Van's Air Force
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Failures in Tail Feathers????
- Thread starter PerfTech
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bobair43
Member
Tail Feathers and nose gear mod
I have just installed the nose gear mod on my 7A.Did a couple of take off landings before reinstalling fairings and wheel pants. Every thing looks good so far. How ever after inspecting my elevator and ruder I have found no cracks or any problems. I,ve had my plane at red line a few times. Been flying it since 2005. Just been to the Bahamas and back. I also have found some rod end nuts loose which I have now tightened. But no cracks at all everything looks good. Question why don't I have cracks think about it flying eight years. Also the balance on my elevator is forward I asked Vans they said ok if a little forward . Its been looped rolled flown at red line #no cracks no flutter. I think your nose mod takes care of a real problem not so sure about the tail failure thing being a vans weak design. Look on utube some sevens have been put through some extreme arobatics. But I will keep paying attention to any new info.
I have just installed the nose gear mod on my 7A.Did a couple of take off landings before reinstalling fairings and wheel pants. Every thing looks good so far. How ever after inspecting my elevator and ruder I have found no cracks or any problems. I,ve had my plane at red line a few times. Been flying it since 2005. Just been to the Bahamas and back. I also have found some rod end nuts loose which I have now tightened. But no cracks at all everything looks good. Question why don't I have cracks think about it flying eight years. Also the balance on my elevator is forward I asked Vans they said ok if a little forward . Its been looped rolled flown at red line #no cracks no flutter. I think your nose mod takes care of a real problem not so sure about the tail failure thing being a vans weak design. Look on utube some sevens have been put through some extreme arobatics. But I will keep paying attention to any new info.
If we are seeing crack growth in fastener holes in the tail attach doubler area mentioned, it can be caused by several things. First, there could have been small manufacturing (e.g. builder) defects in one or more of the fastener holes. Normal cyclic loading could then produce a crack that grows at a certain rate based on the cyclic loads spectrum. (refer to durability and damage analysis DATA methodologies) The crack growth rate can be fast if the doubler was designed for less loads than are actually being encountered. This happens a lot. Often the remedy is to re-design the doubler to accommodate the real loads. However, this often drives the problem to other adjacent areas, because the loads they are subjected to also exceeds their design loads. As a result, they start failing.
I would not recommend putting a beefed up doubler in this area without a more complete engineering analysis. You can make things a lot worse. In a former life I was chief of structural engineering on the A-10A, and A-7 fighter fleets and dealt with these kinds of problems routinely.
I would not recommend putting a beefed up doubler in this area without a more complete engineering analysis. You can make things a lot worse. In a former life I was chief of structural engineering on the A-10A, and A-7 fighter fleets and dealt with these kinds of problems routinely.
Dbro172
Well Known Member
This more simply put is a case of what I commonly refer to as "Sausage Management". You know; squeeze on one end and it just comes out the other
. Truthfully, this was my first though when installing the doubler plate at the vert stab. I certainly don't want to induce higher loading into an adjacent area not intended for those loads. The up side is there are no attachment holes adjacent that could start a crack.
The Vans-supplied part is not a doubler, but rather an attach plate connecting the vertical stabilizer spar to the horizontal stabilizer spar and fuselage. The Splat parts are stiff stainless steel doublers, by nature much stiffer than any aluminum doubler...but I digress.
I'll suggest it is possible to improve the fatigue performance of the aluminum attach plate without a significant change in stress distribution.
(1) add a 1/4" or so edge distance on each side
(2) straighten the outline to eliminate the large scale notch on each side
(3) ensure good edge finishing
(4) in a retrofit hole the locations are known, so eliminate the slots.
(Base photo credit to Bruce Hill, from an old thread)
I'll suggest it is possible to improve the fatigue performance of the aluminum attach plate without a significant change in stress distribution.
(1) add a 1/4" or so edge distance on each side
(2) straighten the outline to eliminate the large scale notch on each side
(3) ensure good edge finishing
(4) in a retrofit hole the locations are known, so eliminate the slots.
(Base photo credit to Bruce Hill, from an old thread)
This is the best advice to come out of this thread...thanks Doug!
grubbat
Well Known Member
Reviving this thread, wondering if any of the resident engineers have possibly done some analysis on the stainless doublers for the forward vertical attach point?
Thanks,
Thanks,
PerfTech
Well Known Member
Guarantees!
