3 Blade MT prop for M5 180

[DeltaRomeo]

Considering an MT 3 blade prop in place of the Hartzell it came with. I know there's a couple Maules here that have made the leap with MT and I would like to follow up on performances differences they have experienced. I'm fairly convinced already that it would be a significant improvement. My questions are pull on take off and cruise penalty with the 3rd blade.

Thanks,
DR.

[Hottshot]

Stick with the 2 blade if you can. everything we have run with the 3 blade ends up back at the 2. Hartzell has a Great new 2 blade we are putting on the Scouts that is working great and is made here in the USA so no more waiting on MT to get parts or repairs

[DeltaRomeo]

What was your reason for returning to the 2 blade props?

[Hottshot]

What was your reason for returning to the 2 blade props?

Better overall performance, more thrust when you need it. As always the 3 blade is smooth but lacks the pull to get you off the ground and pull hard on TO roll.

[DeltaRomeo]

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.

[gbarrier]

That's a pretty low pitch stop setting. Is that what's specified for your bird and that prop?

[DeltaRomeo]

It is lower than the Hartzell and something I was looking for anyway. It is easily dealt with using the blue knob. One thing I noticed about the Hartzell is there were times I would have liked a lower pitch setting because at those speeds it is usable. The upper end of the coarse setting was unusable since the O-360 didn't have the horse power to go to 29º. The MT only goes to 24º and is still beyond the power of the O-360. So in reality this prop is a better match for the available power output.

[montana maule]

It may come out of the box set at 5.5 degrees but you need to follow the installation instructions and set it for your airplane. On my O540 I had to increase it about 5 degrees to work properly.

[pilot]

That does seem low, but if you can make redline with the blue knob turned "off" then it is doing what it is supposed to. With no governor input you should be right at redline static.

[DeltaRomeo]

The single puck brakes can't hold the aircraft still at 2700 rpm

But the governor is doing the job at keeping it from going over.

[gbarrier]

Governor settings and low pitch stops are two different things. When we first got the M-6 it had an almost new prop (less than 100 hours). The prop logbook showed a low pitch stop of 10.7 and it checked as so. The acft. type data sheet called for something like 14.2. We reset it and it was a totally different animal. All the time the governor could be set to stop it at the 2400 rpm redlline. Sure acted different at power back though.

[cooker]

This seems to come up fairly often. When the propeller was installed did the mechanic not "install and perform function test as per manufactures instructions"??

You need to make an adjustment, there are instructions in the manual but they are a little vague.

Rough guild line is 1/4 turn of the nut (on the front of the prop) = 100rpm. If it were mine I would be cranking it back until a static full power yields an rpm just shy of red line.

Adjust governor after this but sounds like yours is right on.

[maules.com]

For what its worth though 235hp not 180hp and 2400 not 2700rpm

Years ago my company developed the STC for McCauley props on the 235hp Maules.
Maule had been using Hartzell 78" then 81" two blades, and it was expected that we did not have optimum performance.
The McCauley props we tested for noise, vibration, thrust (static and in operation), clearance, climb at gross, and anything else the FAA required were an 81" 2 blade, an 80" 3 blade and an 86" 2 blade.
I have the documentation that our DER put together to achieve the STC and they prove from actual field testing with complete calibrated FAA instrumentation and utilizing the same un biased test pilot on the same days with wind, temp, humidity, barometric pressure adjusted for that on a Lycoming IO540 with max rpm of 2400 and sealevel 235hp;
The 81" McCauley gave significantly more thrust than the 81" Hartzell
The 80" 3 blade McCauley gives significantly more thrust, less vibration, less noise, in and out of the plane, than the 81" 2 blade McCauley though there is a weight penalty which is worth it to gain the other advantages.
The 86" 2 blade produced much more thrust than the 81" 2 blade and initially slightly less than the 80" 3 blade but more thrust as the transition from first acceleration to VX developed, however the 86" 2 blade was much noisier and required large tyres or extended gear for correct clearance.

[DeltaRomeo]

For this engine, O-360 C1F, 2700 is the rpm in which the engine delivers rated horsepower. There is no need to decrease it from there.

[aero101]

Prop blade stop angle is relative to blade profiles and other things, so comparing numbers between different manufacturer's is worthless... But on other hand, I'd recommend to adjust governor out of picture completely, then see what prop pulls for RPM's. You should have enough pitch to pull redline only at full power with governor totally out of picture,(this is where you want pitch stops adjusted to) this is a safety precaution in case of governor failure, as well as will get you as big of a bite as possible for best performance. Then you adjust the governor back into the picture, to prevent the increase you will pick up going from static to having airspeed... Yes, the governor will prevent overspeed if prop angle too shallow, but what if governor fails on you? And can make another considerable change in performance with more bite!! You may find that you have enough HP to increase that granny gear ratio, and will pull even harder!!