Corrosion 47 PA-12

Started my annual inspection just recently and found some pinholes in the the large cross tube running from top of the back door post (right side ) on an angle to just behind the baggage on the left side of the plane. This tube is round and larger than the rest. I really need to know what type of steel this is and the thickness, Thanks

Dave

Hey UTb44e,

Your looking at this problem all wrong,I would just cut that piece out of plane,if it aint in the airplane corroding it won't be of any worry, heck who needs it. It would lighten ya up a bunch too. I saw some other extra tubing that I think could come out as well. My daddy always said if you ain't used in the last week get rid of it. Give me a call and we'll get started.

Tubing

This is the data I used on my 337 for replacement of that tube, I believe this is the one you are talking about. Hope it helps.

Tray

(1) Removed diagonal cross tube running from right rear wing attach point at Station +41 to the upper left longeron at Station +77. Replaced the cross tube with a ?Chair? assembly. Welded bracket to apex of ?Chair? for an attachment point for rear seat shoulder harness. Installed a ?Chair? type assembly between right rear wing attach point at Station +41, left rear wing attach point at Station +41, upper right longeron at Station +77, and upper left longeron at Station +77. At apex of chair assembly, installed an attach point to connect a shoulder harness for the rear seat.
(2) The ?Chair? assembly adds additional clearance to the rear of the aircraft.
(3) The ?Chair assembly was installed so as not to impact the freedom of movement of the control cable for the right flap.
(4) Supporting Data:
(a) Piper Aircraft Corporation Frame Assembly Fuselage Drawing Number 20875 with last revision 8/17/49 shows the diagonal cross tube being removed. It is listed as part number 76, is 1-1/8? OD, 0.035? wall thickness, and constructed of AISI 4130 Chromium-Molybdenum Steel Tubing.
(b) Piper Aircraft Corporation PA-14 has similar chair assembly in its original design, refer to Piper Aircraft Corporation Fuselage Assembly Superstructure Assembly drawing 11046 last revised 12/27/48.
(c) The ?Chair? support brace installed is constructed of 7/8? OD, 0.049? wall thickness, and AISI 4130 Chromium-Molybdenum Steel Tubing. A drawing and pictures are attached for further reference.
(d) The shoulder harness attach point for the rear seat is constructed of 1? wide, 1/8? thick AISI 4130 Chromium-Molybdenum Steel, with a 5/16? hole drilled in it. It is shown on the attached drawing and pictures for further reference.
(e) Station measurements are from Datum line located at the leading edge of the wings.
(f) All welding accomplished in accordance with AC 43.13-1B/2A Chapter 4, Section 5.
(5) Weight and Balance has been updated following this modification.
(6) This modification will be added to the list of items on the aircraft inspected in accordance with Federal Aviation Regulations Part 43, Appendix D ?Scope and Detail of Items (as Applicable to the Particular Aircraft) to be included in Annual and 100-hour inspections.

utb 44E said:

Started my annual inspection just recently and found some pinholes in the the large cross tube running from top of the back door post (right side ) on an angle to just behind the baggage on the left side of the plane. This tube is round and larger than the rest. I really need to know what type of steel this is and the thickness, Thanks

Dave

Click to expand...

"Tip of the ice berg" comes to mind. Been there done that, after it was all over 85% of the fuselage had been replaced. Crash

Crash is right on. If you have corrosion in the diagonal tube, you better get real active with checking out the rest. Go right to the bottom longerons by the tailpost, and also the tailpost tube and do some drilling man and check out the wall thickness... Corrosion is a bad thing, and where water collects you can anticipate it. The tail area will show the real story. But corrosion in the diagonal tube... wow..... only time I heard of that is when a plane went upside down into the saltwater, and all of the tubes went to He11 in a handbasket.

