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

AggieMike88

AggieMike88

Touchdown! Greaser!
Joined
Jan 13, 2010
Messages
20,805
Location
Denton, TX
Display Name
Display name:
The original "I don't know it all" of aviation.
The club's 1975 C182P is a fine airplane and we are all very happy with it. It currently has a 2-blade prop.

But I've seen a few Skylanes of the similar era equipped with 3-blade props.

What are the pros and cons of having the 3-blade versus the 2-blade?

(this is for my enlightenment and discussion only. Not to suggest club needs to change anything)
 
Some people think three-blades look better. Two-blades actually out-perform them so there's no tangible gain other than ego gratification. Don't spend any money on it.



AggieMike88 said:
The club's 1975 C182P is a fine airplane and we are all very happy with it. It currently has a 2-blade prop.

But I've seen a few Skylanes of the similar era equipped with 3-blade props.

What are the pros and cons of having the 3-blade versus the 2-blade?

(this is for my enlightenment and discussion only. Not to suggest club needs to change anything)
Click to expand...
 
6 banger engines also run smoother with three blades from what I hear.

4 bangers not so much.
 
We've got a 3-blade on the RV-7A. We figure it's costing us ~5kts or so in cruise. But it does climb like a homesick angel, though. :)
 
Depends on the engine, but you will see some engines with 2 bladed props placarded against continuous operation between certain RPM bands (e.g. 2100 - 2200 rpm) due to destructive harmonics that goes away when a three bladed prop is installed.
 
Things I don't like about my three blade:
1) Extra drag if I have an engine failure (yes, I actually think about things like this).
2) Can't prevent blades from hitting the ground if the gear is up (yes, I actually think about things like this).
3) Additional weight.
4) Slower cruise, supposedly (never have seen numbers on this)

Things I like:
1) Looks good.
2) Better climb, supposedly (never have seen numbers on this)
 
And the no-cost answer to that problem is?

Sac Arrow said:
Depends on the engine, but you will see some engines with 2 bladed props placarded against continuous operation between certain RPM bands (e.g. 2100 - 2200 rpm) due to destructive harmonics that goes away when a three bladed prop is installed.
Click to expand...
 
Sac Arrow said:
Depends on the engine, but you will see some engines with 2 bladed props placarded against continuous operation between certain RPM bands (e.g. 2100 - 2200 rpm) due to destructive harmonics that goes away when a three bladed prop is installed.
Click to expand...

Interesting our M20J's with stock mcauley 2 blades have this placarded region You can feel the vibration.

One of them had a prop strike and the new prop is a 2 blade all metal hartzell. The placarded range is gone
 
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.
 
dell30rb said:
Interesting our M20J's with stock mcauley 2 blades have this placarded region You can feel the vibration.

One of them had a prop strike and the new prop is a 2 blade all metal hartzell. The placarded range is gone
Click to expand...


Its not engine specific, its engine AND prop (And airframe?) combination specific.

O-360 powered Cessna 177 with 2 blade mccauleys have it too.
 
wabower said:
And the no-cost answer to that problem is?
Click to expand...

The question asked was what are some pros and cons of 3 bladed props, not how to comply with operational placards.

dell30rb said:
Interesting our M20J's with stock mcauley 2 blades have this placarded region You can feel the vibration.

One of them had a prop strike and the new prop is a 2 blade all metal hartzell. The placarded range is gone
Click to expand...

Not doubting it. Not all 2 bladed prop/engine combinations have this restriction.

BUT - the harmonics that are actually destructive to the crankshaft are internal and you wouldn't feel them, so the absence of felt vibration in that range if otherwise so restricted does not mean that it's okay to cruise at those RPM's.
 
If you read a POH on a 182, Cessna makes no performance differentiation on 2 or 3 blade props. (From Performance Specifications - "Performance with an optional 3-bladed prop is essentially as shown above") The biggest advantage is increased distance between the blade and the ground during taxi on uneven surfaces.
 
