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2 blade prop or 3 blade prop?

 

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goobersnuftda  (D License)

Nov 28, 2009, 9:08 AM
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2 blade prop or 3 blade prop? Can't Post

Everything in the world is a compromise. You may gain something but you lose something in return. NASCAR is fast but not so good on transport safety, Yellow school bus is awesome on passenger safety (why children take it to school) but has a terrible lap time on the NASCAR circuit :)

For skydiving operations, is a 2 blade prop better than a 3 blade prop? (Cessna 206)

The 3 blade prop Im told is better for comfort and cruising. There are more radians to dissipate the engine vibrations through and therefore, the passengers enjoy the smoother ride.

The 2 blade prop has longer fins because it can use up more surface area as compared to the 3 blades. Im told it can chop through the air more aggressively but the ride is less comfortable.

The 2 blade is also cheaper to purchase so you would have to calculate the benefit you would receive in buying a new 3 blade instead of reconditioning your 2 blade you send in. Im also guessing there are additional dingle widgets to install when converting from a 2 up to a 3 blade.

So what are the issues in choosing between the two?


Para5-0  (D 19054)

Nov 28, 2009, 9:34 AM
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Re: [goobersnuftda] 2 blade prop or 3 blade prop? [In reply to] Can't Post

Save the money buy a King Air or Pac 750


bfilarsky  (C 37619)

Nov 28, 2009, 9:40 AM
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Re: [goobersnuftda] 2 blade prop or 3 blade prop? [In reply to] Can't Post

If I recall correctly, 3 blade props are supposed to climb faster than 2 blade props, but they cruise slower.


NovaTTT  (D 17887)

Nov 28, 2009, 10:25 AM
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Re: [goobersnuftda] 2 blade prop or 3 blade prop? [In reply to] Can't Post

Are you on a runway or a grass strip? If a runway, is it in good condition?

The 2-blade prop has longer blades and will be more likely to strike pebbles, debris, etc. and is better for maintained runways.

For dirt and/or grass strips, or poorly maintained runways, the 3-blade prop would be a better choice.

I don't know about performance but if it were my plane I'd not worry about passenger comfort (it's a Cessna - they're not made for jumper comfort!) but about engine hours and fuel consumption.

.02


Andrewwhyte  (C 1988)

Nov 28, 2009, 4:10 PM
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Re: [goobersnuftda] 2 blade prop or 3 blade prop? [In reply to] Can't Post

From what I have seen the main advantage in skydiving operations of a 3-blade is noise; huge difference. If Neighbours are a concern it might be worth it, but if not the jumpers would prefer more horses.
If you want a better climb-rate get a bigger engine.


totter

Nov 28, 2009, 5:17 PM
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Re: [bfilarsky] 2 blade prop or 3 blade prop? [In reply to] Can't Post

In reply to:
3 blade props are supposed to climb faster

Other way around. Two blades are better for climb, 3 are better for cruise and noise.


captain1976  (D 7183)

Nov 28, 2009, 5:28 PM
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Re: [goobersnuftda] 2 blade prop or 3 blade prop? [In reply to] Can't Post

Not sure about the 206, but installing the 3 blade on the 182 recommends a modified engine mount due to harmonic vibrations which though stronger on the 3 blade, provide a smother cockpit. I put a 3 blade on my 185 only after a couple of years without seeing any adverse reports. I see the exact same performance with both props and its a lot quieter.


kallend  (D 23151)

Nov 28, 2009, 6:42 PM
Post #8 of 40 (3381 views)
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Re: [totter] 2 blade prop or 3 blade prop? [In reply to] Can't Post

In reply to:
In reply to:
3 blade props are supposed to climb faster

Other way around. Two blades are better for climb, 3 are better for cruise and noise.

Nope.

Theoretically, and all other factors being equal, 3 blades should give slightly better take-off and climb performance while two blades should give slightly better cruise.

