MT four blade prop

[Alan Maurer]

Hello Everyone, I saw a photo of an M20R today with an MT propeller. Very good-looking. Anyone have any experience with this prop? 

Any actual difference in performance?

 

 

[philiplane]

It sounds like a weed wacker while taxiing, kind of a whirring noise. It's a giant speed brake when you pull back the power. It doesn't go any faster. It climbs about the same as a three blade prop. There are four leading edges to damage with stones or runway debris.  It's more expensive to maintain and overhaul.

Three blades give the best combination of climb and cruise performance. The four blade doesn't really add anything, other than it looks different.

[ArtVandelay]

It sounds like a weed wacker while taxiing, kind of a whirring noise. It's a giant speed brake when you pull back the power. It doesn't go any faster. It climbs about the same as a three blade prop. There are four leading edges to damage with stones or runway debris.  It's more expensive to maintain and overhaul.
Three blades give the best combination of climb and cruise performance. The four blade doesn't really add anything, other than it looks different.

Isn’t it lighter?

[A64Pilot]

MT prop would be significantly lighter, and I believe shorter meaning more ground clearance.

I’ve not flown one, but woud be surprised if didn’t lose some performance.

‘I woud be surprised if it wasn’t smoother and quieter too.

[StevenL757]

35 minutes ago, Alan Maurer said:

Hello Everyone, I saw a photo of an M20R today with an MT propeller. Very good-looking. Anyone have any experience with this prop? 

Any actual difference in performance?

It looks really cool and is lighter.  Other than that, there’s no performance delta between it and either Hartzell variant for the Ovation.  For the privilege, you get to fork over more than $21k.

One drawback of it on the Ovation...from a previous member here who had one installed in my IA’s shop and since sold his Ovation...is that due to the aft CG shift by installing such a lighter prop is that he started wearing through shock discs on his gear several times faster than when he had his Hartzell installed.

[aviatoreb]

34 minutes ago, philiplane said:

It sounds like a weed wacker while taxiing, kind of a whirring noise. It's a giant speed brake when you pull back the power. It doesn't go any faster. It climbs about the same as a three blade prop. There are four leading edges to damage with stones or runway debris.  It's more expensive to maintain and overhaul.

Three blades give the best combination of climb and cruise performance. The four blade doesn't really add anything, other than it looks different.

Have experience flown with one?  Flown same airplane before? You sound confidentially knowledgeable.

[philiplane]

The four blade only exists because it is needed to meet strict German aircraft noise limitations. By reducing the diameter, you reduce the sound profile. By reducing the diameter, you also reduce thrust compared to a three blade, so they have to add a blade to equal the thrust of a three blade. It's not magic. 

[Alan Maurer]

Guess I will not think about the MT prop

thanks

Alan

[aviatoreb]

4 minutes ago, philiplane said:

The four blade only exists because it is needed to meet strict German aircraft noise limitations. By reducing the diameter, you reduce the sound profile. By reducing the diameter, you also reduce thrust compared to a three blade, so they have to add a blade to equal the thrust of a three blade. It's not magic. 

Is that theory or have you flown with one?

[philiplane]

29 minutes ago, aviatoreb said:

Is that theory or have you flown with one?

I've flown with:

On Mooney, Piper, Cirrus, and Diamond aircraft I've flown the Hartzell 3 blade aluminum, Hartzell 2 blade composite (DA40 only so far) Hartzell three blade composite, MT 3 blade & 4 blade, and Dowty 4 blades and MT 5 blades on a Cheyenne 400 LS. And 3 & 4 blade regular & scimitar version Hartzells on King Airs. Plus the usual assortment of Macauleys on Cessnas. I'm working on a 2 blade Hartzell composite for my Aztec to decrease weight and provide more thrust at higher altitudes.

How about nine blades?

