Hartzell 3 blade Trailblazer

[Mark Goldberg]

Hartzell offered to send me a 3 blade Trailblazer to try on my 540 powered BH. Today we did the swap. See before and after pics. The original two blade is 84", and the 3 blade new one is 82" diameter. My friend Mike Nellis did the flying. The one fact that we know is that the Trailblazer cut the take off roll down by about 1/3. Mike did several with the original prop, and then did several take offs with the new prop. The take off distance went from 250-275 ft down to about 150-175 feet. The blade area of the 3 blade is much more and we expected better take off thrust. It also spins up faster with the composite blades. On landing as well it would seem shorter landing are likely because when you pull the throttle back and the three blades flatten out - the air brakes come on. Steeper approaches. Hartzell's engineers predicted 20% better take off thrust.

Unfortunately my airspeed/pitot system is having problems. This has been the case since Bob Barrows swapped out my wings for the Model B wings. So on climb and cruise we were unable to make any kind of comparison. The pitot error gave variations all over the place in the VS and airspeed indicator. One minute the airspeed would be indicating 100 MPH lets say. And a few seconds later with no change in attitude it would say 80 mph. So no way to get a comparison unfortunately. Climb SHOULD be a little better and cruise speed should be 1 or 2 kts slower according to Hartzell's engineers. But we were unable to confirm. Mark

[swpilot3]

Excellent!! I'm excited to get mine!

[Bdflies]

Even if it's not faster, it sure looks good!

Bill

[JimParker256]

Looks nice! Do they have a comparable 3-blade for the Lycoming 360?

[Mark Goldberg]

No Jim. The Hartzell Trailblazer in 2 blade 80" has been a really popular prop for Patrol since it came out. Also - if you knew the pricing of the 3 blade it might dampen your enthusiasm. Mark

[Bdflies]

Jim, MT makes a gorgeous 3 blade for the O-360. Darned sexy looking fan! As Mark indicated, it's definitely the 'high priced spread'!
I'm curious to see all the comparison numbers, on the 540. My experience with a 3 blade, on a 360, didn't inspire me to go that route.

Bill

[Mark Goldberg]

From the numbers given me, it seems a 3 blade MT Patrol (IO360-180 HP) in South Africa might be the fastest in cruise of all the Patrols flying. So not a bad choice. But I would look at the weight of a three blade MT before committing. Mark

[Flygirl1]

So how fast is it? Donna

[Mark Goldberg]

In his test program which was quite extensive he saw 165 mph TAS at 75%. I am in the 152-153 mph range in mine. With the 26" Goodyear tires. Mark

[Battson]

In our speed testing, we found the 3 blade Hoffman (composite) was about 2-3kt slower than the 2 blade MacCauley. The composite 3-blade definitely pulls harder on take-off.

[Peter Bishton]

Guys what are the weights of the two different options you have tried in lbs? Regards Peter

[Mark Goldberg]

Not sure Peter. I bet the 3 blade composite that is on my 4 place now weighs about what a two blade metal prop weighs. Or maybe slightly less. Going from a two blade metal to a two blade composite will result in 10+ lbs of weight savings. Mark

[Baloo]

That is a sweet looking set up you have there!

Mark not to hijack your thread but a quick question:
I am looking for prop options for the new power plant that I should be getting in the next 3 weeks. I am currently running the 80" 2 Blade Hartzell on the io-360. As we have previously mentioned it will suffice on the 260hp io-540 but is a bit on the short side. You mentioned the best options were a 84" 2 blade or a 80" 3 blade.
There is a 79" 3 Blade MT that just became available locally at a fair price. I want to do it right the first time Would pairing this prop with the 540 instead of lets say a 80" 3 blade make a noticeable difference?

I was going to run with the shorter 2 blade hartzell for a while until the right deal came up but this prop is nice and fairly priced but I don't want o settle when that kind of $$ is involved.. Thanks for your time.....

[Battson]

That is a sweet looking set up you have there!

