Tom, thanks for the guidance as CS prop operation seems to be voodoo in most of the reading I've been able to find. The CFI's I've queried can't answer my questions either because they aren't mechanics. I am a mechanic but I haven't figured out all the components of the system yet and until I do it won't click into place.

Cary, I had already considered the use of full coarse pitch for power out gliding but the Maule it seems quits windmilling at 70 mph; once this happens oil pressure will be lost and the prop goes back to the low pitch stop. I'm hoping I won't have to test this but having the info is always good.

DeltaRomeo wrote:Tom, thanks for the guidance as CS prop operation seems to be voodoo in most of the reading I've been able to find. The CFI's I've queried can't answer my questions either because they aren't mechanics. I am a mechanic but I haven't figured out all the components of the system yet and until I do it won't click into place.

Cary, I had already considered the use of full coarse pitch for power out gliding but the Maule it seems quits windmilling at 70 mph; once this happens oil pressure will be lost and the prop goes back to the low pitch stop. I'm hoping I won't have to test this but having the info is always good.

You'd be surprised how many non-mechanics can answer CS questions--especially those of us who've been around for what seems like centuries. There are no dumb questions! (There may be some pretty dumb answers, though! )

You're right, that if the engine stops developing oil pressure, the prop will go to flat pitch, but all that means is keeping it going at a fast enough airspeed that it doesn't quit turning. Have you actually tried to stop the prop with the engine off? I've done it with several airplanes over the years (and over an airport!) though not a Maule (I have zero experience with Maules), and each time it required that I really slow the airplane way down, to nearly a stall speed. At 70 mph/61 knots, all of them were still spinning the prop at a pretty good clip.

Cary

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.

Here is what I think and have been able to otherwise determine from some research.

The governor's only influence on the prop hub is oil pressure changes. In the hub, that translates to pitch changes. So when the engine develops rpm the centrifugal weights inside the governor limit the engine rpm by increasing pitch to overcome the ability of the engine to turn the prop any faster. This is the static rpm limitation.

The blue knob is an adjustable cable that changes the spring tension on the centrifugal weights in the governor. This is what allows the oil pressure being sent to the hub to modulate based on the settings the pilot chooses. The governor will change pitch in the blades based on load changes making the engine/prop maintain the set speed regardless of load changes (to a point where load exceeds the range of operation). If you are stable and dialed in at a given cruise speed and the aircraft begins to climb slightly, the governor decreases pitch to keep the prop speed unchanged. If the the plane descends slightly, the governor increases pitch to maintain the set prop speed.

What is it when a pilot indicates his prop is "off the governor"? Is that when the load exceeds the operating range of the governor in a given condition or the blue knob is simply in the firewall position?

DeltaRomeo wrote:What is it when a pilot indicates his prop is "off the governor"? Is that when the load exceeds the operating range of the governor in a given condition or the blue knob is simply in the firewall position?

Just the opposite, actually. Being off the governor means the engine is not developing enough power to maintain the governor's selected rpm within the pitch it has available to adjust with.

In other words, if the blue knob is full forward and you're at max power, if you start slowly bringing the black knob out eventually the rpm will start to decrease. In this example, once you decrease from max rpm, you're "off the governor."

Another example is transitioning from cruise to the pattern. If you're cruising with the blue knob set for 2000 rpm and pull the black knob back to idle for a descent, the rpm will decrease below 2000. You're off the governor now. It's smart practice at this point to push the blue knob full forward to prepare for a go-around, but the rpm won't increase because you're already off the governor. To get back on the governor, you'd have to increase power until the engine rpm reached the governor's selected rpm, then the governor could start making adjustments in blade pitch to maintain selected rpm.

I had a Scout with the engine you are talking about...It had a 3 blade Hartzell....Sold it, bought a newer Scout with a two blade MT..What a difference in performance...Used both in Idaho and the 2 blade kicked the 3 blades ass on every strip I went to..

When matching props to engine rpm, the governor is removed from the engine and replaced with a blanking plate.
The engine/prop combination is then run up to full power.
The pitch of the prop blades are then adjusted at the hub adjustment until the engine cannot turn more than the rated rpm of 2700 in your case.
The governor is then refitted to the engine and adjusted accordingly.
The engine manufacturer stipulates a max rpm runaway speed (e.g.. 4% over redline 2700) beyond which you have to do an engine teardown.