 

https://www.mt-propeller.com/en/entw/pro_new.htm

Edited April 22, 2021 by philiplane

[aviatoreb]

46 minutes ago, philiplane said:

I've flown with:

On Mooney, Piper, Cirrus, and Diamond aircraft I've flown the Hartzell 3 blade aluminum, Hartzell 2 blade composite (DA40 only so far) Hartzell three blade composite, MT 3 blade & 4 blade, and Dowty 4 blades and MT 5 blades on a Cheyenne 400 LS. And 3 & 4 blade regular & scimitar version Hartzells on King Airs. Plus the usual assortment of Macauleys on Cessnas. I'm working on a 2 blade Hartzell composite for my Aztec to decrease weight and provide more thrust at higher altitudes.

How about nine blades?

 

https://www.mt-propeller.com/en/entw/pro_new.htm

You have!

I have seen descriptions on this thread which are nothing like my experience in changing from a 3 blade metal McCauley to a composite 4 blade.  You statement was purely one of diameter and thrust assuming otherwise equal blade and equal material.  That's why I asked, because those assumptions don't seem to be true in my transition from what I had to the 4 blade mt I now have.

I had a 76'' round tip McCauley metal prop that was designed in the slide rule era in the 1960s.

I switched to a 4 blade prop that is 74'' primarily motivated by the change in balance and ground clearance.  Better ground clearance is great.

It took 35lbs off the nose which is an extreme station on the balance sheet resulting in over an 1'' shift rearward in balance which was a good thing since my rocket stc had the balance near the front of the envelope.  Now it is more harmonized for hand flying so nice.  It is much more nimble and light feeling road feel from before.  It is not a subtle change. It its a really really nice change of feel for hand flying.

For speed moving weight rearward is a speed saver since it releases some of the counter balance forces on the tail, so that is a reduction in parasitic drag by the tail.  So that's point for more speed.

The prop itself is a scimitar design shape designed in cad which seems aerodynamically more efficient than the old school round tip McCauley blades.  Another point for more speed.  In fact even in 3 blade props we know that some shapes are better than other. aka the famous acclaim prop is supposed to be a bit faster.

The prop blade itself seems to curve under thrust, it scoops the air rather than beats the air like a rigid material blade.  You can see it curve if you stand on the side while the engine is running on the ground.  I think this is the major source a more efficient blade and an interesting whir sound that is distinctly different from the old sound.

It definitely produces more thrust since I remember that immediately before the change I was able to hold brakes hold against full power and immediately the change to 4 blades after I was not.

4 blades is expected to be slower, all things being equal. but all things are not equal. I would say the other factors it seems about the same or a bit better like 1 or 2 knots in cruise. but unfortunately I did not do before and after tests rigorously by a horseshoe test like I wish I had.  Seth just got a 4 blade. He is getting record faster cruise speeds.  I can say the climb inproved for sure.

Durability. get the nickel coated leading edge. That is what I have - it greatly covered the blade and in 6 years I have not had a nick of any kind - less than even the metal blades I had before.

 

[aviatoreb]

1 hour ago, Alan Maurer said:

Guess I will not think about the MT prop

thanks

Alan

Better talk to some people who have owned one on a Mooney if you are serious.  There are a few of us here.

[A64Pilot]

As a general statement, the more blades there are, the smoother and quieter a prop is, even if the diameter is the same as with more blades often require less pitch so the airflow over the tip is slower.

‘Also the more blades there are, the more drag there is, usually more than two blades are used for ground clearance issues, a two blade prop in most cases will perform best.

The Navy Greyhound COD has eight blades I think there is I believe a Russian cargo airplane that may have more than that?

More blades is usually more weight and money too.

[aviatoreb]

8 minutes ago, A64Pilot said:

As a general statement, the more blades there are, the smoother and quieter a prop is, even if the diameter is the same as with more blades often require less pitch so the airflow over the tip is slower.

‘Also the more blades there are, the more drag there is, usually more than two blades are used for ground clearance issues, a two blade prop in most cases will perform best.

The Navy Greyhound COD has eight blades I think there is I believe a Russian cargo airplane that may have more than that?

More blades is usually more weight and money too.

Indeed. 

But speaking specifically instead of generally.  And not generally based on a thought experiment of changing a prop of n blades for a prop of n+1 blades of otherwise identical build, shape, material.

Specifically - switching from a 3 blade round tipped McCauley that was on my airplane.

