issue), that's a different story.

 

[N82VM]

You know what he means by that statement.

Sorry you’re being jumped on with technicality of “no LCP”

The gentleman was trying to say that he wants to tell the prospective buyer that no LCP parts identified in the Laser Cut Parts List R5.6 are in the airframe.

Is that accurate enough?

 

[maxmirot]

I would gladly buy a RV with Green LCPs only.
Claiming no LCP parts on a sale is not dishonest if they are green only IMO.
Any small cracks in a Green LCP are cosmetic.

 

[N82VM]

...As Vans has already stated, laser-cut parts have been included in RV kits for many years. The engine baffle kit is one aforementioned example. Those parts have simply not been an issue.

How many years? When did it start?

 

[tfriske]

My impression is the new angle is to redefine what the primary structure is.

AC 23-13a: “Primary Structure. Primary structure is that structure which carries flight, ground, or pressurization loads, and whose failure would reduce the structural integrity of the airplane.”

Van’s definition: “Primary Structure (typically the skins and spars of the airframe). This stabilizing structure is used to maintain shape and prevent buckling of another part, which increases that primary component’s ability to resist compression or shear loads.”

I can't tell if you are being snarky or you have simply misread the Engineering report. Regardless, what you have quoted above is misleading and is absolutely not the way the report from Van's defines primary structure. That is their clarifying definition of secondary structure.

To quote the report accurately:
"Structural assemblies were analyzed and classified as Primary Structure and Secondary Structure based on their application, relationship to flight loads, and criticality to the safe operation of the aircraft. Primary Structure is essential in maintaining the overall structural integrity of the airplane."

And then two paragraphs below:
"Many parts serve their function at stresses and loads far below that which would make them susceptible to fatigue damage. These are cases where the parts do not directly resist major portions of flight or ground loads and are often functioning to stabilize Primary Structure (typically the skins and spars of the airframe). This stabilizing structure..."

IOW, Van's, like AC 23-13a, defines primary structure as structure that carries (or resists) critical loads -> typically skins and spars.

 

[Jack_G_S]

I can't tell if you are being snarky or you have simply misread the Engineering report. Regardless, what you have quoted above is misleading and is absolutely not the way the report from Van's defines primary structure. That is their clarifying definition of secondary structure.

To quote the report accurately:
"Structural assemblies were analyzed and classified as Primary Structure and Secondary Structure based on their application, relationship to flight loads, and criticality to the safe operation of the aircraft. Primary Structure is essential in maintaining the overall structural integrity of the airplane."

And then two paragraphs below:
"Many parts serve their function at stresses and loads far below that which would make them susceptible to fatigue damage. These are cases where the parts do not directly resist major portions of flight or ground loads and are often functioning to stabilize Primary Structure (typically the skins and spars of the airframe). This stabilizing structure..."

IOW, Van's, like AC 23-13a, defines primary structure as structure that carries (or resists) critical loads -> typically skins and spars.

I mentioned this because Van’s said in their report “ Van’s Aircraft has conservatively classified – and recommends replacement of – laser-cut Primary Structure parts regardless of the magnitude of the stress found in the part.” In my opinion Van’s and the FAA’s definition of a primary part differ.

You and Van’s are using words like “critical loads” or “major loads” in an attempt to confuse. In my opinion AC 23-13a definition for a primary part is a part that carries ANY load in which a failure would reduce the structural integrity of the airplane. I definitely think wing ribs fall into that category.

What’s the primary structure of the fuselage? Just the skin?

 

[Bullpup]

I can't tell if you are being snarky or you have simply misread the Engineering report. Regardless, what you have quoted above is misleading and is absolutely not the way the report from Van's defines primary structure. That is their clarifying definition of secondary structure.

To quote the report accurately:
"Structural assemblies were analyzed and classified as Primary Structure and Secondary Structure based on their application, relationship to flight loads, and criticality to the safe operation of the aircraft. Primary Structure is essential in maintaining the overall structural integrity of the airplane."

And then two paragraphs below:
"Many parts serve their function at stresses and loads far below that which would make them susceptible to fatigue damage. These are cases where the parts do not directly resist major portions of flight or ground loads and are often functioning to stabilize Primary Structure (typically the skins and spars of the airframe). This stabilizing structure..."

