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Service Bulletins 19-08-26 and 16-05-23 Published - Nose gear leg and fork

Always thought ?certificated? referred to having a type certificate not airworthiness certificate, so I don?t see how EAB, ELSA or SLSA could be considered ?certificated?.
 
That would be a neat trick since the FAA would be basically arguing with the FAA.

https://www.faa.gov/aircraft/gen_av/light_sport/media/lsa_cert_8july2013.pdf

Easy enough: check out the bold words in the header of the linked file, “Light-Sport Aircraft Airworthiness Certification”. Note the last word.

Always thought “certificated” referred to having a type certificate not airworthiness certificate, so I don’t see how EAB, ELSA or SLSA could be considered “certificated”.

All aircraft issued an airworthiness certificate are certificated, whether special or standard. “Certified” is colloquially used to mean standard certification.
 
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All aircraft issued an airworthiness certificate are certificated, whether special or standard. ?Certified? is colloquially used to mean standard certification.

All of the people in the FAA, DAR's, etc., that I work with indicate that it is the exact opposite.
 
All of the people in the FAA, DAR's, etc., that I work with indicate that it is the exact opposite.

It’s just English. Certificated simply means issued a certificate. And if you are flying an aircraft without an airworthiness certificate, go ahead and mention that to the FAA...let me know how that goes. ;)
 
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If you are simply debating proper use of the English language, then I agree with you.... certificate is the root word of certificated.

But this is an aviation forum. We deal in the specifics of definition for clarity on a lot of subjects.

The FAA has been very clear that they have a specific definition of Certified and Certificated. When having discussions about the CFR's and other FAA documents, it makes sense to have a proper understanding of what those definitions are.
 
My simple understanding is that a plane that has been "certified" has been built professionally, by a business, and maintained to an airworthiness standard, such that it can be flown for business purposes, flight training schools, and in general, in a manner that can make the owner a PROFIT. It can be rented out, wet, by the hour. It can be used by flight schools.

It is also maintained to a standard such that 100 hour mandatory inspections are required, instead of only Annual inspections, as required in the Experimental LSA aircraft.

If anyone can enlighten me on this, in the LSA aircraft world of the FAA, please do so. Because I am not aware of anyone that instructs, or is a CFI, that uses their own Experimental RV-12 to teach flight in. One can buy their own Experimental RV-12, and then hire a CFI to instruct them in their own plane, if desired, but insurance to do so for the owner and instructor is probably going to be expensive until you build up some hours.
 
It is also maintained to a standard such that 100 hour mandatory inspections are required, instead of only Annual inspections, as required in the Experimental LSA aircraft.

One minor correction. The "100 hr. inspection" is only required if the aircraft is used commercially.
 
An aircraft with a STANDARD category Certificate of Airworthiness (FAA 8100-2 Form) like the typical Cessna, Piper, etc. that people are accustomed to are referred to as Certificated. It meets the definition of a Type Certificate. They are often also referred to as Type Certificated

An aircraft with a SPECIAL category Certificate of Airworthiness (FAA 8130-7 Form) like an SLSA RV-12 is certified to an ASTM standard. Because of this they are referred to as a Certified aircraft, but not Certificated.

Even an ELSA RV-12 can be referred to as Certified once it has been issued Certificate of Airworthiness, but it can't be referred to as Certificated.
 
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We now return you back to front legs, forks, ordering your parts to make your RV-12 current, and newly air worthy certified to best engineering practices, once you get them installed, after your parts get off of back order status.

Must be Friday, middle of winter, and the shack nastys are on strike, along with Oregon Truckers that haul wooden tree logs for a living.
 
Required or Optional

I'm told this retrofit is required for my factory built Van's, just wonder if the homebuilt RV 12 owners are also forced to do this or have the option to assume they won't be putting the same stress on the part as a 1700 hour trainer.
 
I'm told this retrofit is required for my factory built Van's, just wonder if the homebuilt RV 12 owners are also forced to do this or have the option to assume they won't be putting the same stress on the part as a 1700 hour trainer.

Do you use the S-LSA RV-12 commercially? It is recommended but optional for the home built E-LSA RV-12s too, not, per say, mandatory.
 