The prop was 35lb lighter off the nose that changed my W&B significantly.   Especially the balance.

Aerodynamics of the prop were significantly different.  Both for reasons of the shape, and also because the MT blades are a compliant material and they bend under load scooping air but the metal blades did not bend in any significant way.

Speed did not decrease at least and I would say it increased.  Climb increased.  Sound decreased.  Balance harmony road feel improved.

[A64Pilot]

Those were generalizations which don’t mean much of course, but you have to admit your aircraft is a little unusual compared to a normal average GA airplane, It really benefitted from less weight, and any extra ground clearance is a very nice thing to have, most aircraft don’t have those issues, so my guess would be even if you gave up a couple of knots it would still have been a win, and moving the CG aft just might be why you didn’t, possibly, who knows, so long as it worked for you is all that matters.

I personally wouldn’t have an MT prop because the owner is an Ass. He owns a part of Avia propellor also, which means Igor who is an outstanding good person has a cross to bear, he owns the rest of Avia. I think the little German fellow had his butt whipped and his lunch money stolen too many times in grade school maybe, he certainly has that attitude.

Joe Brown who owns Hartzell however is a very nice, genial person, be a great neighbor. Joe would own up to any mistakes, apologize and personally ensure the issue was fixed, but there are few problems.

[A64Pilot]

This airplane also has four blade MT propellers

https://www.airspacemag.com/military-aviation/last-long-distance-escorts-180973974/

[aviatoreb]

11 hours ago, A64Pilot said:

Those were generalizations which don’t mean much of course, but you have to admit your aircraft is a little unusual compared to a normal average GA airplane, It really benefitted from less weight, and any extra ground clearance is a very nice thing to have, most aircraft don’t have those issues, so my guess would be even if you gave up a couple of knots it would still have been a win, and moving the CG aft just might be why you didn’t, possibly, who knows, so long as it worked for you is all that matters.

I personally wouldn’t have an MT prop because the owner is an Ass. He owns a part of Avia propellor also, which means Igor who is an outstanding good person has a cross to bear, he owns the rest of Avia. I think the little German fellow had his butt whipped and his lunch money stolen too many times in grade school maybe, he certainly has that attitude.

Joe Brown who owns Hartzell however is a very nice, genial person, be a great neighbor. Joe would own up to any mistakes, apologize and personally ensure the issue was fixed, but there are few problems.

Well we are talking Mooneys here on Mooney space, so whether or not my airplane is unusual is not as important when the original poster with a Mooney is wondering if such a change would be nice on their individual airplane which is a lot like my airplane.  A stock rocket is more nose heavy than any other Mooney (before the change to MT) but all of the big bore Mooneys are quite nose heavy.  So a change in balance is always good for road feel.

A change from nose heavy to balanced will always be a good factor for speed since as I described the mechanism is less down force required by the horizontal stabilizer meaning less parasitic drag.

All Mooneys are ground clearance challenged - 4 blades vs 3 is a good thing for this challenge.

Anyway I don't care if an MT prop has no benefit for a Beech Baron.

I don't know anything about the owner so I can't speak to that.  But 3 primaries including the original engineer, and older German fellow, came and saw my airplane at Oshkosh (they came out specifically to see it put at For Du Lac where I was parked).

Hartzell seems really nice.  I had one on my diamond years ago - but It is unavailable to me since they doo not have a model for me.  So irrelevant.

[carusoam]

Speaking evil of people is never going to be helpful...  the message gets lost and the speaker looks bad...

Better to stick with the facts...  like what that person did...

 

 

aside from that...

The MT props are on quite a few Mooneys around here...

One sits on the nose of an aero engineer’s M20J...

Bravos were the first long bodies to go four blade MT...

When my Ovation needed a new prop... I compared the TopProp to the MT...

The weight of the TopProp is a REAL challenge...

The weight of the MT is a real benefit...

Compare to what you have now, probably a Mac in the middle, weight wise...

Do the WnB for your machine...  there are 10s of pounds at stake... every pound on the nose has a counter Charley weight in the back...

I went with the TopProp, because the MT didn’t get its STC approval completed in time...  I missed by just a few months...