IOW, Van's, like AC 23-13a, defines primary structure as structure that carries (or resists) critical loads -> typically skins and spars.

I agree with your interpretation of 23-13a and Vans report re: Primary and Secondary structure. That said, while the guidance on Primary structure is very restrictive (hence Vans' red part list), I am not clear on how permissive the treatment of secondary structure is. I doubt the intent is to allow unlimited damage of secondary components, but the line is not well defined in either the AC nor Vans engineering assessment.

Specifically, paragraph 6.5.c.7:

(7) Structures with multiple-site damage, corrosion and stress corrosion cracks. Continued operational flight with known cracks in instances of multiple-site damage, cracks in the presence of corrosion, or stress corrosion cracks should be avoided.

Along with 6.5.d:

d. The approval should provide a limited time for continued flight with known cracks. Under no circumstances can allowance for operation with known cracks be considered more than a temporary condition.

Neither these sections, nor the parent of 6.5 specifically limit the guidance to primary structure. In the absence of further clarification from Vans, I think a reasonable interpretation is to not accept widespread, known cracks in multiple structural components. While wing ribs, for example, may be secondary structure, no one would fly with only spars and skins. Failure tolerance seems (my opinion) to look at the failure of individual elements, not every component.

To their credit, Vans did perform residual strength testing with multiple (every?) ribs compromised, so that does help. Per the engineering assessment that was on an RV-10 wing.

In my prior experience (military vs. experimental aircraft, so take with a grain of salt), the engineering analysis used to make a determination about damaged structure was specific to the case at hand. I'm not familiar with the use of a test program to make a blanket acceptance of known, widespread cracking, even if the cracks are small. If Vans could provide more data and specific recommendations, including acceptance criteria for cracks in dimpled parts, some of the uncertainty would go away.

It is undeniable that the engineering assessment direction violates section 5 of the plans, and could be interpreted as running counter to 23-13a. It is within their power to directly address this discrepancy and update one or more of the documents they control, and I'm pretty upset that they seem unwilling to do so. It leaves me (and many builders, from the sound of it) in a square corner.

 

[Jack_G_S]

“Secondary structure is that structure which carries only air or inertial loads generated on or within the secondary structure.“
It’s things like fairings

 

[scrollF4]

How many years? When did it start?

Ask Van's. I was quoting what Greg said Sunday in this post:

https://vansairforce.net/community/showpost.php?p=1717306&postcount=1495

Greg specifically said: "The baffle parts have essentially always been laser-cut. Those parts fall into the "historically laser-cut parts" category and continue to be made that way. They will not appear as named parts on the laser-cut parts list."

Therefore, there is "essentially" no such thing as an RV with zero laser cut parts, so I urge you not to tell a buyer it's 100% free of LCPs.

Therefore, to me, if a buyer asks, you'll probably want to be able to show him/her which SPECIFIC LCPs from the Vans list are still in the aircraft, what color-code, etc. I know this complicates the sale, but it at least allows you full transparency (if you're inclined to lose sleep over it).

As for my RV-7A (flying for 8.5 years and 1800+ Hobbs hours), I have ZERO cracks anywhere on my 9-year-old laser cut baffles.

 

[tfriske]

I doubt the intent is to allow unlimited damage of secondary components, but the line is not well defined in either the AC nor Vans engineering assessment.

Specifically, paragraph 6.5.c.7:

(7) Structures with multiple-site damage, corrosion and stress corrosion cracks. Continued operational flight with known cracks in instances of multiple-site damage, cracks in the presence of corrosion, or stress corrosion cracks should be avoided.

Along with 6.5.d:

d. The approval should provide a limited time for continued flight with known cracks. Under no circumstances can allowance for operation with known cracks be considered more than a temporary condition.

Neither these sections, nor the parent of 6.5 specifically limit the guidance to primary structure. In the absence of further clarification from Vans, I think a reasonable interpretation is to not accept widespread, known cracks in multiple structural components. While wing ribs, for example, may be secondary structure, no one would fly with only spars and skins. Failure tolerance seems (my opinion) to look at the failure of individual elements, not every component.