I have been so busy this summer, I have not had the chance to monitor this forum as I was able to last year. To this poster and in a nut shell, prop selection for this engine involves MANY variables. It is such a deep subject, Zane & I have discussed an article focused on prop selection options for the Lycoming -360 series engines. Please call me to discuss your plane, how and where it is flown, how the engine is equipped and what your expectations and budget is. We will provide you with several options to consider.

Best regards,
John
Direct: 715-568-3980

CamTom12 wrote:

DeltaRomeo wrote:What is it when a pilot indicates his prop is "off the governor"? Is that when the load exceeds the operating range of the governor in a given condition or the blue knob is simply in the firewall position?

Just the opposite, actually. Being off the governor means the engine is not developing enough power to maintain the governor's selected rpm within the pitch it has available to adjust with.

In other words, if the blue knob is full forward and you're at max power, if you start slowly bringing the black knob out eventually the rpm will start to decrease. In this example, once you decrease from max rpm, you're "off the governor."

Another example is transitioning from cruise to the pattern. If you're cruising with the blue knob set for 2000 rpm and pull the black knob back to idle for a descent, the rpm will decrease below 2000. You're off the governor now. It's smart practice at this point to push the blue knob full forward to prepare for a go-around, but the rpm won't increase because you're already off the governor. To get back on the governor, you'd have to increase power until the engine rpm reached the governor's selected rpm, then the governor could start making adjustments in blade pitch to maintain selected rpm.

Good explanation. For clarification, 2000 rpm isn't necessarily where the "off the governor" situation will occur. It's typically somewhat below that, but for sure by 1500 rpm.

Cary

Cary wrote:

CamTom12 wrote:

DeltaRomeo wrote:What is it when a pilot indicates his prop is "off the governor"? Is that when the load exceeds the operating range of the governor in a given condition or the blue knob is simply in the firewall position?

Just the opposite, actually. Being off the governor means the engine is not developing enough power to maintain the governor's selected rpm within the pitch it has available to adjust with.

In other words, if the blue knob is full forward and you're at max power, if you start slowly bringing the black knob out eventually the rpm will start to decrease. In this example, once you decrease from max rpm, you're "off the governor."

Another example is transitioning from cruise to the pattern. If you're cruising with the blue knob set for 2000 rpm and pull the black knob back to idle for a descent, the rpm will decrease below 2000. You're off the governor now. It's smart practice at this point to push the blue knob full forward to prepare for a go-around, but the rpm won't increase because you're already off the governor. To get back on the governor, you'd have to increase power until the engine rpm reached the governor's selected rpm, then the governor could start making adjustments in blade pitch to maintain selected rpm.

Good explanation. For clarification, 2000 rpm isn't necessarily where the "off the governor" situation will occur. It's typically somewhat below that, but for sure by 1500 rpm.

Cary

"Off the governor" is any time you reduce engine rpm below that which has been selected on the prop control. I used 2000 rpm in my example as a selected rpm, and by reducing the throttle once we see 1999 rpm (perfect world example), you're off the governor.


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I'm bumping this thread because I had an interesting exchange with Larry from MT over the weekend with respect to prop options for my new PPonk. I think it may explain why a 2 blade can match a 3 blade despite less surface area.

I've reversed the order of the email trail for readability.

Larry,
For the same diameter, it strikes me that the 3 blade must have 3/2 more pull but that isn’t borne out in the pull tests.
What am I missing?
Is there a sweet spot in terms of HP where the 3 blade makes more sense than the 2?
Allan

Hi Allan,
It would seem so but it doesn't work that way, the three blader has less pitch at takeoff and make only a bit more thrust. The three blader works best with 280+ plus and the two blader is good from 200hp to 300+....difficult decision as they're both really good. I've run both extensively on both my 185's, one on wheels and one on floats...I now run the three blader on both but the two blader also worked great. Your call, if you buy either one and then decide to go to the other, we'll take the original back on trade.
Best
Larry

maules.com wrote: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.

This is a great post - a valuable post - there's heaps of real information here.

Just when you thought you had it all figured out, we offer up a new prop. The 2-blade, 80" MT Ultra that was developed to out-perform the Hartzell Trailblazer on the Husky, is now STC approved to be installed on the Cessna 170/172/175 series aircraft with ANY version of a Lycoming 360 or 390 engine.

