So, the issue is a Beechcraft airplane which has had sanding done to it in a paint shop; shop contends no damage, but top of rivet is sanded to the point that no dimple identifiable (in most cases).

Is there a simple and accepted (and most importantly, documented) standard for inspection thereof?

I figure if anyone has a readily-cited and clearly-stated resource, they'll be here. Please, if you can, share.

Thanks in advance.

I have nothing to add other than on one of the salvage sites, I saw an airplane that was perfectly fine other than having the rivets sanded down.

Spike

I just took a brief look at AC43.13-1B-2A to see if there was any printed guidance relative to your question. I did not see any (as suspected) and conclude that there is no guidance because there is no acceptable amount allowed. You might try to get an opinion out of Beech (or other OEM), but otherwise I would put the onus on the shop to present evidence that what they did is acceptable.

Sounds like they are being a bit difficult so you may be forced to get a third party involved. I would think if the area is involved in limited, replacing the rivets in an acceptable manner would certainly be the least expensive route for all parties.

Don:

If I did not know better, I'd think you had my cell phone tapped!

Fortunately (for me), this is not my plane. Unfortunately, the area involved is not limited.

We'll see where this takes us.

I'm not claiming expert status in this kind of thing but it seems pretty clear to me that any obvious loss of metal from a significant number of rivets (e.g. more than a few percent over a large area) could impact a plane's structural integrity. Like most metal airplanes, the wings of Bonanzas and Barons get much of their strength from the sheet metal that connects all the ribs and spars (same for the fuselage WRT their skins and structural components) and removing part of the rivet had got to decrease the strength of that connection.

There was a Bonanza hulk sitting in the grass for years at my home base. Looking at it you could see that most of the rivets on the wings were sanded down and the story was the owner decided to use a belt sander to strip the wings before painting and the FSDO grounded the airplane as a result.

Keep in mind that rivets are designed to take load in "shear" not tension. So the heads are not as critical as you might think.

Having said that....if they are worn past the point of identification, they probably need to be replaced.

I too went to AC 43.13 2b and found no guidence on inspecting the heads of rivets due to wear or abraision.

Call your local FSDO.....if you really want to stir the pot.

Which may be a way of getting the shop to fix it. There is no clearer definition of 'unacceptable' condition than FSDO's grounding decision due to rivets sanded down. After such decision the shop can only fix it, they no longer can claim it's acceptable.

Which may be a way of getting the shop to fix it. There is no clearer definition of 'unacceptable' condition than FSDO's grounding decision due to rivets sanded down. After such decision the shop can only fix it, they no longer can claim it's acceptable.

Another unofficial post: Back in the nineties, the shop I use was drilling and replacing many rivets in a plane, I seem to recall it was a Piper, and the guys doing it told me the owner had belt sanded the plane in prep' for painting, then painted it or had it done. The rivets were obviously flattened a bit. They told me that the amount allowed to have been sanded off was zero. However, I've never read any official guide or ruling on it. I would imagine a repair station could tell you for certain.

Spike,

An insurance adjuster told me of a case where a new employee at a paint shop had sanded a king Air in preparation for paint, well the insurance company ended up owning a 4 year old King Air that could not be repaired.....

I another life I painted airplanes (when I was young) we never took sand paper to a airplane. Chemical strip, and we would do some scrubing with "Scotch Bright" pads but never sanding..... Well except for Aerostars lots of bondo on a Aerostar..

Jay

Every area has one of these stories.....

Guy bought a surplus-ed Air Force 310 and not being a pilot himself decided that the plane would be faster and look better with out all those "bumps" all over it. Yep, sanded down all the rivet heads in prep for a paint job before he was going to resell.

Needless to say he had a really nice if not large lawn ornament for many years before I guess it was sold for scrap.

Bob

I suggest you contact Paul New at Tennessee Aircraft Services in Jackson, TN.
paul@tennesseeaircraft.net
731 424 7227

Paul is an expert for aircraft repair, and all the regs related to repair.

Lots of these sanded rivets around, some shops dont care.
It was an eye opener when shopping for a Baron 2 years ago, turned down 2 nice Baron because of sanded rivets.

Please keep us informed. Inquiring minds have nothing better to do than hang out here on BT.

when i purchased last plane my mechanic was fanatical about looking for any sanded rivets and a little dimple on top needs to show. problem with asking a fsdo is the fact that they may all have differing opinions and i certainly wouldn't show them the plane that's in question for that could be a recipe for disaster.

gary

This is from Paul New at Tennessee Aircraft Services:

There isn't anything documented on how far a rivet can be sanded down, to my knowledge. However, the general rule of thumb for structural members is a maximum loss of 10% of the cross sectional area. On a standard universal head AN470AD or MS20470AD rivet, this amounts to about the depth of the dimple on the top of the rivet head. If the head of the rivet has been sanded down till the dimple is no longer evident, the rivet should be replaced. Sometimes paint will fill the dimple so one must ensure the cause.


If enough sanding was done to marginalize the rivet heads, I'd also have some concern about the skins in that area as well.

Tell that to the rivets that are holding you wing upper surface on! When you fly
along, it looks like a rag wing out there! The rivets are the only thing keeping the
skin on! You could calculate the force on each from the pounds per square foot.

They of course work great in shear, also.

BH

"...An insurance adjuster told me of a case where a new employee at a paint shop had sanded a king Air in preparation for paint, well the insurance company ended up owning a 4 year old King Air that could not be repaired....."

I remember that story. Somewhere in central Arkansas... Owner just told Insurance Company to take it. And I heard that later, shop in NY state bought it and replaced the rivets.

Beech aircraaft have specifications for structural rivets. If the heads are sanded down the rivet no longer meets specification and replacement is required since the aicraft is no longer is in complianace with its type certificate engineering drawings. There are nondestructive methods to remove pain. Any paint shop that sands aircraft sheet metal and rivets to remove paint is not a professional shop. All aircraft external sheetmetal is alcad aluminum. It is heat treated to increase strength but tempered aluminum is highly succeptable to corrosion. It therefor has
a thin coat of pure aluminum on eash side to prevent corrosion. That is why it is called alcad. Sanding will remove this thin coat of alcad, thereby setting up a condition for corrosion over all areas that are sanded.

R Martin
A&P AI