I fully agree that there is some uncertainty here and personally find no fault with any builder choosing to completely eliminate this particular uncertainty by replacing all of these parts.

But, just for the sake of discussion... I think the distinction Van's has attempted to draw here is that there is a meaningful difference between a crack that was caused by the loads imparted on an airframe part and a crack that was already there in a specific location--the dimple rim. I think this distinction rings true with the 6.5 language you have quoted above. It makes perfect sense that if operating the airplane has cause a part to fail, then continued operation, with an already failed part and with those same loads still being imparted on the now compromised part, is a significant danger to flight.

I do find it compelling that Van's testing has demonstrated that parts with dimple rim cracks will eventually fail due to fatigue from simulated flight loads, but do not fail at the preexisting crack and do not show signs of the dimple crack propagating. This builds confidence that their finite element analysis on the structural loads, and their resultant determination that the dimple rim carries negligible stress, are correct.

In oversimplified terms, the job of the dimple/rivet combo is to hold a part in its intended place. The 'replacement recommended' vs 'acceptable for use' determination seems to come down to a basic distinction of whether or not there are significant forces trying to move that part out of its intended place. As one example, there is a clear distinction to be made between a part like the rear wing spar and a part like a wing rib in terms of the types of loads/stresses they encounter. Every time you deflect an aileron or extend the flaps there are forces trying to tear the spar out of position via the hinge bracket (likewise the front spar of the control service on the other side of the hinge). The wing ribs on the other hand are mostly there to hold the wing camber shape and in this case it's the web of the part, not the flange, that is doing most of the work. The dimple/rivet just needs to keep the rib from falling over (yes, oversimplified).

 

[lr172]

I agree with your interpretation of 23-13a and Vans report re: Primary and Secondary structure. That said, while the guidance on Primary structure is very restrictive (hence Vans' red part list), I am not clear on how permissive the treatment of secondary structure is. I doubt the intent is to allow unlimited damage of secondary components, but the line is not well defined in either the AC nor Vans engineering assessment.

Specifically, paragraph 6.5.c.7:

(7) Structures with multiple-site damage, corrosion and stress corrosion cracks. Continued operational flight with known cracks in instances of multiple-site damage, cracks in the presence of corrosion, or stress corrosion cracks should be avoided.

Along with 6.5.d:

d. The approval should provide a limited time for continued flight with known cracks. Under no circumstances can allowance for operation with known cracks be considered more than a temporary condition.

Neither these sections, nor the parent of 6.5 specifically limit the guidance to primary structure. In the absence of further clarification from Vans, I think a reasonable interpretation is to not accept widespread, known cracks in multiple structural components. While wing ribs, for example, may be secondary structure, no one would fly with only spars and skins. Failure tolerance seems (my opinion) to look at the failure of individual elements, not every component.

To their credit, Vans did perform residual strength testing with multiple (every?) ribs compromised, so that does help. Per the engineering assessment that was on an RV-10 wing.

In my prior experience (military vs. experimental aircraft, so take with a grain of salt), the engineering analysis used to make a determination about damaged structure was specific to the case at hand. I'm not familiar with the use of a test program to make a blanket acceptance of known, widespread cracking, even if the cracks are small. If Vans could provide more data and specific recommendations, including acceptance criteria for cracks in dimpled parts, some of the uncertainty would go away.

It is undeniable that the engineering assessment direction violates section 5 of the plans, and could be interpreted as running counter to 23-13a. It is within their power to directly address this discrepancy and update one or more of the documents they control, and I'm pretty upset that they seem unwilling to do so. It leaves me (and many builders, from the sound of it) in a square corner.

All great points, but part 23 is referring to cracks that appear from in service use. Any crack that develops during service can be assumed to be caused by stress and/or fatigue in the specific area of the crack and therefore quite serious. Vans tested these parts and the small cracks inside the dimple did not propogate and instead a different crack appeared in a different location from the stress induced by the testing. That seems to be a pretty good indication that the inside area of a dimple is not a highly stressed area, even in those parts that see a lot of stress (the red list parts). Hard to see how this is an issue in secondary structure parts that don't see these kinds of stresses. Pretty sure that by definition, seconary structure doesn't see stresses. It's job is to hold the primary structure rigidly in it's designed position, so that it can properly absorb those stresses. In a simple term example, the bolt and castle nut are primary structure and the cotter pin is secondary structure. If the shear or tension forces are too great, the bolt or threads fail, but the cotter pin survives unscathed, as it didn't see ANY of the stresses that caused the failure.

