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What exactly am I looking at? (horizontal stab attachment)

nplayle

I'm New Here
Hi,

I recently purchased a 'nearly complete' RV6A kit from a fellow builder who unfortunately passed away prior to its completion.

I'm going over the work he's done to come up with a list of things I need to check over / complete, and stumbled across this issue in the tail...

If I'm reading the plans right, this is PN HS-610, HS-614 and HS-602 spar, and they should be attached all the way across with AN470AD4-5 and -7 rivets, but for some reason the outboard rivets were left out.

It appears that during the attachment phase some rivets were left out, or they were drilled in the wrong spot.

See pictures:
https://imgur.com/a/2YHdvFH
Close ups of holes:
https://photos.app.goo.gl/F1hWMJ1F87cuuPfL8


Any thoughts on how to fix? The plane has passed all inspections save for the final inspection (Canada, MD-RA), so the inspector either didn't see this or didn't care.

I'm not planning on completing the spar AD per Van's recommendation, but it would seem to me that something should be done here.

Thanks!
Nick
 

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First, good catch. Looks like the builder left it and hopefully meant to go back to it later. It's hard to tell how messed up the hole through the spar is; if it isn't as bad as the hole in the rib flange you may be able to fix it with a doubler of some sort. Or if the spar hole is mis-shaped also it may be able to be drilled up a size or even replaced with a bolt depending on size and edge distance. Either way I would imagine there is a relatively simple solution, but the blessing would need to come from Vans. Anything related to spars is outside my comfort zone of engineering decisions.

Chris
 
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Thanks - I've got an email out to Van's but I'm not sure they'll respond to me yet since I'm still in the process of getting the kit registered in my name with them, hopefully soon though!
 
While your inspecting this area, now is the time to double check the spar to longeron bolt holes for edge distance. This is a very common build error as it is difficult to see both sides of those bolt holes when drilling. Lots of posts on how to drill these and lots on how to repair. Hopefully they are good.
Also, take close up photos of the area on the spar where the cracking can occur that prompted that AD. You can use those photos at each CI for comparison since cracking can be hard to see. That AD came out way after my airplane was flying. It looked like I might have a potential crack, or was it a scratch from fabrication? Die penetrant was inconclusive. Each year I take a new photo and check it against the old. I have never seen the suspect area change or look like a crack might be “growing”. I wouldn’t do that AD unless there is a problem either but it needs to be on you CI checklist.
 
I would also check the position of that rivet in the upper left corner of the picture. I don't think it is in the right position. You might also want to get an inspector takes a more thorough look at things. It is you in the end that is responsible not the inspector for the construction and airworthiness.
 
On the RV-14 there are similar rivets in this area that the plans have you go back and do much later than you do all the rest. If the 6 is remotely the same I could believe they just forgot to go back and do them.
 
While your inspecting this area, now is the time to double check the spar to longeron bolt holes for edge distance. This is a very common build error as it is difficult to see both sides of those bolt holes when drilling. Lots of posts on how to drill these and lots on how to repair. Hopefully they are good.

Is this the spot you're taking about?
https://www.vansairforce.net/community/showthread.php?t=210006

I'll give it a look next time I'm out in the shop. Thanks!
 
I would also check the position of that rivet in the upper left corner of the picture. I don't think it is in the right position. You might also want to get an inspector takes a more thorough look at things. It is you in the end that is responsible not the inspector for the construction and airworthiness.

That's photo is upside down. I'm not sure where that rivet would be located otherwise?

I believe the inspector that did the inspections on this plane has retired and so I'll be getting a different one for the final inspection. I'll likely have him out before the 'final' inspection to go over everything as well.
 

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While your inspecting this area, now is the time to double check the spar to longeron bolt holes for edge distance. This is a very common build error as it is difficult to see both sides of those bolt holes when drilling. Lots of posts on how to drill these and lots on how to repair. Hopefully they are good.

Well... I'm not sure this is exactly what I had hoped to find.... The longeron holes seem drilled relatively on centre but the edge distance to the reinforcing angle looks a bit close for comfort. Any thoughts?
 

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Ideally the F-810C would have been fitted to nest tightly into the radiused of the longerons but it is not a critical point. To compensate if you have short edge distance on this angle you can simply add an additional piece of bare stock underneath that will span this area with reasonable edge distance.

The critical point is that the holes are located well on longeron flange as short edge distance on the longeron itself is not acceptable and requires a great deal of work to make up for
.


I received this from vans on my -8. It turned out better when i actually drilled it..and longeron edge distance was OK..as it looks to be here.. But I would send pix to vans support.

Also If i remember , some have reinforced this area .. A search may find examples..
 
edge distance

Well... I'm not sure this is exactly what I had hoped to find.... The longeron holes seem drilled relatively on centre but the edge distance to the reinforcing angle looks a bit close for comfort. Any thoughts?

Yep, the outer bolt hole does appear to be very close to the edge of the reinforcing angle. At least the longeron looks OK.

I suggest to unbolt and remove the HS and VS from the fuselage to allow the edge distances to be actually measured. It will need to be disassembled anyway to fix the missing rivets in the root ribs.

Vans has apparently got some "approved" repairs to correct problems with edge distance, because enough builders have had difficulty in this area. There is very little margin for error in the way it's designed!
 
Looks like one of the holes through the longeron has violated edge distance, but would need to see from bottom. The edge distance is blown on the upper angle, but that is easily rectified by adding an 1/8" or 3/16" piece of bar over it to create a sandwich. If the ED is blown on the longeron, that is a more involved repair.

Larry
 
Well, the final verdict isn't exactly what I had hoped for but I guess it is what it is.

The suggestion from Van's is to make a whole new Horizontal Stabilizer for an RV7. They said they allow up to a 5/32 rivet in the affected area which I don't think will drill out to a round hole. They said they have heard of people extracting the spars / ribs but it's not something they'd recommend to try. Coupled with the other SBs and updates to the HS they suggest making a new one..

That said, they also said there's no issue with the longerons, so at least there's that.
 
I’m no expert but it’s a horribly built HS in that area and the new one gets you the SB to strengthen up the spar area. My 7 spar area and I’m thinking of building a new one later on when the fuse is built as I have learnt so much and made a few mistakes. None are structural just think I can do better. Probably won’t in the end but I wish I knew what I know now before building. But yours in the pic I could not live with. Sorry just being truthful.
 

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You can also put the new hinge brackets on and avoid the recurring inspection SB that just came out.
 
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