Swapping stock 2 Blade Prop for a 3 Blade One?

netsurfr

netsurfr

Pre-takeoff checklist
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I'm seriously considering replacing my Dakota's 2 blade prop with Hartzel's 3 Blade Scimitar. My 2 bladed has 1000 hrs since it's last overhaul 13 years ago and it's been spilling grease on one blade so rather than OH I'm leaning w/ paying more and going with a 3 blade.

Would love to hear from those of you who have swapped out your 2 blade prop for a 3 blade in terms of how happy (or not) you are with the change.
 
Have you checked if MT has one for your plane? I'm happy with mine.

It's a two blade, but it dropped 10lbs. off the very front c.g. station in our nose heavy skywagon.

The lighter composite MT spins up faster, and spins down faster acting like an air brake.
 
I cant speak personally about the difference in performance, but I can say that someone swapped a 3 blade onto my Mooney in the past and then later swapped it back out for a 2 blade Hartzell Scimitar. Seems to me they wouldn't spend the money twice unless there was a real difference. The difference in weight is around 35lbs IIRC. From reading most peoples experiences with the same plane I'm really happy they put the new 2 blade on it.
 
No mt stc for my plane.

txflyer said:
Have you checked if MT has one for your plane? I'm happy with mine.

It's a two blade, but it dropped 10lbs. off the very front c.g. station in our nose heavy skywagon.

The lighter composite MT spins up faster, and spins down faster acting like an air brake.
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35lbs is a lot and from what I gather the scimitar design makes a difference but good to know.

StinkBug said:
I cant speak personally about the difference in performance, but I can say that someone swapped a 3 blade onto my Mooney in the past and then later swapped it back out for a 2 blade Hartzell Scimitar. Seems to me they wouldn't spend the money twice unless there was a real difference. The difference in weight is around 35lbs IIRC. From reading most peoples experiences with the same plane I'm really happy they put the new 2 blade on it.
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The considerations when making a prop change are:

1) Weight
2) Takeoff/climb
3) Cruise
4) Noise

Typically more blades will increase weight and hurt cruise speed, but improve takeoff/climb and reduce noise. This equation can vary some, as the Hartzell Schimitar blades are better than the old style ones that you'd likely be replacing, so you need to look at the specifics. I do know of one Dakota that went with a 3-bladed Hartzell following a prop strike, and it was definitely quieter, and the owner was happy with it.

For me, reduced weight and improved cruise speed are the two key metrics, but I'm picky so I'd want to get reduced weight, improved cruise speed, and reduced noise all together. :)
 
Increased weight in the Dakota would be 13lbs and supposedly with the scimitar design no loss of cruise speed according to hartzell and another Dakota owner I know who recently swapped with a 3 blade scimitar. Dakotas climb awesome as it is BUT I fly out of dense urban airports so if I can get altitude even faster while keeping cht below 400 that's good. More prop clearance and quitter and less vibration would be nice too but not if it meant lower cruise speed.
 
netsurfr said:
Increased weight in the Dakota would be 13lbs and supposedly with the scimitar design no loss of cruise speed according to hartzell and another Dakota owner I know who recently swapped with a 3 blade scimitar. Dakotas climb awesome as it is BUT I fly out of dense urban airports so if I can get altitude even faster while keeping cht below 400 that's good. More prop clearance and quitter and less vibration would be nice too but not if it meant lower cruise speed.
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It does mean lower cruising speed. You're already burning 13GPH to go 130, you can't afford more drag. I'd skip the 3-blade.
 
From what I hear, you'll loose some performance, it'll be quieter and smoother, you'll gain a little clearance, and some folks think they look cool.

Check out prices, check out all the sites for deals (ASO, trade a plane, etc), and go from there.
 
Might look at swapping from the stock 2 blade for a 2 blade scimitar. I know my M20C has better performance in pretty much all stages of flight compared to other M20C's with the stock prop.
 
All else being equal, the most efficient prop is a 1-blade like you see on endurance model planes. The nearest thing that is practical for our planes is a 2-blade.

Generally speaking, 3-blade props cost more to buy, go slower, are heaver, and cost more to overhaul. But they look cool. Its clear where many owner's priorities lie.
 
Ted DuPuis said:
The considerations when making a prop change are:

1) Weight
2) Takeoff/climb
3) Cruise
4) Noise
Click to expand...

Aren't some folks also looking for an (admittedly venerable) extra couple of inches of ground clearance?

I believe it's one of the commonly mentioned reasons for nosedraggers anyway, if operated off of bouncy terrain?
 
Keep it stock. If it is throwing grease out the zerts, usually you can just wipe it up and not rebuild anything. Talk to an EXPERIENCED mechanic that's been around the block a LOT before you commit.
 
