The International Cessna^® 170 Association

I was haveing a big debate on line about the klegality of polishing aluminum props. and was told it was ILEGAL. Because all McCauley and Hertzell props now have a statement in the type certificate that states,,

and I qoute.
note the date

May 3, 2002

TYPE CERTIFICATE DATA SHEET NO. P-874

Propellers of models described herein, conforming with this data sheet (which is part of type certificate No. 874) and other approved data on file with the Federal Aviation Administration, meet the minimum standards for use in certificated aircraft in accordance with pertinent aircraft data sheets and applicable portions of the Federal Aviation Regulations

provided they are installed, operated, and maintained as prescribed by the approved manufacturer's manuals and other approved instructions.

end quote

The manual states that paint is required.

My take according to Warner Propeller in Tucson and the local FSDO is that the only props that had factory service instructions to polish were Hamilton Standard and all others are illegal if polished. So if you want a polished prop you'd have to step down to a C195, Staggerwing, Stearman or the likes

My prop has been on my airplane since 1956 - it replaced the bent prop from the mid-air with the DC-3. It was overhauled by Burlington Propellor
in 1997, and came back nice and polished. (I guess MacCauley hadn't changed yet to painting in their overhaul manual.) I repainted the tips red, and got the original decals to set it off...it is exactly original!

I'll be danged if I'll paint it... since it was legal polished when it was overhauled. What, are we supposed to paint props retroactively? I was ramped checked by the FAA almost a year ago, and the guy was gushing over my airplane so much I guess he didn't notice! I'm a stickler for legallity, since my livelyhood depends on aviation, but on this I'm drawing the line...Russ Farris

Russ, I am with you. I have several inquiries in to FSDO, the airworthiness inspector told me they consider the polished prop a properly modified airworthy propeller.

you see polishing, has always been a minor alteration.

My question is

A prop is a type certificated component, as is the aircraft and engine.
aircraft can be stripped and polished and with the proper log entries can be airworthy.

why can't a prop be considered airworthy when it is properly altered just like an aircraft?

FSDO says they will get back. yeah right!

Hi Tom, thanks for the response. BTW, I appreciate the PM about the crankshaft, but I found one in 2002 when I majored my engine. It wasn't cheap either!

The FAA is getting ridiculous, IMHO. These props were bare metal for decades, and with even rudimentary care were certainly airworthy from a corrosion point of view, certainly on a hangar queen like my airplane.

Thanks for trying to get to the bottom of this. As you pointed out, 170s were bare aluminum right from the factory, and so were the props! Russ Farris

If the props can be documented as coming from the factory polished then we have a great argument it seems to me. How can we get this documented?

The gal at Warner props told me that even when they get a polished prop in for OH that looks really good there is often a lot more grinding necessary due to corrosion that is not apparant until they work on it. (maybe around the bolt heads and other areas that don't get polished very well?)

"you see polishing, has always been a minor alteration" I like that approach too Tom.

quote
The gal at Warner props told me that even when they get a polished prop in for OH that looks really good there is often a lot more grinding necessary due to corrosion that is not apparant until they work on it. (maybe around the bolt heads and other areas that don't get polished very well?)
end quote

This is a point I would like to make, the back side should be protected with a black paint. for obvious reasons.

the hub and any thing you can't see should be protected also.

After stripping my prop I was surprised to see all the ugly machining marks that were left by the factory and hidden with paint. After spending twelve hours+ sanding and then polishing I will stand behind the fact that it is more airworthy now, but it would be hard to argue. I will fly my polished prop until it gets red tagged.

Last year I flew about 30 hours in the spring rains and it was hard to keep the paint on the prop and when I let it go it started to corrode. I polished it because I thought the maintenance would be easier under those conditions and I find that to be true. I am keeping it in better condition than if it was painted. If a FAA inspector walked past an airplane that had a stripped propeller that was heavily corroded and didn't do something to get the owner's attention he'd be wrong. But at the same time if he hassled someone with a pretty one, we should gang up and beat his A**!

Kelly

Kelly

My airplane had a polished prop when I bought it. Some time ago I noticed a very slight vibration at certain low rpms and decided to have the prop checked and balanced at a prop shop. I asked them to paint it- it looks great and now no more polishing- hooray !
(I'm just plain lazy)
Rudy

Tom Downey wrote: The manual states that paint is required.

Just curious... Does the manual say paint or protective coating?
jc

What is the best way to bring the shine out on a polished prop? Can I use Nuvite and an electric buffer on a prop or are there ill effects to doing this?

Bill

Nuvite works fine. I just keep the pressures light when I'm working on the prop. A 1/4 lb. of Nuvite will last about 100 years if you are just doing the prop. I like G6 followed by S. Perfectpolish.com has some good polishing advice. http://perfectpolish.com/Nuvite.htm