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  #1  
Old 03-01-2019, 11:45 PM
mbauer mbauer is offline
 
Join Date: Nov 2015
Location: Nikiski, AK
Posts: 461
Default Help: Cracks in Landing Gear Mounts

Today started my annual condition inspection for the RV. Found some cracks in the landing gear mounts. My mechanic is learning about RV's.

Not sure if these are something that can cause issues down the road.

Here is the only photo that is in focus, other side is almost identical to this photo:


Remember reading about cracked landing gear mounts on the big tire thread.

Wondering if these need fixed or ok to continue flying....

Looked on the top side welds, and as far underneath as we could, these cracks are both located in the same spot, on both mounts. No other cracking visible.

Best regards,
Mike Bauer
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N999SN 1998 Syd Nelson RV-6 (purchased 2017)
UTC -09:00 Alaska

Last edited by mbauer : 03-02-2019 at 02:39 AM.
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  #2  
Old 03-02-2019, 07:17 AM
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rocketbob rocketbob is offline
 
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Location: 8I3
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Needs to be fixed. On the older mounts there is an inner sleeve that is only welded around the bottom circumference and yours is coming out judging by the oily residue on the bottom of the socket.

I welded my cracks together, added a reinforcing sleeve over the bottom, and added more filler to the existing welds to repair the bottom.

https://goo.gl/photos/J2LYRKMfiTbY7iAe6
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N9187P PA-24-260B Comanche, flying
N678X F1 Rocket, under const.
N244BJ RV-6 "victim of SNF tornado" 1200+ hrs, rebuilding
N8155F C150 flying
N7925P PA-24-250 Comanche, restoring
Not a thing I own is stock.
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  #3  
Old 03-02-2019, 08:48 AM
Sam Buchanan's Avatar
Sam Buchanan Sam Buchanan is online now
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Location: North Alabama
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Quote:
Originally Posted by mbauer View Post
Today started my annual condition inspection for the RV. Found some cracks in the landing gear mounts. My mechanic is learning about RV's.

Not sure if these are something that can cause issues down the road.

Wondering if these need fixed or ok to continue flying....

Looked on the top side welds, and as far underneath as we could, these cracks are both located in the same spot, on both mounts. No other cracking visible.

Best regards,
Mike Bauer
Cracks such as you are seeing are quite common on RV-6 mounts. I first noticed these cracks a few years after flying my RV-6 and watched them for the next ten years. They never got larger and there was no other cracking. These seem to be compression failures instead of failures in tension.

I finally decided to pull the mount away from the firewall enough to run a weld bead over the cracks. In a couple more years the new weld on the left side had cracked in the same place. I'm back to checking the crack at each condition inspection and don't intend to address it again as long as it doesn't get any worse. I don't have any concern about the mount failing. RV-7 mounts have a gusset in the area and the gussets are available from Vans if someone wants to add them to the RV-6 mounts.

That is my way of dealing with this, others may want to deal with it differently.
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  #4  
Old 03-02-2019, 09:12 AM
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JonJay JonJay is offline
 
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As Sam learned, welding over the top, even grinding the weld down and welding new won’t work. It doesn’t fix the design flaw.
The only fix is to add the gussets and supports, or roll your own as Bob did. The problem was well known when I was building and most newer build 6’s, early 2000 and up, used the newer 7 mount. I believe Vans consolidated when the 7 came out and switched to the 7 in the finishing kits for the 6.
There is a significant difference, probably even overkill, in the mount. Not just plate gussets, but added tubing as well.

You could always follow Sams inspection approach. Thus far, no mounts have left an airplane that I have heard of and I would bet there are hundreds of 6’s flying out there with cracks at that same spot.
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  #5  
Old 03-02-2019, 09:42 AM
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Russ McCutcheon Russ McCutcheon is offline
 
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It?s a little hard to tell just how far along this is from your photo, you and your A/P will have to decide when and if you need to stop watching and take action, When that time comes I have repaired several of these and installed the gussets from Van?s.