I tried all four on my 1955 'Super 170B'. The Ultra and Trailblazer were the fastest in cruise. The Ultra had the least time to climb through 7000'. The 78" 3B MT was the smoothest by far and only 20 seconds less to climb through 7000' than the Ultra. The 3-blade MT also had the shortest takeoff roll by about 20' than any of the others.

Price for either of the 2-blade props is the same. The 3-blade is about $2K more.

Datasheet here:
http://flight-resource.com/PTD/C170-172-175%20Performance%20Test%20Data%20R1.pdf

Best regards,

John

I posted this last month on the Husky website. I thought it may be of interest to some of you here so I am posting it here in this thread.

Kurt



As many of you know I had a 3 blade MT on my 180hp 2012 Husky and decided to try the New MT Ultra. After about 50 hours on it I thought I would share my impressions. I did not want to say too much about it too soon without giving it a fair evaluation. I will comment and compare it with the two metal Hartzell's and the other MT props certified and available on the Husky, I have experience with all these props however I do not have any experience with the new composite Hartzell prop itself and only limited experience with the 80 inch metal Hartzell.

My overall objective was to increase the cruise speed over the 3 blade and hopefully gain some climb rate but for the most part, increase cruise speed was the main objective.

I was very happy with the original 2 blade MT 210cm prop I put on my first Husky I owned in 2004, I was one of the first to put this prop on a Husky and I was glad I did, it was far and above better than the original 76 inch metal Hartzell. This original MT prop has been out long enough and talked about in sufficient depth and detail that I do not need to go over it again here except to say it is a fantastic prop. When I bought my second Husky, a 2012 180hp A1-C, 4 years ago it came with the 3 blade MT. The airplane was an inventory airplane the dealer had in stock so there was no ordering it with the 2 blade MT, also at the time the 2 blade original prop was limited to 2,600 RPM due to noise certification issues with the higher gross weight of the 2,250 pound gross weight of the Husky A1-C, I was not willing to give up 100 RPM, no way. ( I think I have this right, correct me if I am wrong)

In the back of my mind I was wondering how this 3 blade MT was going to perform in comparison to the original 2 blade I had on my previous Husky, my initial thought was it will probably be smoother, pull a bit harder on take off, cruise a bit slower and have more drag at idle. All my initial assumptions were pretty much spot on except it seemed to pull about the same on take off as the original 2 blade MT prop. It took a while to come to these conclusions and actually at times I thought it was a bit faster but then again at times I thought it was a bit slower. This was all pretty much seat of the pants, IAS on the airspeed indicator at various temperatures and so on, not very scientific to say the least. It wasn't until my buddy bought a 2007 Husky with a 2 blade original 210cm MT prop did it really sink in as to the speed difference between the 2 props. He was on 29 inch Alaska Bushwheels and I was on 8:50's and he was only one inch of manifold pressure slower than me. Wow, that was very telling for me. I also asked many of you who had experience with the 3 blade and 2 blade original and 2 blade Ultra your opinions in the past and all of you pretty much echoed what I discovered. 3 blade is slower than both of the 2 blade MT's. Ok, so Im convinced now after bending everyones ear. I did not want to just give it an expensive try without some good reports from others. I know, Larry and John say if you don't like it then return it for a refund but I did not want to go thru that process if at all possible.

I called Larry at Flight Resource, the holder of the STC's for the MT props on the Husky and many other airplanes. I have dealt with Larry in the past when I put the original MT prop on my Husky in 2004 and that was a very nice experience so I knew this time would be no different and it was fantastic. Larry had one in stock so I bought it. AS luck or tragedy would have it, I had to attend a funeral real close to where the prop was located. I called Larry and asked him if I could meet him the next day and pick it up, Larry was out of town but his partner in the company John dropped what he was doing on a Sunday morning and met me at their facility so I could pick the prop on my way back home! Thanks John!

I installed the prop (very easy) and flew the airplane, initial impression were very favorable. I wanted to fly next to my buddy's Husky on 29's for a comparison. Well, he had a failure with one of his tires and put a set of 8:50's on it. I was disappointed I was not going to be able to do a side by side comparison of how it was set up when we flew side by side with the 3 blade. Well, if I had the 3 blade prop on now Im sure he would pass me with both of us having 8:50's, only seems logical, right? I was pleased when at many different power settings I passed him! By how much? Not sure exactly but it was by a noticeable amount.

