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Corrosion in Aileron Push Pull tube

H

hudgin

Well Known Member
Both of my aileron push pull tubes have corrosion on them. One is worse than the other. I seem to remember that 10 % of the thickness is the limit before it has to be replaced. Is that correct?
 
Did you prime them? This tubing isn't alclad, so it needs protection from corrosion.
 
hudgin said:
Both of my aileron push pull tubes have corrosion on them. One is worse than the other. I seem to remember that 10 % of the thickness is the limit before it has to be replaced. Is that correct?
Click to expand...

10% is the generally accepted standard, but Van's doesn't actually spec that number in their manual anywhere so if you want an "official" answer you will need to ask Van's.
 
They were primed with a good coat of zinc chromate. Where they havent corroded the chromate is changing color.

10% is good enough for me, I will change them out. Thanks
 
hudgin said:
Both of my aileron push pull tubes have corrosion on them. One is worse than the other. I seem to remember that 10 % of the thickness is the limit before it has to be replaced. Is that correct?
Click to expand...

Is this from the stick to the bell crank or from the bell crank to the aileron?

I'm wondering because one is a bit easier to inspect on a regular basis than the other...
 
hudgin said:
They corroded under the aileron boot at the net entrance into the fuselage.
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Zinc Chromate is a sacrificial coating offering very little abrasion resistance. It makes sense that the boots wore through the coating defeating its ability to protect the base metal. All that was needed was moisture which probably soaked the boot allowing the moisture to sit for periods of time instead of evaporating.

The color change you are seeing in the chromate layer is it is corroding as it is supposed to. However, once it has converted, it no longer can inhibit and the corrosion will seek its next victim.

I would be curious to know what your boot was?
Regardless, a two part epoxy would protect this area better next time.

Good catch.
 
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The boot material is Naugahyde, is suppose flying in weather IFR captured moisture. The damage has occurred in only a one year time since last annual which is really fast I thought till I learned the tubes are not alclad. The new ones will get epoxy. They say if you learn something new you get to go home but then I'll never get to fly.
 
Currently doing an annual on my RV9A, and much to my surprise it turned out my aileron push / pull tubes were severely corroded under the boots (preventing) air getting into cockpit.
I suggest you to have a look in case you have these boots fitted, especially if your tubes have not been primed
It seems the fabric inside the boot can actually hold a lot of moisture leaving the alutube in a moist environment. Tubes were not primed, but the new ones will!
I plan to have new boots made from same material as light raincoats, a good primer and finally cover the tube under the boot with heat shrink tube…..Comments pls
Any one else since 2005 who have seen this corrosion, and what measures were taken?

Lasse
FPLLE RV9A
Flying since 2017
 

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Thanks. Mine were just going in. I'll bring them home and shoot 2K epoxy primer on them over the P60G2.
 
Several years ago mine were corroded under the boots. Just had self etching primer on them.

New ones made and used 2 part epoxy primer, and 2 coats of the PPG paint the airplane was painted with. Then used some silicone wrap under the boots to keep any moisture away from the tubes. On a side note, once the plane is rigged, you can make the new ones a little longer so more (over half) of the threads are threaded in.
 
Is this the boots to keep the cold air out from the wings? I just put boots on this year. I used sleeves from a Tyvec suit so hopefully I will be ok. I cant believe how much damage from the moisture is shown in those photos. Wow.
 
LykkeEspersen said:
Currently doing an annual on my RV9A, and much to my surprise it turned out my aileron push / pull tubes were severely corroded under the boots (preventing) air getting into cockpit.
I suggest you to have a look in case you have these boots fitted, especially if your tubes have not been primed
It seems the fabric inside the boot can actually hold a lot of moisture leaving the alutube in a moist environment. Tubes were not primed, but the new ones will!
I plan to have new boots made from same material as light raincoats, a good primer and finally cover the tube under the boot with heat shrink tube…..Comments pls
Any one else since 2005 who have seen this corrosion, and what measures were taken?

Lasse
FPLLE RV9A
Flying since 2017
Click to expand...
I would wager you live in a coastal location with plenty of salt air?
 
Walt said:
I would wager you live in a coastal location with plenty of salt air?
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Around 54 Nm to the sea, but as only the part of tubes under the boot is corroded I take it’s due to moisture accumulated in the fabric / synthetic leather that boots are manufactured from
 
LykkeEspersen said:
Around 54 Nm to the sea, but as only the part of tubes under the boot is corroded I take it’s due to moisture accumulated in the fabric / synthetic leather that boots are manufactured from
Click to expand...
Looking at your pictures, it appears that there are signs of corrosion on skins and ribs as well.
Do you regularly fly around the coastal area?
 
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