18" drill bits?

Is having 18" long bits a must? I have a 16" long 1/8" and 12" long 1/4 and 3/8" bits and with a chucked extension can get me to 18". Or is it a skinny pathway to the hole?
 
if you already have a gear mounted i don't understand why you need the long drills at all. why can't you use the old gear as a mirror image against the new gear and match drill or use the old gear and match drill a template to put against the new gear?
 
Back to Back

Back to Back The left and right holes are reversed and the distance from the bottom flange would be hard to match precisely.

And if the holes are oversized the bolts don’t go into shear at the same time



if you already have a gear mounted i don't understand why you need the long drills at all. why can't you use the old gear as a mirror image against the new gear and match drill or use the old gear and match drill a template to put against the new gear?
 
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I suspect that a number of early installers of this SB may offer their three-drill kits for sale on this forum.
 
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We just did this replacement. It's definitely a two person job.
The drill bits work pretty well, but it's not easy for the person in the cockpit to keep the bushings pushed into the hole. Definitely need to drill the holes from the inside, at least until the last bit, to clean it up.
I wrapped the strut fairing with carbon fiber vinyl, and then added a clear layer of protective film on top of that to keep the cowling from scuffing it up when installing or removing.

SBs are mandatory on SLSA aircraft, no matter what they are used for.
 
Completed my SB today - short 1 min clip

img_0143.jpg


https://youtu.be/3PCZEQr1_xU
 
Thanks David for the preview. I received my SB gear leg yesterday and will get started tomorrow.

One question, looks like you notched the tunnel flanges? Was this to get a straight shot to drill the gear leg or had this been done in the past?

Thanks, Pat
 
Straight shot to drill use plenty of boelube. My RV is an EAB, but I don’t remember notching anything.
 
Questions and Conclusions

A little reverse engineering gives me some questions and conclusions.

How much stiffer is the new front landing gear.

The larger footprint on the firewall.

Higher loads on the firewall, tunnel walls and nose gear.

The point that the inside tube ends.

If it is only welded to the outer tube at one end, is there friction between the tubes at the un-welded end.

Does the point of the stress riser move when the tubes flex at a different rate.

My deliberations
 
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Since Joe opened this door, I?ll add a question: Did the revised FEA predict an interior wall circumferential crack like the one that was found in the failed gear leg without a preexisting flaw? We engineers are curious about everything,🤓
 
Helpful hint

I always dread putting the safety wire back on the Gascolator. Such a tight space.
Service the Gascolator during your Condition inspection when you have removed the old gear leg. Easy peasy
 
Bob,
After your question on my post I went back and reread a lot of the thread to see if I had missed something. What I?m not clear on is did the failed gear leg failure initiate at the predicted point from the FEA? A slightly different location might mean there was some preexisting flaw.
 
Bob,
After your question on my post I went back and reread a lot of the thread to see if I had missed something. What I?m not clear on is did the failed gear leg failure initiate at the predicted point from the FEA? A slightly different location might mean there was some preexisting flaw.

The original leg design has an inherent focused area of high stress concentration, which under significantly high (but possible) loads on the leg can cause the material at the point of focused stress concentration to yield. The result is an affected/yielded area in the tube, from which a progressive fatigue process will start at that same point, once the material has yielded. The progressive fatigue path propagates circumferentially around the tube, starting at the initial tube material yield point and in a non-visible/non-inspectable location (obstructed from view by the metal plate that is welded around the outside of the tube).

Both the FEA and the actual leg failure agree and indicate no other underlying flaw present that creates a risk of initial material yield; there is no other point from which the fatigue crack occurs. The failed gear leg failed exactly how and where the FEA analysis predicted it would after being subjected to the initial event: an operational load sufficient to cause the material to yield, followed by a progressive fatigue crack initiating at that focused yield point.

We fully verified this with our FEA review of the original design. The issue was, of course, verified as no longer present in the FEA of the new leg design. We also validated that no additional or newly-introduced issues were detectable.
 
...which under significantly high (but possible) loads on the leg can cause the material at the point of focused stress concentration to yield.

