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By:    Dale Vandever (N2DV)


Holger von Bulow, a PA-39 driver has been thoughtful enough to share with members his experience with a very serious corrosion problem. The problem was discovered during disassemble of the aircraft for painting.

Be sure to check this on your next inspection. Or maybe sooner!




Comanche Tail Corrosion-by Holger von Bulow

During dismantling for painting of PA-39-114 severe corrosion was found on the right aluminum block assembly holding the tail torque tube, which itself has been the subject of several articles in the FLYER.

A picture is attached showing how about ONE QUARTER of the material is missing on the top part of the block.  (Part Number 20208-08)

The block was inspected during the annual in May and no corrosion was seen.

However, the block had been painted and the paint cover was still intact although the material under it had turned into powder.  This did not become evident until the block was touched with a screwdriver during disassembly of the tail.

I can only advise that during inspections these two blocks (right and left) be probed with a pointed tool for hardness and integrity.





I purchased my third Comanche this summer. N7998Y.  It is a great airplane and I'm thrilled with it. I always use experienced Comanche mechanics on pre-buy inspections and this time was no exception. During the inspection my mechanic found several interesting things that most mechanics probably would not have since he knows the hot spots for this type and where to look.

Among the items he found was a torque-tub bearing support block that was extensively corroded due to paint stripper. Just like the other gentleman in the prior posts.  The seller had my mechanic replace it with a new unit in a couple of hours.  They found it by pulling the tail access panel on the starboard side and looking aft.  Using a dentist's pick, he poked the material on the blocks and it gave way to reveal powdered metal.  Same situation. This appears to be a sore spot that gets hurt during paint jobs.  This aircraft was painted about ten years ago.

Several points.  First, get a thorough pre-buy from an experienced Comanche mechanic. Fly him/her in if you must.  Second, look at this area closely if the aircraft has been painted. (You can also see how careful the painters are buy looking at the win g skin above the landing lights.  My last Comanche had corrosion there from paint stripper removing the corrosion protection.

We found about $3,000 worth of items that needed to be fixed; they were.

This was an aircraft that was represented to be in excellent mechanical shape.  To be fair, the seller was not a Comanche nut, bought the airplane with the intention of keeping it for a short time, and thought they knew its weaknesses.  The seller (and the seller's mechanic) just did not know where to look. The seller was scrupulous about fixing the squawk list and I would buy another plane from them in a heartbeat.



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