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New Service Bulletin 00053

Almost seems like a doubler plate could be added on outside of skin similar to triangle plates on bottom of aircraft near wing center section. Crack appears to be in the skin and not the bulkhead. Otherwise, I have to find a 10 year-old kid to crawl into tail cone...
 
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Are you required to re-weigh the aircraft if you close it back up with a small person in the tailcone? :D
 
Are you required to re-weigh the aircraft if you close it back up with a small person in the tailcone? :D

I'm more worried about getting myself stuck. A bit claustrophobic here.

Maybe Van’s can furnish specifics on aircraft that had issue – TT, climate, hard surface/turf, trainer, etc.
 
Interesting the SB says to... remove the seats and baggage bulkhead to gain access....just didn't mention that pesky fuel tank most of us have in the way?!!

Oh well, says this whole job only takes 2.4 hours to complete, so surely half of us should have this completed in less time than that, right?
 
I'm being punished, aren't I? I just finished my annual and buttoned it all up.

It could not possibly be in a worst spot. Seems like an excellent opportunity to damage my aircraft and for my hanger mates to learn more imaginative profanity.
 
Unlike Steve I am in the midst of my annual and have everything opened up so I will order the parts and if I get them I will complete this Service Bulletin.

Yeah, don’t look forward to the journey into the cone!
 
I guess it's a good thing I haven't attached the tail cone yet. I have the finished tail cone sitting on a stand in my garage. However, I think I might be less likely to cause any damage by putting some padding on the floor and then performing the service bulletin with the tail cone to the floor. Any thoughts?
 
I guess it's a good thing I haven't attached the tail cone yet. I have the finished tail cone sitting on a stand in my garage. However, I think I might be less likely to cause any damage by putting some padding on the floor and then performing the service bulletin with the tail cone to the floor. Any thoughts?

That's exactly what I was thinking. Mine is sitting on sawhorses right now, while waiting for wing kits.

I think I'm going to drill out the skin rivets from below, then put it on the floor on a layer of padding, then crawl in and make the fix. I don't think I'll need the plywood if it's on the floor that way.

Just placed the order for the service kit...

joe
 
I guess it's a good thing I haven't attached the tail cone yet. I have the finished tail cone sitting on a stand in my garage. However, I think I might be less likely to cause any damage by putting some padding on the floor and then performing the service bulletin with the tail cone to the floor. Any thoughts?

I wonder how hard it would be to support the tailcone vertically and stand inside to do the work?
 
Almost seems like a doubler plate could be added on outside of skin similar to triangle plates on bottom of aircraft near wing center section. Crack appears to be in the skin and not the bulkhead. Otherwise, I have to find a 10 year-old kid to crawl into tail cone...

I’m with you Jim. Why not just put three doublers on from the outside and be done with it, cracks evident or not.
 
This Service Bulletin is another reason for delaying the final installation (i.e., glueing) of the rear window.

To assist me in crawling into the tailcone, I previously cut pieces of two inch thick extruded styrofoam to replace seat bottoms, cover the baggage area and fit into the tailcone between the bulkheads and stringers. It creates a more level surface to lay on.

Looks like I will be making more sections to go further back into the tailcone.

Brett H
RV-12, Installing the propeller
Columbus, IN
 
I wonder how hard it would be to support the tailcone vertically and stand inside to do the work?

That's an interesting idea, Turner. The ceiling is too low to try this in my garage, but maybe the tail cone could be moved outside on a day when there isn't any wind!
 
i would like to know a lot more about the failure and why the other bulkheads won't follow . from what i read so far i think i would use the gusset vans is supplying and use it for a model to make brackets for the other bulkheads. crawling back there once more is bad enough.
 
i would like to know a lot more about the failure and why the other bulkheads won't follow . from what i read so far i think i would use the gusset vans is supplying and use it for a model to make brackets for the other bulkheads. crawling back there once more is bad enough.

To prevent cracks in the other bulkheads, the service bulletin says to add clips to all three bulkheads. The F-1208 and F-1209 bulkheads get two clips, and the F-1210 bulkhead gets one clip. All five clips are included in the 00053 service bulletin parts kit.
 
That's an interesting idea, Turner. The ceiling is too low to try this in my garage, but maybe the tail cone could be moved outside on a day when there isn't any wind!

My thought was definitely under very controlled conditions with assistance, and more like supported relatively close to floor, crawling in to stand up - probably not a great idea overall.
 
