Smoking Rivets - repair advice

I just noticed a few "smoking rivets" on the underside of the horizontal stabilizer of my -4. The aircraft is about 16 years old and has about 800 hrs TT. The rivets shown in the attached photo fasten the skin to the flange of the aft spar. One is loose. The others seem secure. Here are my questions:

What is the urgency to repair these?
?Before further flight?
?At my convenience (within the next month or 2)?
?At annual (November)?

Should I drill them out and replace with new, or re-squeeze?

Should I install a new rivet between each smoking rivet?



Fortunately, these rivets are reasonably accessible (must remove only the elevator), and can be squeezed.

Thanks,

If they are that easy to get to, I'd go ahead and replace. Usually a smoking rivet or two isn't a huge concern, but something I address whenever I find one.

Fairly common problem.

http://www.vansairforce.com/community/showthread.php?t=60955

A lot of good advice in this thread and seemingly a not uncommon problem on the early kits. The problem seems to stem from overly deep countersinks in .032 skin, so any repair will need to take this into account. Simply replacing the rivets will probably just result in them smoking again down the road. If its only a few then I would lean toward new rivets in between.

First, I'd make sure they are all smoking. Oftentimes, rivet dimples can collect oil and exhaust and look like they are smoking, but really are nice and tight. If one is verifiably loose, then by all means replace it - but some of them may just be dirty. I never casually replace rivets, because you always end up with oversized holes (at least a little bit).

I agree with Paul, it looks like dirt/oil to me.

A one time fix

Give them another slight squeeze. I know A&P's that use this fix on certified aircraft. If they continue getting loose after that they need to be replaced. Steve

I'm hesitant to 're-squeeze' a loose rivet. Rivets work harden in the process of being set initially and squeezing a hardened rivet might cause cracks to form.

I prefer to carefully replace a loose rivet if it is a safety issue.

I believe that a significant factor in the development of "smoking rivets" is poor dimpling/countersinking practice. It results in the dimples not "nesting" well, kinda like stacking tea cups, they don't fit inside of each other well and leaves them open to "rock" under tension from flight loads.

Dittos on hardening vis-a-vis resqueezing/setting.

Honoring Mr. Dye's opinion, fresh rivets, if carefully driven, will reduce further enlargement and skin distortion.

For more, consider attending my sheet metal workshop at the Capital Air Show in Sept. in Sacramento, CA.

Z-EDD said:

http://www.vansairforce.com/community/showthread.php?t=60955

A lot of good advice in this thread and seemingly a not uncommon problem on the early kits. The problem seems to stem from overly deep countersinks in .032 skin, so any repair will need to take this into account. Simply replacing the rivets will probably just result in them smoking again down the road. If its only a few then I would lean toward new rivets in between.

Click to expand...

Thanks to all for the input. After machine countersinking the HS skin so many years ago, I recall wishing I had dimpled the skin, instead. Subsequent to the HS, dimpling was the 1st choice, machine countersinking was used only when the thickness made it impossible to dimple.

I think I will add a rivet in between each of the smoking rivets and I will remove all the smoking rivets. I had hoped to dimple for the new rivets, but I am concerned about simultaneously dimpling 2 layers of 0.032 stock - especially given Scott's warning in the thread referenced above. I think I will borrow a pneumatic squeezer and make some samples using scrap. For the rivets to be removed, I will try to use the NAS 1097 rivets in #4 size.

I'll post some pictures after the task is complete.