Yeah, many of the Bearhawk 4-place and Patrol (2-place) builders swear by the Hartzell Trailblazer. Others prefer the simplicity of fixed-pitch props and go with Catto. A few have used ground-adjustable props, so they can optimize for the planned mission.

I can't find the reference now, but I saw a table showing static pull testing that was done on a Bearhawk comparing the Trailblazer, an MT (2-blade), one of the new Whirlwind composite constant-speed props, and a Catto fixed-pitch prop. The Trailblazer produced the most static pull. The surprize to me was that the MT came in last, as both the Whirlwind and Catto props out-pulled the MT.

The Hartzell Trailblazer was far and away the most expensive prop tested, but placed first in static pull. The next most expensive prop was the MT, which placed dead last in the static pull test. The CS Whirlwind composite prop placed in between the other two, but cost a good bit less than either Hartzell or MT. The biggest surprize to me was that the Catto prop, which cost about 1/4 as much as the Trailblazer, basically tied the Whirlwind's static pull numbers, and cleanly beat the MT's numbers.

Of course, there's no guarantee that "static pull" results translate directly into "real-world" performance, but it seems reasonable to expect it would translate at least into initial takeoff roll acceleration and climb performance. The Catto's performance has me seriously thinking about going fixed-pitch for my 180-hp Patrol...

2 blade on its way. Will keep you posted with performance perceptions. Looking forward to being able to use the 2000 to 2250 rpm range again

Zzz wrote:I'd argue that a three blade does have some advantages: smoother balance, and shorter blades for more prop clearance are two I can think of.

There is also the noise reduction with shorter blades - that's a big factor these days; in certain places for some people it makes all the difference.

Battson wrote:

Zzz wrote:I'd argue that a three blade does have some advantages: smoother balance, and shorter blades for more prop clearance are two I can think of.

There is also the noise reduction with shorter blades - that's a big factor these days; in certain places for some people it makes all the difference.

Aviation Consumer did a "noise test" evaluation of 2-blade and 3-blade props on otherwise identical airplanes. All the people who sat in the planes during the comparisons thought the 2-blade props were significantly louder than the 3-blade props. They were quite surprised to see that the actual measured dB readings showed just the opposite - the 3-blade props were louder then the 2-blade props at the same power settings and RPM. (Tests were both static run-ups and fly-overs, IIRC.) They concluded (correctly, I believe) that the 3-blade props produce a sound that resonates differently than the 2-blade props, and are thus perceived as being less noisy.

So for my money: perception = reality. If everyone involved perceives 3-bladed props to be less noisy, that's what matters, regardless of the decibel readings produced!

I remember back in the early 1980's when Hughes Helicopter (developers of the Apache, Hughes 300MD, and several other helicopter prototypes) found that going from 2-blades to 4-blades (90* offset) on the tail rotors had a small effect in reducing the noise signature, but when they went to a 4-blade 120*/60* (i.e. "staggered" arrangement) for the blades, the noise signature was reduced by WAY more than 50% over the 90 degree 4-blade design. We got to see/hear it for ourselves, and it was an incredible difference. Something about the sound wave offsets, kind of like what ANR headsets do, I suppose...

There is definitely a quality of sound difference between 2 and 3 blades.

JP256 wrote:

Battson wrote:

Zzz wrote:I'd argue that a three blade does have some advantages: smoother balance, and shorter blades for more prop clearance are two I can think of.

There is also the noise reduction with shorter blades - that's a big factor these days; in certain places for some people it makes all the difference.

Aviation Consumer did a "noise test" evaluation of 2-blade and 3-blade props on otherwise identical airplanes. All the people who sat in the planes during the comparisons thought the 2-blade props were significantly louder than the 3-blade props. They were quite surprised to see that the actual measured dB readings showed just the opposite - the 3-blade props were louder then the 2-blade props at the same power settings and RPM. (Tests were both static run-ups and fly-overs, IIRC.) They concluded (correctly, I believe) that the 3-blade props produce a sound that resonates differently than the 2-blade props, and are thus perceived as being less noisy.

So for my money: perception = reality. If everyone involved perceives 3-bladed props to be less noisy, that's what matters, regardless of the decibel readings produced!

I remember back in the early 1980's when Hughes Helicopter (developers of the Apache, Hughes 300MD, and several other helicopter prototypes) found that going from 2-blades to 4-blades (90* offset) on the tail rotors had a small effect in reducing the noise signature, but when they went to a 4-blade 120*/60* (i.e. "staggered" arrangement) for the blades, the noise signature was reduced by WAY more than 50% over the 90 degree 4-blade design. We got to see/hear it for ourselves, and it was an incredible difference. Something about the sound wave offsets, kind of like what ANR headsets do, I suppose...

I'm curious if they were 2 and 3 blade props of the same length? Not any of the 3 blade versions for our smaller engines are as long as the 2 bade variants. On my 180 I have an 80" hartzell. It is way quieter then an 88" 2 blade Mac. I still want a 2 blade mac though...