Unfortunately, all other factors aren't equal so it comes down to flight testing the changes for a particular installation to determine if there's been a performance change


vpjr  (D 14158)

Nov 29, 2009, 12:12 PM
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Re: [goobersnuftda] 2 blade prop or 3 blade prop? [In reply to] Can't Post

I went from the Mac 2 blade to the hartzell 82in super simitar, Same day, same weight and conditions. 125 fpm climb improvement at 5,000 ft. 5 Mph IAS faster cruise at 10,000. This prop does have a harmonic that is eating vacuum pumps and alt belts. They also sell an 80in of that blade design that might reduce the harmonic. C U206 IO-520. One of my 206s has the 80in Top Prop round tipped. Climbs well but with reduced cruise, draws in fod compaired to the simitar that doesnt have a nick.


goobersnuftda  (D License)

Nov 29, 2009, 2:46 PM
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Re: [vpjr] 2 blade prop or 3 blade prop? [In reply to] Can't Post

I am reading the companies sales presentations but I don't trust everything they say.

What I am looking for is real world experience in what DZO have found. Does one need more service than the other? At replacement time is one always condemned because of too much work where as the other can be reconditioned and good to go again?

Google is great at finding blind facts like the 3 blade kit (including all parts and the STC) sells for $9,750. I can buy a new McCauley two blade prop for $4,250. Is what you gain worth double the price?


vpjr  (D 14158)

Nov 29, 2009, 4:04 PM
Post #11 of 40 (3161 views)
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Re: [goobersnuftda] 2 blade prop or 3 blade prop? [In reply to] Can't Post

If you are going to fly only 10 loads a day at your busy time stick with the cheapest. If you have to fly 20 loads a day a lot of days the time starts to add up and the investment will pay back. 2 blades tend to shake the carb airbox, oil cooler, and alternators off. If you have to turn away 20 tandems on a Sat what is the cost to you?


davelepka  (D 21448)

Nov 29, 2009, 7:31 PM
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Re: [goobersnuftda] 2 blade prop or 3 blade prop? [In reply to] Can't Post

 
Check with Randy Allison, he's got a 182 with a 3 blade prop and I think he's flown the same plane with a 2 blade as well. He's a Regoinal Director (or something) for the USPA, so his contact info is in Parachutist, or on the website.

It's a nice 182 and it climbs quick (for a 182).


jumpwally  (D License)

Nov 30, 2009, 7:55 AM
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Re: [goobersnuftda] 2 blade prop or 3 blade prop? [In reply to] Can't Post

How does a 4 blade prop figure in all this ?


skydived19006  (D 19006)

Nov 30, 2009, 8:12 AM
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Re: [vpjr] 2 blade prop or 3 blade prop? [In reply to] Can't Post

In reply to:
I went from the Mac 2 blade to the hartzell 82in super simitar, Same day, same weight and conditions. 125 fpm climb improvement at 5,000 ft. 5 Mph IAS faster cruise at 10,000. This prop does have a harmonic that is eating vacuum pumps and alt belts. They also sell an 80in of that blade design that might reduce the harmonic. C U206 IO-520. One of my 206s has the 80in Top Prop round tipped. Climbs well but with reduced cruise, draws in fod compaired to the simitar that doesnt have a nick.

I have the hartzell 82in super simitar on my 182 as well, but it went on with the new Texas Skyways O520U/TS engine. Removed a O470 with 82" Mc prop, I needed the third blade and couldn't go longer two blade. Climb time in cold weather at GTOW is 13 to 14 min (1300 msl to 11,500 msl).

Edit to add: we did the engine and prop, flew some in the dead of winter, then installed the ART Wing-X extensions which shaved another 1 to 2 min off the climb at the same weight (from 15 to 13 min). This STC also made me legal to 2950 lbs, as opposed to 2650.


(This post was edited by skydived19006 on Nov 30, 2009, 8:14 AM)


totter

Nov 30, 2009, 1:53 PM
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Re: [totter] 2 blade prop or 3 blade prop? [In reply to] Can't Post

I was tits backwards on this one. Not thinking of recent improvements and technology to props.

