When doing a prebuy how do you determine if a part was lasar cut?

Without knowing the kit date I don't believe you can tell.

are the delivered holes full size or can the whole problem. Bad pun.. be fixed by drilling full size before dimpling. Drill #31 hole to #30 then dimple?

That, and I also considered going to the next diameter, and using NAS1097 reduced head rivets. But yes, definitely dimple after the final ream and deburr.

Without knowing the kit date I don't believe you can tell.

I am so glad my RV-8 kits were built and delivered 2-3 months prior to the LCP debacle.

That, and I also considered going to the next diameter, and using NAS1097 reduced head rivets. But yes, definitely dimple after the final ream and deburr.

The consistency of the crack position, seemingly always in the same relative spot, suggests it is primarily caused by the laser start position. That is, where the laser first tries to punch through the metal. This makes one part of the circle different than the others.

A quality laser cut often starts in the center of the hole, blasts through, and only then works the perimeter. I bet they didn't do that and just blasted right on the perimeter to start, which is faster.

Here is a video that shows how starting is quite different than cutting:

[youtube]https://youtu.be/JF3K-98kQ4Q[/youtube]

Mike C.

The consistency of the crack position, seemingly always in the same relative spot, suggests it is primarily caused by the laser start position. That is, where the laser first tries to punch through the metal. This makes one part of the circle different than the others.

A quality laser cut often starts in the center of the hole, blasts through, and only then works the perimeter. I bet they didn't do that and just blasted right on the perimeter to start, which is faster.

Here is a video that shows how starting is quite different than cutting:

[youtube]https://youtu.be/JF3K-98kQ4Q[/youtube]

Mike C.

The common thread here is an inadequate system to manage vendor quality. In the case of the primer Vans says the change was made without their knowledge. Likewise they claim they validated the process for laser cut parts but the vendor changed the process without informing them.

I can see/imagine how the primer thing happened. Someone in the PI should have called and asked, but apparently they didn't. The lead times and substantial cost of the QB kits put a lag into the system such that by the time Vans received the first defective QB kit, there was a ton of ruined inventory in the pipeline.

On the laser stuff, I can't believe they didn't have a QC process on the front end to pick up on it as soon as the poorly cut parts began to arrive. If they'd hit the brakes when they got the first shipment, it would have been a relatively minor issue. But they allowed it to rock on for months and months, which created problems for a ton of builders and in-process QB kits.

Have done lots of validations over the years for various processes. Also have heard the "vendor changed the process" many times. Sometimes they did, sometimes they didn't and the team had missed a nuance between the nominal 100% inspected parts used for process qualification vs. the ones coming off after the validation is complete.

Also, did they validate the process up to and through actually building structures out of the parts? Or were the valid in the sense that the dimensions or whatever their critical-to-quality specs were ok?

Another BT'er posted the bulletin of recommended replacement parts - these are real structural parts (spars and stringers, seemingly mostly in the tail, but did not peruse) where multiple instances of crack propagation could lead to loss of structural integrity.

Here is Van’s assessment of the risk from cracks. https://www.vansaircraft.com/wp-content ... nR11.5.pdf

If I understand it correct it says that for most of the affected parts even if the dimples crack, there no safety risk and the life of the airframe is not reduced. For some parts there is a tiny risk and those parts should be replaced or remediated. They use a combination of modeling and actual testing of structure with intentional defects. I’m not sure I would be happy to build and accept some cracks but it does seem that vans is heading toward a policy of only providing no cost replacement for the parts they classify as critical.

Here are Van's general build instructions see page 9 bottom left:

https://www.vansaircraft.com/wp-content ... ALL_05.pdf

Regarding dimpling and cracks:

"Occasionally, a hole will crack when dimpled. This does not necessarily mean that the part must be scrapped. The criteria below provide guidance
on how to evaluate cracks in dimple. Cracks exceeding the criteria stated below not only present a safety risk from a structural standpoint, but also
could crack further in the future:

• A crack in a dimple countersink may not extend more than 1/3 the height of the dimple measured from the bottom edge of the dimple."

Now look at the latest laser cut part crack from the above posted link where they now say all will be fine, seems to me that is WAY more than 1/3 the height:

The “selling too much airplane for the money” problem continues to repeat itself throughout the history of General Aviation. The Republic Seabee, the North American Navion and the Globe Swift are all classic examples.

With the Swift, Globe didn’t even discover the problem. TEMCO, who was building Swifts under contract for Globe to help Globe meet their demand, discovered that each Swift cost more to build than Globe was charging for it. TEMCO management “informed” Globe of the problem and eventually bought the Type Certificate at the Bankruptcy Sale.

Vans has this cost / pricing issue plus an extensive Quality Control issue to deal with as well. They have quite a challenge in front of them.