....We currently have about 650 of this mod installed, many with considerable hours of service. No reported ill effects, and best of all, no departed tail feathers. Regardless of ones ability to accept, or admit the fact that a known issue of cracking is taking place in this area. The fact remains, it is happening, and we have received many e-mails and calls from customers who found this crack when they went to install the mod. If you feel this is not for you, then don't take advantage of its availability. Someone made a statement to the effect that "you can make things worse". I don't agree. Very difficult to make things much worse than the tail leaving in flight. That event in not survivable, and this mod will definitely do what it was intended to do, and nothing else. I assure you, should they find myself, my aircraft, or any aircraft, with this mod properly installed in a smoking hole. The tail will be in there, and these brackets will be in tact, doing their job. Thanks, Allan...
....We currently have about 650 of this mod installed, many with considerable hours of service. No reported ill effects, and best of all, no departed tail feathers. Regardless of ones ability to accept, or admit the fact that a known issue of cracking is taking place in this area. The fact remains, it is happening, and we have received many e-mails and calls from customers who found this crack when they went to install the mod. If you feel this is not for you, then don't take advantage of its availability. Someone made a statement to the effect that "you can make things worse". I don't agree. Very difficult to make things much worse than the tail leaving in flight. That event in not survivable, and this mod will definitely do what it was intended to do, and nothing else. I assure you, should they find myself, my aircraft, or any aircraft, with this mod properly installed in a smoking hole. The tail will be in there, and these brackets will be in tact, doing their job. Thanks, Allan...
grubbat
Well Known Member
Tip toe
Allan,
My question was only seeking input from an engineer who may have looked at this particular mod or area and did said analysis as a previous poster recommended. I do not have any issues with your products and I understand what you are trying to accomplish. Please do not take my asking the question as being negative. I just wanted to hear feedback, if there was any, on analysis by an engineer. Sorry if I came across another way.
Allan,
My question was only seeking input from an engineer who may have looked at this particular mod or area and did said analysis as a previous poster recommended. I do not have any issues with your products and I understand what you are trying to accomplish. Please do not take my asking the question as being negative. I just wanted to hear feedback, if there was any, on analysis by an engineer. Sorry if I came across another way.
....We currently have about 650 of this mod installed, many with considerable hours of service. No reported ill effects, and best of all, no departed tail feathers. Regardless of ones ability to accept, or admit the fact that a known issue of cracking is taking place in this area. The fact remains, it is happening, and we have received many e-mails and calls from customers who found this crack when they went to install the mod. If you feel this is not for you, then don't take advantage of its availability. Someone made a statement to the effect that "you can make things worse". I don't agree. Very difficult to make things much worse than the tail leaving in flight. That event in not survivable, and this mod will definitely do what it was intended to do, and nothing else. I assure you, should they find myself, my aircraft, or any aircraft, with this mod properly installed in a smoking hole. The tail will be in there, and these brackets will be in tact, doing their job. Thanks, Allan...
....We currently have about 650 of this mod installed, many with considerable hours of service. No reported ill effects, and best of all, no departed tail feathers. Regardless of ones ability to accept, or admit the fact that a known issue of cracking is taking place in this area. The fact remains, it is happening, and we have received many e-mails and calls from customers who found this crack when they went to install the mod. If you feel this is not for you, then don't take advantage of its availability. Someone made a statement to the effect that "you can make things worse". I don't agree. Very difficult to make things much worse than the tail leaving in flight. That event in not survivable, and this mod will definitely do what it was intended to do, and nothing else. I assure you, should they find myself, my aircraft, or any aircraft, with this mod properly installed in a smoking hole. The tail will be in there, and these brackets will be in tact, doing their job. Thanks, Allan...
When just a bit of the info smells bad, it makes me inclined to assume that the entire thing is rotten.......
If as many people as you imply have actually found cracks, have, Van's would be hearing about it.
It is not something that has been reported.
This type of marketing is shameful.
You are implying that if the few RV's that have had accidents in which some type of failure of the emp. was involved, that the accident wouldn't have happened if your parts had been installed.
Anyone can read the accident reports. From them it is easy to see that a failure or lack of strength in the vertical stab. fwd spar attach area was not even remotely considered to be a cause.
Hopefully moderators wont delete this for vendor bashing because it is not.
It is calling attention to shameful marketing strategy being used here (and it is not the first time).
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JonJay
Well Known Member
If Alan did all of the engineering and testing (on most of his products), you couldn't afford them.
You either "have faith", or you don't.