I’m with you Jim. Why not just put three doublers on from the outside and be done with it, cracks evident or not.

I'm with Steve and Jim. I wish Van's would re-think this repair/SB. I am not an engineer but the "clips" do not look robust enough and I suspect cracks will form even with the clips installed. I'm in favor of the external doublers cracks or not.
 
Checked the three bulkhead locations on my tail cone today and they were fine, but I have the SB on order and will install it. It would be interesting to know how many aircraft have experienced these problems and their time in service. Any in flight schools?
 
I'm with Steve and Jim. I wish Van's would re-think this repair/SB. I am not an engineer but the "clips" do not look robust enough and I suspect cracks will form even with the clips installed. I'm in favor of the external doublers cracks or not.

We can assume that Vans have done their analysis on the effectiveness of the clips, and personally I would prefer to install those than have to install and paint an external doubler, which by itself might not be enough to fix the problem. If it was, Vans may have gone that route as they did with the wing skin doublers. Without more information, we're just guessing.
 
Well, I guess now I feel like an aircraft owner rather than a collector of oddly shaped metal parts. I also just closed out my tailcone and am waiting for wings. I guess I'll have something to keep me occupied for a while.
 
I'm not a structures engineer, and I didn't stay at a Holiday Inn Express last night :p

That being said, I believe the cracks are caused by vibration and movement of the bulkhead, leading to the skin flexing - hence causing the fatigue cracks. An external gusset would transfer loading, but would probably just move the cracking to another location. It seems the clips are designed to support the bulkhead and reduce/eliminate the relative movement to the skin.

Just my .02

And FWIW - I'm 5'7" and go about 230# on a good day. I've no idea how I'm going to accomplish this feat!
 
My phone is gonna be ringing...

5' 10" and 134 pounds. A walking broomstick, but it comes in handy now and then.

My entire USAF career working on SR-71s and RF-4Cs was a clamor of "Go get Gamble - that little &^%$ can fit anywhere!"
 
5' 10" and 134 pounds. A walking broomstick, but it comes in handy now and then.

My entire USAF career working on SR-71s and RF-4Cs was a clamor of "Go get Gamble - that little &^%$ can fit anywhere!"

Dave - I moved here to Florida from Grove City 20 years ago. If I was still in the 'hood, I'd let you name your price to crawl back into my tailcone for this repair! :D
 
I am also 5' 7" over 200#, plus I'm 70 years old. I have no idea how I'm going to get this done.
I guess try to recruit someone smaller and younger.
 
mike, i spent a week back there last fall, i am 70. lots of padding on the skin so the plywood kind of floats on the padding and doesn't really bear weight on the bulkheads. a led light for little heat and a forced fresh air supply back to where you are working. make sure the tail is solidly in place or you will be standing on your head, trapped. i was surprised that my cell phone worked fine in there. also, a layer of cardboard on top of everything so you can slide easily.
i know one afternoon i made 20 trips into the tail then back to the workbench.
once you get set up it wasn't bad but setup was time consuming. once the tank and everything is out of the way you and a helper [inside the tailcone] could knock it out in a day. someone has to be on the outside drilling rivets , right?
 
mike, i spent a week back there last fall, i am 70. lots of padding on the skin so the plywood kind of floats on the padding and doesn't really bear weight on the bulkheads. a led light for little heat and a forced fresh air supply back to where you are working. make sure the tail is solidly in place or you will be standing on your head, trapped. i was surprised that my cell phone worked fine in there. also, a layer of cardboard on top of everything so you can slide easily.
i know one afternoon i made 20 trips into the tail then back to the workbench.
once you get set up it wasn't bad but setup was time consuming. once the tank and everything is out of the way you and a helper [inside the tailcone] could knock it out in a day. someone has to be on the outside drilling rivets , right?

according to Vans, it only takes 2.4 hours. ;)
 
Well I guess that's good when shops charge based on the official Van's time, but it will take me almost that long to get the interior pulled and get myself in a position to start drilling out rivets.

I'm 6' tall and 150 lbs, but 60 yrs old. I told myself I'd never crawl back there again after installing my ADSB antenna last year. Hopefully I can find that 20ish year old kid that works with his A&P dad a few hangars down!
 
mike, i spent a week back there last fall, i am 70. lots of padding on the skin so the plywood kind of floats on the padding and doesn't really bear weight on the bulkheads. a led light for little heat and a forced fresh air supply back to where you are working. make sure the tail is solidly in place or you will be standing on your head, trapped. i was surprised that my cell phone worked fine in there. also, a layer of cardboard on top of everything so you can slide easily.
i know one afternoon i made 20 trips into the tail then back to the workbench.
once you get set up it wasn't bad but setup was time consuming. once the tank and everything is out of the way you and a helper [inside the tailcone] could knock it out in a day. someone has to be on the outside drilling rivets , right?

