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Just MT Propeller

RVjim

RVjim

Well Known Member
My purpose in starting this thread is to provide a place for the exchange of information in the form of an interactive discuss about MT Propellers. Since MT Propeller is a manufacturer of propellers with both aluminum and wood (natural composite) blades with from 2 to 6 blades, a fairly broad discussion could result.

Since I am more than a little concerned about off topic comments, and advocates that "require" their choice for everyone, Doug Reeves has offered to monitor this thread more closely than usual.

I would like to start this thread with some basic information.

First, the MT propeller number is almost like a finger print of the aircraft for which the propeller was designed. This is because the propeller blades are designed to the aircrafts performance and engine being used. Of course, a family of aircraft with the same performance and engine (like an RV with a 180 hp Lyc (I)O-360) would use the same propeller design. Although the propellers designed for the RV family could have either two or three blades.

I have two MT Propellers for my RV-6A. A 3 blade MTV-12-B/183-59b and an aluminum 2 blade MTV-15-B/183-402. The first part of the number before the / defines the propeller hub. The number after the / defines the blade.

The first part of the propeller assembly number identifies the engine used. So, to me, the blade definition is the more significant portion of the propeller number. For examble, on my 3 blade MT propeller, /183-59b, indicates the propeller has a 183 cm (72 inch) diameter. And the -59b is a specific wood blade design in the symitar style of blade.
And on my 2 blade propeller, 183-402, is again a 183 cm (72 inch) diameter propeller, while the -402 is a specific aluminum blade design.

I should mention that MT Propeller ships the propeller assembly from the factory with a finished spinner assembly to match your cowling installation. If the customer provides the correct spinner diameter and cowling information, the propeller and spinner assembly simply bolts to the engine and is ready to go.

Why have both aluminum and wood blades available?
The 2 blade Aluminum blade propeller makes a very good propeller for the Lycoming (I)O-360 180 horsepower engine. And this is the typical propeller design we usually see and operate here in the USA.

However, the weight of the aluminum blade propeller has some limitations. Particularly the weight of the aluminum blades themselves.

For the Lycoming (I)O-360 engine, the MT Propeller Aluminum 2 blade propeller assembly weighs about 56 pounds, while the ?Natural Composite? 3 blade propeller assembly weighs about 44 pounds. Most of this lower weight is due to the light weight of the 3 ?natural composite? blades.

So, the first advantage of the 3 blade MT propeller is that it has 60% less gyroscopic load than the Aluminum 2 blade propeller. This means the propeller has a lower flywheel effect on start up and shut down. And the aerobatic loads to the propeller crankshaft are greatly reduced.

A second advantange of the lighter weight 3 blade propeller is not so obvious. By adding counterweights to the propeller blades, the propeller can start in the coarse pitch (low RPM) position, and be controlled to the low pitch (high RPM) position by the governor.

So what good is this?
With the loss of oil pressure, the counterweighted blade propeller automatically goes to a cruise flight pitch. In this position, the propeller drag is reduced to 5/8ths of the drag from the standard propeller blades in the low pitch (high RPM) position.

The counterweighted blade propeller is excellent insurance for aerobatic flight. Even with an inverted oil system, in zero G maneuvers, it is fairly common to momentarily loss oil pressure. With the counterweight blade propeller, the RPM decreases as the blades move to a higher pitch, thereby preventing engine and propeller overspeed that would otherwise normally occur.

In the event of an actual engine failure, the propeller blades will again go to a cruise pitch position with the resultant lower propeller drag. I understand the Lancair people really like this feature.

I would think the RV-8?s with the Sam James cowl would like this propeller, also. Even with the extended hub to clear the cowl and counterweighted blades, there is no aerobatic restriction on this engine/propeller combination.

MT Propeller also makes fixed pitch propellers. The blades are manufactured to the same processes and standards as the constant speed propeller blades. Each blade has the same stainless steel leading edge that is three times more resistant to water and sand erosion than Aluminum.

Briefly about myself:
I operate an FAA certified propeller repair station.
At this time, the only propellers I service and sell are MT Propellers.
I find I have really enjoyed talking with people about their project and how they plan to fly their aircraft. (Some low and fast. Some high and fast. A few actually wanted economy. J )
I originally spent $6,000 to get my RV-3 flying. And have spent at least twice that since then with various changes, including a new engine. Even so, to spend another $10,000 (5 years ago) for an electric CS propeller was a tough decision. But it has been the one most significant change I have made in the overall perfomance and reliability of my RV-3.

Regards,
Jim Ayers
RV-3 sn 50 LOM M332A engine MTV-7-C/L175-112 propeller - 650 hours TT airframe
 
Jim,
With a thread title of "Just MT", do you not want any discussion comparisons of the MT to other manufacturers? Seems most folks who are interested in MT discussions are interested in the discussions as they pertain to the alternatives. Without comparitive discussions for baselines, how do we discuss any attributes?

