What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

SB16-08-24 Loose engine mount bracket rivets

Great timing!

Thanks mate!
I was going to attach these brackets this weekend.
Would it make sense to use Cherry rivets for all the holes on the brackets?

Cheers
Oleg
 
Thanks mate!
I was going to attach these brackets this weekend.
Would it make sense to use Cherry rivets for all the holes on the brackets?

Cheers
Oleg

Can't see any problem with that unless you're building E-LSA, but a quick email to Vans will make sure you get the right answer.
 
Will be approaching this soon.

Looking at the print, any reason why you can't use AN470's and buck them as normal - job done !

Access underneath looks OK on the print.
 
rivets

I question why only the smoking rivets (6 on each side) get replaced with the Cherry rivet.
This is a shear application and the reason the designer chose 18 rivets was to transfer the calculated load in shear from the WD-1204 engine mount bracket to the F-1202 panel base. The LP4 rivet pull stem does not break even with the manufactured head thus filling the hole solid. The manufactures MINIMUM SHEAR for 1/8" LP4 rivet is 162 pounds.
Minimum shear for the Cherry CR3213-4 is 236 pounds
Minimum shear for the MS20470 solid driven rivet is 664#
The smoking is from movement, once those are repaired with a more solid Cherry we now have those 6 carrying a greater load than the other 12 in the bracket.
I am building an ELSA to the plans so I am just wondering if Mike Newall
has the right idea here.
Waiting for Scott to weigh in on this.
Jerry
 
We don't build to the same rules in the UK.

If I wish to replace with solid and my Inspector is OK, we move forward.

I just felt that with access and a solid bucked rivet - job done, etc.

Totally understand the Vans philosophy though.
 
I question why only the smoking rivets (6 on each side) get replaced with the Cherry rivet.
This is a shear application and the reason the designer chose 18 rivets was to transfer the calculated load in shear from the WD-1204 engine mount bracket to the F-1202 panel base. The LP4 rivet pull stem does not break even with the manufactured head thus filling the hole solid. The manufactures MINIMUM SHEAR for 1/8" LP4 rivet is 162 pounds.
Minimum shear for the Cherry CR3213-4 is 236 pounds
Minimum shear for the MS20470 solid driven rivet is 664#
The smoking is from movement, once those are repaired with a more solid Cherry we now have those 6 carrying a greater load than the other 12 in the bracket.
I am building an ELSA to the plans so I am just wondering if Mike Newall
has the right idea here.
Waiting for Scott to weigh in on this.
Jerry

Actually the minimum shear rating for the CR3213-4 rivet is 655 lbs
The shear rating for an AN470AD4 rivet is somewhere close to 388 lbs (I don't remember the exact #)

In a structural bracket such as this, the load is often not distributed equally through all fasteners. There as often a slightly higher load at the outside most faster(s). If that fastener begins to yield, it can transfer addition load to the next one in line and the process begins again. So replacing any fasteners that have evidence of yield with ones that are higher rated gets the bracket back were it started, but with a higher margin on the outside most fastener(s).

Another factor here is that the load is not 100% in shear on the bracket rivets. Because the location of the engine mount bolt is above the web of the bracket, the tension force induced by the engine weight and thrust loads on the bolt in the fwd direction, also induces some tension load on the rivets (as in trying to left the bracket upward at the back).

Regardless of the cause (engine / prop. combo not well balanced, etc), if loose rivets are detected at the location described in the SB, the higher rating Cherry rivets should resolve it.
 
I used AN470 rivets in place of LPs throughout the build of the super structure; actually almost everywhere LPs were called out, except for the skin. I personally felt that they were stronger. I was comfortable doing this as I built EAB and have the tools and some riveting experience. My inspection, after 215 hours revealed no smoking rivets in that area. With Scott's comments about AN470s having less sheer strength than Cherries, I will continue to keep a an eye on that area, but I don't plan on changing them out unless trouble shows up in that area. Yeah, it added a little build time, but I am glad that I did it...

Tom
 
Scott, on the two planes that had a problem, do you know if the rivets had been installed correctly, or at least in the preferred way with the manufactured head on the panel base side? Two aircraft out of nearly 500 is a very small sample, but just wondering if rivet orientation could be a contributing factor in this case.
 
Last edited:
It seems that you could inspect for smokey rivets in there a lot easier than removing the top of the cowl under the wind shield as described in the SB. That could be done by simply removing the Skyview display, if installed, or any other such display and the glover box and looking in the bay behind the fire wall with a mirror and a flashlight. '

Does this make sense...or not?

EBB
 
'

Does this make sense...or not?

EBB

Yes, and no.

It would be pretty easy to inspect the left side this way.... the right side not so much.

A procedure written in a SB is a suggested way that assures the expected result. If a different method is possible because of special tools available (articulating inspection camera, etc.) there is no reason that method couldn't be used.
 
Scott, on the two planes that had a problem, do you know if the rivets had been installed correctly, or at least in the preferred way with the manufactured head on the panel base side? Two aircraft out of nearly 500 is a very small sample, but just wondering if rivet orientation could be a contributing factor in this case.

