Wing Lower Spar Cap Corrosion

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4 months 1 week ago #3244 by STEVE ELLS
Replied by STEVE ELLS on topic Wing Lower Spar Cap Corrosion
Sam;

50 hours should be enough flight time to get to Key West and back.

You need to suspend flying until you are able to work out the details of when Paul can fit it in.

Then pick a good weather day to get the airplane to Tennessee.

Let me know how it is going.

Steve

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4 months 1 week ago #3243 by Sam Parish
Replied by Sam Parish on topic Wing Lower Spar Cap Corrosion
Steve I sure appreciate you and your detailed explanation, I will contact Paul and see what we can work out. I am in Fort Worth, Texas and wondering if a ferry flight to Paul would be possible as the SEL allows 50 hours of flight time if corrosion is found but no crack, which is what I have. Thanks again and I will sure keep you posted on this issue.

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4 months 1 week ago #3239 by STEVE ELLS
Replied by STEVE ELLS on topic Wing Lower Spar Cap Corrosion
Hi Sam;

Paul New at Tennessee Aircraft got back to me. He said he has seen this type of problem on Cardinal wings before. For what it's worth, yours is not the worst he's seen.

He told me that if you bring it to his shop he would remove all (32) of the rivets in that line. Then would get a good look at the corrosion. If it's not too bad he would clean up the surfaces and then apply Ardrox AV-8 corrosion inhibitor to both surfaces.

The next part is where it gets tricky. New discovered there's no method (going to next bigger holes, etc.) that seemed to prevent the rivets from "smoking" again. When a rivet "smokes" it means that there's motion between the rivet and the part--the smoke is aluminum oxide.

New came up with a method that fills the holes, and provides for rivets that can be bucked to the dimensions called out in AC 43-13-2A.

New uses DD rivets. These are often called icebox rivets because aft being heated to soften them, they must be stored at a low temperature prior to using or then harden.

New bought the correct size rivets, then had to buy a temperature controllable kiln to heat the rivets to 870 def F to soften (heat treat) them. These rivets are excellent for this purpose because when they are driven in the softened state that "fill" holes that are slightly oversize.

The rivets will begin to harden within in 30 minutes after heating.

The next step in the process is to manufacture a bucking bar that will fit between the spar cap and the attach part. New made one out of tungsten because it's much heavier than steel and a smaller bucking bar is needed in that area.

The difficult part of this task is getting the equipment to do it right, the driving of the rivets take less than an hour.

Once the rivets--which are 30 percent stronger than the original AD rivets--are driven they will get to half strength in approximately one hour. Don't fly before they reach full strength in four full days.

I believe your best bet for an effective one-time repair is to find a well equipped structural repair shop and ask them if they have ever done a repair like this. If not, keep searching or book an appointment with New at Tennessee Aircraft.

Please keep me in the loop on how things work out.

Steve

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4 months 1 week ago #3231 by STEVE ELLS
Replied by STEVE ELLS on topic Wing Lower Spar Cap Corrosion
Hi Sam;

Ouch! Based on the fact the manufactured head of one of the rivets is missing, and the extend of corrosion is not known, my opinion is that a detailed extension to discover the extent of the corrosion will require the rivets along that line to be removed.

The best shop I know for that type of inspection is Tennessee Aircraft in Jackson, Tenn. The owner is Paul New--his shop knows a great deal about Cessna airframe corrosion.

I have sent him this picture and asked for his opinion on what steps need to be taken to go forward.

When he replies I'll get back to you.

Steve
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4 months 1 week ago - 4 months 1 week ago #3230 by Sam Parish
Wing Lower Spar Cap Corrosion was created by Sam Parish
The new year is not off to a great start for me! During the annual on my '73 , C-177B, I found no cracks but some corrosion while accomplishing the wing spar cap inspection, SEL-57-03. Quirried Cessna for guidance and now need a repair station that can address the corrosion issue. Anyone have a suggestion? I am in Texas. Thanks!

Note the photo shows the white corrosion emanating from under the spar cap--it does not look too bad on the skin but what we do not know is the extent of corrosion between the spar cap and the skin. The mark indicates a rivet that was missing from the bottom of the wing skin and of course dictated further investigation! The location is 8" from the wing root.
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Last edit: 4 months 1 week ago by Sam Parish. Reason: Added photo

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