As for sound...  that is a holy cow kind of difference...

Prop noise is about 90% of the sound, as a plane passes by....

Full power, Rocket T/O, Erik’s plane is noticeably different than the other 25 Mooneys at a fly-in...

Big sound... used to mean big power... but if you have ever driven one of those awesome Teslas.... the really high powered, fast accelerating.... no sound.... ones....

The four blade really makes sense when you exceed 300hp... and like short T/O runs.... and strong climb rates.... and cruise in the lower FLs....  put VGs on your wings at the same time....   

I liked the quality MT provides... it has taken a while to get it right... the right leading edge material, and the right paint to stay in place...

As far as TopProp goes... I am still disappointed with the spinner... it was supposed to get swapped out when a proper one became available....  it is about a half inch too small... and looks non-aerodynamic at the cowling... that was ten years ago...

As far as big sound and big power... nothing is bigger than 310hp on a Mooney turning 2700rpm..! 
 

Now for the cool part...

If you have ever seen the Mooney compared to the P51 Mustang...   There are two visual stand out differences... the really long cowling for the extra cylinders, and the four blade prop...

Hmmm.... painting an MT prop with D-Day stripes on the tips may be interesting....

Best regards,

-a-

 

 

[FoxMike]

I put a 4 blade MT on my Bravo and love it.  If you do it put the nickel steel leading edges on it.  The stainless leading edges get nicked and need work more often.  What I like is smoothness and lower noise level.  Also the nose is lighter when flaring.  

[philiplane]

12 hours ago, aviatoreb said:

You have!

I have seen descriptions on this thread which are nothing like my experience in changing from a 3 blade metal McCauley to a composite 4 blade.  You statement was purely one of diameter and thrust assuming otherwise equal blade and equal material.  That's why I asked, because those assumptions don't seem to be true in my transition from what I had to the 4 blade mt I now have.

For speed moving weight rearward is a speed saver since it releases some of the counter balance forces on the tail, so that is a reduction in parasitic drag by the tail.  So that's point for more speed.

It definitely produces more thrust since I remember that immediately before the change I was able to hold brakes hold against full power and immediately the change to 4 blades after I was not.

Durability. get the nickel coated leading edge. That is what I have - it greatly covered the blade and in 6 years I have not had a nick of any kind - less than even the metal blades I had before.

 

The 4 blade will produce slightly more static thrust, but that does not add speed. It adds climb capability. And speed brakes when power is reduced.

The reduction in weight will occur with any change from aluminum to composite blades, it's not specific to the MT. Hartzell composites are also lightweight. This reduction in weight on the nose is what gives you more speed, not the extra blade. If the 4 blade weighed the same, you would lose 3-5 knots over the 3 blade, because of no change in CG. As you noted, the CG change due to the weight reduction reduces the tail load, which in turn reduces the wing lift required, increasing speed. If you want the most speed, you want a 2 blade composite propeller. 

Before and after tests, swapping a Hartzell composite 3 blade for a 4 blade MT showed the same acceleration from 0 to 90 MPH, a 50 FPM climb rate increase, and a 3 knot cruise decrease on a normally aspirated IO-550N equipped M20R. Same swap on a Cirrus produced the same results. Swapping a Hartzell aluminum 3 blade for the MT 4 blade produced a 2 second reduction in acceleration time, a 75 fpm climb rate increase, and a 2 knot speed increase. 

For turbocharged planes, the best prop is the Hartzell 3 blade composite. It was optimized for thinner air, and it retains the static thrust due to the blade shape. 

I've seen plenty of damaged leading edges on planes operated in the Bahamas, where runways aren't very clean. Damage than can be dressed out of an aluminum blade will require replacement of a leading edge on the MT prop. Which is pretty time consuming.

Be careful with the MT leading edges, small stones cause big problems-

Edited April 22, 2021 by philiplane

[aviatoreb]

19 minutes ago, philiplane said:

The 4 blade will produce slightly more static thrust, but that does not add speed. It adds climb capability. And speed brakes when power is reduced.

