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Thread: FAA request for info

  1. #1
    Farmboy's Avatar
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    FAA request for info

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    wireweinie's Avatar
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    Someone needs to explain to me the part about the corrosion preventative oil being burned off as a result of powder coating.

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    I'd be more interested in whether these planes parked outside and if/how the rudders were locked. The prejudicial statements about powder coating sound like a witch hunt.

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    BC12D-4-85's Avatar
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    I've had a couple cub rudders with Whelen rotating beacons faired to them with a large fiberglass mount. Don't recall any vibes in the rudder pedals. It was a big heavy unit. Stewart's prior use of a gust lock question is a good one. Cooking powder coating (https://www.wisoven.com/blog/your-po...tions-answered) if common might fry internal oil. Don't know but it'd be an easy test to cut one apart and have a look.

    Gary

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    If I was in that engineering department, I might mount some cameras and go flying. I used to be able to turn around and look at the empennage on climb-out - with an O-360 in a Super Cub the flapping around back there is impressive.
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  6. #6
    BC12D-4-85's Avatar
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    As I recall the rudder isn't a sealed from weather unit.

    Gary
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  7. #7
    wireweinie's Avatar
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    Quote Originally Posted by BC12D-4-85 View Post
    As I recall the rudder isn't a sealed from weather unit.

    Gary
    That's a good question. And are the stock rudders built/sealed any differently than other manufacturer's?

    What Is the typical temps used to bake powder coat? I just don't believe that it's hot enough to cook the oil (if present, to begin with).

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  8. #8
    BC12D-4-85's Avatar
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    The powder coating link in #4 suggests a range of 350-450F. Airframes and others would know more per their temp specs. I don't. The type of internal oiling might affect any cooking during powder coating. Linseed or flaxseed oil has a smoke point of about 225F so if that's used and the powder coating exceeds that then.....Tubeseal oil has a MIL-spec [MIL-L-21260E] that notes a flashpoint of 300F. Not sure what happens if heating meets or exceeds that.

    The FAA's concern notes failures but these questions are often a fishing trip in search of a problem. Control failure is unacceptable but determining the correct cause is critical. It's possible to blame something that's not and generate an AD, as in the assumed Taylorcraft strut failures that never happened.

    Gary

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    skywagon8a's Avatar
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    Quote Originally Posted by BC12D-4-85 View Post
    ...... Don't know but it'd be an easy test to cut one apart and have a look.

    Gary
    Just turn the rudder upside down, take off the tail wheel steering horn, drop a light on a wire into the tube and look. The tube is not closed.
    Most likely the rudder had been abused during it's lifetime as Stewart mentioned. Just look at a unlocked rudder in a big blow from behind. They get banged around violently.
    N1PA
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    AkPA/18's Avatar
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    Quote Originally Posted by skywagon8a View Post
    Just look at a unlocked rudder in a big blow from behind. They get banged around violently.
    It helps to make sure the tailwheel is centered and locked. This allows the springs to lessen the shock to the rudder. On floats leave water rudders down. On amphibs I run a bungee from water rudder steering arn to the rear float cleat. It can help when lacking gustlocks which I rarely use
    http://thrustline.com/

    Takeoffs are optional--Landings are mandatory

  11. #11
    BC12D-4-85's Avatar
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    Drifting some here but stout bungees added between the lift handles and rudder arm while parked can be better than a rigid gust lock. Especially if tailed into the wind.

    The FAA's RFI above seems concerned about beacon-mounts potentially having an adverse affect over time on tubing structure. And concerns about corrosion compromising the vertical tube. Next may be a SB or ? to remove the rudder arm and tap the rudder looking for exiting debris. If noted then further borescope or similar. Being as how floatplanes have been involved that may add another layer of questions and inspection requirements. In Old Alaska they'd try to slide a liner up that tube if welds or obstructions permit and go fly.

    Gary
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  12. #12

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    After observing my own rudder with a gust lock I stopped using one. Either way is bad with any wind component from the back. With the rudder free to move the wind deflects it so the vertical part of the rudder is safe enough but the top is trying to fold over. Do it long enough and something's got to give. Adding a rudder lock doesn't solve that problem and with a little disc lock up top it may make things worse by adding a torque load.
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  13. #13
    mike mcs repair's Avatar
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    Quote Originally Posted by stewartb View Post
    I'd be more interested in whether these planes parked outside and if/how the rudders were locked. The prejudicial statements about powder coating sound like a witch hunt.
    Yes Dave has prejudice against powder coating. He keeps banging this drum yet he’s dumb enough to not know the rudder doesn’t have oiled tube(only maybe the leftover manufacturing oil) Same thing he tried to do with lift struts & powder coating.