Not that many DZs use one, but with the Beaver going from the 2 bladed Hamilton Standard to a 3 bladed Hartzell you lost a little in take-off/climb but it is much, much quietter.


riggerrob  (D 14840)

Dec 1, 2009, 9:40 AM
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Re: [totter] 2 blade prop or 3 blade prop? [In reply to] Can't Post

"... but with the Beaver going from the 2 bladed Hamilton Standard to a 3 bladed Hartzell you lost a little in take-off/climb but it is much, much quieter...."

........................................................................................

Yes, sometimes the most important factor (to keeping the DZ operating) is allowing the neighbors to sleep in Sunday mornings.


riggerrob  (D 14840)

Dec 1, 2009, 9:44 AM
Post #17 of 40 (2774 views)
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Re: [goobersnuftda] 2 blade prop or 3 blade prop? [In reply to] Can't Post

"... Does one need more service than the other? ..."

..................................................................................................

For example, if a larger diameter propeller increases climb rate, BUT picks up too many rocks, it may be prohibitively expensive to buy new blades every year.
Remember that you can only file out the nicks "X" number of times before the propeller is scrap.
When operating from a gravel runway, it may be cheaper to stick with a smaller diameter, slower climbing propeller that picks up fewer rocks.


riggerrob  (D 14840)

Dec 1, 2009, 10:10 AM
Post #18 of 40 (2757 views)
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Re: [goobersnuftda] 2 blade prop or 3 blade prop? [In reply to] Can't Post

"... At replacement time is one always condemned because of too much work where as the other can be reconditioned and good to go again? ..."

.............................................................................................

That depends whether the old propeller can be re-conditioned or whether it needs to be replaced (big bucks).
Few DZOs consider replacing propellers until they are faced with a CAN$15,000 overhaul.
Then they might consider spending $20,000 on a fancier, faster-climbing propeller.


Premier MidwestFreefall  (D 11112)

Dec 3, 2009, 3:25 AM
Post #19 of 40 (2648 views)
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Re: [davelepka] 2 blade prop or 3 blade prop? [In reply to] Can't Post

Hey Dave...

My 182 isn't really a fair comparison. I changed too many things to give you a real a/b comparison between 2-blade and 3-blade. My 3-blade prop was a project in itself - I have a field approval for an 86" C401 3-blade McCauley. That is basically a 3-blade seaplane prop (6" longer than a normal C-401) that requires me to have a heavy duty nose fork (Landes kit) and 6.00 x 6 nose tire (normal is 5.00 x 5) to assure ground clearance in the event of flat tires/flat nose strut.

I also have a Pponk 0-520 engine with high compression pistons (close to 300 hp). The engine can turn up to 2750 rpm, so the noise generated with the big prop can be really high. I need to dial the RPM back right after take off to keep the neighbors from having issues.

Along with XTOL wing extensions (2950 lb gross) and a Sportsman STOL leading edge cuff, it's a pretty fun airplane to fly. Doesn't require much runway for takeoff or landing. Times to altitude are 10 - 13 min depending on load size.

Cruise is at the top of the green arc. I think it's a great set-up, but the noise could be a real issue for some.

Randy


totter

Dec 3, 2009, 8:54 AM
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Re: [MidwestFreefall] 2 blade prop or 3 blade prop? [In reply to] Can't Post

In reply to:
The engine can turn up to 2750 rpm, so the noise generated with the big prop can be really high.

I know what you mean. We have quite a few operators here that have 185s, seaplanes, with the 3-bladed prop. They are the loudest aircraft in the harbor on take-off. They are louder than the Turbine Otters and the 2-bladed Beavers.


Premier MidwestFreefall  (D 11112)

Dec 3, 2009, 9:36 AM
Post #21 of 40 (2607 views)
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Re: [totter] 2 blade prop or 3 blade prop? [In reply to] Can't Post

The increase in static thrust is real, however, from the longer prop. You can really feel it in acceleration on take-off roll. Check Steve Knopp's website for some details:

http://www.pponk.com/...AGES/propellers.html

In regard to the OP's question, I don't believe you will see much difference in "skydiving" performance with a stock 0-470 between a C-66 (or a C-201 or C-203) at 82" and a C-401 at 80". A friend of mine did the 3-blade converstion on a 1958 C-182 several years ago and was disappointed.

