psm(at)att.net
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 Posted: Mon Apr 11, 2011 12:10 pm Post subject: Final Report on the Markermeer accident has been published |
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Hi Bill,
I agree with everything you said - I think. I admit I didn't really understand all the technical details of the Dutch report, but I think it points to flutter and weak wings as the cause of their particular accident.
They also added a lot of details to the whole story that I hadn't heard before. One interesting point was the French in-flight failure that didn't result in a fatality because of a ballistic 'chute. The pilot of that incident reported flutter before the wing failed. Another interesting point (to me) was the report that the solid rivets holding the wing spars together failed in the shear direction. I can't imagine how this could happen in a properly designed wing. That could be just my shortcoming.
I think they clearly said they "Think" flutter caused the start of the incident in the Netherlands. The FAA managers I have spoken to told me they had evidence of flutter in the accidents they investigated but they couldn't determine if the flutter caused the structure failure or the structure failure caused the flutter. They also told me in no uncertain terms that before the upgrade the aircraft did not meet the appropriate design standards and after the upgrade it does.
For me the bottom line is we should all install the upgrade package in our planes. This is what the FAA demands, the folks at ZAC tell us to do and now the Dutch seem to agree with. The Dutch report singles out aileron balance and reinforcing RR-7 as key elements, but I think they also said the spar structure needs help too.
Paul
Nearly finished installing upgrade.
On 4/11/2011 11:49 AM, japhillipsga(at)aol.com (japhillipsga(at)aol.com) wrote: [quote]I read the Dutch report and found it sufficiently informative. I may be the only builder and flyer that sees that the report says the ZAC host modifications and upgrades though painful to perform are the solution. Maybe not, maybe so??? Not knowing much about metallurgy, force torsion and compression issues I have to rely on folks educated differently than I. I suppose those dull Dutch experts may have really screwed up by publishing this report and failing to ask our expert, Mr. Paul R., to approve their investigation and findings. I know I'd feel more secure if they had got some more opinions from such experts as I fly my XL-B around the sky's of Georgia. Seems like about half of the 24 page report spoke to the issue of weak wing strength, weak rear spar attachment material, unbalanced ailerons and the propensity for loose control cables in flexible wings to get even more slack and nurture flutter conditions. I think the Dutch folks make it fairly clear that flutter took the wing off or did I miss something? I made the ZAC modifications and several others to my XL-B last year and fly her now. She flys well and stronge, but she always did. I also have a RV-8a I built and I think the XL-B wing spar I assembled is about as strong, maybe stronger. Course, I don't suppose the value of my plane will ever rise much above salvage value for possible sale and we all have our ZBAG Busy Body folks to thank for the many thousands of dollars of cost to each of us. Wonder if this whole business could have been handled a different way? Lots of plane crash. Why was the XL and ZAC singled out for this treatment? This is my last thought I'm going to waste on the subject, fly happy and often, Bill Phillips
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