3-blade vs. 2-blade prop (Cessna 182)

For performance it is so much horsepower per blade. Im not sure of the numbers but I think its 100 hp per blade and this is actual horsepower, not engine rated maximum.

So ideal for 200-300hp engine is 2 blades, 300-400hp for 3 blades etc.

Trouble is its just something I heard, not substatiated. And the 100hp may be wrong, they might be other actual hp numbers. But the principal makes sense. More hp more blades.

Three blades look cooler. Three blade might be smoother.
 
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coloradobluesky said:
For performance it is so much horsepower per blade. Im not sure of the numbers but I think its 100 hp per blade and this is actual horsepower, not engine rated maximum.

So ideal for 200-300hp engine is 2 blades, 300-400hp for 3 blades etc.

Trouble is its just something I heard, not substatiated. And the numbers may be wrong, they might be other actual hp numbers.

Three blades look cooler. Three blade might be smoother.
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It's okay within a limited parameter of a direct drive prop on a recip engine driving a plane. Once you change those parameters by say adding a gear reduction, it is no longer a functioning statement.

The planes I noticed benefit most from the 3 bladed prop are on the 285hp IO-520; 185, 210, 206/207, Bonanza... They are all really loud sporting the 2 blade prop because they are so long, and turn 2700rpm (then some people will turn them up to 2850 for 300hp), they are really noisy. The 3 blade gets enough length off of them that it brings the tip speed down to a lower, quieter, fraction of Mach, without giving up take off and climb performance. I heard an Alaska operator refer to it as his 'city prop'.
 
Single-blade propeller ...

P1040748.jpg


http://flysafe.raa.asn.au/magazine/everell_propeller.pdf

http://www.ladieslovetaildraggers.com/blog/no-way-a-one-bladed-propeller/
 
I used to race a little hydro with a 402x outboard and a single bladed prop, that sucker screamed.
 
Henning said:
They are all really loud sporting the 2 blade prop because they are so long, and turn 2700rpm (then some people will turn them up to 2850 for 300hp), they are really noisy. The 3 blade gets enough length off of them that it brings the tip speed down to a lower, quieter, fraction of Mach, without giving up take off and climb performance. I heard an Alaska operator refer to it as his 'city prop'.
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Many,many Cessna 185s have been converted to the P-Ponk "401" McCauley. It is 86" or 88" long and MUCH noisier than the standard 88" 2 blade Cessna Seaplane prop.

Trouble with the "401" is the drastic reduction in cruise speed. That and it is heavy, expensive, loud, and did I mention SLOW!


Probably the best Cessna 185 prop is the 88" 2 blade followed by the MT.
 
kgruber said:
Many,many Cessna 185s have been converted to the P-Ponk "401" McCauley. It is 86" or 88" long and MUCH noisier than the standard 88" 2 blade Cessna Seaplane prop.

Trouble with the "401" is the drastic reduction in cruise speed. That and it is heavy, expensive, loud, and did I mention SLOW!


Probably the best Cessna 185 prop is the 88" 2 blade followed by the MT.
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Yeah, I could tell the guys up in Anchorage who were sporting those. All the rest of the 185s are obnoxiously loud, then the dude takes off that's painfully loud.
 
I've seen several iterations(not inperson) of a 1 bladed prop.

J2-Cub-Single-blade-prop.jpg
 
Three blades are nice for lower noise, higher clearance, and a little smoother, 2 blades offer better performance.

I had a 2 blade on my first plane, three blade on my current plane, not a huge deal.


If it was just a matter of checking a box I'd get a three blade, that said I wouldn't turn down a potential plane just because it had a 2 blade vs 3 blade.
 
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If the 182 has been upgraded to a 520? Most of the 180s and 182s that you see with 3-blades have big engines. The availability of props is better with more horsepower. A 3-blade is smoother and pulls harder. I switched my 180 from an 0-470 w/88" 2-blade to 0-520 w/86" 3-blade and the performance advantage is incredible. A buddy did the same thing at the same time but stayed with an 88" 2-blade. I'm faster.

An 88" 2-blade spins the same RPM as an 88" 3-blade so unless you specifically select shorter blades there is no noise advantage. Your engine needs to spin full RPM to make full power.
 
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gismo said:
With the same blade design, a one blade prop should be the most efficient if it can adequately absorb the available power. I suspect the biggest issue with them is the radial bending load they impart to the crankshaft.
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The blade is offset from a counter weight. The blade does move fore and aft slightly on the pivot with rpm changes.
 
