3-Blade or 2-Blade Prop on a Single (200 HP) Engine?

How many blades are better on a single 200 HP propeller engine?

  • Total voters
    52
I have a 3-blade Hartzell on my 180hp Mooney. It does pushnthe CG forward a little bit. Despite what everyone thinks, it runs smoothly and was dynamically balanced back in 2003; I rechecked it a couple years ago, it was still 0.01.

It's also supposed to be slow. Some people call it an air brake. My Owners Manual is pretty clear that at 7500 / 10,000 msl my plane should run ~163-166 mph [pretty near 140 knots]. But I consistently run 145-148 KTAS when I punch everything into the Garmin WAAS box. Typical indicated airspeed at those altitudes is 145mph or a little more. So Mooney and Hartzell apparently know more about propellor design and aircraft performance that the old guys around the airport or the wags on the interweb.

My plane also climbs very well with that extra blade. :D

Check the plane. Look for STCs supporting whatever prop it has, if it's not original to the plane. Chances are it will do fine.

Oh, the "extra maintenance" is really bad--I squeeze #5 grease into 3 grease ports on the prop instead of two . . . .
 
Interesting sidelight comparing fixed-pitch and constant-speed props ...

Up until the early 1970s, the Cherokee 235 and the Cherokee Six 260 came with fixed-pitch props standard, constant-speed optional. The performance charts in the manuals for both of them show the fixed-pitch versions to be two to four mph faster in cruise, but they give it up in takeoff and climb performance.

PA-32-260 perf.jpeg
 
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Hank S said:
I have a 3-blade Hartzell on my 180hp Mooney. It does pushnthe CG forward a little bit. Despite what everyone thinks, it runs smoothly and was dynamically balanced back in 2003; I rechecked it a couple years ago, it was still 0.01.

It's also supposed to be slow. Some people call it an air brake. My Owners Manual is pretty clear that at 7500 / 10,000 msl my plane should run ~163-166 mph [pretty near 140 knots]. But I consistently run 145-148 KTAS when I punch everything into the Garmin WAAS box. Typical indicated airspeed at those altitudes is 145mph or a little more. So Mooney and Hartzell apparently know more about propellor design and aircraft performance that the old guys around the airport or the wags on the interweb.

My plane also climbs very well with that extra blade. :D

Check the plane. Look for STCs supporting whatever prop it has, if it's not original to the plane. Chances are it will do fine.

Oh, the "extra maintenance" is really bad--I squeeze #5 grease into 3 grease ports on the prop instead of two . . . .
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I did say for a given propeller geometry. ;)

The newer blade airfoil designs are significantly more efficient than the older ones, so upgrading from an old style 2 blade with decades of wear and maintenance to a new style 3 blade will very likely improve performance.

That third blade does add 50% more blade drag, however, and I would bet that the same blade design in a two blade configuration would eke out a bit more speed on a 180 horse engine than the three blade does.

(I also fly a Mooney, BTW)
 
It will help with avoiding prop strikes, though those aren't a huge problem with Arrows (people seem to bend the back ends much more readily). They are a bit smoother, having done about 15-20 hours in a 2 blade Arrow and about 100 in a 3 blade Arrow. The 3 blade Arrow tends to be faster and the 2 blade tends to burn less gas, though that may be a factor of those two aircraft in particular. It sounds like that one TSO Hartzell mentioned might make the 2 blade the best choice, though an expensive one. I guess you have to factor the AMUs saved in your personal flying.

Stewartb said:
At 200 hp I'd stay with 2 blades. With 4 cylinders I wouldn't even consider 3 blades.
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A lot of Arrow and Mooney owners disagree with you.
 
230 HP or less , you wont gain anything with a 3 blade prop, a 2 blade will be more beneficial, and the best to me is the MT propeller, great performance and lightweight, you motor will love it.
 
I think it depends on the technology. The new scimitar technology gives better performance all around over legacy props. The 3 blade scimitar on the Diamond DA40 reports 10% better take off and climb performance as well-as 2-3 knots in cruise. Weight with composites may not be different. We have a 5 blade Hartzell scimitar on our bird, that Hartzell says gives 20% better takeoff and climb performance over the metal 4-blade and is 15 lbs lighter. We are at least 6-8 knots faster in cruise over the POH. So smoother, lighter, performs better.... Costs more ;-). Small differences, but noticeable. Did someone once say each additional knot in an airplane costs $1000 ;-)
 
The 3 blade MT composite on the IO360 DA40 is very light, but requires addition of weights to the front of the engine to maintain the W&B, so there is no useful load benefit although Diamond claimed less noise and better performance. Mine was very susceptible to FOD damage. A camloc departed my cowl and did an impressive amount of damage to one of the blades, but it was still repairable. Always lusted over the Hartzell 2 blade composite, but could never justify the cost.
 

