Graham,
If you don't mind me asking, exactly what experience do you have in this matter? I am not trying to be snarky when I ask, but rendering such an opinion, when Vans is currently unable to say what is good and what is bad, appears uninformed.
It is clear from what Vans has stated, that visual inspection of a laser cut hole is currently insufficient to establish a determination of its airworthiness.
Sorry if I sound a bit short. I just think such statements as yours diminishes the seriousness of this.
Mike
Mike,
I referred to my experience to date working with Van's parts, and what they have told us now and previously about laser cutting. I was not aware that posting an opinion required one to state one's credentials, e.g. lead design engineer on the F-35, ATPL with 25,000 hrs and 20 space shuttle landings, but am aware aviation can be a bit like that. It has generally been my experience that those who wish to preface their opinion with a brag about their experience are usually the least worth listening to, and the most valuable contributors to intelligent debate are those who simply make their point logically and let it stand on its own merits.
It seems Van's conducted extensive fatigue testing of laser cut parts prior to going into production. They were satisfied with the results of these tests and I trust them on that. It is reasonable to assume a fair amount of visual inspection happened before the fatigue testing, and that Van's were happy with the state of the holes - i.e. after normal final reaming and deburring processes the holes did not crack when dimpled or riveted. The parts subsequently passed the fatigue tests - let's call these 'good' laser-cut parts. As Greg has told us, not all laser-cut parts are bad - the problem is parts from one particular contractor between certain specific dates - an issue with one or more batches.
If you have been lucky / unlucky enough to receive both, the 'bad' laser-cut parts are very apparent, with holes significantly out-of-round and with significant notches that cannot be cleaned up within the maximum allowed hole diameter. The problem is evidently worse with final-size kits where the builder is very limited in the amount of material they can remove before reaching maximum allowed hole diameter.
For those of us who have held both in our hands, the difference between good and bad parts is like night and day. You cannot fail to notice it. My emp kit contained good laser-cut parts and I experienced no cracking on dimpling or riveting. I think it's reasonable to assume therefore that these parts are akin to those originally tested by Van's and thus I have confidence in them. There is the heat-affected zone issue of course, but I think it is reasonable to presume this issue passed the original fatigue testing. My wing kit contains bad parts, therefore it remains on the shelf pending resolution / replacement.
Van's is now testing
bad laser-cut parts (stuff with cracks, oversize and out-of-round holes) and will report back to us. The results of these tests would seem principally of interest to those who did not notice the bad parts (that cannot be many builders), those who built on as instructed by support and painted themselves into a corner, and those with QB assemblies who have no idea what's in there.
That's the basis of my position. I simply observed that the fellow who posted a picture had something which looked like a good laser-cut part, based on the comparisons I've done between good and bad. I am not aware of Van's having stated that visual inspection of a part prior to assembly is insufficient to establish airworthiness, but I am aware of them having stated that not all laser-cut parts are bad. After all, we all (as builders) establish airworthiness or not based on visual inspection alone all the time, outside of this particular issue.
If you read my prior posts, it will be apparent that I am in no way diminishing the seriousness of the issue. Because there does not appear to be traceability down the level of who exactly received what, it may be that Van's needs to instruct replacement of all laser-cut parts in certain locations in the structure, even though some of these parts (the good ones) will be fine.