Greg, sorry to keep this going when you've already given such detailed answers, but knowing that the original gear leg was load tested, how much load or rather overload under impact is needed to cause the initial yielding? Given that there is a long wait now for delivery of upgraded legs, it would be useful to have some idea of what kind of impact is required to trigger the fatigue sequence.

I know the history of my plane and have at least an anecdotal idea of what sort of forces the gear may have been subjected to, but would like to get a better sense of how much risk I may be running by continuing to fly it. I suspect there are others who are probably wondering the same thing.
 
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Thanks, Greg, for a complete and definitive answer. Van?s is a class act, and I?m glad I picked them for my build choice.
 
Greg, sorry to keep this going when you've already given such detailed answers, but knowing that the original gear leg was load tested, how much load or rather overload under impact is needed to cause the initial yielding? Given that there is a long wait now for delivery of upgraded legs, it would be useful to have some idea of what kind of impact is required to trigger the fatigue sequence.

I know the history of my plane and have at least an anecdotal idea of what sort of forces the gear may have been subjected to, but would like to get a better sense of how much risk I may be running by continuing to fly it. I suspect there are others who are probably wondering the same thing.

I'm not Greg but I think I can cover this one...... ;)

With the time of compliance given as "At or before the next annual condition inspection", the risk judgment has already been made for you based on what is known regarding how many hrs an RV-12 generally fly's per year, etc.

If there was any concern that there could be a bunch of RV-12's that have nose gear legs with a potentially imminent failure, the time of compliance would have been adjusted accordingly.

Additionally, if the exact load that would begin the fatigue process that has been described, was published, there would still be no way for any RV-12 owner to know whether their nose gear had ever been subjected to that load.

This would be adding a judgement based on unknowns into the compliance process and could have a reverse effect by causing people to not comply with the S.B. when they should be.

I hope that helps.
 
Can you please clarify time of compliance?

Scott
Can you please clarify time of compliance?

A RV 12 with 30 hours has his annual inspection due today and he cannot fly until the new landing is available and installed.

A RV 12 with 1400 hours has his annual inspection due January 2021, he can fly on his old gear until then.

I am waiting for a DAR inspection and I have no time on my old gear, can I fly for one year after my DAR inspection?

Thanks

Joe Rhodes
 
Scott
Can you please clarify time of compliance?

A RV 12 with 30 hours has his annual inspection due today and he cannot fly until the new landing is available and installed.

A RV 12 with 1400 hours has his annual inspection due January 2021, he can fly on his old gear until then.

I am waiting for a DAR inspection and I have no time on my old gear, can I fly for one year after my DAR inspection?

Thanks

Joe Rhodes


I assume your airplane will be certified as an E-AB so you are not by any regulation required to comply with the SB.
But even if someone disagreed with that, what you built is not an aircraft until after certification, and the "next condition inspection" will be due 12 months after your certification date (I.E., one year later, at the end of the month which your certification took place).
 
Thanks Scott

Yes, I am EAB however I will comply with all safety bulletins for the safety of my passengers and myself.

It would be foolish to ignore service bulletins by some sort of loophole.

My View

Joe Dallas




QUOTE=rvbuilder2002;1407686]I assume your airplane will be certified as an E-AB so you are not by any regulation required to comply with the SB.
But even if someone disagreed with that, what you built is not an aircraft until after certification, and the "next condition inspection" will be due 12 months after your certification date (I.E., one year later, at the end of the month which your certification took place).[/QUOTE]
 
I can't help but feel like a shot messenger.....;)

I don't see that I implied that you could use a loop hole. S.B.'s are purposely issued applying to all aircraft certification levels and the hope is that all owners will follow them.
But as a company, Van's also assumes that customers are able to use logical reasoning in how a particular SB or revision might apply to them.

In a case such as yours, I think most people would assume that if an 800 Hr airplane were safe to fly for a year until the next condition inspection, that a brand new one with zero flight hours would be as well.

Having made that decision, a person would then be allowed the freedom to defer it for a year since the S.B. is not regulatory.