Noise is something that is difficult to quantify. My airstrip is surrounded by VERY close neighbours. I changed from a 2 blade to the 3 blade MT on my 185 purely for noise abatement, yes spendy just to keep neighbours happy BUT after leaving my strip a few times I returned home to find a neighbour jumping the fence from his property onto my airstrip, he came running over going "what the hell have you done to that plane"? .... "It's so much quieter".
Perception or reality it doesn't matter if that's the type of response I get from the neighbour, to me it was worth the change. And BTW none of the neighbours are aviation enthusiasts so a reduction in noise is seen as a good thing for them. Although having said that I did have a distant neighbour about a mile down the road mention that he missed the classic scream of the old long 2 blade and the 185 of an early morning [emoji1]
Like everything YMMV.

NZMaule wrote:Noise is something that is difficult to quantify. My airstrip is surrounded by VERY close neighbours. I changed from a 2 blade to the 3 blade MT on my 185 purely for noise abatement, yes spendy just to keep neighbours happy BUT after leaving my strip a few times I returned home to find a neighbour jumping the fence from his property onto my airstrip, he came running over going "what the hell have you done to that plane"? .... "It's so much quieter".
Perception or reality it doesn't matter if that's the type of response I get from the neighbour, to me it was worth the change. And BTW none of the neighbours are aviation enthusiasts so a reduction in noise is seen as a good thing for them. Although having said that I did have a distant neighbour about a mile down the road mention that he missed the classic scream of the old long 2 blade and the 185 of an early morning [emoji1]
Like everything YMMV.

I think your scenario may be uniquely....Skywagon in nature. You had the 88" McCauley, right? For other configurations it may be splitting hairs but that 88" seaplane prop is damned loud, and any other prop is likely significantly quieter.

IMHO a Ponked 180 with a 3-blade Mac seems significantly louder than a stock 180 with an 88" 2-blade (.908 mach vs .894 mach at 59*F). A buddy of mine has a Ponk with an 86" C401 and the prop sound seems to project forward and echo through the whole airport when he's taking off. To me it's not objectionable, but I could see where it would be to a non-aviator or if it was happening over and over again in a short period of time or if it was coming straight at and right over you.

A guy at my airport has an amphib Husky with a 3-blade MT, and that thing is not only loud but has an unpleasant sort of a low-frequency "blatting" sound on takeoff. Like the 3-bladed Ponk, the sound seems to project more than with a 2-blade, but to me the howl of a 3-bade equipped Ponk is less obnoxious.

One of the wild cards that's a little hard to determine with regard to noise is the distance of the prop from the observer. For certification, a given aircraft/propeller combination is flown over fixed microphones at specific distances from the start of the takeoff run. The sound recorded must be lower than the certification standards, which have become more strict in the US, and have been incredibly strict in many other countries for some time.

Point is, several things affect the measured noise in these tests. For example, when Aviat increased the gross weight of the Husky from 2000 pounds to 2200 pounds with the introduction of the A-1C model, they had to dial max rpm back from 2700 rpm to 2600 rpm to meet the sound certification requirements......heavier airplane with same power equals a lower height passing the microphones, hence louder sound signature.

Perception is a whole different kettle of fish, though, and while it's important, it's virtually impossible to measure.

Also, sound INSIDE the airplane is not a certification issue....only the fly over sound. Passengers can and often do wear hearing protection....

MTV

Of course, as we've discussed in another thread, some folks on the ground would complain if the airplane's perceived noise signature was little more than a whisper. They're not interested in facts or measurements or anyone else's perception, only their own agenda of being anti-airplane and anti-airport.

Cary

OK.

Made the leap and got a 2 blade MT.

So far, what I see is:

The original Hartzell had a low speed pitch stop of 12º.
The MT is 5.5º
This means i have a new "granny gear". It also means that to continue to climb and accelerate I need to adjust pitch to allow for it, otherwise the plane just stays at redline and about 65 mph (I'm still figuring out CS props )

With this granny gear, it spools up and accelerates quickly. I seem to still have about the same cruise speed after 1.7 hrs cross country today. It seems to be smoother but we also did some tuning work on the engine and with the new prop it would be best to do a prop balance before much further operation. Once I get that completed we'll have further updates on the smoothness.

So far, it is a good upgrade, and it is especially nice to not have the 2000 to 2250 rpm range limitation.

If you have other questions about the prop, please let me know so I can investigate it further; I want to know as much as anyone what else to check.

DR,

Next time you fly, slow that 2 blade MT down in cruise. Try a power setting of 1,800 to 1,900 RPM and 22 to 23 inches of manifold pressure and lean no matter your altitude. If you have a fuel computer you will be shocked. That power setting in a 360 Lyc should burn about 6.5 to 7.0 gallons per hour. You speed will drop off a little but not much. This is a great miles per gallon setting.