JHW said:
All else being equal, the most efficient prop is a 1-blade like you see on endurance model planes. The nearest thing that is practical for our planes is a 2-blade.

Generally speaking, 3-blade props cost more to buy, go slower, are heaver, and cost more to overhaul. But they look cool. Its clear where many owner's priorities lie.
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Not only do they look cool, but they give more ground clearance and they are quieter. And when I went from a two to a three, I went from about 110 kts to 167 kts. Of course my 3 blades came attached to a Bonanza.
 
JOhnH said:
Not only do they look cool, but they give more ground clearance and they are quieter. And when I went from a two to a three, I went from about 110 kts to 167 kts. Of course my 3 blades came attached to a Bonanza.
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Clearly the prop. :)


Sent from my iPad using Tapatalk HD
 
It's confusing as some people say they haven't lost any cruise speed (with the scimitar 3 blade) and ride is a lot quitter. I came across some info that if you have a mid-time engine (like I do), swapping from 2 to 3 may increase vibration as the engine has sort of adjusted to the existing prop. Plus the 3 blade creates more drag so would shorten/reduce your glide for engine failures???
 
Will be thinking about this option the weird thing is that the STC for a Hartzel 2 blade scimitar prop for my plane is actually held by some other company than Hartzell (Professional Pilots) so not sure what exactly that is all about??? Checked their website and the 2 bladed scimitar is about $2K cheaper than the 3 blade and can even use existing spinner.


StinkBug said:
Might look at swapping from the stock 2 blade for a 2 blade scimitar. I know my M20C has better performance in pretty much all stages of flight compared to other M20C's with the stock prop.
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I'm not experienced with your airframe but I am with mine. I switched from 2 to 3. A few dollars more and a few pounds heavier but the improvement in performance is undeniable. I'll never go back.
 
denverpilot said:
Aren't some folks also looking for an (admittedly venerable) extra couple of inches of ground clearance?

I believe it's one of the commonly mentioned reasons for nosedraggers anyway, if operated off of bouncy terrain?
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Yes, good point. I forgot to include that.

netsurfr said:
It's confusing as some people say they haven't lost any cruise speed (with the scimitar 3 blade) and ride is a lot quitter. I came across some info that if you have a mid-time engine (like I do), swapping from 2 to 3 may increase vibration as the engine has sort of adjusted to the existing prop. Plus the 3 blade creates more drag so would shorten/reduce your glide for engine failures???
Click to expand...

The mid-time engine swap idea is a load of BS. Do a dynamic prop balance.

netsurfr said:
Will be thinking about this option the weird thing is that the STC for a Hartzel 2 blade scimitar prop for my plane is actually held by some other company than Hartzell (Professional Pilots) so not sure what exactly that is all about??? Checked their website and the 2 bladed scimitar is about $2K cheaper than the 3 blade and can even use existing spinner.
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That's not unusual. Sometimes the OEM will do the STC, and sometimes another company will do it. In the prop world both are common. Think about the number of engine swap STCs exist, and almost none are owned by the engine OEM.
 
I'm running a Hartzell three blade (standard, not a scimitar) prop on the Arrow. I don't really see a cruise performance loss compared to a two blade. It may be there but it isn't enough to be noticeable.

The three blade has better climb performance. Power settings (more accurately, RPM settings once the prop is out of governing range) in the pattern are different. I generally need to carry a higher RPM and cutting to idle slows the plane down quicker that a two blade.

The prop has some weird audible harmonics around 2100-2300 rpm as you do a power reduction which is disconcerting the first time you hear it, but other than that I don't see any negatives.
 
As others have said
a 3 blade prop will
Add Weight
Increase Climb Rate
Decrease Cruise Speed
Looks Sexy:wink2:
 
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Some places actually require a three blade prop.

image.jpg
 
James331 said:
Some places actually require a three blade prop.

image.jpg
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Interesting. But the requirement is for seaplanes, so I would assume the OP is free and clear to land his Dakota at the seabase with a two blade prop if he wishes.
 
Sac Arrow said:
Interesting. But the requirement is for seaplanes, so I would assume the OP is free and clear to land his Dakota at the seabase with a two blade prop if he wishes.
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Of course he can, taking back off might be tricky :D

I'd wager there are some odd ball airports or fly in communities with the same requirement.

For the OP I'd just stick with the 2 blade unless he's getting noise complaints or needs the clearance.
 
See what it does to your W&B. We have a three blade prop on the club's Arrow. If I have two full sized adults up front I need weight in the cargo compartment to bring the CG back behind the forward limit. Kind of annoying for just a $100 hamburger run.
 
Yeah this would be annoying and the Dakota w/ the heavier O-540 infront may be even more sensitive to this when you consider I clock in at 225lbs! How do I estimate the change to W&B from a prop change?

