Two-blade vs three-blade prop on C182?

Brian Austin

Brian Austin

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Brian Austin
I can't remember the advantages/disadvantages between a 2 and 3 bladed prop. I can think of a few:

Two blades:
1. Pro: less drag with two vs three surfaces
2. Con: longer blade required for same power reduces ground clearance
3. Pro: Less cost for overhaul/purchase

Three blades:
1. Pro: Higher off of ground for better clearance
2. Con: higher cost
3. Pro: faster RPM due to speed of sound issues at tips

I'm looking at Cessna 182's right now for possible purchase next year.

Thanks!
 
Three blade:
Pro - looks cooler

Two blade:
Pro - goes faster

Unless I needed the ground clearance, I wouldn't base my purchase decision on the prop. However, all things being equal, I need all the "looks cooler" I can get.

Chip
 
gibbons said:
Three blade:
Pro - looks cooler

Two blade:
Pro - goes faster

Unless I needed the ground clearance, I wouldn't base my purchase decision on the prop. However, all things being equal, I need all the "looks cooler" I can get.

Chip
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So two blade props will pull a plane faster? On average, what would be the advantage in speed?

Would a two blade prop be more efficient with regard to higher density altitudes?

Ground clearance could be an issue. A goal is to have a large tract of land up in the mountains with a dirt strip in place for this plane.
 
Having flown jumpers in many old 182's... I can tell you that the three blade will climb faster (100 fpm) & the 2 blade will cruise faster (2 kts).

I have a three blade on my 59' It looks very sexy :)

Eamon
 
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Why does the 3 blade cruise slower vs. the 2 blade climbing slower? Are we talking fixed pitch? Or is there another factor involved?
 
A 3 blade cruises slower because the blades have more drag. A 3-blade climbs faster because the airplane likes to have it installed.

The HUGE difference between the two -- and the deciding factor, IMO -- is the sound "bestowed" on the pilot. At the same RPM, a 3-blade hits the airplane with a frequency 50 percent higher. If a 2-blade thrums, a 3 glade growls. The higher frequency is easier to block by insulation/headsets/ANR, so the perception is that a 3 blade is much quieter, even if in fact it is only marginally so.

I had a Lance that I changed from 2 to 3 blade. No other changes at that time. Climb went up by about 100 fpm at max gross. Cruise speed appeared identical, the airplane was noticeably smoother. But, oh, that quiet. I would never have gone back on that airplane.

However, in some airplanes the cruise penalty is substantial. Mooney comes to mind. A lot of J models got converted, then converted back. Don't have any specifics on that at the moment, but I'll be talking to a Mooney expert tomorrow and will ask him for numbers.
 
Our clubs 182RG was converted from a 2 blade to a 3 blade. When applying full power to take off it's markedly smoother, climbs better. I haven't noticed a big hit in cruise but I do notice it seems quieter.

Here's a link about 3 blade vs 2 blade pulling power.

3 blade Vs. 2 Blade Pulling Power
 
There are two penalties to the three-blade, and two big advantages.

Disadvantages:

1) Additional drag (more blade area) means slower cruise speed. The easy way to say it is: you just simply have more stuff out in the wind.

2) Weight. The three blade is substantially heavier, and adds forward moment to the W&B. On my Commander, which is weight-heavy and nose-heavy to start with, this is a big impact. You can counteract some (but not all) of the impact by going to a light-weight starter. The AOPA Commander will get the turbo-normalizing kit... if it gets the 3-blade prop, the STC requires a light-weight starter. For W&B. This is not insignificant.

Advantages:

1) Improved climb. There is more blade area to "grab" the air, improving climb.

2) It just plain looks cool. :)

That's way oversimplified, but I don't really feel like doing the full aerodynamic explanation right now.....

W&B is a killer on some planes....
 
Not all three-blades give you more clearance. I was surprised to find for my Mooney that the two and three-blade options were the same diameter.

Eric
 
I would agree that 3 blade propellers are markedly smoother than 2 blade, and do seem to sound overall better in the airplane

What's interesting to me is that there aren't a lot of four blade props around. And while a three blade looks really cool the four blade not so much. There are a handful of Cirrus out there with four blade props and I always thought they look odd

Now on a twin engine though, for blade looks properly badass.. and two just downright weird

maybe it is an odd number thing, as the five bladed props on the turboprops and then more look really sick too.. I was once told that odd number props are inherently easier to balance and smoother

Ryanb said:
Not so fast. The gold medal goes to me.
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technically, yes, however a thread like that doesn't really count. That's basically just a tech support piece with no replies
 
Traded the 2-blade on our 182RG for a Black Mac last year. Mac accelerates faster during take-off, climbs better, significantly quieter (pilot perception of noise). No obvious change in cruise speed, but then again the 2-blade was found to be out of tolerances, which lead to the Mac purchase. FWIW...