The risk of balance and vibration problems is real as well. I had good luck with mine (and I have a stock engine mount), but the best answer is the heavy duty engine mount. More $$$$.

Randy

(This post was edited by MidwestFreefall on Dec 3, 2009, 9:37 AM)


totter

Dec 3, 2009, 9:57 AM
Post #22 of 40 (2599 views)
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Re: [MidwestFreefall] 2 blade prop or 3 blade prop? [In reply to] Can't Post

In reply to:
The risk of balance and vibration problems is real as well.

So true. You're only allowed to keep the prop at 2750 for one minute before you have to pull it back.


skykank  (D 18591)

Apr 27, 2012, 10:39 AM
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Re: [MidwestFreefall] 2 blade prop or 3 blade prop? [In reply to] Can't Post

Hi Randy:

What is the elevation (above sea level) of your drop zone?? Just wondering because my plane is finishing the Pponk conversion O470-50 (275 hp with the mc cauley 401 tri blade prop) and the wing X extension , my DZ is 2300' ASL , just trying to make a guess on how much time it ll take to 10.000'.

Thanks ...


Ron

Apr 28, 2012, 4:01 PM
Post #24 of 40 (2038 views)
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Re: [goobersnuftda] 2 blade prop or 3 blade prop? [In reply to] Can't Post

In theory, the three blade is going to give you more power at the start of your rollout and in climb. Depending on the HP of your engine, it may not make much difference since the added drag of the third blade might require you to fly at very low prop pitch settings.

Of course, there are more factors than just number of blades to consider. Blade airfoil, tip shape, engine HP, blade size, and blade material all have to be considered.

In the world of fixed pitch props:
Two blade is for cruise
Three blade is for climb and short field work.

My plane is fixed pitch and low HP..... So a three blade prop was worthless unless I was on floats and then I still would have needed to have tapered tips due to the extra drag.

But the debate two vs three is one of the old ones..... And the only real way to know is to try each. Since that is not economically feasible for most people.... Find a guy that has as close to an airplane as yours but has something you are interested in and ask. But if you have a 200 HP plane and he has a 280 HP plane... That is not really going to give you a good comparison.

Just for general comment, I called the manufacturer of my plane and told him my mission and requirements and plan on just doing what he told me: Two blade, carbon fibre, tapper tipped.


skydived19006  (D 19006)

Apr 30, 2012, 7:37 AM
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Re: [skykank] 2 blade prop or 3 blade prop? [In reply to] Can't Post

In reply to:
Hi Randy:

What is the elevation (above sea level) of your drop zone?? Just wondering because my plane is finishing the Pponk conversion O470-50 (275 hp with the mc cauley 401 tri blade prop) and the wing X extension , my DZ is 2300' ASL , just trying to make a guess on how much time it ll take to 10.000'.

Thanks ...

I have the hartzell 82in super simitar on my 182D, it went on with the new Texas Skyways O520U/TS engine. Also have the Wing-X STC. Flying out of 1350, in winter we make it to 10,000 in 13 to 14 minutes. Summer climb times are more like 17 to 18 minutes.

Possibly of some interest, I own two 182Ds, N8882X, and N8884X. 82X is the jump plane with the 520, 84X is in standard configuration with 470, seats, etc. I took off the other day in 84X right behind 82X going up with jumpers. I was light in 84X, just pilot and light fuel. I was keeping up with the jump plane, but it was a tight race. I stayed with them to 6500 msl, then went back down. So anecdotally, with the upgrade (520, three blade, and Wing-X) you'll climb at 2900 lbs as if you were loaded to 2000 lbs in a standard configuration bird.

Another plus is that you'll likely burn less fuel. We're running around 6 gal per load. Obviously burning at a higher rate, but for considerably less time. Or as I figure, every bit of additional power and fuel burn rate goes to the "up."

Edit to add the picture


(This post was edited by skydived19006 on Apr 30, 2012, 7:41 AM)
Attachments: N8882X and N8884X.jpg (242 KB)


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