 

[Bullpup]

All great points, but part 23 is referring to cracks that appear from in service use. Any crack that develops during service can be assumed to be caused by stress and/or fatigue in the specific area of the crack and therefore quite serious. Vans tested these parts and the small cracks inside the dimple did not propogate and instead a different crack appeared in a different location from the stress induced by the testing. That seems to be a pretty good indication that the inside area of a dimple is not a highly stressed area, even in those parts that see a lot of stress (the red list parts). Hard to see how this is an issue in secondary structure parts that don't see these kinds of stresses. Pretty sure that by definition, seconary structure doesn't see stresses. It's job is to hold the primary structure rigidly in it's designed position, so that it can properly absorb those stresses. In a simple term example, the bolt and castle nut are primary structure and the cotter pin is secondary structure. If the shear or tension forces are too great, the bolt or threads fail, but the cotter pin survives unscathed, as it didn't see ANY of the stresses that caused the failure.

Appreciate the thoughts, and I have no background on pre-existing vs. in-service cracks, nor do I, as an EAB builder, have the expertise to evaluate my particular set of blue parts with respect to the original intent of the AC, or the original design margins of the aircraft. I do have an aerospace engineering backgound, but my focus was not structures.

Given that this AC is for damage mitigation in-service, I'm not surprised that it doesn't address manufacturing defects. In my previous career, build defects in excess of tolerances on plans or written practices required individual engineering assessment, with specific applicability to the specific defect. I've never heard of a situation like this, where an expanded test program was used to give a blanket waiver.

We can all agree that there are build quality/workmanship issues which would reject a particular part (drill out and redo). Vans themselves gave "not to exceed" guidance for holes in wing ribs to support wiring, etc. Now we have nothing other than "these parts don't matter and there are no standards". I don't think that is then intent, but this is how it is written, and the larger community will notice.

I'm less concerned about the forensics of the terms (primary/secondary) than with the current, conflicting guidance. I'm not a professional, building to the published standard to the best of my ability is my assurance that the finished plane is safe for my family and friends. Vans completely has the power to update build guidance to reflect higher tolerance for cracked parts in certain (Vans would say secondary) structure. Until they do, as a builder, I have to choose which document I follow. I get a lot of choices building an experimental, but this isn't the area I want to explore.

I can appreciate them, as a company, not wanting to write a document that says "cracks are OK" - that will get attention from both customers and the FAA. They should have thought of that before committing to this path - the test program had to have cost hundreds of thousands of dollars, which could have paid for a lot of replacement parts.

 

[Bullpup]

All great points, but part 23 is referring to cracks that appear from in service use. Any crack that develops during service can be assumed to be caused by stress and/or fatigue in the specific area of the crack and therefore quite serious. Vans tested these parts and the small cracks inside the dimple did not propogate and instead a different crack appeared in a different location from the stress induced by the testing. That seems to be a pretty good indication that the inside area of a dimple is not a highly stressed area, even in those parts that see a lot of stress (the red list parts). Hard to see how this is an issue in secondary structure parts that don't see these kinds of stresses. Pretty sure that by definition, seconary structure doesn't see stresses. It's job is to hold the primary structure rigidly in it's designed position, so that it can properly absorb those stresses. In a simple term example, the bolt and castle nut are primary structure and the cotter pin is secondary structure. If the shear or tension forces are too great, the bolt or threads fail, but the cotter pin survives unscathed, as it didn't see ANY of the stresses that caused the failure.

The picture they added to the engineering assessment seems to show (I'm not completely sure) that the fatigue crack extended to the hole edge, although in a different location from the LC crack.

They say they tested a variety of crack orientations, but I find it impossible that had the LCP feature been aligned with the eventual crack that wouldn't have accelerated the crack formation.

If Vans has enough test documentation to address this question they are welcome to publish it!

 

[Jack_G_S]

From AC 23-19A:

Definition: Secondary structure is not a primary load-carrying member. Failure of secondary structure neither reduces the airframe structural integrity nor prevents the airplane from continued safe flight and landing.