Best,
 
Fixed pitch MT

Jim,
I am thinking of using a fixed pitch MT on my simple, light weight O320 RV4, currently in the finishing stages of construction. I live in the northwest US. The rain has me desiring the metal edged MT. Plus, it would be interesting to try something different. I'm concerned about spending so much money and possibly ending up with a prop that is pitched too far on either end of the RPM spectrum. Do you have any experience with a set-up like I'm describing?

Sincerely,
 
Hi Jim,

I have an MTV-15-B/183-33 bolted to a Lycoming angle valve A1A 200HP. I have 410 hours on it in only 18 months sense its last O/H, the O/H was done at MT USA in Florida, they did a great job I think but it took about 4 or 5 months. The prop had been badly neglected by its previous owner and required a hole new hub assembly and new custom blade ferrels to accommodate mounting my old blades to the new hub. I also wanted new erosion strips (metal leading edges) but they neglected to do this and just filled the pit marks which have now eroded out again from flying in the rain, not to mention a new ding caused by me after the O/H.

I like what I got from MT USA but I am looking for someone closer for next time and someone that will have my prop for weeks not months, You seem to have a passion for MT props so you are in the running along with maybe American Propeller.

So are you the full meal deal MT prop shop? Authorized to do any and all service including the blade lag bolts if necessary, erosion strips and refinishing?

Hear is what I want next time.

1. standard hub O/H
2. new erosion strips
3. blade re finish
4. And I want this done without the ferrels being removed if at all possible, this is expensive and they just put them on there last time.

So can this be done and if it?s straight forward what would the cost be? And if we set it up well in advance can you have the parts so you can do the work in short order?

So far getting this prop serviced correctly and in a timely fashion at the same time has proven impossible!!!! I love this prop but I want some good service!!!!

Don?t PM me just answer hear so everyone can hear what you offer at your shop, everyone with an MT will be interested in your answers.

Russ
 
Ditto for me...
DM



Brian Vickers said:
Jim,
I am thinking of using a fixed pitch MT on my simple, light weight O320 RV4, currently in the finishing stages of construction. I live in the northwest US. The rain has me desiring the metal edged MT. Plus, it would be interesting to try something different. I'm concerned about spending so much money and possibly ending up with a prop that is pitched too far on either end of the RPM spectrum. Do you have any experience with a set-up like I'm describing?

Sincerely,
Click to expand...
 
Be sure to specify RV4 (narrow body)

Brian Vickers said:
Jim,
I am thinking of using a fixed pitch MT on my simple, light weight O320 RV4, currently in the finishing stages of construction. I live in the northwest US. The rain has me desiring the metal edged MT. Plus, it would be interesting to try something different. I'm concerned about spending so much money and possibly ending up with a prop that is pitched too far on either end of the RPM spectrum. Do you have any experience with a set-up like I'm describing?

Sincerely,
Click to expand...

MT has TWO (2) different pitches for the 2-blade props offered for the O-320. There is a difference between the one for an RV6/7 ("wide-body") and an RV4 and I think RV8 ("narrow body") sporting 160 HP.

Just be sure an make sure your order is clear if you decide to go that route.

James
 
Sensenich

Brian Vickers said:
Jim,
I am thinking of using a fixed pitch MT on my simple, light weight O320 RV4, currently in the finishing stages of construction. I live in the northwest US. The rain has me desiring the metal edged MT. Plus, it would be interesting to try something different. I'm concerned about spending so much money and possibly ending up with a prop that is pitched too far on either end of the RPM spectrum. Do you have any experience with a set-up like I'm describing?

Sincerely,
Click to expand...
Really for a fixed pitch prop consider the Sensenich, which is made for RV's. A prop is not designed as a stand alone component, it must match the airframe and engine to get the most efficiency. For props one size does NOT fit all. Yes it weighs more but maintence and rain wise, its a no brainier. Also a RV-4 needs weight on the nose with a O320 to get full pass and bag weights, while not exceeding aft CG. Metal also can be re-pitched. Lets say a few years from now you do some plane mods and reduce your RV's drag, with new wheel pants, cowl and other clean ups. YOU CAN REPITCH the Sensenich. Also the performance of a metal props and their thinner blades are better than thicker wood blades. Van tested 8 props, all constant speed props except one, a Sensenich. It came in 2nd behind the Hartzell BA prop!


(Note: the Sensenich if allowed to over speed was faster in this typical cruise condition at 8,000'. Van estimated 2,500 rpm cruise would be about 207.9 mph (from 210.0 mph at 2730 rpm). I believe that est is a little high. Regardless the Sensenich is an efficient prop you can bolt on and forget about.)
 
Last edited:
I have an RV3. It had a fixed pitch wood prop and was flying just dandy. In the interest of higher performance and higher tech, I replaced the fixed pitch prop a few years ago with an electric MT constant speed one, bought it through Jim Ayers.