The reasons tails left the only two known failures are well documented in the NSTB reports and theorized the cause as exceeding the design limits of the airframe, by more than a little. If you fly that way, something is going to give. If it isn't the tail, what next? Don't exceed VNE and find out.
The cracks that have occurred have been theorized by Vans as build error.
To state that "no tails have departed since the mod" gives credibility to the 8000 plus airframes that are flying and have been flying as designed with tens of thousands more hours than those with mods.
Personally, I don't get it, but as Alan states "it might not be for everybody", like me.
If I have misstated any of the facts surrounding tail departures, please let us know. This thread is quite old and I didn't pour back through it or the NTSB reports.
I think your question was, and still is, a good one. I would want to know before I bolted anything on my airframe.
You either "have faith", or you don't.
The reasons tails left the only two known failures are well documented in the NSTB reports and theorized the cause as exceeding the design limits of the airframe, by more than a little. If you fly that way, something is going to give. If it isn't the tail, what next? Don't exceed VNE and find out.
The cracks that have occurred have been theorized by Vans as build error.
To state that "no tails have departed since the mod" gives credibility to the 8000 plus airframes that are flying and have been flying as designed with tens of thousands more hours than those with mods.
Personally, I don't get it, but as Alan states "it might not be for everybody", like me.
If I have misstated any of the facts surrounding tail departures, please let us know. This thread is quite old and I didn't pour back through it or the NTSB reports.
I think your question was, and still is, a good one. I would want to know before I bolted anything on my airframe.
PerfTech
Well Known Member
...Sorry Craig! I didn't take your post wrong, and you were only seeking information and that is good. I just saw what was about to take place and had some things to say, no problem. Thanks, Allan..
PerfTech
Well Known Member
...I didn't specify a number of cracks found, intentionally. In our opinion one is too many! I have photos of the attach brackets from these accidents you refer to. Every one has separated into two pieces at exactly the same location. This was why we decided to manufacture and market this product in the first place. I can't say if the outcome would have been different or not, just the dynamic. I feel better with a stronger attachment on my V/S and I have every right to voice that opinion. You say "This type of marketing is shameful" I am not trying to market this very inexpensive little part for any reason other than to possibly help someone else feel more confident as well. I have many places on my airplanes that I elected to improve aerodynamics, structural integrity etc. This particular bracket has always made me nervous, as it is different than most other aircraft. A better option is the more conventional way the RV-10 attach is done. Thanks, Allan...
JonJay
Well Known Member
Let's stick with facts, and please correct me. No RV, any model, has ever lost a tail that led to an accident, ever. If we start second guessing the factory design, where does that stop?
If you truly want to help, do the engineering and testing and prove the factory design is not correct or adequate, or is. That would lay this to rest. Don't second guess based on assumption or your "gut" and then sell something to the general public to fix problems that may not, and likely don't, exist. That isn't helpful.
I know your heart is in the right place Alan, but this is a small community and many folks are subject to persuasion. There isn't a problem with the tail attach until someone "thinks" there is. This is where many of us feel your not being helpful marketing this particular product, especially the nature and environment in which you started this thread - to sell a product, albeit in your mind to "help". Telling folks "it isn't for everybody" just leaves me wondering and questioning even more. Why wouldn't it be? Perhaps We just don't get the belt and suspenders approach when the belt has never broken.
I state this respectfully:
"A feature not needed or required is a liability.
If you truly want to help, do the engineering and testing and prove the factory design is not correct or adequate, or is. That would lay this to rest. Don't second guess based on assumption or your "gut" and then sell something to the general public to fix problems that may not, and likely don't, exist. That isn't helpful.
I know your heart is in the right place Alan, but this is a small community and many folks are subject to persuasion. There isn't a problem with the tail attach until someone "thinks" there is. This is where many of us feel your not being helpful marketing this particular product, especially the nature and environment in which you started this thread - to sell a product, albeit in your mind to "help". Telling folks "it isn't for everybody" just leaves me wondering and questioning even more. Why wouldn't it be? Perhaps We just don't get the belt and suspenders approach when the belt has never broken.
I state this respectfully:
"A feature not needed or required is a liability.
Haters gonna hate!
