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RV-12 landing gear analysis: Update Oct 12, 2012

Thanks for posting this notice. I am still at a point where I can flip the fuselage and drill out the 8 rivets.

JAL
 
Gotta applaud

Van's team of engineers and kit developers. This notice will help us to make a better and safer aircraft. Thanks, Van's people, for getting to this asap.:cool:
 
A retro fit for painted planes could be coming?

Ouch!

:mad:

Oh boy, looks like maybe a big doubler is headed our way. Get out your drills and rivet guns boys and girls! And paint guns too......?

(Just thought I would be the first to start the speculation.) ;)

On a more serious note - I'm guessing the recent announcement from the mother ship is having an influence on this issue. I'm sure Van's wants to put this problem to bed with a robust fix that dispels any chatter about any sort of weakness in the RV-12 airframe. So even if the short term fallout for owners of completed airplanes involves the inconvenience of some retrofit work, the long term result will be positive in that we will have a stronger airplane and a better resale value.
 
it may not be an SB but rather a fix for those that have wrinkled skin (in that hidden area). many of us with lots of hours have nothing to fix. I would hope that completing an SB would be more important than fixing something damaged in terms of resale. Of course it would also be nice if the fix included their conclusion of what caused the issue in the first place...landings? braking?
 
as I've said before ...

Once you're a builder, you're a builder for life ... not my intention during my 3 year build ... :(
 
Several have made their own similar doublers already. Ron Russ actually put his on the INSIDE of the fuse. No paint problems other than rivet heads, and they are hidden by the wing when installed.
I am happy to see the doubler shown by Vans, will be a snap to install on mine at my stage of construction.
 
Behind the wing

Tony this is my quote from 9-20-12 (260)
This will be the same profile as the wing rib and be hidden by the wing

From Loose Main Gear Legs (260)


A few more thoughts
The fuel tank on the right side of the aircraft adds weight and stiffness right behind the spar.

If the channel is rotating back ( back flange up 70% front flange down 30%) most of the stress would be at the front of the fuel tank.

The left side would have a larger area to flex and absorb the loads

A skin doubler from the back of the spar about 12" back and the size of the wing rib on the outside would add a strength to this section and would not be visible behind the wing.

And in my view the channel is rotating.

I will not rivet this area on my side skins until vans reports their findings,

And for the people that have damage removing the rivets in this area, taking out the wrinkles with a body dolly and a hammer and installing the skin doubler should be easy.





It actually looks like that would be almost all be hidden by the wing.
 
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Front Flange

This skin doublers will add strength to the sides of the fuselage and a little more stress on the front bolt and the bottom web of the C-Channel.

I'm very interested on how vans will move the stress point from the bottom web to the front flange of the C-channel?
 
The question I would like answered is whether the cracks and wrinkled skin are due to operation outside " normal" expected loads or if there is a design deficiency in the original configuration.
 
The design ?

This is not a question that I am totally qualified to answer so this is by opinion based on years of experience of handling construction design problems.
The loose bolts are most of the problem with the cracks in the C-Channel, the cutout in the flange is not the best idea vans has ever had.

The design is probably on the edge of the engineering requirements and will work if you do not exceed normal operation of the aircraft.

The normal over design was a little short of vans normal standards. However vans trying to get a high useful load number, removable wings and a low stall speed probably added to the short coming ?

MY View



The question I would like answered is whether the cracks and wrinkled skin are due to operation outside " normal" expected loads or if there is a design deficiency in the original configuration.
 
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The question I would like answered is whether the cracks and wrinkled skin are due to operation outside " normal" expected loads or if there is a design deficiency in the original configuration.

Van's note on the Landing Gear and Side Skin Update (4 Oct) addresses this question, and states that the loads required to permanently deform the test fuselage exceeded the design limits:

http://vansaircraft.com/images/open/RV-12 landing_gear_update10-4.pdf

The skin doubler (assuming that's what they are planning), won't significantly alter the way the structure responds to the loads that are applied but will increase the strength of the fuselage in a critical area, and therefore provide a greater safety margin against failure. As I read it, they do appear to be working on an alternative way of attaching the gear legs to the channel, presumably to reduce the risk of under-torqued bolts causing fatigue failure.
 
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Static or dynamic ?

Robert
I agree However I think the tests were Static not dynamic.


Van's note on the Landing Gear and Side Skin Update (4 Oct) addresses this question, and states that the loads required to permanently deform the test fuselage exceeded the design limits:
 
Robert
I agree However I think the tests were Static not dynamic.

I don't know Joe, they didn't say. The drop tests they have to do are certainly dynamic. Either way, the aircraft doesn't know the difference. Once the load exceeds the capacity of the structure, it fails.
 
It just seems strange that so many owners have reported no cracks or skin deformation. I'd really like to know what the operating history was on the planes with cracks or wrinkled skin. My concern is that I keep flying on the original design and would like to know that I'm not placing the structure at risk by just routine operation. My gut feel is that I won't have these problems if I don't have hard landings or operate from unprepared surfaces, but it sure would be nice if Vans confirmed my assumption.
 
Have all these engineering quirks been updated with the newer RV-12 IST trainer model now in production since 2018?

Thoughts from those with a structural engineering backround?
 
The RV-12iS design process included evaluating the entire airplane and considering what could be updated or improved.

Taken from the Van's web site....


Feature Improvements
But, that’s just the beginning! We listened and learned from RV-12 owners, made many improvements to the RV-12 airframe and systems based on real-world customer feedback.


RV-12iS Features – Click to enlarge
Newly designed cowling that’s easier to remove. Plus, it provides greater cooling on the ground and in climb
New throttle quadrant design eliminates the need for special carb return springs used on the 912 ULS model engine
Quick-reacting electric flaps
New throttle actuation allows the pilot to easily select full-power (rich) or economy (leaned) mode
Cup holder (Limited to positive G maneuvers)
Improved canopy latch design
Quick-adjust seat back feature with even greater range of adjustability and greatly improved ease of use
Panel-mounted cockpit handle to aid entrance and exit
Horizontal stabilator tips are now available as an option
Dual USB power outlets
New and improved main landing gear attachment. More rugged and better suited to the training environment — Check out our gear tear-off test video below to see for yourself how and why we designed and tested it
New transversely mounted fuel tank results in more baggage volume and easier loading
Same tank capacity at 20 gallons, but much more usable fuel in climb/takeoff attitude
Larger fuel filler neck is now mounted below the rear window on the co-pilot side — easier to reach less prone to splashing
Increased baggage capacity to 75 lbs


RV-12iS page on the web site

Gear test video - https://www.youtube.com/watch?time_continue=7&v=yFfLBz2AVcw
 
Does the new training design take into account stalling and perhaps coming down hard vertically on the main landing gear or a rough drop with a 3 point landing too from gusty winds?
 
Does the new training design take into account stalling and perhaps coming down hard vertically on the main landing gear or a rough drop with a 3 point landing too from gusty winds?

It is understood that those would be common with training, so Yes, that was also considered.
The video is not comprehensive. There were many other test conditions that were done but are not included in the video.
 
The link I provided above works fine for me. You could also search through Van's Aircraft's website for their various videos.
 
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