The reduction in weight will occur with any change from aluminum to composite blades, it's not specific to the MT. Hartzell composites are also lightweight. This reduction in weight on the nose is what gives you more speed, not the extra blade. If the 4 blade weighed the same, you would lose 3-5 knots over the 3 blade, because of no change in CG. As you noted, the CG change due to the weight reduction reduces the tail load, which in turn reduces the wing lift required, increasing speed. If you want the most speed, you want a 2 blade composite propeller. 

Before and after tests, swapping a Hartzell composite 3 blade for a 4 blade MT showed the same acceleration from 0 to 90 MPH, a 50 FPM climb rate increase, and a 3 knot cruise decrease on a normally aspirated IO-550N equipped M20R. Same swap on a Cirrus produced the same results. Swapping a Hartzell aluminum 3 blade for the MT 4 blade produced a 2 second reduction in acceleration time, a 75 fpm climb rate increase, and a 2 knot speed increase. 

For turbocharged planes, the best prop is the Hartzell 3 blade composite. It was optimized for thinner air, and it retains the static thrust due to the blade shape. 

I've seen plenty of damaged leading edges on planes operated in the Bahamas, where runways aren't very clean. Damage than can be dressed out of an aluminum blade will require replacement of a leading edge on the MT prop. Which is pretty time consuming.

Be careful with the MT leading edges, small stones cause big problems-

That is a picture of a stainless steel leading edge MT which is their older style protection.   The nickel leading edge is a much broader sheath.  See my pick.

I am sure the Hartzell is a great shape and so hard for MT to beat it on shape.  A rocket has stock that McCauley round tip prop which is not modern in any way so easy for a modern prop such as hartzel or mt to beat it on shape.

It would be hard to pull off keeping all other variables constant, but the effect of a compliant prop such as any composite curving as it scoops air must do something for efficiency vs the same shape in a rigid material like the metal props.

Other companies make composite props but not all are available for each mooney.  I think the key for weight is the material and the road feel of a lighter nose is nothing to sneeze at.

[rgpilot]

I've had one for 3 years on my TKS  Ovation. Replaced 3 blade Maccaully. Changed weight and balance. Plane is now much less nose heavy and lighter. Lands much easier without all that nose weight. Prop acts as speed brake when slowed for landing. Full flaps seems to trim much easier. Don't need full up trim so a go around would be much less of a problem. No big speed changes but climbs much better. Very smooth and starts very quickly. Added ground clearance. I am totally satisfied.

[BravoWhiskey]

Very nice!  Getting my 4 blade in this week... the overhaul on the engine will delay getting in the air but I’ll be happy to share some performance numbers when I do

[A64Pilot]

Without getting nasty an MT is a composite prop. it’s a fiberglass covered wooden prop, which by definition is a composite. But it really shouldn’t be grouped with the Carbon fiber blades of other manufacturers 

Performance wise the “Scimitar” etc blades are really more about looking cool. from a performance perspective there just isn’t much difference if any, although there may be some slight noise reduction from a swept blade, that’s really more tip speed dependent.

Any prop blade that flexes reduces pitch, a force is applied and causes the blade to flex to reduce the force, they don’t flex and increase pitch or scoop more air, they will also “cone” which means the blades will flex and the prop disk become cone shaped. The BIG advantage of metal blades over wooden ones is that they don’t flex as much.

Nickel from a sand erosion point is far superior to either aluminum of course or SS, the BlackHawk’s blades leading edges are Nickel, the Apache’s are Titanium, the Nickel seemed to wear as well as the Titanium in the desert.

Some of the old round tip fat blade props perform very well, they may not look as cool. but performance wise they are tough to beat, and some of course perform poorly.

‘I’m not sure for example that there is a better prop for my J than the factory round tip Mac.

 

Depends on what you want in a prop, I assume most of us Mooney guys want high cruise speed, while a C-185 on floats may want high bollard pull to get onto plane fast.

‘Any speed increase or decrease shouldn’t be hard to quantify, however if it comes with a new engine, then the new motor ought to give some speed by itself as usually an old tired motor is down on power some when compared to a new one.