Last edited:
Challenged said:
Things I don't like about my three blade:
1) Extra drag if I have an engine failure (yes, I actually think about things like this).
2) Can't prevent blades from hitting the ground if the gear is up (yes, I actually think about things like this).
3) Additional weight.
4) Slower cruise, supposedly (never have seen numbers on this)

Things I like:
1) Looks good.
2) Better climb, supposedly (never have seen numbers on this)
Click to expand...

Isn't it advised not to try this when you have a gear failure?
 
Challenged said:
2) Can't prevent blades from hitting the ground if the gear is up (yes, I actually think about things like this).
Click to expand...

What are you flying? A gear up failure in a Piper is very unlikely. More of an issue with a Cessna or Bo. If you're doing an intentional gear up landing, it's probably because you're ditching the plane in the water, or landing in a rough field, in which case it won't make much difference what position the prop is in. Most gear up landings are unintentional, with the prop spinning.

MultiMediaWill said:
Isn't it advised not to try this when you have a gear failure?
Click to expand...

If you mean trying to bump the starter to level the blades, I suppose if you have time to deal with it then go for it, but it wouldn't be my priority.
 
School 182 is very nearly identical to mine and recently got a new McCaulley 3 blade prop.


It now greatly out performs mine in climb and is not any slower for it. All things being equal a three blade will usually be slower than a two, but when you change out a dated 2 blade for a much more modern three it may not be the case.
 
Skylane81E said:
School 182 is very nearly identical to mine and recently got a new McCaulley 3 blade prop.


It now greatly out performs mine in climb and is not any slower for it. All things being equal a three blade will usually be slower than a two, but when you change out a dated 2 blade for a much more modern three it may not be the case.
Click to expand...


You SIR need to update your avitar then :lol:
 
wabower said:
Some people think three-blades look better. Two-blades actually out-perform them so there's no tangible gain other than ego gratification. Don't spend any money on it.
Click to expand...

This is another example of someone with no clue spouting on a subject they know little about. In the experimental world we know better. Look at Reno racers and make that same incorrect statement.....! :mad2:
But hey, it's a forum and opinions are like ___________ and we all have one. Facts tell the story. Ever seen a Mustang with a freaking 2 bladed prop - helloooooo
 
Have you ever owned and flown two 180's side-by-side with a two-blade on one and a three blade on the other? Yes or no? If you haven't and you want to run your yap after doing so, have your young ass on the KADS ramp at 1000 am tomorrow. Otherwise STFU.



Goofy said:
This is another example of someone with no clue spouting on a subject they know little about. In the experimental world we know better. Look at Reno racers and make that same incorrect statement.....! :mad2:
But hey, it's a forum and opinions are like ___________ and we all have one. Facts tell the story. Ever seen a Mustang with a freaking 2 bladed prop - helloooooo
Click to expand...
 
Goofy said:
This is another example of someone with no clue spouting on a subject they know little about. In the experimental world we know better. Look at Reno racers and make that same incorrect statement.....! :mad2:
But hey, it's a forum and opinions are like ___________ and we all have one. Facts tell the story. Ever seen a Mustang with a freaking 2 bladed prop - helloooooo
Click to expand...

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.
 
I read somewhere that a one-bladed prop is theoretically the most efficient prop possible. I'm not sure about that, though.
 
jpower said:
I read somewhere that a one-bladed prop is theoretically the most efficient prop possible. I'm not sure about that, though.
Click to expand...

Seen any?
 
wabower said:
Have you ever owned and flown two 180's side-by-side with a two-blade on one and a three blade on the other? Yes or no? If you haven't and you want to run your yap after doing so, have your young ass on the KADS ramp at 1000 am tomorrow. Otherwise STFU.
Click to expand...