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Yeah, Hartzell makes a better prop. Just not available for all installations. We have the Hartzell Kevlar prop. Almost indestructible. Although ours did get hit by a tug. They were able to replace just the damaged blade.
 
More blades will be less efficient, since the blade is following more closely the disturbed air from the previous blade. The only reason (other than marketing) to go with more blades is if you're diameter limited due to tip speed or ground clearance and a 2 blade prop can't absorb all of the power produced by the engine.
 
More to a prop than the number of blades. The new OEMs, commercial and military ops aren’t going to more blades for looks.
 
bnt83 said:
Right except many spam cans have the CG so far forward as it is that its practically impossible to load it out of the aft CG anyway.

Then they flare & land like crap when flying solo with little in the back.
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Not my C150. It is the rear CG that I have to worry about. Guess I have to get a 3 blade.
 
Dana said:
More blades will be less efficient, since the blade is following more closely the disturbed air from the previous blade. The only reason (other than marketing) to go with more blades is if you're diameter limited due to tip speed or ground clearance and a 2 blade prop can't absorb all of the power produced by the engine.
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So you wonder how much more performance Raptor could get ditching the 5 blade he's got, but he's probably diameter limited?
 
Racerx said:
So you wonder how much more performance Raptor could get ditching the 5 blade he's got, but he's probably diameter limited?
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I don't think any number of blades is going to solve Raptor's problems...
 
I think everyone has pretty much listed the benefits of each. When I did this photo shoot with @Travis L in his 182 (formerly @timwinters plane), I shot it from a 182 with a 3-bladed prop. His has a 2-bladed prop. When I finished the air-to-air portion, I told I would let him pass me and I'd meet him on the ground for the rest of the photos. He left me like I was standing still! I watched him pull away quickly and it wasn't a long flight. To be fair, the 182 I'm flying has the Horton STOL STC, but I'm convinced it's mostly the prop that makes the difference.
 
I'd cast a vote, but I'm not sure what it would be. When the club had an Arrow it had a three blade prop. The extra weight meant we had to put some "stuff" in the cargo area to bring the CG aft of the forward limit. I never flew it with anyone in the back seat (nobody I'd want to take flying that I disliked enough to inflict that lack of legroom on), so that meant that there was something in the back, even if it was just a block of cement tied down. The 182 we had (and still have) has more hp and a two blade prop. As a result, I really wouldn't care.
 
Learning a lot from this post. I knew 2 blades are more efficient than 3, but didn't think about higher HP needing more blades.

No one has mentioned altitude. I know they put more blades on planes that go high to cope with the thinner air. So does a 3 blade prop make sense if you are routinely flying in the teens vs under 10,000'?
 
I kept the 2-blade on my 210 HP turbocharged plane. It was a matter of weight (mostly) and balance for me. If you've still got a heavy starter, you can reduce the weight gain a bit.

Mine was perfectly fine in the teens.
 
Already said above. I've always been told that you fit with the HP. So 2## HP you go with a 2 Blade, and starting at 300 you go with a 3 blade. But, I'm sure that's a massive over simplification. I like the looks of the 3 blade on the ground. In a 200HP I like the performance of a two blade.
 
Juliet Hotel said:
I think it varies by plane and by prop but generally yes. The thing to keep in mind is while 3 blade are generally slower, we're not talking big differences in speed in most cases. A couple knots usually. Close enough any number of other factors could all but make the difference non-existent when comparing any two similar planes. A bigger factor is probably the weight difference and cost difference in most cases.
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I want my 2 dollars. Or 2 knots in this case. At less cost, and less weight.
 
Pilawt said:
Interesting sidelight comparing fixed-pitch and constant-speed props ...I'

Up until the early 1970s, the Cherokee 235 and the Cherokee Six 260 came with fixed-pitch props standard, constant-speed optional. The performance charts in the manuals for both of them show the fixed-pitch versions to be two to four mph faster in cruise, but they give it up in takeoff and climb performance.

View attachment 73337
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I'm no expert in aerodynamics, but I'm assuming that's all associated with prop drag slowing the engine when it's not running at higher RPMs. I guess turbo props can have 5 because they have the hp and torque to easily overcome the drag.
 
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