Skylane81E said:
Start adding monster HP and you will need more blade to absorb it, so you can increase the diameter, have the tips go way super sonic and destroy efficiency OR you can add blades. Fact is that on a typical GA plane a two blade prop will out run a three blade of equivalent blade design.
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I believe that. My boss and I fly two different Cardinals - both maintained about the same, good engines, etc... his is faster with the 2 bladed prop and we like the way it handles better. Also, I like the weight and balance on that other plane better with the 2 bladed prop, FWIW. It probably does affect the cruise a tiny bit.
 
The 182 has some very specific characteristics that make a 3 bladed prop really not worth it unless you have a lot of horsepower. 3x yes 3x I have put a new prop on a 182 everytime I did it first thought was "well there is $5k I can't get back...." Look it looks cooler and it is marginally quieter on takeoff. It will slow you down faster coming home, stick to the 2 blade. Get a good one with no AD's. The 182 is hard enough to trim up on landing save the weight... Take the $5k and buy weather and traffic.
 
One thing about three bladed props you have to be cautious with, especially during transitional seasons where it freezes. A lot of pilots put one blade up because of the tow bar, push it into their tie down, then leave the one blade pointing straight up nice and pretty. What this causes is a puddle to form in the bottom of the spinner in the rain, and mixed with the mineral salts from the surface, and the stainless steel screws, it creates electrolysis in the spinner and back plate. On top of that, in freezing rain conditions, that puddle turns into a big assed chunk of ice that will destroy the backing plate as soon as the engine fires. I watched a Navajo eat one like that, looked like the engine was going to jump off the wing. Luckily it went so fast he didn't even try to start the other.

So when you have a three blade prop, make sure you park it outside with a blade pointing straight down.
 
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gismo said:
Without a gear reduction you get to the point where two blades simply cannot transfer the available HP without transonic tip speed and the associated huge drag and noise that creates. IIRC, that's generally accepted to be around 300 HP. For anything less the primary practical advantage of 3 blades is greater ground clearance. They are often touted to have greater climb performance but I think that's often not the case, at least not in any significant way. 3 blade props also tend to be quieter (assuming the blade length is less than the appropriate 2 blade) at full power and the perceived cabin noise is likely less but that's more about the 50% higher fundamental frequency of the noise and the greater attenuation available at higher frequencies than an actual lowering of the noise level at the prop.
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I can verify that fact...;);)
 
gismo said:
With the same blade design, a one blade prop should be the most efficient if it can adequately absorb the available power. I suspect the biggest issue with them is the radial bending load they impart to the crankshaft.
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BillTIZ said:
The blade is offset from a counter weight. The blade does move fore and aft slightly on the pivot with rpm changes.
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Gismo is correct. Under higher power loading, the single blade creates some significant a-symmetrical stresses on the crank.

The static balance is good, but the forces are pulling on an un-balanced lever arm. Think of pulling the plane forward with a couple hundred horsepower worth of force distributed evenly on all the blade tips. The force on the crank stays inline with the engine axis.

Now put the entire force on one blade, while spinning it around. This creates a rotating bending moment on the crank. Not good if the engine hasn't been designed for it.
 
ElPaso Pilot said:
Gismo is correct. Under higher power loading, the single blade creates some significant a-symmetrical stresses on the crank.

The static balance is good, but the forces are pulling on an un-balanced lever arm. Think of pulling the plane forward with a couple hundred horsepower worth of force distributed evenly on all the blade tips. The force on the crank stays inline with the engine axis.

Now put the entire force on one blade, while spinning it around. This creates a rotating bending moment on the crank. Not good if the engine hasn't been designed for it.
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Fortunately, aircraft crankshafts are designed to cope with it as they see the bending moment anyway (though granted to a lesser effect) due to gyroscopic forces when maneuvering. This is one of the main issues using an automotive crank, this is not a design consideration there, and the end main is typically 1/3rd to 1/4th the depth of that on an aircraft engine crank.
 
Henning said:
Fortunately, aircraft crankshafts are designed to cope with it as they see the bending moment anyway (though granted to a lesser effect) due to gyroscopic forces when maneuvering. This is one of the main issues using an automotive crank, this is not a design consideration there, and the end main is typically 1/3rd to 1/4th the depth of that on an aircraft engine crank.
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Nearly all auto conversions use a gearbox. Wouldn't that transfer the load to the gearbox and save having to reinforce the engine? (Of course, the gearbox would have to be designed for it, but that's a lot easier than redoing an engine.)
 
arnoha said:
Nearly all auto conversions use a gearbox. Wouldn't that transfer the load to the gearbox and save having to reinforce the engine? (Of course, the gearbox would have to be designed for it, but that's a lot easier than redoing an engine.)
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My prop is driven off the redrive, which absorbs all the gyro and thrust forces....

