Corrosion On Propeller Leading Edge

TylerSC

TylerSC

Pre-takeoff checklist
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TylerSC
Coming back to my plane yesterday, a week or so after a washing, I found a salt-like substance on the leading edges of my fixed aluminum prop. Upon close inspection there was a lot of roughness and some minor pitting in the leading edge. After reading up on corrosion, I decided to take some 220 sandpaper and smooth it out. It didnt take much hand sanding at all to get to clean metal. I followed up with some Flitz by hand, and wiped the edges with a little motor oil on a rag as a protectant.

Does this sound like a reasonable solution to the problem? Is there a better way to prevent future corrosion?
 
The whole thing probably needs to be redone. The paint is gone from the leading edge and the back side is pretty rough. A previous owner polished the front face and who knows whether that was done properly. I'll send it out to be overhauled at annual.

I don't think I did enough to change it aerodynamically, we are talking about a few strokes by hand with some fine sandpaper.
 
do a google search on the legalities of polishing a prop. for most props, it is considered a un-airworthy modification. the paint is an corrosion protection from the manufacturer and must be maintained. I asked hartzell about it before I polished my constant speed and they said not to do it, I admit i did it anyway. (its on an EAB so it is legal, even if it is unwise)
bob
 
TylerSC said:
I don't think I did enough to change it aerodynamically, we are talking about a few strokes by hand with some fine sandpaper.
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May not have, but keep in mind the leading edge of a airfoil is the most critical part, it sets up the entire airflow. Propeller manuals state that origional contour must be maintained. An example of airfoil criticality: a wing leading edge dent greater than 0.125" depth on a Boeing 727 requires repair before further flight.
 
TylerSC said:
Coming back to my plane yesterday, a week or so after a washing, I found a salt-like substance on the leading edges of my fixed aluminum prop. Upon close inspection there was a lot of roughness and some minor pitting in the leading edge. After reading up on corrosion, I decided to take some 220 sandpaper and smooth it out. It didnt take much hand sanding at all to get to clean metal. I followed up with some Flitz by hand, and wiped the edges with a little motor oil on a rag as a protectant.

Does this sound like a reasonable solution to the problem? Is there a better way to prevent future corrosion?
Click to expand...

Oh My! o_O
 
unsafervguy said:
do a google search on the legalities of polishing a prop. for most props, it is considered a un-airworthy modification. the paint is an corrosion protection from the manufacturer and must be maintained. I asked hartzell about it before I polished my constant speed and they said not to do it, I admit i did it anyway. (its on an EAB so it is legal, even if it is unwise)
bob
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That is funny. "I was told not to do it, but I did it anyway". Sounds like someone else around here! lol
 
TylerSC,

My aluminum prop, 37 years old and 900+ hours, had the same condition (white powdery corrosion) on the leading edge on the curved side .

Polishing it out ( I'm an A&P) and coating it with oil was only a temporary fix. The corrosion returned.

I sent it out for overhaul, and gained a small amount of performance due to the flat side being smooth, the leading edge being returned to the correct profile, tracking and angles, etc. being checked/reset.

Bob.
 
TylerSC said:
Coming back to my plane yesterday, a week or so after a washing, I found a salt-like substance on the leading edges of my fixed aluminum prop. Upon close inspection there was a lot of roughness and some minor pitting in the leading edge. After reading up on corrosion, I decided to take some 220 sandpaper and smooth it out. It didnt take much hand sanding at all to get to clean metal. I followed up with some Flitz by hand, and wiped the edges with a little motor oil on a rag as a protectant.

Does this sound like a reasonable solution to the problem? Is there a better way to prevent future corrosion?
Click to expand...


Are you kidding? Now that you put oil on it, it must be washed with a mild detergent and rinsed in distilled water and wiped dry with a kitten.
 
biplanebob said:
TylerSC,

My aluminum prop, 37 years old and 900+ hours, had the same condition (white powdery corrosion) on the leading edge on the curved side .

Polishing it out ( I'm an A&P) and coating it with oil was only a temporary fix. The corrosion returned.

I sent it out for overhaul, and gained a small amount of performance due to the flat side being smooth, the leading edge being returned to the correct profile, tracking and angles, etc. being checked/reset.

