M20J upgrade from 2 Blade McCauley to 3 Blade MT Prop

[DEGWS]

Hi,

looking for some experience about the MT 3 blade upgrade for the M20J. Now have the McCauley 2 blade.

Especially some numbers about cruise speed would be great. Fester, equal or slower….?
 

thanks!

[dlthig]

The MT is the lightest 3 blade. Have you looked at the 2 blade scimitar? The MT is expensive. I'd expect better T/O runs, but that's about it. 

[A64Pilot]

As a general rule, the more blades, the smoother and quieter the prop, and also due to increased drag, it loses some performance.

An argument against that is if the multi blade prop is a more advanced blade design it can offset the increased drag.

Multi blade props are most often used for ground clearance, the Big Mooney’s for instance just couldn’t run a two blade I’m sure, too much HP for a small diameter two blade I’d suspect.

The biggest draw to a three blade over a two blade is ramp appeal. it’s hard to argue that a three blades don’t look cooler than two.

But most often the two blade will outperform a three.

Actual test data is hard to find and very often there is a “placebo” effect, it’s just human nature for someone who spent a whole pot full of money for an “upgrade” to convince themselves that it is in fact an upgrade.

So if being slightly quieter, smoother and ramp appeal is important, then a three blade is probably a good choice, but if your one that is hiding antennas and removing steps for a  speed gain, then it’s likely not.

 

Edited October 2, 2021 by A64Pilot

[philiplane]

The Hartzell 2 blade composite prop would be the best choice, if it is available for your plane.

The MT simply isn't very durable. They leak grease, and there are no grease fittings to replenish what's lost. The fiberglass covers delaminate at the trailing edge. The leading edges come loose. The leading edges crack. Don't get their chromed spinner, the chrome peels off. The latest problem I've had is the trailing edge delamination on a prop that was overhauled less than two years ago and only has 1700 total time, with less than 600 since overhaul using MT factory overhauled blades. But yes, it performs well and is lightweight.

Edited October 2, 2021 by philiplane

[Hank]

5 minutes ago, A64Pilot said:

As a general rule, the more blades, the smoother and quieter the prop, and also due to increased drag, it loses some performance.

An argument against that is if the multi blade prop is a more advanced blade design it can offset the increased drag.

Multi blade props are most often used for ground clearance, the Big Mooney’s for instance just couldn’t run a two blade I’m sure, too much HP for a small diameter two blade I’d suspect.

The biggest draw to a three blade over a two blade is ramp appeal. it’s hard to argue that a three blades don’t look cooler than two.

But most often the two blade will outperform a three.

Actual test data is hard to find and very often there is a “placebo” effect, it’s just human nature for someone who spent a whole pot full of money for an “upgrade” to convince themselves that it is in fact an upgrade.

So if being slightly quieter, smoother and ramp appeal is important, then a three blade is probably a good choice, but if your one that is hiding antennas and removing steps for a  speed gain, then it’s likely not.

I can't say for sure about the newer Mooneys, but for most of us there is zero difference in prop diameter between 2 blades and 3 blades. We're all right there at 74-76". But I think the 4-blade MT is certainly smaller. @aviatoreb can fill us in on how well it performs on a 6-cylinder Mooney, another blade:cylinder ratio that people dislike without data--so many people insist that a plane "must have" one blade per pair of cylinders or it will shake the plane to pieces.

Many people insist with no data that 2-blade props cruise faster, but I think that depends on prop airfoil and how the pitch angle changes along its length. Many people also say that 3-blade props vibrate badly on 4-cylinder engines, but I'd say that vibration is determined by the installation not the blade count.

My 4-cylinder Mooney sports a 3-blade Hartzell, which was dynamically balanced at installation by the previous owner. After a decade of my flying around in it, I had the balance checked and it was still 0.01 ips. And my 140-knot C model cruises at 145-148 KTAS at altitude, so it's not slower. I like to think that I also climb faster than book, but really have nothing to compare against.

