Stab Horn Question

[Jim Worley]

All,
I am gearing up to inspect my horn, hopefully in the next few weeks. My A&P brought up a question. Does the NDT need to be done by a certified test person/station or can it be done using a dye penetrant kit like you can buy from Spruce? She was talking about sending it off to have it tested. It doesn't seem that others have done that. I just want to make sure that the test, when complete, will have the best chance of being accepted bythe FAA when the AD eventually comes out.
2nd Question: I'm based on the gulf coast. I can see light surface corrosion on the torque tube between the stab and the fuselage. After removing it, prior to reassembly, is zinc chromate the right thing to use to paint the entire thing to try and prevent furture corrosion?
Previous owner had the bearings replaced a couple years ago, but did not do anything other than a visual horn inspection. Hopefully the bearings and bolts will be good.
Sorry if these topics have already been addressed. I couldn't find them in previous posts. Thanks to everyone for all the great information they put in this forum.

[Kristin Winter]

Jim,

A dye penetrant check is satisfactory for actually finding the crack. All the horns that have been discovered to be cracked, didn't even need the dye pen. the cracks were visible.

As for the horn, refer to SB 1160, which addresses the torque tube. Assuming it is not undersized, I would recommend that it be cad-plated before reinstalled. You will also likely need new hardware.

The horn bolts can be difficult to remove if they are corroded inside the horn. You may need a bead blaster or a wire brush on an extension so you can get down in there and remove the corrosion from the bolts. You will have to turn the bolts a couple of times to get the corrosion off the whole thing. Liberal use of penetrating oil is a good thing.

[JIMICS2452]

I have been involved in three horn inspections. No cracks found, but all of the torque tubes had light corrosion and we undersized in the corroded area. Peninsula Metal fininsheing in Orland has the recommended process from the AD and has done a good job for ~ $350.

Jim Hiatt

[Bruce Thumann]

[Revyskibum]

[Jim Worley]

Well, it's out! Hopefully tested in the next couple days. New bolts on order. No visible cracks. Fingers crossed that the testing will come back good as well. I keep everyone advised of the progress and fill out Hans' questionaire as soon as I know!

v/r
Jim

[Zach Grant L1011jock]

If its cracked...you will see it. Not one yet that was cracked that wasn't immediately visible.
-Zach

[RLF]

[9089P]

[RLF]

[RLF]

[9089P]

[Diller]

[RLF]

[Jim Worley]