The original comment was based on the fact that if your airplane were an S-LSA, compliance is regulatory.



Thanks Scott

Yes, I am EAB however I will comply with all safety bulletins for the safety of my passengers and myself.

It would be foolish to ignore service bulletins by some sort of loophole.

My View

Joe Dallas
 
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Thanks Scott. I understand that attempting to define, in an SB, when certain load events might become critical would simply confuse the issue and make compliance problematic. Vans really has no choice other than to require replacement, since a problem that most of the fleet will probably never experience has been traced to an area that can't be inspected. Clearly the risk to the fleet has also been thought about and is reflected in the time for compliance. It would still be nice to know a bit more about what it takes in terms of impact and fatigue loads to fail a gear leg in this way, which is why I asked the question, but you've answered as well as could be expected. Thanks again to you and Greg for taking the trouble to respond in so much detail in these posts.
 
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Sorry Scott

Sorry Scott

I did not take it that way.

The fact that you said I could wait to do the SB until I have some time in the aircraft and would not have to wait until the gear was available helped me a lot.

I know that you weren’t suggesting that I should not do the SB, I am sorry that you took it like that.

I know that it is important to do all Service Bulletins.

I want to know that I complied with the SB within the requirements of Vans Aircraft.

Thanks Again Scott

Joe Dallas




I can't help but feel like a shot messenger.....;)

I don't see that I implied that you could use a loop hole. S.B.'s are purposely issued applying to all aircraft certification levels and the hope is that all owners will follow them.
But as a company, Van's also assumes that customers are able to use logical reasoning in how a particular SB or revision might apply to them.

In a case such as yours, I think most people would assume that if an 800 Hr airplane were safe to fly for a year until the next condition inspection, that a brand new one with zero flight hours would be as well.

Having made that decision, a person would then be allowed the freedom to defer it for a year since the S.B. is not regulatory.

The original comment was based on the fact that if your airplane were an S-LSA, compliance is regulatory.
 
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Engine hoist

When parts arrive will need engine hoist...none available locally...shipping costs run $100 or more...anyone know of a web site that has a cheap hoist and/or free shipping?

Saturday 2/22 update The best deal I could find on an engine hoist was $205 including shipping from Simmit Racing....after I am done with it you can have it fo a "song"
 
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How about a scissor Jack? Harbor Freight SKU: 96406
It can also be used to lift the tail when setting the RV-12 on saw horses by yourself.
Another option is to lift the engine using a fulcrum and lever made from 2x4 wood.
I have not received the new gear yet, so have not tried either of the above.
 
a few years ago i picked up a used 1/2 ton chain hoist. handiest thing there is for hoisting. a comealong is a major pain. i think i paid $40. you will find other uses for it.
 
I have two questions…

The fairing on the nose gear strut is fastened with two #10 screws – could this also be source of stress concentration. I would imagine the long straight section of the nose strut flexes considerably with poor landing technique.

The broken nose gear that set this SB in motion – was the tube completely severed or did it just develop a crack and bend?
 
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I have two questions…

The fairing on the nose gear strut is fastened with two #10 screws – could this also be source of stress concentration. I would imagine the long straight section of the nose strut flexes considerably with poor landing technique.

I was also concerned about drilling a hole for those screws. I think I'm going to use some double sided tape to capture the nose strut fairing in place.

Planning to install the new gear this weekend. Had to rent an engine hoist and pickup truck to carry the lift. As recommended by another poster plan to use ½" PEX counter bored to 31/64" to capture drill guide bit and cut to length to provide an extension arm to hold drill guide in place against the new gear flange.

Edit: It turned out I had to use a ½" drill to counter bore a hole in the PEX to capture the drill bushing. Kudos to the OP in a different thread that came up with this idea!
 
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I was also concerned about drilling a hole for those screws. I think I'm going to use some double sided tape to capture the nose strut fairing in place.

I too had second thoughts about drilling holes into the nose gear tubing ... so I decided to not install the nose gear leg fairing at all. Any potential speed gains I may lose by not installing the nose gear fairing have probably been negated by the main gear leg fairings I installed.

