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  #1  
Old 02-20-2017, 09:09 AM
TrondM TrondM is offline
 
Join Date: May 2012
Location: Bodoe, Norway
Posts: 6
Default Cracks in upper engine mount brackets

During the annual inspection of our RV-4, we discovered cracks in the brackets where the upper engine mounts attach to (the aft side of) the firewall. The aircraft was built in the late 1980s and has around 1360 total hours with an O-320 150 hp engine and a fixed pitch prop.

The picture is from the right side, on the left side smaller cracks were also beginning to form.

I have e-mailed Van's for recommendations. When searching this forum most threads seem to be about cracking related to the lower engine mounts and gear mounts, but this thread from 2005 appears to discuss the same problem: http://www.vansairforce.com/communit...ead.php?t=3663

Does anyone have experience with this issue? Suggestions would be welcome.

Regards,

Trond M.

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  #2  
Old 02-20-2017, 09:24 AM
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acam37 acam37 is offline
 
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Location: Lufkin Tx
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Just order new brackets from Vans. The top ones are real easy to change out. But I would suggest replacing all 4. The bottom weldments will eventually crack also if they are the old style.
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  #3  
Old 02-20-2017, 09:28 AM
RV Jerry RV Jerry is offline
 
Join Date: Jan 2009
Location: Chino, CA
Posts: 142
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I have replaced several RV-4 mount weldments , it's not too difficult, but would recommend an experienced builder help. You have the early mounts which are of a lighter construction you also need to replace lower weldments , if they are not cracked now chances are they will be. The motor and motor mount needs removed, you can leave motor and gear legs attached and remove as assembly, then you need to remove enough rivets to allow you to peel back fuselage skin to gain access to weldments rivets , some weldment rivets are shared with the skin and some are riveted to longeron only. Reinstall new weldments and use hole in firewall to locate engine mount hole. If you are carefull upper removable fuselage skin and gear leg intersection fairings will hide most of your rivet work and only minimal touch up pain will be required
Jerry
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  #4  
Old 02-22-2017, 09:13 PM
Ham Ham is offline
 
Join Date: Jan 2005
Location: Salmon Arm, BC
Posts: 15
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"Does anyone have experience with this issue? Suggestions would be welcome."

I made a similar discovery in my RV-4 in 2011. I called Gus at the factory. He said that this was not an uncommon problem with older 4s (mine was completed in '91), and added that the solution was straightforward. Take the engine off, remove the offending weldments, rivet the new ones in, put the engine back on, and "Bob's your uncle". He said an experienced builder could do it in about 180 hours. He added that the repair kit came with all 4 weldments and a new lower firewall. I checked, and there were cracks around the rivets attaching the lower firewall to the fuselage. Clearly, the factory knew what this problem required.

I did not build my 4, and had no sheet metal or riveting skills. Fortunately one of the experienced guys at our little field (an AME and restorer of L-19s) offered to mentor me. Though he did often note that he had seen glaciers move faster than I worked, I did eventually complete the repair. In 2013. I haven't had any airframe issues since. I'm in the middle of my annual right now, and the new (beefier) brackets look like new.

Take lots of pictures as you take your airplane apart! It will help putting it back together!
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  #5  
Old 02-23-2017, 02:35 PM
RV-4 RV-4 is offline
 
Join Date: Oct 2007
Location: St-Jerome,Quebec,Canada
Posts: 915
Default UPPER ENGINE MOUNTS BRACKETS

Exactly the same results as mine a few years ago..

I simply could not believe how cheapo these brackets were for an aircraft that was capable of +6G...

Ordered the new brackets from Vans and replaced them right away..

There should be an AD asap to replace them I believe, totally unsafe in my book..

Bruno
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  #6  
Old 02-25-2017, 12:14 PM
TrondM TrondM is offline
 
Join Date: May 2012
Location: Bodoe, Norway
Posts: 6
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Thanks for the input. It seems like a good idea to replace these brackets with new and stronger ones, according to Van's "new production parts are built differently than what it looks like you have with the square plate where the bolt goes through being .125 where I expect yours were .050".

From what I can find in "the list" it looks like we need the following parts (upper and lower):
FIREWALL MT-UPPER LFT WD-402-L
FIREWALL MT-UPPER RT WD-402-R

FIREWALL MT-LOWER LFT WD-403-L
FIREWALL MT LOWER RT WD-403-R

Does anyone know if additional parts are needed, for instance part numbers of nuts, screws and bolts that we may want to replace while we are at it?

"He said an experienced builder could do it in about 180 hours. He added that the repair kit came with all 4 weldments and a new lower firewall."

I could not find a repair kit in the Van's store - do you know the part number? How much time did you guys spent doing this work..?

