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What prop hub internals can look like after 19 years of neglect


SpamPilot

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As mentioned in a separate post, I'm overhauling the McCauley C505 prop on my Rocket.  I was initially hoping for a simple reseal, but then the prop shop called me and said, "you should really come take a look at this".  Pic attached.  Fun!

The last time this prop was overhauled was 1996, and the last time it was opened up for service was 2001.  It has been hangared all its life, well inland, south of the Bay area, and pampered by its previous owner, except of course for not doing the McCauley recommended 6 year calendar time overhauls.  I am told that an overhaul (or at least a reseal) on a more regular basis would have caught and corrected the corrosion early enough that so many parts would not have needed to be replaced.  As it is, the overhaul is going to cost me 8 AMU, as opposed to 4 AMU if the parts were still in good shape, or 2 AMU if all I needed were new seals.

My shop says it's not like the blades were about to fly off because of this - the bearing races and retaining rings aren't cracked yet (corrosion pitting can initiate cracks), and the prop roots are still in good condition.  The blade pitch control was working fine.  The only clue I had was that I was starting to get grease spatters on my cowl, and maybe if I had been paying attention I would have said the leaked grease might have looked rust colored.

 

Bearings and Springs Small.jpg

Edited by SpamPilot
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Just curious what would make it rust like that?  The only thing I can think of is when the engine cools down the air cools and contracts, sucking in what ever is in your hangar environment?  And I'm not sure  what one would do about that.

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Well I hate to say it, but my propeller looked the same on the inside after 15yrs. It’s not really neglect that your seeing on the part of the pilot, it’s neglect from the guy that built that propeller.

The C505 propeller is a grease lubricated propeller vs the Red Dye oil filled variant, so it uses a very limited about of grease on the blade thrust bearings. Thats really the only place inside the hub you put grease other that some on the feathering spring. That leaves all the other steel components nice an clean for the technician to assembly the propeller without a rag to wipe his hands off, but it leaves the propeller Parts vulnerable to corrosion. You can use this method of assembly with an oil filled propeller cause when it’s built it will be filled with SAE 30 Weigh Red Oil. But it never works with a greased propeller.

In my shop my guys get greasy, an we use a lot of towels. We use acid brushes to paint a film of grease all over the inside of the hub, an it’s steel parts. Then the bearings are packed an the propeller is assembled. Yes it’s time consuming, Yes it’s nasty work, But it has to be done.

Without that step the outcome is all to predictable. The 500 Series propeller is a breathing propeller. Meaning outsIde air(very slight amount) enters the hub when the propeller actuates. It’s not sealed like the oil-filled version.

Once moisture lays on the steel components, it’s rusts. A film of grease painted on said parts will ensure this doesn’t happen. 
 

3772F678-595E-445A-A0D9-A687FA0C91E5.png

Edited by Cody Stallings
Fat Fingers
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