Bob.
Click to expand...

Thanks Bob, the plan is to have it overhauled at annual time.
 
unsafervguy said:
the paint is an corrosion protection from the manufacturer and must be maintained.
bob
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Show me a FAR "regulation" saying that?
think about it, if what you say is true, every prop in GA is unairworthy soon as the leading edges are bare.

After the prop leaves the props shop, and begins service there is no FAR enforceable requirement for you to do anything to it.
the finish placed on the prop, under the paint is called "Anodizing" That is an electro-chemical process of producing a Hydroxide coating that is resistant to corrosion. You can not do this in the field.

SO how can it be maintained in service?
 
TylerSC said:
Thanks Bob, the plan is to have it overhauled at annual time.
Click to expand...

If you like your prop, never have it overhauled.
take it to the prop shop and have them IRAN it. Inspect and repair as necessary, they will then strip, clean, inspect, and repair as necessary to return to service.
When you have it overhauled the prop shop is bound to do the complete processes contained in the overhaul manual. and many props fail those requirements, simply because they have been overhauled before and were ground down to the minimum blade profile at that time, and now can't be ground as required and meet minimum blade profile.
 
Timbeck2 said:
Are you kidding? Now that you put oil on it, it must be washed with a mild detergent and rinsed in distilled water and wiped dry with a kitten.
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You've been reading ICAs again.
 
Naw, I can't stand those. Waaaaay too bitter. Sam Adams Octoberfest at the moment.
 
Tom-D said:
If you like your prop, never have it overhauled.
take it to the prop shop and have them IRAN it. Inspect and repair as necessary, they will then strip, clean, inspect, and repair as necessary to return to service.
When you have it overhauled the prop shop is bound to do the complete processes contained in the overhaul manual. and many props fail those requirements, simply because they have been overhauled before and were ground down to the minimum blade profile at that time, and now can't be ground as required and meet minimum blade profile.
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Thank you, that is very good advice.
 
TylerSC said:
Thanks Bob, the plan is to have it overhauled at annual time.
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Consider having it dynamically balanced as well after the overhaul. The dynamic balancing balances the prop and engine combination for the smoothest operation. Cost, about $350.
 
flyzone said:
Consider having it dynamically balanced as well after the IRAN. The dynamic balancing balances the prop and engine combination for the smoothest operation. Cost, about $350.
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FTFY,
 
Tom-D said:
FTFY,
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No, meant OVERHAUL ... this from AOPA ... https://www.aopa.org/news-and-media/all-news/2013/july/16/propeller-care-overhauls

"... One maintenance option that is available to owners operating under Part 91 is the “inspect and repair as necessary” or IRAN. As opposed to a complete overhaul, this procedure involves disassembly, inspection, and repair on an as-needed basis versus the overhaul requirements set by the manufacturer, which may be much more stringent on component replacement. It’s better than waiting beyond TBO, but it is also a false economy, depending on your situation. The difference in cost between an IRAN and an overhaul may be quite close, and you will still have a propeller with the same “time since overhaul” when you’re all done. Communication with the propeller shop is the key to making good decisions here. Check in with them as soon as they have completed the inspection, discuss the options, and make an informed decision. ..."
 
flyzone said:
No, meant OVERHAUL ... this from AOPA ... https://www.aopa.org/news-and-media/all-news/2013/july/16/propeller-care-overhauls

"... One maintenance option that is available to owners operating under Part 91 is the “inspect and repair as necessary” or IRAN. As opposed to a complete overhaul, this procedure involves disassembly, inspection, and repair on an as-needed basis versus the overhaul requirements set by the manufacturer, which may be much more stringent on component replacement. It’s better than waiting beyond TBO, but it is also a false economy, depending on your situation. The difference in cost between an IRAN and an overhaul may be quite close, and you will still have a propeller with the same “time since overhaul” when you’re all done. Communication with the propeller shop is the key to making good decisions here. Check in with them as soon as they have completed the inspection, discuss the options, and make an informed decision. ..."
Click to expand...
Who cares if an arbitrary clock gets reset or not? Even in that article they say time isn't really a factor.
 