Happy flying,
 
Maybe Van's can run a quick Finite Element Analysis and tell us if the two screw holes are stress riser in the the gear leg...
 
If there was a concern about drilling holes in the gear leg for the leg fairing attach screws, they would have never been specified there originally, and/or they would have been deleted when the new nose gear leg was designed, so no FEA on the screw holes is like to happen (see below for reason).

Sorry if that sounds a bit sarcastic.... I don't mean it to be, but it is the reality.

A bit of engineering and physics needs to be applied to understand why these holes are not an issue.

One, would be to understand what the bending loads are along a beam or arm such as the nose gear leg. The bending loads are the highest at each end where the arm attaches to other members (think of the effect that a long lever arm can have to amplify force). The bending loads are the lowest at the very mid point of the arm (that is where the lever arm is the shortest distance to other members where the loads are being applied).

That is why the screw holes are at the very mid point of the leg, vs a pair of holes at the upper end, and a pair at the lower end.

Another factor is the way the loads are distributed through the arm.

In the case of the nose gear leg, when a high upward load (hard landing for example) is applied, and the leg tries to bend, the material along the very top of the tube is being compressed along the length of the leg, and the material along the bottom edge of the tube is being stretched as the tube tries to bend into a curved shape.

The screw holes are purposely located on the sides of the leg, which puts them in the neutral axis of the tube..... the portion of the tube where there is no compression or tension load when the leg is being loaded vertically.

This is an overly simplified explanation.

Go to this reference (or just google "neutral axis") for more details.
https://www.quora.com/What-is-the-neutral-axis-of-a-beam
 
Anyone else here that has to perform their annual and complete it by March 31st, or Feb 29th, 2020?

I don't think ours is going to arrive in time by 3-31, and we'll be grounded until it arrives and we get it installed. E-LSA
 
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My annual is due 3/31. I haven?t decided yet what I am going to do. I want to put an endoscope down the gear leg and see if it?s possible to get a good look at the area where the crack initiates. Since mine is an ELSA I have some latitude that SLSA owners don?t.
 
Let Vans know when your annual is. They were very helpful getting my leg to me in time. BTW. Not difficult to replace. Mostly time consuming
 
Parts Delay?

Anyone else get an email this week that parts ordered for the SB maybe delayed until July or August? I sent Van's an email stating my condition inspection is due in May and I believe I have ordered parts in a timely fashion. Would not wish to loose the summer without the aircraft!
 
If there was a concern about drilling holes in the gear leg for the leg fairing attach screws, they would have never been specified there originally, and/or they would have been deleted when the new nose gear leg was designed, so no FEA on the screw holes is like to happen (see below for reason).

Sorry if that sounds a bit sarcastic.... I don't mean it to be, but it is the reality.

A bit of engineering and physics needs to be applied to understand why these holes are not an issue.

One, would be to understand what the bending loads are along a beam or arm such as the nose gear leg. The bending loads are the highest at each end where the arm attaches to other members (think of the effect that a long lever arm can have to amplify force). The bending loads are the lowest at the very mid point of the arm (that is where the lever arm is the shortest distance to other members where the loads are being applied).

That is why the screw holes are at the very mid point of the leg, vs a pair of holes at the upper end, and a pair at the lower end.

Another factor is the way the loads are distributed through the arm.

In the case of the nose gear leg, when a high upward load (hard landing for example) is applied, and the leg tries to bend, the material along the very top of the tube is being compressed along the length of the leg, and the material along the bottom edge of the tube is being stretched as the tube tries to bend into a curved shape.

The screw holes are purposely located on the sides of the leg, which puts them in the neutral axis of the tube..... the portion of the tube where there is no compression or tension load when the leg is being loaded vertically.

This is an overly simplified explanation.

Go to this reference (or just google "neutral axis") for more details.
https://www.quora.com/What-is-the-neutral-axis-of-a-beam

Scott,

Thank you for your detailed explanation. I decided to forego the screws. Today I wrapped 3 bands of weather stripping on the gear leg. The foam from the weather stripping captures the nose gear fairing securely. The protruding nose gear tow hook also captures the fairing in place.

Regards,
Tom
 
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