MOONEY M20j : Propeller 2 or 3 Blades?

[Pedro Costa]

Good night.  I wanted your opinion on which is the best propeller for the Mooney M20J: 2 or 3 blades;  Hartezell or McClauley?

[A64Pilot]

I believe the prop that gives the fastest cruise speed is the stock McCauley. Three blades look cool, but do to the higher weight and increased drag usually don’t perform as well, They are usually smoother and make less noise though.

Sometimes a three blade prop can outperform a two blade, if it’s a better designed blade, and that happens sometimes so you can’t make the blanket statement that a two blade always outperforms a three blade.

 But from what I’ve heard it’s tough performance wise to beat the stock J model prop.

Edited March 25, 2022 by A64Pilot

[WaynePierce]

I agree with A64Pilot. Three blades is sexier but I have the stock 2 blade McCauley. I think that he is wrong on the noise though, I think the 3 blade is louder (three tips breaking the sound barrier rather than two (I could totally be wrong on this)) You wont get any more ground clearance with a three blade over a two blade something I thought you would get... I think I've also read that the two blade will pull you faster than the three blade in cruise.

[201Mooniac]

For 3 blade, you can get the MT prop which is lighter than the 2 blade McCauley by about 20 lbs if I remember correctly and gives more ground clearance.  The climb is slightly better and I didn't notice any impact to cruise speed.  Looks great.

[A64Pilot]

Prop tips don’t go supersonic, ideally not even very close really, but often a three blade is less diameter and tip speed is driven by RPM and length.

There are several tip speed calculators on line, this is one

https://www.warpdriveprops.com/propspd2.html

For instance the little Thrush, the S2R-T34 is the loudest we made as it’s 106” prop at 2200 was at .9 mach at 20C which made it loud

We have a 74” prop? if so then at 2700 RPM it’s only .77 Mach at 20C so we aren’t noisy at all really

Compare that to a C-185 with an 86” prop turning 2850 RPM, and that defines noise on a mountain lake in the morning at .95 Mach

Yeah I know they aren’t supposed to turn the 86 at 2850, just the 80, but I assure you some do

Edited March 26, 2022 by A64Pilot

[David M20J]

in the most simplistic and basic way I've been told, is a 3 blade if you want climb and T/O performance, 2 Blade if you want cruise performance.  I'm sure technology and materials are catching up or are going to catch up where it will be negligible.  So I guess the question would be would you rather have climb and t/o or cruise speed and then do research from there that will minimize the gap between the two

[gacoon]

2 hours ago, David M20J said:

in the most simplistic and basic way I've been told, is a 3 blade if you want climb and T/O performance, 2 Blade if you want cruise performance.  I'm sure technology and materials are catching up or are going to catch up where it will be negligible.  So I guess the question would be would you rather have climb and t/o or cruise speed and then do research from there that will minimize the gap between the two

How about weight and balance, is there a significant difference?

[KSMooniac]

The 3 blade MT is the lightest option for the J by 12+ lbs over all of the metal props, even the 2 blades, and it is the only one that is a smaller diameter. It also has no RPM restrictions and can be dynamically balanced to an exceptional level of smoothness for increased comfort and fatigue life for everything attached to the airframe.

I installed mine in 2010 and would choose it again today.

Sent from my LM-V405 using Tapatalk

[KSMooniac]

How about weight and balance, is there a significant difference?

It is 12 lbs lighter than the original J prop from 77, and I believe 14 lbs lighter than the fatter chord props that appeared later. I think it is 20+ lbs lighter than metal 3 blade props.

It has a very favorable impact on cg as well since it is as far forward as it gets... Do a sample update to your W&B and you'll see that it moves aft... A good thing for mid body Mooneys!

Sent from my LM-V405 using Tapatalk

[NotarPilot]

3 hours ago, KSMooniac said:

The 3 blade MT is the lightest option for the J by 12+ lbs over all of the metal props, even the 2 blades, and it is the only one that is a smaller diameter. It also has no RPM restrictions and can be dynamically balanced to an exceptional level of smoothness for increased comfort and fatigue life for everything attached to the airframe.

I installed mine in 2010 and would choose it again today.

Sent from my LM-V405 using Tapatalk
 

Any idea what that MT 3 blade prop goes for now?

[Will.iam]

7 minutes ago, NotarPilot said:

Any idea what that MT 3 blade prop goes for now?

If you have to ask you can’t afford it. Jk I think it’s 13.5 but what’s the lead time?

[carusoam]

17 minutes ago, Will.iam said:

If you have to ask you can’t afford it. Jk I think it’s 13.5 but what’s the lead time?

Use caution with affordability humor…

Not everyone will find it very funny…

Some may take you seriously, and this can be pretty harsh …

When trying to be funny…. Drop one of these at the end….  
 