Installed correctly - Yes
Installed the preferred way - Yes

It is a small sample, but they are two airplanes that are more to the higher time side compared to the average of the fleet (and time is what will make something like this show up). As a result it was issued as an inspect/monitor type SB.
 
Scott, thanks for the background.

I thought I noticed one of the early S-LSA RV-12s at Oshkosh a couple of years ago that had the screws, holding its upper forward fuse skin, painted over. Not sure they still do that or not. It would probably not be easy/clean to remove the screws without messing up the paint to some degree. I made sure my painter didn't do that as I suspected I would need to get into the avionics shelf periodically which I do (and that this SB calls for). Suggest that for anyone who hasn't painted their RV-12 yet.
 
I've tried to remove that section of my SLSA before, when I experienced a troublesome avionics issue early on, and was unable do to the "sealant" used by Synergy Air when assembled. Its essentially glued in place.

I'm hoping that I'll be able to get a good look with a scope via the Skyview access which is where the avionics shop had to do all their work. If a repair is needed then I'm not sure what I'll do.
 
Scott, would it be acceptable to have the shop

head on the top for these rivets? Not sure I can get under there anymore to put the rivets "up", especially with the brakes, etc., in the way.

Wayne 120241 (402.5 hours)
 
head on the top for these rivets? Not sure I can get under there anymore to put the rivets "up", especially with the brakes, etc., in the way.

Wayne 120241 (402.5 hours)

Yes

Manufactured head on the thinner material is best practice but it is not a requirement.
 
Of course this SB came out literally two days after I had finished a little avionics tinkering and re-installed my forward top skin. I'll pull it again his fall when I build the new canopy. I bought the rivets and will install them regardless of whether there's a problem -- it's a few bucks, a few minutes of work, and one less thing to have to remember to document during every condition inspection.
 
Lee,

I helped an SLSA owner remove the avionics bay cover. They way over did the sealant and we had to slowly work a knife blade along all the sealed surfaces to free the avionics bay cover.

Rich
 
Lee,

I helped an SLSA owner remove the avionics bay cover. They way over did the sealant and we had to slowly work a knife blade along all the sealed surfaces to free the avionics bay cover.

Rich

Thanks Rich,
That's good to hear, I contemplated that approach but didn't have the patience at that time.
On another note we should have a gathering of 12's here in Az.
Lee
 
The last time I had mine off I sealed it with RTV after lightly oiling the skin, per the SB instructions. When I went to remove it this time it was stuck tight. I was almost ready to panic and break out the razor, but found a better way. I started at one end and got it to break loose, then slid a fingertip in and gently worked my way over to the other side. The "peeling" action did the trick, it just took patience and finesse. I generally lack both, but this time I managed.
 
head on the top for these rivets? Not sure I can get under there anymore to put the rivets "up", especially with the brakes, etc., in the way.

Wayne 120241 (402.5 hours)

I no longer have the physical flexibility to access the manufactured heads of those rivets. What techniques are some of you using? If I remove the wings and stand along side of the cockpit, I can kind of reach the rivets but can't hold that position for long which implies I may do more damage due to misalignment with the drill.

I would prefer to do the mod however my engine is 35 pound lighter than the Rotax. I might just pull the displays (dual EFIS) and use a borescope to inspect the rivets. However, I'm still interested on how some of you are accessing those rivet heads.
 
SB-16-08-24

Regarding the SB for loose engine mount bracket rivets, I took the FWD fuse cover off and had a look. The rivets look fine, no sign of greasy or smoky film. If I do replace them, I am thinking I need to remove the bracket that supports the radio just to get a clear shot at drilling out the old rivets as well as getting a rivet gun down in there.
Has anyone completed this SB on a finished -12 ?.
And, I am unsure what sealant to use when re-assembling. I don't want to glue it down permanent as I read others had by using RTV.
Any ideas welcome.


right side
i6xxe1.jpg


left side
20k6oua.jpg
 
Regarding the SB for loose engine mount bracket rivets, I took the FWD fuse cover off and had a look. The rivets look fine, no sign of greasy or smoky film. If I do replace them, I am thinking I need to remove the bracket that supports the radio just to get a clear shot at drilling out the old rivets as well as getting a rivet gun down in there.
Has anyone completed this SB on a finished -12 ?.
And, I am unsure what sealant to use when re-assembling. I don't want to glue it down permanent as I read others had by using RTV.
Any ideas welcome.


right side
i6xxe1.jpg


left side
20k6oua.jpg


It appears those rivets are installed the wrong way (manufactured head should be on the bottom of the avionics shelf ). We replaced the suspect rivets during condition inspection even though they were all ok. Punch the mandrel out and the rivet heads pop off pretty easily.
 
I did not catch that

Are you able to get underneath the avionics shelf to install new rivets from below ?.
Doesn't look like much fun:eek:
 
if the plane is up on sawhorses as described in the MM, that gives you a few extra inches to work with. I was able to do all the work standing outside the cockpit. Used a hand pulled for the cherrymax rivets called out in the SB. Did two rivets at a time, drill out old and install new. It's Not overly difficult work so if your not as limber as you think, maybe find a helper to get underneath and you could always watch and supervise ��
 
Last edited:
Back
Top