Mark not to hijack your thread but a quick question:
I am looking for prop options for the new power plant that I should be getting in the next 3 weeks. I am currently running the 80" 2 Blade Hartzell on the io-360. As we have previously mentioned it will suffice on the 260hp io-540 but is a bit on the short side. You mentioned the best options were a 84" 2 blade or a 80" 3 blade.
There is a 79" 3 Blade MT that just became available locally at a fair price. I want to do it right the first time Would pairing this prop with the 540 instead of lets say a 80" 3 blade make a noticeable difference?

I was going to run with the shorter 2 blade hartzell for a while until the right deal came up but this prop is nice and fairly priced but I don't want o settle when that kind of $$ is involved.. Thanks for your time.....

I have read over and over again that long two-blade props (>84") make a great deal of extra noise, but generate limited additional thrust.

But too short a prop leads to a sharp drop-off in thrust! I'll post some number to support this (below).

The optimum length is a function of RPM and blade tip velocities. Optimum tip speed is .88 to .92 mach apparently. Much above that and you're just making noise. I think about 84" is the point where longer propellors are wasting effort at 2750rpm. Optimum is about 88" at 2600rpm. The extra length is (obviously) at the tips of the prop, where the speeds are highest and approaching mach 1.0.

Of course those long props do pull a tiny bit harder... and you can notice it through the seat of your pants... But you only use that during take-off, practically.

So, here's some stats for your consideration:
With an empty plane, I get off the ground in 34m with my current 82" prop, which is a little short (but all I could find at the time). That's only using about 240 of my 260 hp potential (because my blade stops are set too coarse to reach 2750rpm at take-off speeds).
If I had an 86" prop and turned 2750 at static (a big increase from horsepower, a tiny increase in prop efficiency) it would feel more exciting for sure, I might get airborne three metres sooner...
Practically, would that make any difference to how I use the plane.....................??? No, not a bit. It wouldn't change a thing about the way I use it. But it would make it a lot more antisocial!

Three blades is a different kettle of fish.
All I can say is, extra weight on the nose will help your load hauling capabilities by improving the CG range aft.
It will also be a fraction more work during ultralight-weight landings (the flare only). But you'll soon grow used to that if you fly often. Oh, and should the engine fail then you'll glide like a stone...

I found the following useful tidbits:
Flight Resources testing Aviat Husky O-360 (180hp) (probably 2700 rpm)

Propeller Static Thrust

Hartzell 76” 672 pounds
Hartzell 80” 784 pounds
MT 2 Blade 83” 799 pounds
MT 3 Blade 78” 815 pounds

And from Pponk (Cessna 180 probably 2575 rpm):

MacCauley 82" 2-blade 940 lbs
MacCauley 86" 2-blade 1016 pounds (+8.1%)
MacCauley 88" 2-blade 1019 pounds (+8.4%)

One Skywagon pilot (230hp) reports losing 4 knots cruise speed by replacing an 82" C66 to 88" C203 prop. But a lot more "power out of the hole" (acceleration).

[Mark Goldberg]

FYI - The Hartzell engineers said I could have gone with an 84" three blade without the tips going supersonic since my engine redlines at 2575 RPM. But I went with an 82". The weight of this new carbon fiber prop is no more than my old 84" metal Hartzell. Probably less. Mark

[Baloo]

So if I go with the 79" 3 blade MT which is a bit on the short side will I be able to make up some of the initial pull by coarsening the pitch for 2700rpm? Given the smaller prop id imagine that the pitch would be coarser to reach 2700rpm then its 1-5" longer brothers.... Or is my reasoning off?

I am set to do the deal on the 79" 3 Blade MT but I don't want to come up short in the performance department simply because its a good deal.

advice?

[Battson]

So if I go with the 79" 3 blade MT which is a bit on the short side will I be able to make up some of the initial pull by coarsening the pitch for 2700rpm? Given the smaller prop id imagine that the pitch would be coarser to reach 2700rpm then its 1-5" longer brothers.... Or is my reasoning off?

I am set to do the deal on the 79" 3 Blade MT but I don't want to come up short in the performance department simply because its a good deal.

advice?

You are potentially giving up maybe 5-8% thrust (guessing) because of the shorter blades. It's likely you'll never notice the difference though.

The 79" three blades will be a fractionally slower prop in the cruise, and won't maximise your takeoff potential like a longer prop would. But it will still pull harder than a 2 blade from a standstill. On the plus side, it will help with ground clearance.