Are you trying to imply a failure of a, or all, wing rib(s) would not “reduce the airframe structural integrity”? You probably are also confusing the definition of “structure” and “part”. AC 23-13a for the most part does not allow cracks within a primary structure.

 

[TX_Flyer]

Are you trying to imply a failure of a, or all, wing rib(s) would not “reduce the airframe structural integrity”? You probably are also confusing the definition of “structure” and “part”. AC 23-13a for the most part does not allow cracks within a primary structure.

Not at all, what i am saying is that the definition of Secondary Structure can mean far more than an air or inertial loaded piece.

To be honest I doubt that failure of a large portion or maybe even all of the ribs would have significant impact on the strength of the wings, nearly all of the load is in the skin and spars.

Vans tested the strength of the wing with the ribs defeated/failed and found the load carrying ability of the wings still met design criteria.

 

[lr172]

The picture they added to the engineering assessment seems to show (I'm not completely sure) that the fatigue crack extended to the hole edge, although in a different location from the LC crack.

!

It didn't. It started at the rounded edge of the dimple next to flat area, right where I speculated it would start and moved out from there. You can clearly see in the pic the original crack at the dimple center and it DIDN'T grow. This was confirmed by the testing company and am sure they used magnification to confirm that. We can all agree that cracks are never good and should be avoided. However, just because a crack is never good, does not necessarily mean it is bad. It is ALL about stress loading and fatigue. Just look at all the SBs. Plenty of punched parts have developed cracks when the parts saw greater loads in the real world than were accounted for in the design stage. Sorry, but punched parts is not the universal answer to parts that don't crack. It is all about the mechanical engineering assumptions and parts specifications that go into the design. This a why I can't seem to grasp all of this disbelief in the Vans engineers statements about LCP cracking when folks are trusting 1000's of other design choices they have made on your behalf. The folks out there seem to think that Vans is lieing through their teeth about this particular issue, yet seem to have absolute trust in all of their other design choices. I just cannot comprehend how someone could ever fly in a plane designed by someone they don't trust completely. IMHO, Vans has earned a level of trust in their design choices and this has been proven over the years. People like that don't just wake up one day and say, let's just lie about this one issue so we can save a few bucks.

 

[Bullpup]

It didn't. It started at the rounded edge of the dimple next to flat area, right where I speculated it would start and moved out from there. You can clearly see in the pic the original crack at the dimple center and it DIDN'T grow. This was confirmed by the testing company and am sure they used magnification to confirm that. We can all agree that cracks are never good and should be avoided. However, just because a crack is never good, does not necessarily mean it is bad. It is ALL about stress loading and fatigue. Just look at all the SBs. Plenty of punched parts have developed cracks when the parts saw greater loads in the real world than were accounted for in the design stage. Sorry, but punched parts is not the universal answer to parts that don't crack. It is all about the mechanical engineering assumptions and parts specifications that go into the design. This a why I can't seem to grasp why all of this disbelief in the Vans engineers when folks are trusing 1000's of other design choices they have made on your behalf.

I don't mistrust the Vans engineers. I just want them to finish the job and update the guidance so I don't have to pick between two incompatible directives! And if they can't/won't do that, they need to replace all the parts. Simple.

And, as you pointed out, plenty of other cracks have grown from punched parts that were not expected by the engineers in design. The speed and scope of this LCP process (test thousands of combinations, of hundreds of parts, on multiple airframes, with multiple variations in part quality, build quality, and crack orientation, in 3 months) seems primed for future "discoveries". I'm not insulting or mistrusting the engineers, but I think these are reasonable doubts to have.

As for the single(!) photo they included in the engineering assessment, I agree 100% that the LC crack didn't grow. It appears to me (not sure though), that the fatigue crack extended to the hole edge, below and to the left of the LCP feature (yellow arrow in my edited pic).

If the LCP feature had been aligned with the fatigue crack location, it seems reasonable to think it may have grown faster. Thoughts?

 

[lr172]

I It appears to me (not sure though), that the fatigue crack extended to the hole edge, below and to the left of the LCP feature (yellow arrow in my edited pic).