TylerSC said:
Coming back to my plane yesterday, a week or so after a washing, I found a salt-like substance on the leading edges of my fixed aluminum prop. Upon close inspection there was a lot of roughness and some minor pitting in the leading edge. After reading up on corrosion, I decided to take some 220 sandpaper and smooth it out. It didnt take much hand sanding at all to get to clean metal. I followed up with some Flitz by hand, and wiped the edges with a little motor oil on a rag as a protectant.

Does this sound like a reasonable solution to the problem? Is there a better way to prevent future corrosion?
Click to expand...

Yes, that does sound reasonable. There are a few more steps, including certifying the preventative maintenance, but you got the general idea. Anything more, a mechanic should be consulted.
Excerpt from the Sensenich repair manual below.

upload_2017-10-15_8-37-26.png
 
Your prop may be an indication that your soap of choice promotes corrosion on aluminum. What did you use to wash the plane?
 
Stewardb has a good point. When I was in the Navy we dressed the props on the P-3 with 300 grit (or so) emery cloth then fine scotchbrite then alodine. It was a Hamilton Standard prop.
 
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Float pilots wipe prop leading edges with Pledge or Plexus after cleaning the windscreen. Erosion is the enemy there but the prevention is the same.
 
Tom-D said:
Show me a FAR "regulation" saying that?
think about it, if what you say is true, every prop in GA is unairworthy soon as the leading edges are bare.

After the prop leaves the props shop, and begins service there is no FAR enforceable requirement for you to do anything to it.
the finish placed on the prop, under the paint is called "Anodizing" That is an electro-chemical process of producing a Hydroxide coating that is resistant to corrosion. You can not do this in the field.

SO how can it be maintained in service?
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From ac 20-37e

e. Blade Polishing. The FAA receives frequent inquiries from airplane owners and maintenance personnel asking whether it is acceptable to polish propeller blades. It is almost always not acceptable. Corrosion protection such as paint and anodize should not be removed from the surface of a propeller blade. Propeller blades must be maintained to the type design. If the original design had corrosion protection and the instructions for continued airworthiness call for corrosion protection, then the corrosion protection should be maintained to those instructions.

Yes, I know ac's are not regulatory, but why do something that the faa says is not
acceptable and could get your aircraft red tagged, and the manufacture does not find acceptable.

If your poi say nothing great, until somebody else in the faa sees it and does not like it and issues a red tag. Yes you can fight it, and probably win, but why stir up the hornets nest.

Bob
 
Tom-D said:
After the prop leaves the props shop, and begins service there is no FAR enforceable requirement for you to do anything to it.
Click to expand...

You mean like an annual or 100 hour inspection? FAR 43, appendix D below:

(h) Each person performing an annual or 100-hour inspection shall inspect (where applicable) the following components of the propeller group:

(1) Propeller assembly - for cracks, nicks, binds, and oil leakage.

(2) Bolts - for improper torquing and lack of safetying.

(3) Anti-icing devices - for improper operations and obvious defects.

(4) Control mechanisms - for improper operation, insecure mounting, and restricted travel.
 
JAWS said:
You mean like an annual or 100 hour inspection? FAR 43, appendix D below:

(h) Each person performing an annual or 100-hour inspection shall inspect (where applicable) the following components of the propeller group:

(1) Propeller assembly - for cracks, nicks, binds, and oil leakage.

(2) Bolts - for improper torquing and lack of safetying.

(3) Anti-icing devices - for improper operations and obvious defects.

(4) Control mechanisms - for improper operation, insecure mounting, and restricted travel.
Click to expand...

Can you as the owner "DO" the inspections

"DO was meant "DO" maintenance repairs or what ever.

there is nothing saying the prop needs anything repairs during service.
Inspect it is all there is.
 
AKBill said:
Stewardb has a good point. When I was in the Navy we dressed the props on the P-3 with 300 grit (or so) emery cloth then fine scotchbrite then anodized. It was a Hartzell prop.
Click to expand...
And when they came to AIMD we worked the hell out of them with a big file.
then balance them with a static balancer.
and by the way, P-3 props are Hamilton Standard.
and you at the squadron level can't do Anodizing. All you had was Alodine 1200. We at AIMD couldn't even do Anodizing
When a blade needed anodizing it went to Depot level.
 
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