One crack in a thousand is not bad odds, unless it's your plane (mine was cracked!!!). I made a new bracket and purchased the mod. I was unable to use it on my six as the holes did not line up on my non-prepunched vertical stab. Allen took it back no questions asked and I just fabricated a doubler. The doubler is likely not necessary, but it makes me feel better and my plane is a little nose heavy anyway so ... a little piece of mind! I have several of Allens products and they all seem very well designed / built and priced affordably. Additionally, I have called him a couple times with questions about his products and he has always taken as much time as needed to answer all of my questions. Remembering several of the past posts about his products it strikes me as interesting how much drama they have generated. Why is it so inconceivable to imagine that the design of our planes could be slightly improved in a couple of places here and there particular by someone with access to some very modern and high tech equipment? If they were perfect there would be no SB issued for them, and we know that is not the case. Allen has access to this type of machining equipment and I for one, appreciated the time he has spent on his products and would be willing to bet the money he has actually made on them does not even come close to paying for any if the equipment. Belt and suspenders... Maybe, but "shameful marketing",really??? Haters gonna hate.
One crack in a thousand is not bad odds, unless it's your plane (mine was cracked!!!). I made a new bracket and purchased the mod. I was unable to use it on my six as the holes did not line up on my non-prepunched vertical stab. Allen took it back no questions asked and I just fabricated a doubler. The doubler is likely not necessary, but it makes me feel better and my plane is a little nose heavy anyway so ... a little piece of mind! I have several of Allens products and they all seem very well designed / built and priced affordably. Additionally, I have called him a couple times with questions about his products and he has always taken as much time as needed to answer all of my questions. Remembering several of the past posts about his products it strikes me as interesting how much drama they have generated. Why is it so inconceivable to imagine that the design of our planes could be slightly improved in a couple of places here and there particular by someone with access to some very modern and high tech equipment? If they were perfect there would be no SB issued for them, and we know that is not the case. Allen has access to this type of machining equipment and I for one, appreciated the time he has spent on his products and would be willing to bet the money he has actually made on them does not even come close to paying for any if the equipment. Belt and suspenders... Maybe, but "shameful marketing",really??? Haters gonna hate.
Since you quoted me specifically.....
First off, it is not fair to refer to me as a hater. I am not.
If someone is able to develop something innovative for RV's that 650 people want to buy (I am as skeptical of that # as I am of some of his previously posted sales figures) at $55 each (that adds up to a gross sales of $35,000+), I am all for it. Free enterprise is good.
When the sales are primarily the result of the tactics used to sell it and not factual info that strongly supports it as a good idea, I am not for it at all (but that doesn't make me a hater).
I think most of the drama you speak of is the result of the marketing scheme that Allan uses.
You mentioned "a little piece of mind".....
That is the entire theme of the marketing of this item.
Placebo pills fall into the same category.
Have you ever ever looked up the definition of fear mongering?
the deliberate use of fear based tactics including exaggeration and usually repetition to influence the public in order to achieve a desired outcome.
Marketing an improvement (I don't disagree... there are always things that can be improved) is one thing.
Marketing it in a manner that takes advantage of an opportunity of fear and doubt, when there is no real facts or data to support the basis of it, is another all together.
Experimental Aircraft
From a Exp. stand point I think its a great thing that we can make changes to our airplanes that's the reason I built a Vans Rv6 along with the fact its a good airplane design but there is no debating it can be improved.From what I understand there has never be a inflight structural failure of a Cessna 172,and from what I understand that's not the case for Vans aircraft.That point proves that there can be improvement!After the loss of one of our brothers from Ny in his RV I decided to make a home made improvement (in my on mind) by doubling the thickness of the front vertical attach bracket and I would have put a doubler on the vertical front spar if my fin was not already closed up.Having said all that I'm glad Allen stepped up to the plate I don't have any of his products but I like that he tries to make things better when he knows there is a need.As an example who besides him has tried to make the nose wheel problem any better? So the point is less all keep experimenting to try to make our planes better.
Bob
From a Exp. stand point I think its a great thing that we can make changes to our airplanes that's the reason I built a Vans Rv6 along with the fact its a good airplane design but there is no debating it can be improved.From what I understand there has never be a inflight structural failure of a Cessna 172,and from what I understand that's not the case for Vans aircraft.That point proves that there can be improvement!After the loss of one of our brothers from Ny in his RV I decided to make a home made improvement (in my on mind) by doubling the thickness of the front vertical attach bracket and I would have put a doubler on the vertical front spar if my fin was not already closed up.Having said all that I'm glad Allen stepped up to the plate I don't have any of his products but I like that he tries to make things better when he knows there is a need.As an example who besides him has tried to make the nose wheel problem any better? So the point is less all keep experimenting to try to make our planes better.
Bob
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