KITPLANES is reporting that Van’s Aircraft has released the technical reports on the use of parts with laser cut holes and it has determined there are no safety or durability issues with them. But it has also pledged to replace dozens of parts it has identified as being structurally critical in each of the plane kits it manufactures. In video postings on its website, Van’s says it had third-party engineers thoroughly assess the metal fatigue vulnerability of the parts and the conclusion is that they will stand up to heavier use than is actually possible and last far longer than the expected life of an RV aircraft. “Aircraft usage calculations assume that the airplane is flown 30 minutes of each hour at full aerobatic air show loads, and the remaining 30 minutes of each hour at flight-school loads,” Van’s said in a statement.
The issue arose after Van’s contracted the creation of rivet holes in metal parts to a third party that used a laser machine to make the holes to help fill a backlog for parts. Van’s normally uses a mechanical punch to make the holes. When builders applied rivets to the lasered holes, they sometimes created small cracks around the holes. The tests showed the parts are safe to use, according to Van’s. “Given these extreme calculations, the aircraft’s lifespan is considerably higher than would be expected for an RV aircraft and is considerably longer than any flying RV,” the company said. “In short, the results of extensive testing of laser-cut parts manufactured for Van’s Aircraft shows that the parts are safe for use in aircraft construction.”
This seems to go counter to everything we’ve been told about deburring aluminum.
Pay no attention to the cracks around the rivets!
Hmmmm… Ok. No problem. I believe everything everybody says. Even if they change their conclusions on a regular basis. It’s the new normal.
Does this mean a newly-built airplane with cracks around rivet holes exhibits the product life characteristics of an airplane which has accumulated enough hours in service to have developed cracks around rivet holes? I guess this explanation will sit well with people who pay extra for “distressed” clothing or “road-worn” guitars.
While this is good news, it has nothing to do with the successful, widespread use of laser cutting in the aerospace industry for many, many years. A punch press can also create bad holes when tooling is worn or other setup procedures are not followed. Laser cutting is rapidly replacing sheers, punches and routers for sheet metal fabrication due to the lack of tooling costs and high flexibility. Not to say that punching is bad. All CNC equipment has its pros and cons, but all must be set up and operated correctly for each material and application. Criticism of modern laser cutting equipment for cutting thin aircraft aluminum is akin to “throwing the baby out with the bathwater”.
Heat-related embrittlement of the hole surface, maybe exacerbated by the sharp corners? Question would be do the cracks tend to propagate beyond that surface layer.
My understanding is that the flaws in the holes led to cracking when dimpled. This would probably be the same when dimpling flawed punched holes. Stress concentration in notches leading to crack propagation during dimpling, which stretches the material. Why we always debur any part before dimpling and riveting, whether laser cut, routed, or punched, to remove the larger flaws. Many holes in aluminum aircraft however are not dimpled, so less of a cause for concern. Mine is however just speculation from someone with experience in sheet metal fabrication from equipment manufacturing. I am definitely not an expert on aircraft aluminum. Lasers though, in my opinion, are not the source of the problem when used correctly.
If I were constructing a kit plane, there is no way I’d be accepting cracks no matter how safe they are supposed to be. I don’t think building a plane is just about getting a plane in the end.
I doubt I’m alone in this.
This is nuts and counter factual on everything that Vans has said over decades. Now we’re supposed to accept cracks, from a kit manufacturer that is in dire financial straights, because suddenly, their paid “experts” say so? Then they enlist four RV fan boys who depend on Vans in some way or have had a long, inside relationship with the people in the company?
In the certificated world, the FAA would have independent engineers looking at this matter befor approval. In this case, we’re on our own, and the “evidence” is coming from inside the house.
You stay alive in aviation by being objective. The same people would excoriate Boeing or Airbus or Cessna for proposing the same thing.
Yes. Laser cut holes are successfully used on Aluminum skins and substructure in the aerospace industry. From what I understand in the Van’s case the issue wasn’t the fact the holes were laser cut it was how they were cut. I was led to believe that when Vans farmed out the lasering the CAD design dataset provided to the contractor by Vans had the NC programming pierce the holes in the center and then cut out to the hole edge and then cut the hole periphery. Somewhere along the line the contractor figured it could save time by eliminating piercing the center of the hole and instead start the hole by piercing at the finished edge of the hole and then completing the hole. Having the pierce point a permanent part of the hole edge caused two problems:
1.) The piercing is done with the laser stationary, prior to the laser moving quickly around the diameter. This extra time heats the pierce point more than the rest of the cut which could thermally damage the material right at the hole’s edge at the pierce point. Hence Van’s engineering design calling for the centered pierce point to be completely contained within the discarded hole material.
2.) During the piercing operation as the pierce hole is burnt through the part molten aluminum is pushed through the thickness of the hole. This combined with the required time to create the pierce point causes the pierce to have a larger diameter hole than the moving cut action of the fine point laser. This results in the pierce point leaving a small nick on the finished hole edge along the diameter.
There is no question Vans should have caught this in receiving with it’s internal quality assurance procedures. Perhaps when the first batch of parts passed with flying colors Vans let it’s guard down and didn’t catch the later change made by the contractor by fiddling with the pierce point location to save a few milliseconds per hole.
Thanks for the deets!
It seems non engineering managers seem to think quality inspections are not value added. I think quality inspections are rather like insurance, it may cost some, but when things go south, it was well worth it.
Q: Is it a common practice in the aircraft industry to employ laser cutting?
Historically, it has not been standard practice to laser cut aircraft components, but this was based on the technology commonly used 20 years ago when only CO2 lasers were available. Aircraft manufacturers, especially at the large commercial level, now use laser cutting as an approved manufacturing process. Modern high-wattage fiber lasers cut much faster and have a narrow-focused beam. A modern, high-quality fiber laser using the proper operating parameters leaves a very small heat-affected zone that has little if any effect on the fatigue life of a component.
Q: Has Van’s performed testing to ensure the metal does not anneal or suffer any other negative effects (strength, corrosion, etc.) in the area of the cut?
The amount of testing we performed has been a significant contributor to the time it has taken to increase our production rates. We knew we needed to increase part production, but we did not allow this pressure to rush us through the testing process. At Van’s, we have a commitment to testing, a principle that has resulted in the trust in our kit designs over the past 50 years. Our testing results showed little or no change in the fatigue life of the parts – between laser cut parts, punched parts, deburred parts, or parts with a machined edge – for the parts we’ve approved for laser cutting.
Update: January 8, 2024
Laser Cut Parts List updated to R7.2
Clarifications of the parts classification Status Key (R7)
RV-12iS Empennage Part Classification Revisions (R7)
Corrected missing Flap and Aileron components in the RV-14 Wing Section (R7.1)
Corrected missing components in the RV-8 Fuselage Section (R7.2)
Added revision level and date to each section (R7.2)