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  14. #14
    mike mcs repair's Avatar
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    that rudder probably was damaged & straitened earlier in life.... but no one is fessing up..
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  15. #15
    mike mcs repair's Avatar
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    Quote Originally Posted by skywagon8a View Post
    Just turn the rudder upside down, take off the tail wheel steering horn, drop a light on a wire into the tube and look. The tube is not closed.
    Most likely the rudder had been abused during it's lifetime as Stewart mentioned. Just look at a unlocked rudder in a big blow from behind. They get banged around violently.

    those rudder horns are usually corroded in there solid.... like you must destroy horn to remove it....
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    How do you remove powder coating for a repair? Heat?

    I love it on my rocker box covers, and don't think I would do it to a fuselage or engine mount. Tail feathers, maybe.

  17. #17

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    On the J3s, at least, the rudder horns are often loose and need re-bushing. On the other hand, the vibration back there is minimal.

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    If there was a violent tail wheel shimmy combined with a strobe or beacon for mass on the other end of the tube I could see the tube under some significant torsional strain. Assume the light on top wasn't a perfect seal to the weather and maybe even acted as a funnel and you have water in the tube for corrosion. But floatplanes can't have tailwheel shimmy unless they are on wheels.
    You can't get there from here. You have to go over yonder and start from there.

  19. #19
    mike mcs repair's Avatar
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    Quote Originally Posted by bob turner View Post
    How do you remove powder coating for a repair? Heat?

    I love it on my rocker box covers, and don't think I would do it to a fuselage or engine mount. Tail feathers, maybe.
    Just hit it with a torch then brush it off with wire brush. Simple.

    We use it on everything metal if possible since whenever they opened. Maybe 1994??


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    Saw one break there on an -18. Well maintained airplane with recent fabric and no corrosion and no damage- parked indoors most of the time. Always wondered if it had to do with the beacon... Agree that the powder coat/burnt oil theory is phony; that would be about the last place for that tube to corrode.
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    I thought Piper had a letter out on PA-18's about rust and or corrosion on the rudder tube or the tail tube , i think you are supposed to fill it up with a mixture they can provide, its supposed to keep the water out.

    Made of polyurethane and something else to inhibit corrosion.
    I will try to find letter and repost.

    It would seem like that any letter by manufacture on PA-18 would apply on the older cubs as well , Same type of frame and control surfaces, or am i totally mistaken and opening up a can of S$!&. ??????

  22. #22
    BC12D-4-85's Avatar
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  23. #23
    skywagon8a's Avatar
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    Quote Originally Posted by ak49flyer View Post
    Saw one break there on an -18. Well maintained airplane with recent fabric and no corrosion and no damage- parked indoors most of the time. Always wondered if it had to do with the beacon... Agree that the powder coat/burnt oil theory is phony; that would be about the last place for that tube to corrode.
    This makes me question the mechanic who replaced the fabric. What inspection did he/she do before installing the new fabric?

    What size beacon was on the rudder? The old style heavy Grimes motor driven rotating beacons had been installed on top of rudders of most fabric Pipers for years. This has never been a big issue before now.
    N1PA

  24. #24
    mike mcs repair's Avatar
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    The powder coater doesn’t always inspect stuff well after blasting. I got this back


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  25. #25
    wireweinie's Avatar
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    Was that chewed up before the bead blasting? Bondo'd up?

    Web
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  26. #26
    mike mcs repair's Avatar
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    Quote Originally Posted by wireweinie View Post
    Was that chewed up before the bead blasting? Bondo'd up?

    Web
    No idea. It was a costal cub so lots of salt air & saltwater beach.


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  27. #27
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    Don’t you throw them out and install atlee tie downs?


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  28. #28

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    Install them if you want to use wing jacks.
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  29. #29
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    Quote Originally Posted by mike mcs repair View Post
    that rudder probably was damaged & straitened earlier in life.... but no one is fessing up..
    Cub pilots NEVER abuse rudders, or any other tail pieces for that matter.
    I don't know where you've been me lad, but I see you won first Prize!
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  30. #30
    mike mcs repair's Avatar
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    Quote Originally Posted by mike mcs repair View Post
    Yes Dave has prejudice against powder coating.
    ...also had a beef with powder coating aluminum.... couple decades ago, as in like the pork chops for floats that go in a Cessna gear box.... long standing grudge he has been playing....
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  31. #31
    Crash, Jr.'s Avatar
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    Not sure on the temp the powdercoaters use but its up towards 300 degrees or over. You would have to call Advanced PC to see what they use. I do know that if you have to re-coat sealed struts they smoke like crazy as the oil burns off inside (if you drill them to vent of course).

    The rudders are definitely not oiled inside. All steel tubing comes from the manufacturer with a certain amount of oil on it to keep from rusting in transit and it normally stays there outside of welded areas. That could be the black residue referred to.
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