I’m 78 and understand, I wonder if Vans would entertain adding a couple inspection plates in that area.
My Bonanza and Cessna has them in that area. That’s an area that needs to be inspected regularly anyway.
 
Bob,
Thanks for the encouragement and your suggestions. I guess the rivets on the bottom skins could be drilled out before crawling into the tail cone, drilling out the rivets on the bulkheads seems to be more problematic. I think I would definitely want someone on the outside to insert clecos and pull the rivets on the bottom skins after riveting the stiffeners to the bulkheads. This might eliminate multiple trips into the tailcone.
At least that's what I'm thinking right now.
 
We can assume that Vans have done their analysis on the effectiveness of the clips, and personally I would prefer to install those than have to install and paint an external doubler, which by itself might not be enough to fix the problem. If it was, Vans may have gone that route as they did with the wing skin doublers. Without more information, we're just guessing.

You should assume that, since it's true. :) SBs like this one are based on real-world experience and careful, detailed studies performed by our engineering team, including stress/fatigue modeling and analysis.

I'm not a structures engineer, and I didn't stay at a Holiday Inn Express last night :p

That being said, I believe the cracks are caused by vibration and movement of the bulkhead, leading to the skin flexing - hence causing the fatigue cracks. An external gusset would transfer loading, but would probably just move the cracking to another location. It seems the clips are designed to support the bulkhead and reduce/eliminate the relative movement to the skin.

I stayed at a Holiday Inn Express the last two nights. Didn't do me any good, I can tell ya that! But I do have access to one of our terrific engineers who can fill in my knowledge gaps while I'm sitting inside a pressurized tube at 35,000 feet on a Saturday afternoon. So.... here you go:

This is not a high-time issue. We have seen it on relatively new aircraft as well as older ones. The lowest time-in-service aircraft with this issue reported was at 177 hours. The highest time aircraft was over 2600 hours.

A doubler on the skin does not resolve the issue, since we are intending to stiffen the area. A doubler won't do that.

The J-stiffener feature in the RV-12 tailcone provides stiffness in the skin and a load path. Since that feature (the J-stiffener) is discontinuous at the bulkhead in the original design, there is flexing occurring at the bulkhead area. The clips in the SB kit are installed to make that J-stiffener structure continuous. This provides a continuous load path through the bulkhead to increase stiffness and prevent the flexing of the skin at the bulkheads.

So, a doubler will not address the issue. It might prolong the time it takes to form a crack. Maybe. And, it very well could transfer undesirable loads elsewhere.

Install as described. This is all part of airplane ownership - maintenance and ongoing improvement based on field experience is the second half of design quality and safety. Our team doesn't guess at these things, they engineer them. We won't be telling anyone it's ok to install differently than the SB design specifies.
 
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Bob,
Thanks for the encouragement and your suggestions. I guess the rivets on the bottom skins could be drilled out before crawling into the tail cone, drilling out the rivets on the bulkheads seems to be more problematic. I think I would definitely want someone on the outside to insert clecos and pull the rivets on the bottom skins after riveting the stiffeners to the bulkheads. This might eliminate multiple trips into the tailcone.
At least that's what I'm thinking right now.

Mike,

You are correct on having someone on the outside to insert clecos on the bottom skin and set rivets. I added my own version of these brackets on the tailcone bulkhead a couple of years ago and had to cleco from the inside, get out and rivet from the outside and go back in to remove the clecos, then back outside to finish riveting. I was also match drilling holes, so add two more trips in and out of the tailcone. It looks like a 90 deg drill may also be useful to drill out the bottom rivet on the bulkheads given the proximity to the skin.

Somewhere on VAF was a general discussion about cracks developing in the area between a stiffener and a bulkhead if you did not tie the two together with brackets of the type now being added.

John Salak
RV-12 N896HS
 
I'm almost 70 years old and not thrilled about crawling into tail cone. Slightly claustrophobic doesn’t help either. I fly off turf private strip, and when ground is soft, I use a winch to pull airplane back into hanger with connection to the tail tiedown hook. This SB has me thinking that might not be such a good idea. I might make a bridle and attach winch to main gear legs instead. Weather is going to warm next couple of days, and I owe a visit out to the airplane anyway, so I’ll examine belly of tail cone and report back soonest…
 
First to admit I don't know much about building experimental planes that get riveted together out of aluminum, but it seems to me, within weight considerations... would additional stringers/ribs have decreased the level of risk of cracks being developed, in addition to the clips, in the original cone design?