[ArtVandelay]

I always thought the rule of thumb was 1 blade per 100 horsepower, so Js were better with 2, Os were better with 3?
TBMs have 5!
Edit; I was surprised how heavy our 2 blade props are. I certainly wouldn’t want to add weight.

[Hank]

Just now, ArtVandelay said:

I always thought the rule of thumb was 1 blade per 100 horsepower, so Js were better with 2, Os were better with 3?
TBMs have 5!

So how do I and thousands of fellow C owners get 1.8 blades to go with our 180 hp? And the poor Ks need 2.1, Bravos 2.7 and some lucky upgraded R, S, TN, U and V models need 3.1! 

[Tim Jodice]

I made this when I got mine.

 

[A64Pilot]

You could reduce prop diameter with a three blade prop. but would you buy a short prop? Most likely no, and marketing and curb appeal is very important with props as with anything else.

There are other considerations of course, for example the best performing prop for the GE H-80 engine on a crop duster was the Avia three blade, Hartzell looked at it, but to build a similar blade design would exceed the centrifugal force limits of any hub they currently make, so they designed a four blade for us, it was a very tip loaded prop and exceeded the performance of the Avia three blade, even with an extra blade.

Actual performance testing on the same airplane under identical conditions would tell the tale, but unfortunately it almost never done.

But ask yourself this, when Mooney built the J. they were very, very interested in going as fast as they possibly could, if they could have gone faster with a three blade, don't you think they would have?

 

Edited October 2, 2021 by A64Pilot

[A64Pilot]

14 minutes ago, ArtVandelay said:

Edit; I was surprised how heavy our 2 blade props are. I certainly wouldn’t want to add weight.

Need to do a W&B to actually tell, often the CG shift is more important than the weight, a three blade Hartzell added 12 lbs to my Maule and moved its CG forward, as the real weight limit of a Maule is when you run out of aft CG, so the weight for it was a good thing, maybe not on a Mooney though.

Neighbor took his heavy three blade Hartzell off of his V tail Bonanza and installed a three blade MT as he was told it would be faster, well it’s not, but as a Bonanza is easily loaded out of aft CG, the lighter prop now has it so that he can’t carry as much due to CG limitation, so it depends on aircraft of course. On paper the lighter prop added useful load, but due to the arm where you put stuff, it actually reduced useful.

I’m not saying don’t  buy a three blade, there are several good reasons to, just don’t buy it to get a performance increase, because you may not.

The three blade cost me a kt or two on my Maule for whatever that’s worth and the three blade was a Scimitar prop and the two blade wasn’t. 

[Mooney Dog]

Coming rights from Hartzell https://hartzellprop.com/are-more-propeller-blades-better/

"...the most efficient number of propeller blades for an aircraft depends on the combination of (these) factors..." and "... the 3-blade prop will be inherently smoother and therefore quieter. In general, the 3-blade propeller will have a smaller diameter than the 2-blade propeller that it replaces, which also serves to reduce the tip speed and noise."

 

TLDR, Every prop is going to preform like its engineered to preform, and its all based on the airplane, engine, and the prop itself. Actual change in number for cruse are going to be minimal.

From personal experience in a 182Q. The 2 blade normally saw 115 in a low cruise and when it was upgrade to 3 it was 114. The 3 blade was also noticeably quieter and easier to climb to altitude with. 

 

...On the other hand.

 

Edited October 2, 2021 by Mooney Dog

[KSMooniac]

I have a scimitar MT on my J since late 2010 and would choose it again. It is the only smaller prop available for our planes. It is dramatically lighter and smoother than the OEM 2 blade. An aft shift of the CG is a very good thing for mid bodies too. It has infinite life blades, but they will also fail if you hit something, which will in turn most likely not create damage to the engine, but you'd still have to do a tear down inspection. I have the fake chrome spinner and love it as well, but I'm not sure they still offer it. I had some early paint failures that were fixed under warranty as I've documented here long ago.