True, but chances are VERY low that it started there. If that was the stress point, I have all confidence that the stress crack would have propagated from the original crack and worked outward. WAY less stress required to grow a crack than start one. We have learned a lot about micro fractures and grain structure irregularities over the last 20 years and now understand how they can start cracks with far less stress than a sound part. The fact that a brand new stress crack started right next to the dimple crack just proves how benign the dimple cracking is. I just don't comprehend how folks don't see that, especially with highly trained scientists and engineers telling you that.

 

[GrahamF]

I wonder when we're going to get any sort of news about what happens next, when we might get parts, etc?

I note that the practice of starting the date of the next update has ceased.

 

[Bullpup]

True, but chances are VERY low that it started there. If that was the stress point, I have all confidence that the stress crack would have propagated from the original crack and worked outward. WAY less stress required to grow a crack than start one. We have learned a lot about micro fractures and grain structure irregularities over the last 20 years and now understand how they can start cracks with far less stress than a sound part. The fact that a brand new stress crack started right next to the dimple crack just proves how benign the dimple cracking is. I just don't comprehend how folks don't see that, especially with highly trained scientists and engineers telling you that.

I understand your point, and I agree the risk is low. But aviation, thankfully, has moved into risk probabilities well below 1% as the standard. I have nearly 3000 affected holes in my wings alone, that is a lot of chances for things to line up the wrong way.

I'm under no illusions that I don't have other issues (amateur builder!), but I struggle to accept known problems which, by definition, eat into the margins.

This could be solved with better documentation. But if I have to choose between following section 5, with thousands of flying airplanes, or this engineering assessment with probably zero completed airplanes, I pick section 5. Both Vans documents (so don't say I don't trust them), but they are the ones forcing the choice, because these documents are currently incompatible.

 

[bmellis11]

We are also assessing the time required to produce punched parts for those who want to go that route.

Greg, does this mean you haven't started production on replacement parts for all affected parts yet?

 

[MIKE JG]

Anyone have a realistic guess at when they might start shipping replacement parts?? Winter is coming and I am trying to decide if I should just put the project away until next spring or hold out hope that I might see useful parts before winter is over here in the Great Lakes area.

 

[bertschb]

Anyone have a realistic guess at when they might start shipping replacement parts??

I don't know if it's realistic but I expect to see some replacement parts this winter. I don't expect to get all of my replacement parts until next summer.

 

[N82VM]

We have learned a lot about micro fractures and grain structure irregularities over the last 20 years and now understand how they can start cracks with far less stress than a sound part. The fact that a brand new stress crack started right next to the dimple crack just proves how benign the dimple cracking is. I just don't comprehend how folks don't see that, especially with highly trained scientists and engineers telling you that.

These Scientists and engineers are not the ones building and therefore applying my or others workmanship standards.
There are many builders that don’t want to except a low bar of good enough or build on.

 

[Walt]

Would the part have cracked under the same circumstances/test parameters if it was a non LC part? Seems to me the entire edge of the LC hole is still in the HAZ which would be more likely to crack from temper. Did they test LC and non LC parts under the same testing parameters? (maybe I missed that).

 

[SwissVolts]

True, but chances are VERY low that it started there. If that was the stress point, I have all confidence that the stress crack would have propagated from the original crack and worked outward. WAY less stress required to grow a crack than start one. We have learned a lot about micro fractures and grain structure irregularities over the last 20 years and now understand how they can start cracks with far less stress than a sound part. The fact that a brand new stress crack started right next to the dimple crack just proves how benign the dimple cracking is. I just don't comprehend how folks don't see that, especially with highly trained scientists and engineers telling you that.

You really don't understand?

I invite you to build a plane with many LCP, and enjoy many acrobatic sessions with family and friends... Would you really do it with complete security and confidence for many years? Pushing the plane close to its G limits, maybe 20 years later?

Engineers are people too and have the right to make mistakes! And they have been wrong in commercial airplanes that pass much more demanding tests!
Leaving safety aside, resale value, aesthetics, not feeling cheated... do you think there are few reasons not to want LCP?

My plane should last many years, I hope my children can continue enjoying it after me... I don't want to start building a plane with defects. Is this so difficult to understand? I only want what I paid for, it's as simple as that.