Oh Wayne, you're so smart, excuse me please......:eek:
PS: there's a lot more to this type of comparison than blade count but Wayne is too smart to consider blade material, length, twist, tip design etc. But then he's probably stuck with the crap they put on Cessna's, silly me! Sorry I won't stoop to nasty little letters to hide filthy comments, I'll leave that to you and your's......:nono:
 
Last edited:
The new props are routinely evaluated and fly-offs conducted by the 180 owner's group. An extensive write-up was posted last week on the most recent two-blade replacement of a three-blade. Read them before you continue the doofus blathering.
Goofy said:
Oh Wayne, you're so smart, excuse me please......:eek:
PS: there's a lot more to this type of comparison than blade count but Wayne is too smart to consider blade material, length, twist, tip design etc. But then he's probably stuck with the crap they put on Cessna's, silly me! Sorry I won't stoop to nasty little letters to hide filthy comments, I'll leave that to you and your's......:nono:
Click to expand...
 
I think the point is well taken that it isn't worth money to "upgrade" to a three blade prop just to be doing it. My Arrow II has a three blade prop but it was on it when I got it. I don't really see a big difference over it and other two blade prop Arrows with the same engine, except it runs smoother (probably more of a balance issue) and it climbs faster. Cruise seems to be about the same. If I'm taking a hit its not enough to notice.

But then again we're also talking about a Hartzell vs. a Macauley, which could be as much if not more of a difference than the number of blades.
 
Goofy said:
Seen any?
Click to expand...

Actually yes. Not in person, but they do exist, in motorgliders especially.

silentclub_14.jpg


I think they use them mainly for space concerns when the engine is folded away, though. After a few minutes of googling, there seem to be a ton of people asking about it and nobody with definitive answers.
 
jpower said:
Actually yes. Not in person, but they do exist, in motorgliders especially.

I think they use them mainly for space concerns when the engine is folded away, though. After a few minutes of googling, there seem to be a ton of people asking about it and nobody with definitive answers.
Click to expand...
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.
 
jpower said:
I read somewhere that a one-bladed prop is theoretically the most efficient prop possible. I'm not sure about that, though.
Click to expand...

I have heard that, too. I believe the reasoning is that with a single-blade prop, the blade is always in 'clean' air instead of dirty air caused by the preceding blade.

The downside of a single blade prop is the loss of counterbalance from a second (or 3rd or 4th, etc.) blade which causes nasty vibration.
 
CJones said:
I have heard that, too. I believe the reasoning is that with a single-blade prop, the blade is always in 'clean' air instead of dirty air caused by the preceding blade.

The downside of a single blade prop is the loss of counterbalance from a second (or 3rd or 4th, etc.) blade which causes nasty vibration.
Click to expand...

The highest performance control line model airplanes all run counterbalanced single blade props turning insanely high RPM (sometimes 40k+ rpm).
 
Goofy said:
Oh Wayne, you're so smart, excuse me please......:eek:
PS: there's a lot more to this type of comparison than blade count but Wayne is too smart to consider blade material, length, twist, tip design etc. But then he's probably stuck with the crap they put on Cessna's, silly me! Sorry I won't stoop to nasty little letters to hide filthy comments, I'll leave that to you and your's......:nono:
Click to expand...

Look, Goofy. Wayne is right in an apples to apples comparison. On the same air frame with the same prop design, two blades outperform three.

And you have been the one that has been nasty in this thread. Wayne only got a little testy when YOU wouldn't shut up. Just my opinion. YMMV
 
Greg Bockelman said:
Look, Goofy. Wayne is right in an apples to apples comparison. On the same air frame with the same prop design, two blades outperform three.

And you have been the one that has been nasty in this thread. Wayne only got a little testy when YOU wouldn't shut up. Just my opinion. YMMV
Click to expand...

Feeling a little necro today Greg?
 
AggieMike88 said:
The club's 1975 C182P is a fine airplane and we are all very happy with it. It currently has a 2-blade prop.

But I've seen a few Skylanes of the similar era equipped with 3-blade props.

What are the pros and cons of having the 3-blade versus the 2-blade?

(this is for my enlightenment and discussion only. Not to suggest club needs to change anything)
Click to expand...

My experience with a 182 I flew through the change over: Lost a couple knots speed, climbed a bit better (operating SL airport), got off the runway marginally (but inconsequentially) sooner. It was quieter and smoother though. That was the difference that left an impression, noticeably quieter and smoother, the rest didn't amount to a hill of beans really.
 
You must log in or register to reply here.
Back
Top