2 blades versus 3 on a J... The MT is the only one I'd choose, and I wish they made a 2 blade for us but oh well. The modern scimitar shape is more aerodynamically advanced compared to the 70's and 80's era props designed without computers, so I expect that is why they're equal or better performance. I believe the newer Hartzell 2 blade Top Prop is slightly faster and much heavier, but I won't buy a Hartzell due to their repeated spinner failures and propensity to release AD's when they need more sales. They've done that since the 80's at least...

Sent from my LM-V405 using Tapatalk

[A64Pilot]

The “composite” or wooden if you will prop blades are more likely to dampen or absorb vibrations and or or be less susceptible to vibration fatigue than metal as well.

This maybe relevant as if you choose to advance timing in an engine as it will change the vibe profile and could possibly over time fatigue metal blades and or hubs, or might not.

As many know one of the most important tests conducted on an aircraft when Certifying a new prop is the Vibe survey, that’s how avoid ranges etc are found and Hartzell in particular has gotten enough data so that usually they can conduct a Vibe survey by analysis, but unless things have changed, and they may have the data on a variable timing ignition system is somewhat unknown as they don’t do vibe surveys on anything other than conforming engines and aircraft, or used to anyway.

Of course call the MT folks and ask if they dampen vibes and or less likely to fatigue from vibrations, My guess is they will say they are.

If so then it’s likely that an MT prop may be a better choice for a modern variable timing ignition.

[Hank]

9 minutes ago, A64Pilot said:

If so then it’s likely that an MT prop may be a better choice for a modern variable timing ignition.

Who has modern variable timing ignition on their Mooney? I thought Sure Fly, et. al., just replaced one mechanical magneto with an electronic one. The other magneto continues to fire at its fixed timing, so varying timing on the one electronic one would be self-defeating. 

[A64Pilot]

9 minutes ago, Hank said:

Who has modern variable timing ignition on their Mooney? I thought Sure Fly, et. al., just replaced one mechanical magneto with an electronic one. The other magneto continues to fire at its fixed timing, so varying timing on the one electronic one would be self-defeating. 

I believe the Surefly can advance timing, and whatever mag fires first will initiate combustion, one could argue maybe the the second mag to fire does little except provide redundancy.

I don’t have a Surefly, and haven’t researched one, but from what I read here it has timing advance as an ability.

[Mooney Dog]

10 minutes ago, Hank said:

Who has modern variable timing ignition on their Mooney? I thought Sure Fly, et. al., just replaced one mechanical magneto with an electronic one. The other magneto continues to fire at its fixed timing, so varying timing on the one electronic one would be self-defeating. 

You can replace both mags with the electro ones for that variable timing, but the variable timing actually comes in handing for low RPM settings. We have EIS on many of our club 172s and they have little (20-50rpm) drops in the runups from this. The EIS is just way better. 

 

Ive heard rumor that cirrus is going to go full electric here soon as well. 

[Tim Jodice]

1 hour ago, bluehighwayflyer said:

Assuming your J is a 1978 or later model, the Mac C214 propellor that it came with is a pretty darn fine and highly optimized one.  Unless you really want to take weight off the nose and increase smoothness and ground clearance a bit, oh, and spend a boatload of cash, you really should just keep what I you have.  If those factors are important to you and you don’t mind also possibly sacrificing durability a bit, get a MT.  Everything else is substantially heavier than what you have already in the worse place possible and is not really much of an improvement for most of us.  

I agree with everything here. Based on my experience the original propeller is all about top speed. Better take off performance doesn't sell Mooneys, Going 2.05 knots faster does.

Comparing equal technology propellers it makes sense that a 3 blade would give up some top speed in exchange for the benefits any 3 blade propeller gives. 

Like everything in avation there is no free lunch so in order to gain all of the benefits with no performance loss. It is going to co$t you. I paid $14K a year ago.