Regards,

Trond M.
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  #7  
Old 02-25-2017, 06:06 PM
markscogg markscogg is offline
 
Join Date: Mar 2005
Location: Charlotte, NC
Posts: 297
Default Not that big a job for pro

Quote:
Originally Posted by TrondM View Post
Thanks for the input. It seems like a good idea to replace these brackets with new and stronger ones, according to Van's "new production parts are built differently than what it looks like you have with the square plate where the bolt goes through being .125 where I expect yours were .050".

From what I can find in "the list" it looks like we need the following parts (upper and lower):
FIREWALL MT-UPPER LFT WD-402-L
FIREWALL MT-UPPER RT WD-402-R

FIREWALL MT-LOWER LFT WD-403-L
FIREWALL MT LOWER RT WD-403-R

Does anyone know if additional parts are needed, for instance part numbers of nuts, screws and bolts that we may want to replace while we are at it?

"He said an experienced builder could do it in about 180 hours. He added that the repair kit came with all 4 weldments and a new lower firewall."

I could not find a repair kit in the Van's store - do you know the part number? How much time did you guys spent doing this work..?

Regards,

Trond M.
I had this done in a shop in Camden, SC for $3800. It was 6 or 8 years ago.
This included the 4 brackets, replacing the lower firewall, sending the landing gear legs off to be straightened and touch up paint.
Guy said he would have the engine, (still in the mount with landing gear) hanging on a hook in 4 hours. These guys are pros.
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  #8  
Old 02-26-2017, 11:49 AM
Ham Ham is offline
 
Join Date: Jan 2005
Location: Salmon Arm, BC
Posts: 15
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Trond:

There isn't a repair kit. You make it up according to what you need. Here's the parts list I needed from Vans to replace all four brackets and the lower firewall.

WD-403-R
WD-403-L

WD-402-R
WD-402-L

F-401A (lower firewall)

Total Price: about $250 US in 2011.

I had to fabricate F-442 from 6061-T6 aluminum angle .187" X 2" X 2- 1/2" (see dwg 27 top left, if you have the drawings). I had to replace some other 6061-T6 angle as well.

I replaced all the hardware and made my list from the plans and the construction manual. Here's my hardware order from Aircraft Spruce.

Qty Ship B/O Item Unit Price Total Price
24 0 AN3-5A BOLT UNDRILLED AN3-5A 0.120 2.88
7 3 AN6-30 BOLT DRILLED AN6-30 1.310 9.17
7 0 AN310-6 NUT, CASTLE AN310-6 1.040 7.28
7 0 AN960-616L WASHER, FLAT AN960-616L 0.040 0.28
14 0 AN960-616 WASHER, FLAT AN960-616 0.050 0.70
24 0 AN365-1032A MS21044N3 ELASTIC STOP NUT 0.100 2.40
48 0 AN960-10 WASHER, FLAT AN960-10 0.030 1.44
1 1 09-00919 PTI ZINC CHROMATE YELLOW QT 42.650 42.65
Subtotal: CAD 66.80 (2011 price)

I checked my old emails - Gus at Vans said that it would take an experienced builder 50 hours to do the job (not the 180 hours I reported earlier). In fact, it took me two years to do it. But then I had no experience and wasn't naturally handy. I certainly learned a lot.

I hope that helps.

I visited Bodoe once - watched kids play soccer at midnight in the sunshine! Then rented a car and drove back to Bergen. Beautiful country!

Cheers,

Hammy
RV-4 C-GWYR
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  #9  
Old 02-26-2017, 09:03 PM
Sodbuster Sodbuster is offline
 
Join Date: Mar 2010
Location: Danville, IN
Posts: 28
Default Cracks in upper engine mount brackets

I had to repair all 4 weldments many years ago on my first RV-4 (now flying my fourth) long before there was the new style. Probably about the first 4 to have this problem. I did not change the part riveted to the firewall. I made 4 new weldments to replace the part attached to the longeron. Much easier than changing the whole weldment. No need to pull the engine mount. Give me a call for details. Jim Winings 317-718-3415
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  #10  
Old 03-08-2017, 12:57 PM
TrondM TrondM is offline
 
Join Date: May 2012
Location: Bodoe, Norway
Posts: 6
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Thanks, appreciate the info!

We have ordered the parts from Vans and will be consulting a local builder for advice. The lower ones seem to be fine, so unless we can find indications of trouble there I think we'll keep those.

Hammy, good to hear that you were able to experience the midnight sun while you visited! Looks pretty nice in your part of the world as well, I have been to Vancouver and Whistler but not further eastwards (yet)

Jim, thanks for the tip, maybe we'll give you a call when the parts arrive..!

Regards,

Trond M.
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