I fly my Husky at 1,800-1,850 rpm and 22-24 inches, 5.5 to 6.5 gallons per hour at speeds not much slower than higher RPM power settings. Incredible miles per gallon. I have a 3 blade MT on my current A1-C Husky, it is NOT a disaster like some seem to think. It is a good prop for the 2,250 GW A1-C Husky since I do not have to restrict my RPM to 2,600 like I would have to do with a 2 blade MT.

Now don't get me wrong, if I had a choice, I would choose a 2 blade MT if I did not have to adhere to the 2,600 rpm restriction. I had a 2 blade MT on my A1-B Husky that did not have the RPM restriction, I thought that prop was a bit faster in cruise and maybe a tad bit less in initial pull. My point is the 3 blade prop is not a dud by any means. They are close.

Kurt
aka "The peanut gallery"

Thanks, Kurt. Will add that to the list of things to check. Haven't flown the MT enough to determine the effect on fuel consumption, but with the Hartzell we were getting 7.5 to 8 gph (no fuel or engine monitors; old fashioned math )

This has probably been covered, but why did the A1-C get the rpm restriction? Noise?


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DeltaRomeo,

Not sure what you meant by:

"This means i have a new "granny gear". It also means that to continue to climb and accelerate I need to adjust pitch to allow for it, otherwise the plane just stays at redline and about 65 mph."

Your saying that the rpm stays at redline?
A constant speed prop will stay at the rpm you set regardless of airspeed and throttle setting (within limits).
On Takeoff you set it for full rpm to get the low speed thrust you need for TO kinda like low gear on a bike or car.
After TO depending on the specs for your setup you set up a climb MP and RPM by first reducing MP to an inch or so below that you want then reduce rmp. At cruise same procedure.
If its a bit confusing please ask.

Tom

a3holerman wrote:DeltaRomeo,

Not sure what you meant by:

"This means i have a new "granny gear". It also means that to continue to climb and accelerate I need to adjust pitch to allow for it, otherwise the plane just stays at redline and about 65 mph."

Your saying that the rpm stays at redline?
A constant speed prop will stay at the rpm you set regardless of airspeed and throttle setting (within limits).
On Takeoff you set it for full rpm to get the low speed thrust you need for TO kinda like low gear on a bike or car.
After TO depending on the specs for your setup you set up a climb MP and RPM by first reducing MP to an inch or so below that you want then reduce rmp. At cruise same procedure.
If its a bit confusing please ask.

Tom

I believe what he means is that he can leave it full fine and fly a lot slower then his old prop would. Going from a 12* low pitch to a 5.5* low blade pitch would definitely allow that.

CamTom12 wrote:This has probably been covered, but why did the A1-C get the rpm restriction? Noise?


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Cam,

Yes, at the higher all up weight of the C model, the airplane passed over the sound sensors at a lower height, therefor increasing the sound measured. To meet certification standards, they turned the rpm back 100 rpm.

MTV

I do apologize if I am missing something here but Delta Romeo said he was still figuring out CS, which I took to mean Constant Speed props.
The prop control governs the prop speed not the pitch directly. The pitch is changing whenever speed and MP change. If for instance he was at full MP and full rpm and nose down high airspeed the pitch would be much coarser than fine.

Tom

a3holerman wrote:I do apologize if I am missing something here but Delta Romeo said he was still figuring out CS, which I took to mean Constant Speed props.
The prop control governs the prop speed not the pitch directly. The pitch is changing whenever speed and MP change. If for instance he was at full MP and full rpm and nose down high airspeed the pitch would be much coarser than fine.

Tom

...and the rpm wouldn't go over redline.

As a general proposition, CS props are easier to fly than fixed pitch, because the rpm remains constant at whatever setting the pilot is using, whether the airplane slows because it's climbing or speeds up because it's descending. Basically, climb out at highest rpm, level off for cruise and reduce both MP and rpm to cruise power settings, and leave it there. When descending toward the next landing, just point the nose down and let the speed build--helps somewhat to make up for the slower speed during the climb. Then typically when slowing to land, reduce the MP (pull out the throttle), let the airplane slow to approach speed, and push in the prop control to the high rpm setting again, but it won't actually increase rpm if the MP has been already reduced at the lower airspeed. The only reason for pushing in the prop control is so that if a go around is necessary, it'll be set already.

One really cool benefit to a CS prop that seems not to be widely known occurs if it's necessary to make an emergency landing without power. By pulling the prop control all the way out, the coarser pitch of the prop will have less drag, which may be helpful if the intended landing spot is a little farther away than you'd like.

I learned this during my first ATCO (135 charter) checkride, from the FAA Inspector giving me the ride, many years ago. He had had me do an emergency landing from downwind, which went OK--immediately when he pulled the power, I turned to the runway and was able to get the airplane lined up and landed, but the turn from base to final was at a very low altitude. So he had me do it again, asked me to set it up exactly like the previous circuit, but this time as I turned toward the runway, he said "now pull the prop control all the way out"--and it was like a kick in the pants. That last turn could then be made at a much more comfortably high altitude.

Cary