MS is full of people from all levels of the economic spectrum…

 

And… yes, props are incredibly expensive…. To anyone…

 

Best regards,

 -a-

[David M20J]

while I have been in professional aviation for about 10 years ive only been a plane owner for about a month and I am actually running into prop issues and might need a new one, currently have a TP 3 blade mccauley i need to replace and was going to swap with someone for a 400hr stock m20j, but what is a MT, my google powers are not wise enough to understand what I was asking

[carusoam]

2 minutes ago, David M20J said:

while I have been in professional aviation for about 10 years ive only been a plane owner for about a month and I am actually running into prop issues and might need a new one, currently have a TP 3 blade mccauley i need to replace and was going to swap with someone for a 400hr stock m20j, but what is a MT, my google powers are not wise enough to understand what I was asking

This will get you close…

http://www.mt-propellerusa.com/en/mtusa/stcs/mooney_8.htm

-a-

[David M20J]

4 minutes ago, carusoam said:

This will get you close…

http://www.mt-propellerusa.com/en/mtusa/stcs/mooney_8.htm

-a-

ah gotcha, way out of my league, at least for my bare min knowledge, I'm a dumb helicopter pilot still learning the ways, Thanks @carusoam

Edited March 26, 2022 by David M20J

[KSMooniac]

I don't know the current MT pricing, sorry. I've seen ads on barnstormers for at least one in stock with a US distributor.

Sent from my LM-V405 using Tapatalk

[DCarlton]

I have the 3 blade McCauley on my F.  I like the look.  It climbs great.  It doesn't really float and slows down nicely on final.  I do feel a slight vibration at lower RPMs and there are RPM restrictions at low manifold low RPM settings (can't remember the numbers).  If I had to do it again, I would consider going with a 2 blade particularly if it's cheaper.  I would base it on price, weight, and any operational limitations.  Will be interesting to see what you choose.  

[Ragsf15e]

17 hours ago, David M20J said:

while I have been in professional aviation for about 10 years ive only been a plane owner for about a month and I am actually running into prop issues and might need a new one, currently have a TP 3 blade mccauley i need to replace and was going to swap with someone for a 400hr stock m20j, but what is a MT, my google powers are not wise enough to understand what I was asking

I also have a 3 blade mccaully and I’m curious why you think you need a new one?  Generally an overhaul or reseal will be 50-75% less than price of new and fix almost anything.  If you have a prop strike or need new blades due to damage, maybe that’s another thing.

You'll find performance differences are very small.  Weight gain for the 3 blade over 2 is something like 20-30lbs, but that doesn’t make or break my weight and balance.

Mine is smooth and performs well.  Maybe others have issues with 3 blade, but mine is fine.

[Rjfanjet]

I just resealed my 3 blade and paint. $1800

[David M20J]

2 hours ago, Ragsf15e said:

I also have a 3 blade mccaully and I’m curious why you think you need a new one?  Generally an overhaul or reseal will be 50-75% less than price of new and fix almost anything.  If you have a prop strike or need new blades due to damage, maybe that’s another thing.

You'll find performance differences are very small.  Weight gain for the 3 blade over 2 is something like 20-30lbs, but that doesn’t make or break my weight and balance.

Mine is smooth and performs well.  Maybe others have issues with 3 blade, but mine is fine.

when it was put on they had a -A3B6D engine and when they overhauled they put a -A3B6, there is no STC that I have found for it, she is grounded till I figure it out

 

[carusoam]

4 hours ago, David M20J said:

when it was put on they had a -A3B6D engine and when they overhauled they put a -A3B6, there is no STC that I have found for it, she is grounded till I figure it out

 

That sounds like you need to speak with a good prop guy…

Wait a sec…

MS has a good prop guy… @Cody Stallings (Prop, STC, M20J, engine mismatch…?)

Or see if @jetdriven can sift through all that alphabet soup….

Best regards,

-a-

 

 

[NotarPilot]

On 3/26/2022 at 1:33 AM, carusoam said:

Use caution with affordability humor…

Not everyone will find it very funny…

Some may take you seriously, and this can be pretty harsh …

When trying to be funny…. Drop one of these at the end….  
 

MS is full of people from all levels of the economic spectrum…

 

And… yes, props are incredibly expensive…. To anyone…

 

Best regards,

 -a-

I took no offense to that. I actually joke like that too. It’s all good here. 

 

On 3/26/2022 at 1:11 AM, Will.iam said:

If you have to ask you can’t afford it. Jk I think it’s 13.5 but what’s the lead time?

Maybe a nice retirement present to myself in a few short years.

[Ragsf15e]

3 hours ago, bluehighwayflyer said:

Both of those engines are listed on the M20J’s type certificate.  So there is no STC required.  It is a very common conversion that effectively only eliminates the single D4LN3000 “dual” magneto in favor of a traditional two magneto configuration.  

Is that prop on the J as well?  I think he’s worried that his prop/engine combination isn’t approved although both appear to be approved on the J… clear as mud?

[carusoam]

10 hours ago, David M20J said:

when it was put on they had a -A3B6D engine and when they overhauled they put a -A3B6, there is no STC that I have found for it, she is grounded till I figure it out

 

 

Good news!

The results are in…

See JimR’s post above aka blueskytraveler…

With the ‘second’ from JetDriven…

All is good in The Mooney World… 

 

Best regards,

-a-

[David M20J]

4 hours ago, bluehighwayflyer said:

Both of those engines are listed on the M20J’s type certificate.  So there is no STC required.  It is a very common conversion that effectively only eliminates the single D4LN3000 “dual” magneto in favor of a traditional two magneto configuration.  

like @Ragsf15e mentioned its the Engine/Prop combination that there isnt anything for.  The STC i have for the prop lists the -A3B6D but not the -A3B6.  Half the people I talk to say its fine and the other half say it isnt lol