About the grease, Bob could be right but also the legs are usually greased when they are installed so it?s pretty common to see some working out from around the leg.
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  #6  
Old 03-02-2019, 11:02 AM
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Toobuilder Toobuilder is offline
 
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The engine mount is primary structure. You have experienced a partial structural failure. IMHO, The question is not "IF" you should fix it, its HOW should you fix it. Obviously, rewelding is going to simply kick the can down the road until it cracks again. The joint needs additional support, which Vans has very conveniently engineed for the product line. If I know Van's, the gusset plates can be had for a paltry sum, and installation will not require any unusual skills. Blast and powdercoat should be inexpensive (my Rocket mount was done for $60).

This is not a military jet or airliner that needs to support a particular ops tempo - its a sport airplane that can sit for a few weekends. Very simple choice, really.
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1940 Taylorcraft BL-65
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  #7  
Old 03-02-2019, 03:01 PM
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Sam Buchanan Sam Buchanan is online now
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Quote:
Originally Posted by Toobuilder View Post
The engine mount is primary structure. You have experienced a partial structural failure. IMHO, The question is not "IF" you should fix it, its HOW should you fix it. Obviously, rewelding is going to simply kick the can down the road until it cracks again. The joint needs additional support, which Vans has very conveniently engineed for the product line. If I know Van's, the gusset plates can be had for a paltry sum, and installation will not require any unusual skills. Blast and powdercoat should be inexpensive (my Rocket mount was done for $60).

This is not a military jet or airliner that needs to support a particular ops tempo - its a sport airplane that can sit for a few weekends. Very simple choice, really.
Oh good grief....this situation doesn't call for a bunch of hand wringin'.......

My RV-6 (and who knows how many others) has "experienced a partial structural failure" for nearly twenty years with no consequences. If the OP decides to pull his firewall-forward apart and weld in some gussets that is just fine. But to place this particular matter in the category of "structural failure" is uncalled for. In the two decades I've been in the RV community I don't recall any gear failures attributed to these small stress cracks.
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  #8  
Old 03-02-2019, 03:24 PM
Pittsartist Pittsartist is offline
 
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Have a browse through this - I think we have the same problem.

My repairs still holding - so far so good.

http://www.vansairforce.com/communit...d+engine+mount
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  #9  
Old 03-02-2019, 07:09 PM
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Toobuilder Toobuilder is offline
 
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Quote:
Originally Posted by Sam Buchanan View Post
Oh good grief....this situation doesn't call for a bunch of hand wringin'.....
Hand wringing? Please spare us the hyperbole. As much time as people spend on theoretical failures, I can't believe there is even a debate on this actual one.

The part is not up to the task and has cracked. Would anyone submit this airplane to a DAR or the Feds for initial certification with a known crack? Does anyone think a DAR or Fed would let it slide? Why is there even a discussion here?
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WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

Michael Robinson
______________
Harmon Rocket II -SDS EFI
RV-8 - SDS CPI
1940 Taylorcraft BL-65
1984 L39C
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  #10  
Old 03-02-2019, 07:18 PM
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rocketbob rocketbob is offline
 
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I also had a "partial structural failure" and let it go for a couple of years but kept an eye on it. On one flight I noticed a change in how the airplane tracked down the runway so I pulled the cowl to have a look. Look at the pictures I posted and you'll see the size of the crack it turned into. Its better to fix it now than have a sudden failure away from home. In hindsight I shouldn't have let it go.
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Bob Japundza CFI A&PIA
N9187P PA-24-260B Comanche, flying
N678X F1 Rocket, under const.
N244BJ RV-6 "victim of SNF tornado" 1200+ hrs, rebuilding
N8155F C150 flying
N7925P PA-24-250 Comanche, restoring
Not a thing I own is stock.
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