Jim
 
**maybe someone can educate me on the "3-blade goes slower because more drag" thing

I know at face value you are spinning 3 things in the air, vs 2, so the face-value logic makes this sound true. But theoretically on a 3 bladed prop each of the blades are doing less work than each blade on a 2 blade.. so some of the drag must actually go down? There's a reason catamaran and trimaran sailboats are faster, and skies faster, than monohull and snowboards. Tangerines:bananas I get it.. but from the examples in this thread doesn't seem like anyone actually noticed their plane going slower after going to 3 blade
 
Brian Austin said:
I can't remember the advantages/disadvantages between a 2 and 3 bladed prop. I can think of a few:

Two blades:
1. Pro: less drag with two vs three surfaces
2. Con: longer blade required for same power reduces ground clearance
3. Pro: Less cost for overhaul/purchase

Three blades:
1. Pro: Higher off of ground for better clearance
2. Con: higher cost
3. Pro: faster RPM due to speed of sound issues at tips
4. ALMOST ALWAYS WEIGHS MORE​

I'm looking at Cessna 182's right now for possible purchase next year.

Thanks!
Click to expand...

I would never trade an aluminum two blade for a three blade in any form.
 
Save the 3-blade for a 520 ci power upgrade. Stick with a 2-blade with a 470.
 
Frankly not a huge difference ether way.
 
The ONLY place a 3 blade on a 180/182/185 does any good it pulling a seaplane onto the step.

Speed, climb, looks, weight.............all favor a 2 blade.
 
I fly a 182 470 2 blade. Anytime a see three blade 182 I’m thinking wow. That guy looks cool bet he has a 520 or p-ponk in there. 470 3 blade is like a Mazda with a Mercedes emblem on the hood lol
 
Tantalum said:
**maybe someone can educate me on the "3-blade goes slower because more drag" thing

I know at face value you are spinning 3 things in the air, vs 2, so the face-value logic makes this sound true. But theoretically on a 3 bladed prop each of the blades are doing less work than each blade on a 2 blade.. so some of the drag must actually go down? There's a reason catamaran and trimaran sailboats are faster, and skies faster, than monohull and snowboards. Tangerines:bananas I get it.. but from the examples in this thread doesn't seem like anyone actually noticed their plane going slower after going to 3 blade
Click to expand...


Because you're failing to account for parasite drag and focusing on induced drag only, which is a lessened effect in cruise versus takeoff (aka effective angle of attack). Parasite drag is higher period dot, there's no getting around it. Drag is the square of velocity, so it's even more undeniable. People just see what they want to see. They want the 3 blade to cost them nothing, so it costs them nothing.

The reality is that at the power levels we are talking about the weight penalty over what extra performance you get is generally not "marginally positive". This is a decision of aesthetics wrapped in aerodynamic cherry picking. This is why the 4 bladed on a sub 500HP application is even more retarded, nevermind at the aircraft heights of most spam cans, the blade lengths of a 4-blade prop end up being "trump hands" in ratio. :D

To be fair, the penalties will be most pronounced at the fastest airspeed, which means the slower you go the less the penalty delta will be. This is why airframes like a Mooney Ovation, which relies on large drag reductions via streamlining in order to hit the 170s, is more pronouncedly affected by a 3 blade in cruise than say a drag @ss 182, which is already behind the drag curve on a good day. So the drag penalty at its nominal cruise speeds is already the square of a smaller number.

In the case of WB challenged airplanes like the Beech 33/35 products, due to sitting everybody well behind the wing spar and putting all the fuel in the leading edge, you run into a situation where prop weight out front helps you, even if the mechanism for attaining balance is inefficient (throwing dead weight). Getting 100fpm more or so is the rationalization for something that is merely a sunk cost if you want to stay in the WB envelope. Most Cessna and Piper products don't have that problem, so the motivations to slap a 3-blade would have to reside elsewhere.

Don't get me wrong, I think even an ovation would be benefited from losing 5 knots at the top end in order to bring the 2-bladed takeoff distances back down to the breathable atmosphere. Ditto for designed abortions like the T-arrow and T-lance et al.
 
Just don’t put your 2 blade on floats and try to go into NYC (6N7)

FB826600-CCE5-498-F-BDB2-855-EF5036-AE4.jpg
 
Holy necropost!

I wonder how Brian, Chuck, Chip, and Eamon are doing? Chip I last saw in person about 6 or 7 years ago, haven't heard a peep from the others in forever.
 
But, as long as we're talking about props...

For what it's worth, we looked at a 3-blade Top Prop for the R182 when we needed a new one, and it was the same length as the two-blade, so you're not necessarily gaining prop clearance by going with a 3-blade.
 
When you have enough torque that a 3-blade pulls you out of the hole better than a 2? You get a 3-blade. If you want max cruise? Stay with 2. If you're on the fence and need a nudge? A 3-blade on a 6-banger is smooooth.
 
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