Flight Resource claims about 4-7 mph faster than the 3 blade MT and I can honestly say that is about right. I also noticed an improvement in climb, a couple hundred feet per minute or so, not scientifically measured but seat of the pants and VSI indications. So, all in all I am very pleased with the switch.

Some differences other than speed between the New 2 blade Ultra and the 3 blade.
3 blade smoother but not by much, both incredibly smooth, 2 blade lighter, 3 blade has much more drag at idle which makes it better for descent control and spot landing, the 3 blade makes the Husky come down like a tool box when throttle closed! 3 blade may be a better choice for Idaho back country for the wider descent envelope, they pull on take off about the same, 2 blade better if you fly over water and need to extend glide in the event of an engine failure.

Overall my objective was met with the switch to the 2 blade Ultra.

So, what should you do you ask? Should you switch? Well, tough call since it involves money. If you have either of the metal Hartzell's I would say definitely switch! The 80 inch Hartzell performs ok but it is HEAVY and having a lot of friends that have been stung by the Hartzell hub AD's in the past makes me leery of them. I considered the new Hartzell composite but since from what I gather the performance between it and the MT Ultra are close and with the Hartzell AD's and how they treated my friends who were affected I chose the MT, I have always had great success with the MT. Now if you have the original 2 blade MT that makes the decision to switch to the Ultra more difficult. I think the Ultra is a better prop all the way around than the original 2 blade MT but they are close enough that only you could decide if the money difference is worth it to you. If you are ordering a new Husky I would definitely order it with the new 2 blade MT Ultra, no question. As far as switching from the 3 blade MT to the 2 blade MT Ultra, well, I think you know where I stand on that, I took a leap and did it and for me it was well worth it.

All 3 MT props are fantastic props, they do not have ANY RPM restrictions that the metal Hartzell's have but for me, the Ultra is my choice, great prop.

john54724 wrote:Just when you thought you had it all figured out, we offer up a new prop. The 2-blade, 80" MT Ultra that was developed to out-perform the Hartzell Trailblazer on the Husky, is now STC approved to be installed on the Cessna 170/172/175 series aircraft with ANY version of a Lycoming 360 or 390 engine.

That is really encouraging. My Avcon converted O-360 CS prop on my P172D is a McCauley. When it started leaking a few years back, I was really hoping that it didn't need an overhaul, because overhauls on that one are not possible due to lack of parts. Fortunately all it needed was resealing, so I'm still good with it. But when it comes time to replace it, the problem was going to arise again that it's hard to find one that will fit and will be approved. At the time my IA was doing some looking, the best he could come up with was one suitable for a twin Comanche, as neither Hartzell nor MT nor McCauley had one specifically for a converted P172D. I like that it's a shorter one, too--a bit more ground clearance would be nice.

Cary

Cary wrote:..... But when it comes time to replace it, the problem was going to arise again that it's hard to find one that will fit and will be approved. ...

I believe that there's a 3-blade "Black Mac" that's approved for the 180hp C170/172.

hotrod180 wrote:

Cary wrote:..... But when it comes time to replace it, the problem was going to arise again that it's hard to find one that will fit and will be approved. ...

I believe that there's a 3-blade "Black Mac" that's approved for the 180hp C170/172.

Not with the Avcon conversion that already uses a McCauley, apparently--I contacted a Hartzell dealer on that.

But honestly, I've never wanted a 3 blade, anyway. It looks cooler on the ramp, maybe, but once it's turning, the only benefit for my airplane is that it's likely a bit smoother. John's comments echo what I learned years ago, when the owner of the Mooney 231 I was flying for him asked me to look into swapping his 2 blade for a 3 blade, which was a factory option for the 231. My research showed that it would slow the airplane in cruise, and only marginally improve short field performance and climb rate, neither of which was critical with the Mooney where we normally flew it. Only once in 2 years did I fly him into a ranch strip, near Walsenburg, CO, which was about 3000' long, and although I often flew it to the ranch strip near Sundance, WY, to visit my Ma, getting in and out of that 2100' strip was easy. So although he had more money than sense, he elected not to swap props for the +/- $4,000 it would have cost at the time.

Cary

I thought that those Avcon 180hp conversion STC's spec'd out a (76"? ) Hartzell.

hotrod180 wrote:I thought that those Avcon 180hp conversion STC's spec'd out a (76"? ) Hartzell.

I claim no expertise, just that mine's a McCauley.

Cary