The motor has no idea it is in a plane...:no:....;)
 
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arnoha said:
Nearly all auto conversions use a gearbox. Wouldn't that transfer the load to the gearbox and save having to reinforce the engine? (Of course, the gearbox would have to be designed for it, but that's a lot easier than redoing an engine.)
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Nearly all conversions greater than 120hp, and that does eliminate the problem. However,mother majority of auto conversions are direct drive VW, Corvair, and Subaru engines and I have seen several cracked cranks at the bolt holes from gyroscopic effects.

I recommend a gear reduction regardless if you are going to run on gasoline. Gasoline with a 5" piston wants to run 3400rpm, 4200 with a 4".
 
How does the Scimitar prop compare on the standard 0-470 engine with the two blade?
 
I know this is a heated topic but wondering about Hartzell Scimitar top prop conversion. The main reason I am considering is for ground clearance in backcountry. Does it loose much in the way of TAS during cruise? I know the climb will be better.
 
I switched from a 2 blade McCauley to a 3 blade Hartzell Scimitar Top Prop.

3 blade pros: Looks cool, pulls & climbs like a homesick angel, slightly less cabin noise, no noticeable reduction in cruise performance, 6 year 2400hr TBO, 2 inches of extra ground clearance (remember not just clearance for prop strikes but sucks up less rocks too.

3 blade cons: Extra weight on the nose - (wrong side of the datum which harms useful load), extra cost Like $1800, cowling harder to remove for 182's older than S model.

The ramp appeal is fantastic, everyone loves the look. BTW, when I mean likes to climb.... after turning cross-wind to downwind I have to cut power or in a snap I'm 300' over TPA. Cruise was really unaffected. I'm still getting ~132kts 24/2450 in my 182P.

Big Big plus for the 2 blade is Cowl removal and useful load.
 
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Bojon01 said:
How does the Scimitar prop compare on the standard 0-470 engine with the two blade?
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From Hartzell Website:
The 82-inch diameter, “blended” airfoil, Scimitar blades have successfully proven themselves in engineering flight tests. Compared to standard propeller models, the kit improves climb performance by 8.5%, and cruise performance by 2-4 knots or even more at altitude, and also enhances ramp appeal. In line with the latest FAA and international standards, the prop’s noise emissions are at a globally-accepted level of 77.5 dB(a).

This has been my experience, which matched the marketing claims; though I'm not sure cruise has improved (it's really hard to fully confirm 1 or 2 knots difference, but it was NOT slower in cruise.
 
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NordicDave said:
3 blade cons: Extra weight on the nose - (wrong side of the datum which harms useful load), extra cost Like $1800, cowling harder to remove for 182's older than S model.
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The only plane I've flown with a 3 blade prop is an Arrow. It had the same problem. You needed weight in the baggage compartment unless you had more than 400 pounds in the front seats just to get the CG aft of the forward limit. A 50 pound concrete block, tied down with the safety straps, usually did the trick. What a waste of useful load.
 
Ghery said:
The only plane I've flown with a 3 blade prop is an Arrow. It had the same problem. You needed weight in the baggage compartment unless you had more than 400 pounds in the front seats just to get the CG aft of the forward limit. A 50 pound concrete block, tied down with the safety straps, usually did the trick. What a waste of useful load.
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Sometimes it works out better: short-body Bonanzas. 3-blade props are perfect for aircraft like these that suffer aft loading problems.
 
I wouldn't have imagined someone putting a 3-blade prop on an Arrow.

My 182P upgrade from McCauley 203 to the Hartzell 3 blade Scimitar Top Prop changed my weight & balance by -1.1" on the arm and -28.9 for useful load, moment decreased 1156.

I gained back 13lbs of useful load to 1100lbs and .5" on the arm by removing old avionics like ADF and old marker beacon antenna, etc. Next adding the "fresh pick" STC will put useful load up to 1250lbs for take-off and 1100lbs for landing.
 
NordicDave said:
I wouldn't have imagined someone putting a 3-blade prop on an Arrow.
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Pilawt said:
Turbo Arrows had three-blade props from the factory, at least as optional equipment, since 1979.
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The one I flew (and the club has since sold) had a normal fuel injected 200 hp engine. It had the 3-blade prop when I joined the club in 2000, so I have no idea when it was added, or why. A 1969 PA-28R-200.
 
Seems like a lot of prop for that plane and motor. Something funny...

The Hartzell factory guy I spoke with said:
"yeah, aircraft owners really like the ramp appeal of the 3 blade. If we made a 4 or 5 blade people would buy it! I know because people ask."
 
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