Ghery said:
See what it does to your W&B. We have a three blade prop on the club's Arrow. If I have two full sized adults up front I need weight in the cargo compartment to bring the CG back behind the forward limit. Kind of annoying for just a $100 hamburger run.
Click to expand...
 
netsurfr said:
It's confusing as some people say they haven't lost any cruise speed (with the scimitar 3 blade) and ride is a lot quitter. I came across some info that if you have a mid-time engine (like I do), swapping from 2 to 3 may increase vibration as the engine has sort of adjusted to the existing prop. Plus the 3 blade creates more drag so would shorten/reduce your glide for engine failures???
Click to expand...
for speed comparisons, you have to remember that many people buy a new 3-blade and compare the performance to what they had with their worn-out 2-blade that had the blades cut down to nothing.
 
denverpilot said:
Aren't some folks also looking for an (admittedly venerable) extra couple of inches of ground clearance?

I believe it's one of the commonly mentioned reasons for nosedraggers anyway, if operated off of bouncy terrain?
Click to expand...

That's sometimes the case, but you have to look at the prop and the particular plane. For some planes the 3 blade is the same diameter as the 2 blade.
 
Pponk has a blade tip speed calculator on their website.

I'd run my planes numbers through it OP.

Beyond a certain point, you're just making noise.
 
Thanks figured it out. Just wasn't sure how to estimate the weight and arm change so I added an extra data pong to my WB calculator and added 13 lbs (extra weight of 3 blade vs stock) at ARM 15" (estimating from Dakota poh) and no w&b issue so no concern there.

FastEddieB said:
I hope this advice doesn't come across as obnoxious, but...

Here's a link to The Pilot's Weight and Balance Handbook:

http://www.faa.gov/regulations_policies/handbooks_manuals/aircraft/media/faa-h-8083-1a.pdf

All the tools you need should be there.
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Yeah good point. I'm now curios about the 2 blade scimitar as an option too.

JHW said:
for speed comparisons, you have to remember that many people buy a new 3-blade and compare the performance to what they had with their worn-out 2-blade that had the blades cut down to nothing.
Click to expand...
 
The problem here is that the props these days are simply outrageously priced - I have good hub but need blades for my Hartzell. They want $9000 for two pieces of aluminum. Or $10500 for a new prop - nonscimitar- or $14k for a 2 blade scimitar.

MT is similar - they don't really have a marketing system in place here in the US - one wholesaler who is truly an installer . . . not a wholesaler. So everyone pays full retail for their propellers.

And people wonder why GA is dying.
 
A business opportunity for you! Teach them how to be in the prop business!
 
Stewartb said:
A business opportunity for you! Teach them how to be in the prop business!
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Don't need to - I know their profit levels . . . . I know the CFO for Hartzell . . . . there is no real competition.
 
What's interesting is that 2 bladed non-scimitar props seem to be priced higher than 3 blade scimitar ones and 2 blade scimitar kits are more expensive than 3 blade scimitar. That's what's odd to me.

comanchepilot said:
The problem here is that the props these days are simply outrageously priced - I have good hub but need blades for my Hartzell. They want $9000 for two pieces of aluminum. Or $10500 for a new prop - nonscimitar- or $14k for a 2 blade scimitar.

MT is similar - they don't really have a marketing system in place here in the US - one wholesaler who is truly an installer . . . not a wholesaler. So everyone pays full retail for their propellers.

And people wonder why GA is dying.
Click to expand...
 
comanchepilot said:
The problem here is that the props these days are simply outrageously priced - I have good hub but need blades for my Hartzell. They want $9000 for two pieces of aluminum. Or $10500 for a new prop - nonscimitar- or $14k for a 2 blade scimitar.

MT is similar - they don't really have a marketing system in place here in the US - one wholesaler who is truly an installer . . . not a wholesaler. So everyone pays full retail for their propellers.

And people wonder why GA is dying.
Click to expand...




MT was great to work with for mine. No, they're not cheap...

I wanted grey blades, they put grey blades. I wanted red safety stripes, they put on red safety stripes.

I told them I was going to paint the spinner red to match, and low and behold a shiny red spinner came with the prop! No charge! It all came in a very nice wooden box secured out the wazoo. My A&P installed it, balanced it, and it's been tailwinds ever since. :)

 
Nice! Unfortunately MT doesn't have an stc for my plane.

txflyer said:
MT was great to work with for mine. No, they're not cheap...

I wanted grey blades, they put grey blades. I wanted red safety stripes, they put on red safety stripes.

I told them I was going to paint the spinner red to match, and low and behold a shiny red spinner came with the prop! No charge! It all came in a very nice wooden box secured out the wazoo. My A&P installed it, balanced it, and it's been tailwinds ever since. :)

Click to expand...
 
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