Just trying to visualize and learn here... maybe some Boeing or Lockheed engineers can share some valuable experience in aircraft design and construction techniques, especially in faster planes that are fully pressurized to fly above 18,000 ft.
 
First to admit I don't know much about building experimental planes that get riveted together out of aluminum, but it seems to me, within weight considerations... would additional stringers/ribs have decreased the level of risk of cracks being developed, in addition to the clips, in the original cone design?

Just trying to visualize and learn here... maybe some Boeing or Lockheed engineers can share some valuable experience in aircraft design and construction techniques, especially in faster planes that are fully pressurized to fly above 18,000 ft.
Not a Boeing engineer but as Greg Hughes said, the issue is the lack of continuity of the bottom J stiffener either side of the bulkheads which interrupts the load path and also creates a sudden change in stfffness locally which allows flexing of the skin and leads to fatigue cracking. There are cutouts in the bulkhead in other locations to allow the stiffeners to pass through, but not on the bottom skin.
 
Not a Boeing engineer but as Greg Hughes said, the issue is the lack of continuity of the bottom J stiffener either side of the bulkheads which interrupts the load path and also creates a sudden change in stfffness locally which allows flexing of the skin and leads to fatigue cracking. There are cutouts in the bulkhead in other locations to allow the stiffeners to pass through, but not on the bottom skin.

Accurate, and thanks for explaining.

Sidebar: We have amazing engineers working at Van's who spent years and years of time working at Boeing, Cessna, and a bunch of other big-league employers, people who left amazing jobs and careers to come work here. We also have engineers on staff who have designed and redesigned some well-known aircraft, and of course we have people who have been involved in the design of almost every RV made. I'm not sure our customers are really aware of the level of talent and the pedigree of engineers we have at our company, and what they're capable of. So, if you want a Boeing engineer, or someone who worked on crazy stuff at Scaled Composites, or someone who did flight test engineering for the military, or any of a number of other unique talents and experience... We got 'em, and they're truly terrific and talented people, one and all. But, since folks out in the world may not always know that's the case, I believe I know how to bridge this ... awareness discontinuity. (see what I did there?)
 
As a data point...

Posting purely as a data point, I did a careful exterior inspection of my plane's belly last night and found no evidence of cracking.

I'd be curious, now that we are all focusing on this area of our airframes, if anybody finds anything awry. When I start my CI in the next few weeks, I'll stuff my 6' tall, 130 pound, 18 year old borescope into the tailcone and with his help, we'll git'r done!
 
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When I start my CI in the next few weeks, I'll stuff my 6' tall, 130 pound, 18 year old bore scope into the tailcone and with his help, we'll git'r done!

Careful, people might start asking if they can borrow your tools! Heck, there're a lot of RV-12s in the Pacific Northwest. If the borescope can drive a car, it might even find a way to make some money having done the inspection and installation once already, hah.
 
Careful, people might start asking if they can borrow your tools! Heck, there're a lot of RV-12s in the Pacific Northwest. If the borescope can drive a car, it might even find a way to make some money having done the inspection and installation once already, hah.

:)LOL! Maybe I could get all his buddies together and train up an army of them and send them out for a small fee. :D On second thought, just the food bill alone...:eek:
 
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Maybe Vans could post the size of the plywood needed to be placed in the tail one for this service bulletin
.Then we can have that ready when we start not have to run home to cut those pieces
 
Maybe Vans could post the size of the plywood needed to be placed in the tail one for this service bulletin
.Then we can have that ready when we start not have to run home to cut those pieces

The aluminum skin in that area is not flat, I don't understand how a piece of plywood will fit in there and not cause marks on the skin when the weight of a person is applied. Maybe Vans is suggesting a thin plywood that will conform to the curve of the skin? I would like more clarification on this part of the process, some serious damage could be done if not performed correctly.
 
Greg,

It looks like (24) LP4-3 rivets are required to replace the ones drilled out. Are all the rivets used in this SB LP4-3?

The SB-00053 Installation Kit does not list the rivets as included. The service bulletin does not list the rivets in the list of “materials required”. Do I order rivets or not?
 
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