[carusoam]

About a decade ago…

I went from a three blade Mac… (ground strike killed it) 

Had the choice of Hartzell vs. MT…

1) The MT was much lighter, had good performance, was still going through leading edge material selection and paint issues… came with four blades… ask @aviatoreb

2) The Hartzell TopProp was heavier, and it’s spinner wasn’t the exact diameter for the application…

I wanted to choose the MT, with one really good input from Scott from Kansas (above)…

Unfortunately, for me… their STC wasn’t finished for my plane for a couple more months…

The extra weight of the new prop required shuffling things like getting the (N) vs (G) version of the IO550 (lighter cylinders) and selecting a heavier battery in the tail… to avoid adding dead Charlie weight…

 

PP thoughts only, not a mechanic…

Best regards,

-a-

 

[DEGWS]

Hey guys,

a lot to read, but no real numbers…. a lot of useless stuff.

Anybody have some details about switching from 2 blade McCauley to a 3 blade MT on a M20J?

[Guest]

49 minutes ago, DEGWS said:

Hey guys,

a lot to read, but no real numbers…. a lot of useless stuff.

Anybody have some details about switching from 2 blade McCauley to a 3 blade MT on a M20J?

You’ve come the right place for useless information and opinions.  I have a 3 blade MT on my airplane, with it I can out perform most other piston powered airplanes.  I’ve had none of the issues listed above.

Being in Germany having an MT should make support easier

Clarence

[carusoam]

4 hours ago, DEGWS said:

Hey guys,

a lot to read, but no real numbers…. a lot of useless stuff.

Anybody have some details about switching from 2 blade McCauley to a 3 blade MT on a M20J?

Pretty much an indication that there isn’t a lot of useful stuff to share…

Or… the question wasn’t asked in a way that is conducive to getting useful information…

One way you can target asking a better question…

Take the answers given, and ask more specific follow up questions…

 

It takes extra effort to get the right answers out of a large group of people… they have them… you need to coax them out…

 

Use well thought out questions to not accidentally be insulting… 

People supplied what they thought may be helpful for you… you just called their responses useless… 

or maybe Google translate did that… 

Either way, that wasn’t a very nice thing to do… and it probably won’t get you more detailed answers…

Stay focussed.

Best regards,

-anthony-

 

[DEGWS]

3 hours ago, carusoam said:

Pretty much an indication that there isn’t a lot of useful stuff to share…

Or… the question wasn’t asked in a way that is conducive to getting useful information…

One way you can target asking a better question…

Take the answers given, and ask more specific follow up questions…

 

It takes extra effort to get the right answers out of a large group of people… they have them… you need to coax them out…

 

Use well thought out questions to not accidentally be insulting… 

People supplied what they thought may be helpful for you… you just called their responses useless… 

or maybe Google translate did that… 

Either way, that wasn’t a very nice thing to do… and it probably won’t get you more detailed answers…

Stay focussed.

Best regards,

-anthony-

 

Sorry, you are right. Of course there are a few useful answers here.

Nevertheless, I am looking for more details regarding cruise performance, switching from 2 Blade McCauley to the 3 blade MT on a M20J. ;-)

Thanks

[DEGWS]

7 hours ago, M20Doc said:

You’ve come the right place for useless information and opinions.  I have a 3 blade MT on my airplane, with it I can out perform most other piston powered airplanes.  I’ve had none of the issues listed above.

Being in Germany having an MT should make support easier

Clarence

I know the MT Props from other planes, but not on a Mooney.

The only issue I know is the leaking grease. MT support is great, they fixed it for free after  5 years.

[Guest]

1 hour ago, DEGWS said:

Sorry, you are right. Of course there are a few useful answers here.

Nevertheless, I am looking for more details regarding cruise performance, switching from 2 Blade McCauley to the 3 blade MT on a M20J. ;-)

Thanks

If MT is confident that their propeller out performs the original McCauley propeller ask them if they’ll take it back if it doesn’t?

Clarence

[dlthig]

11 hours ago, M20Doc said:

You’ve come the right place for useless information and opinions.  I have a 3 blade MT on my airplane, with it I can out perform most other piston powered airplanes.  I’ve had none of the issues listed above.

Being in Germany having an MT should make support easier

Clarence

With 400 horses, I don't think it matters what you are swinging out front. There is no replacement for displacement! I think MT props are good, just expensive. It was double to hang a MT on the PA24 I flew, so the owner decided on a traditional 3 blade.