Corrosion search

It is very unlikely that you have found the only corrosion. Do not begin repairs until you have checked all the tubing at its lowest point. If you find corrosion anywhere else chances the fuselage is rotten in many more places. Most PA-12's and 14's are on their last legs. It will likely be cheaper in the long run to replace the whole fuselage than repair multiple sites. Remember, with a repaired fuselage you will always be dreading every annual because you will be waiting to discover new corrosion somewhere else. With a new fuselage you can be confident that the corrosion problem is over for many years and the resale value will be much higher.

delete

Ya, it's only pushing 60 years old, the rest of it must be sound. Sand blast it and I bet you $100.00 you will find holes from end to end. You'll wish you'd saved the money you wasted on sand blasting. Fix the tube, sell it and buy a late model PA-18. Thats the best advice I can give you. Crash

I agree with TJ. Just because one tube has corrosion doesn't necessarily mean there is more. Is the tube corroded from the inside or outside? If outside it may be due to some external cantamination in that area, like a spill of some chemical , or water dripping on it. It's worth a check. If I spend $100 sandblasting and find the rest ok, then I've saved $12000. If I find extensive corrosion, then I've only lost $100. And if I'm going to spend $12000 on a new fuselage, what's a hundred bucks?

TJ, I think I know the answers also!

John

utb 44E said:

Started my annual inspection just recently and found some pinholes
Dave

Click to expand...

Dave-

Since this is an annual and not a total rebuild, answer these questions:

When was it rebuilt?
Did they sand blast the frame and check for corrosion?
If so, what kind of corrosion proofing was done?
What kind of climate was the plane in?

The answers to these questions will help you make a decision on if a total tear down & inspection is the right decision.

Tim

Tim, to answer your questions;
Plane was rebuilt 92-94 and was stored indoors.

I do not know if the frame was sandblasted or treated for corrosion.

Climate was Minnesota and then Nebraska for a couple months.
I bought the plane May of 04 and the only time it was outside was at New Holstein.

All comments and help are greatly appreciated and I thank you all! Final decision belongs to my AP/IA since he has to sign it off.

To complicate matters we found only this one isolated spot of corrosion, and no other places. FYI I removed the paint from the entire length of the tube. Corrosion free except the one area. Area is only about 2" long and the pinholes form an oval. Theorizing now it appears that the battery may have leaked at some time in the past and an inadequate clean up was performed. Theory # 2 whatever the solvent /glue/ cleaner was that the installer of the previous headliner used caused the corrosion. Def a mystery.
Dave

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utb 44e,
Now I am confused, 'battery leak'? Are we talking the diagonal above the headliner that runs from aft left to front right? Either way, investing in a good sandblasting of the entire fuse is $$ well spent. Even if you do pony up for a new one, you know what parts you've got to sell on the surplus market.
Good luck, and NOT ALL -12's and -14's ARE ON THEIR LAST LEGS. Restored, it's a great airplane. No the limits of it's envelope aren't as extreme as a -18, but they come close and it all depends on what you want to do with it. Every airplane is a compromise.
Regards
Chris

Just be sure to get it repaired by July 22, 2005.

FORTYSIX12 said:

Just be sure to get it repaired by July 22, 2005.

Click to expand...

OK I'll bite----why??

Me too.
OSH Departure????????????

New Holstein Departure

Tj is right. Great and funny post.

I guarantee it is not just a 12,000 dollar fuselage, it is a 40,000 dollar fuselage, or more. It is no simple "swap" it is a total restoration. Be careful before you jump off that cliff. After a thorough check you may have to jump but I would not do it based on finding one small spot.
Good luck, hope to see you at New Holstein.

Bill

I also agree with TJ. I ran into the same problem on my '47 12 during the reconstruction in the same place. I will post a photo. My IA found a pinhole and upon further probing, was able to punch through with ease. He blasted the entire fuselage and found a few other areas of pitting. Punch tests (hard as he could with an ice pick in the pits) didn't penetrate anywhere else on the longerons. The handle on the lower right looked like swiss cheese though after being cleaned. Sections of the aft longerons had been replaced in previous repairs.

As for an acid bath, there was little evidence on the diagonal tube of external corrosion. It appeared that most was from the inside out. The rear doorpost was in good condition. The IA sleeved and rosette welded a replacement of the bottom 6 " of the diagonal Replacing the entire tube would have gotten into the right rear wing attach point.

Was it a good choice to go with this fuselage instead of a new one ? Cost of repairs is a consideration. Increasing the budget another 5000-7000 above the cost of repair could (or would have) put the project beyond reach.

Wayne

How did this ever turn out? I'm at a similar stage needing to decide to go full new fuselage or blast inspect repair mine on my 14