On edit, even if there is no speed gain, the lower weight which of course increases useful load and the better CG along with increased ground clearance (I assume there is some?) is worthwhile.

Different kind of airplane, but I went from an old round tip straight blade two bladed Hartzell to a cool looking three bladed Hartzell Scimitar, lost slightly in climb and lost 2kts cruise and gained 12 lbs on the nose which of course pushed the CG to the forward limit, and I believe that CG shift may have been responsible for the loss in performance

‘In my case the CG shift was a good thing because then I could really load the aircraft heavy before it got out of aft CG.

Edited April 22, 2021 by A64Pilot

[aviatoreb]

14 minutes ago, A64Pilot said:

Without getting nasty an MT is a composite prop. it’s a fiberglass covered wooden prop, which by definition is a composite. But it really shouldn’t be grouped with the Carbon fiber blades of other manufacturers 

Performance wise the “Scimitar” etc blades are really more about looking cool. from a performance perspective there just isn’t much difference if any, although there may be some slight noise reduction from a swept blade, that’s really more tip speed dependent.

Any prop blade that flexes reduces pitch, a force is applied and causes the blade to flex to reduce the force, they don’t flex and increase pitch or scoop more air, they will also “cone” which means the blades will flex and the prop disk become cone shaped. The BIG advantage of metal blades over wooden ones is that they don’t flex as much.

Nickel from a sand erosion point is far superior to either aluminum of course or SS, the BlackHawk’s blades leading edges are Nickel, the Apache’s are Titanium, the Nickel seemed to wear as well as the Titanium in the desert.

Some of the old round tip fat blade props perform very well, they may not look as cool. but performance wise they are tough to beat, and some of course perform poorly.

‘I’m not sure for example that there is a better prop for my J than the factory round tip Mac

Why is a compliant prop bad vs a rigid prop?  I am certainly not privy to the design details in the prop companies, but I see no reason that the twist scheduling across the blade length could not be designed so that it will attain the designed perfect angle of attack when curved and under load.  That's I would want to do if I were designing a prop out of a compliant material.  It is a simple and straight forward geometry problem that I presume any competent engineer in this field would understand and make part of their design process.  Just like we already can see the changing pitch as a function on radius in every prop due to the changing velocity as a function of radius at constant radial velocity, further designing in the pitch for structural load and flexing is obvious and simple. do they actually do this obvious thing?  I don't know but I sure hope so.  So tell me again more detail please why metal's obvious advantage is it doesn't flex is so obvious?

Ti is an awesome material. I have 3 Ti bikes and a Ti watch.  Love the stuff.  Light, hard, great vibration dampening properties, and essentially never corrodes.  I wish my entire mooney were made of Ti.  I wish my prop leading edges were made of Ti.

Yes, an MT is made of composite wrapped wood.  Wood is a fantastic material.  It is literally "grown" carbon fiber with tremendous structural properties.  Another beautiful material (not for this purpose) is bamboo - amazing stuff.  There is a bike builder named Calfey who makes bamboo bikes that he joins with carbon fiber sleeves.  Those bikes are supposed to ride beautifully.  I don't understand if your point its wood wrapped composite is bad, good or just factual.

I don't fly in the desert but a few of us have gone to burning man - not for me!

Your phoo phoo of modern scimitar designs vs old school round tips, sure I believe that there may be some pretty good round tip designs and some poorly designed scimitars.  But surely modern cad and cfd design cycle is capable of designing a more aerodynamically perfect prop to eek out a few more points of efficiency for a given purpose.  I don't know if the prop people actually do this but I know a good bit of the sort of thing that goes on under the hood in such shape optimization in general terms.  If this technology has not reached the prop engineering industry then shame on them.  We do know that post hoc, test pilot engineers as end users have tried a variety of props on their specific make and model airplane and been able to select one that beats the others. e.g. the story of the acclaim prop selection.

If I could get a 2 blade prop made of the same material and same shape as my 4 blade mt I am sure it would be faster once in the air.  Lighter too!  I bet it would be physically dragging on the pavement, so I would need taller landing gear.  But I can't so I do like my 4 blade if nothing else because the ground clearance is a nice and practical thing.