Last week I saw someone on FB comment about how you're not supposed to swap props on an engine with much time on it. That it's best to wait until either a new or overhauled engine is put on the plane. I'd never heard this before and would like some more info. I understand that a new prop will have new harmonics and vibrations, but how detrimental is it? Are there specific components that have a history of failing early due to this? What kind of data is there out there in this? As we all know, sometimes a "Don't do this" in aviation is sometimes more rooted in wives tales than fact. So, let's hear it.

My curiousity stems from my situation. I've got a1400 hour engine with 800 on the top and would like to go to a three blade prop at some point. Thing is, assuming that all ran well and I got say, another 1000-1500 hours out of it, that would be 10-15 years before I'd have a chance to upgrade to a three blade prop. So I'm curious how real the pitfalls of switching now would be. Plus, it's something new to learn!

Sounds like an OWT (Old Wive's Tale) to me. I know literally hundreds of aircraft owners who have put new props on their planes for various reasons (2 to 3-blade upgrades, blades chipped or otherwise damaged beyond repair, prop-hub failures, etc.).

Ask the folks who are telling you this for their rationale behind such a statement. There might be valid reasons under certain circumstances (though I cannot think of any), but absent any logic, if has to fall into "superstition" or "OWT" territory.

Let's think this through for a bit... A new prop should be balanced as well as it will ever be - it just came off the assembly line. If it's a direct replacement (same part number) you'll be back to the same conditions as when your engine was new, so any "harmonics" would have been already addressed in the type certificate (RPM restrictions, etc.). If it's a different prop, presumably you're installing an STC'ed system (assuming your airplane is certified). During the STC process, one of the things that has to be done is an analysis of vibration modes, to determine if any restrictions in RPM ranges need to be established.

Just my two cent's worth...

One of the many wives tales of aircraft maintenance... I'm sure someone broke their big toe falling off the hangar roof three days after they changed props, so obviously you should not change props except at overhaul

The way I heard it is that the counterbalance weights "take a set" after running for a long time with a prop.
That's an old wives tale that doesn't seem to make sense. But...
Last year I removed the 82" (actually 80-1/2") C203 prop that was on my C180, and replaced it with an 88" C201 I'd just had OH'd at a quality prop shop. Got a shake at traffic pattern power settings, so I swapped it end-for-end which got rid of that shake (which in itself doesn't make sense). However, even after dynamic balancing, it's not as smooth as the 1250-SOH prop I took off. Bummer, but that's life. It does pull harder, which was the main thing, so that part is good.

Interesting. I was thinking that dynamic balancing would sort out the majority of issues, but there must be more at play here.


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So I had a few minutes while waiting for a bus today and called both Hartzell and McCauley. Here is what they had to say:

McCauley: Never heard of it.

Hartzell: He said that occasionally people that do their Top Prop conversion from a 2 bald to a 3 blade will experience a new vibration that they can't explain. They will chase it...changing engine mounts, dynamic balance it, etc...to no avail. He says they have a 100% return policy and those people who had the vibration find to goes away when they go back to a 2 blade.

Both agreed that if the prop was approved for the engine, it should be fine.

So, now I have to just figure out which prop and whether it's too much a gamble to buy a used prop that may not have the return policy.


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Last week I saw someone on FB comment

Should be true, everything on FB is true so I've been told.

I've heard this as well. My 180 was switched to a 3 blade at around 1000 SMOH and nothing changed. I'd sure like to go back to a long 2 blade. So help e find one of those and maybe we can make a deal on a 3 blade top prop.

Schwarz wrote:

Last week I saw someone on FB comment

Should be true, everything on FB is true so I've been told.

I should have clarified the FB statement. It was made on the Big Tire page by one of our BCP brothers...if I remember right. That's why I considered it credible.


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A1Skinner wrote:I've heard this as well. My 180 was switched to a 3 blade at around 1000 SMOH and nothing changed. I'd sure like to go back to a long 2 blade. So help e find one of those and maybe we can make a deal on a 3 blade top prop.

What prop do you have? Best I can tell I'd need either of these two:

HC-J3YF-1RF
PHC-C3YF-1RF. Replaces McCauley C58. (My current prop).


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I would personally be leery of using a Hartzell prop, they seem like they're are usually plagued by AD's- more so than McCauley. The again, you may not have a choice if you want a 3-blade.
Does your new airplane (205?) have the IO-470?
There might not be a 3-blade Mac approved for that aplication.

A1Skinner wrote:... I'd sure like to go back to a long 2 blade. ....

Are you looking for a particular model prop?

hotrod180 wrote:

A1Skinner wrote:... I'd sure like to go back to a long 2 blade. ....

Are you looking for a particular model prop?

88" Mac. Probably a 203 as they are still serviceable. If I could find a C66 with good blades I'd jump on it.

hotrod180 wrote:I would personally be leery of using a Hartzell prop, they seem like they're are usually plagued by AD's- more so than McCauley. The again, you may not have a choice if you want a 3-blade.
Does your new airplane (205?) have the IO-470?
There might not be a 3-blade Mac approved for that aplication.

The new plane is a 205 but it has an IO-520-A on it. From talking to the two prop guys, it sounds like Hartzell is the only type that was put on that engine. The McCauley guy said a C401 might work, but I've not been able to find any reference that it's been married to that engine. As icing in the cake, since this engine was a field approval on the 205, I'll have to get a field approval for the prop too. So that even more so necessitates the path of least resistance, i.e., something already approved.


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Grassstrippilot wrote:

A1Skinner wrote:I've heard this as well. My 180 was switched to a 3 blade at around 1000 SMOH and nothing changed. I'd sure like to go back to a long 2 blade. So help e find one of those and maybe we can make a deal on a 3 blade top prop.

What prop do you have? Best I can tell I'd need either of these two:

HC-J3YF-1RF
PHC-C3YF-1RF. Replaces McCauley C58. (My current prop).


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Cory, pretty sure mine is the PHC-C3YF-1RF. I'll check when I get out to the plane later today. It's an 80" 3 blade Hartzell. OH'ed Feb 2014 and only 160TT. Plane sat for 8 years before I bought it and we have to OH our CS props every 10 years up here in Canada, regardless of hrs.

Interesting. This is a back burner upgrade for me, but if you find a replacement and end up looking to sell yours, I may be able to move it up on the priority list. Keep me posted. From what I've seen, my gut tells me that is the prop I'll need and will be the most likely for the FAA to sign off on where it specifically says it replaces my current prop.


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Grassstrippilot wrote:Interesting. This is a back burner upgrade for me, but if you find a replacement and end up looking to sell yours, I may be able to move it up on the priority list. Keep me posted. From what I've seen, my gut tells me that is the prop I'll need and will be the most likely for the FAA to sign off on where it specifically says it replaces my current prop.


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Ya, keeping things simple with the FAA will make it simpler for sure. I'll let you know. Upgrading my prop is also a backburner upgrade for me. Lot of $$ for something not neccasary. Just looking to save some weight on the nose to bring my CG back a bit. Heading to school in a couple weeks, then buying a business and building a hangar are priority right now.

Western Propeller in Troutdale Oregon has a freshly-overhauled 88" C29 listed on Barnstormers right now for $4500. It's listed with the 180's for sale, about halfway down the first page. The ad's dated 8/8/16.