The conversion process was straightforward, although it does affect your pocketbook to a fairly large degree ($8000). I ended up making a new instrument panel to fit the governor, and that entailed even more money spending for new goodies, but that is not the fault of MT.

The MT came with it's own spinner, fits fine but does not have the same profile shape as the original so the lines of the fuselage/cowl/spinner are not quite as nice as they used to be.

The take off performance was great and is now stellar. Initial climb is unbelievable. I fly from a 2000 foot strip and when at the departure end I am at 900 feet AGL. That is a huge improvement, not to say it was a needed improvement..

Cruising speed is the same, but at a lower rpm. Fuel burn might be a tad lower at the same cruise speed.

Max speed is at most 1 mph higher noted by flying next to an RV6. I have a Lycoming O-320 E2D by the way.

Landing is drastically different. The plane is a brick with the throttle closed in the pattern, you have to keep 2000 rpm to make a normal gliding pattern approach. I think there is such a great percentage of airplane in the propwash, and the prop is such a fine windmill sucking energy from the air that the braking effect on a light airplane is enormous. We leave the prop governor set at 2100 rpm and leave power in on approach. You can easily do a go around at that prop setting since the plane is light and powerful.

I can now safely fly in rain, and that happens here in the NW, so that is a great benefit.

Would I do it again? No. Just not worth it. But I would never know that without having done it, and that is what experimental is all about.
My $0.02.

Peter
 
Sensenich O320 prop

Hi George,
I have previously communicated with you about the Sensenich props. Your knowledge and insights are very much appreciated. I agree with all you say and would rather have aluminum. I particularly agree with you about re-pitching and prop weight. The article you have posted is for the unrestricted prop designed for the O360. I am installing an O320. The RPM restriction is a deal killer because of my desire to fly sport aerobatics. Cruising at 2,600 RPM's or less is not an issue for me.

I attempted to order a prop from Catto but they would not return my phone calls or email. With more than a 12 month wait for delivery I can understand why.

The fixed pitch MT is a viable option. Weather resistance is a huge plus, and the price is reasonable (same as Sensenich). Rob Ray (Smokey) is very happy with the fixed pitch MT on his O320 RV-4. He is the only data point I am aware of. I would love to hear from anyone else that is operating an O320 - RV4 with a fixed pitch MT. Or anyone using the restricted Sensenich and occasionally over speeding it for brief moments, like in a diving maneuvers. Is occasional over speeding an issue? I?m trying to learn all I can.

Sincerely,
 
Just MT

hydroguy2 said:
how about some real performance numbers from the 2 blade aluminum MT on a IO-360 RV-7?
Click to expand...

I don't have any. I also don't have a RV-7, or an IO-360. Sorry.
I do have a MTV-15-B/183-402 (aluminum 2 blade) MT Propeller that you could borrow the next time you're at Oxnard, California. Just let me know when, so I can take it off of my O-360 RV-6A.

I should mention that MT Propeller now recommends the MTV-15-B/183-402 propeller for the 180 hp (I)O-360 engine only. With dual mags, or LASAR electronic ignition only.

Regards,
Jim
 
I'll be in Hemet next month. What time should I come by?:D:D:D just kidding my -7 doesn't even have a motor yet.

Have you done any testing or gotten any numbers on your 6A. I know of a couple of guys(-7a , -8a) who say their Aluminum MT 2blades are faster than the BA it replaced, but I didn't get their numbers.
 
Just MT

Kahuna said:
Jim,
With a thread title of "Just MT", do you not want any discussion comparisons of the MT to other manufacturers? Seems most folks who are interested in MT discussions are interested in the discussions as they pertain to the alternatives. Without comparitive discussions for baselines, how do we discuss any attributes?

Best,
Click to expand...

Just a discussion on the MT Propellers I know seemed like a big enough challenge to me. Aluminum blade? "Natural Composite" blade?
What characteristics are important in determining which is really better?

On the MTV-15-B/183-402 (72" dia. aluminum 2 blade) MT Propeller, if you damage the blade tips, they can be trimmed off too as little as a 68" diameter.
On the MTV-12-B/183-59b (72" dia. "Natural Composite" 3 blade) MT Porpeller, if you damage 4 7/8" of the blade tips (62 1/4" dia.), the blades can be overhauled to their original 72" diameter.

Regards,
Jim Ayers
 
Russ McCutcheon said:
Hi Jim,

I have an MTV-15-B/183-33 bolted to a Lycoming angle valve A1A 200HP. I have 410 hours on it in only 18 months sense its last O/H, the O/H was done at MT USA in Florida, they did a great job I think but it took about 4 or 5 months. The prop had been badly neglected by its previous owner and required a hole new hub assembly and new custom blade ferrels to accommodate mounting my old blades to the new hub. I also wanted new erosion strips (metal leading edges) but they neglected to do this and just filled the pit marks which have now eroded out again from flying in the rain, not to mention a new ding caused by me after the O/H.

I like what I got from MT USA but I am looking for someone closer for next time and someone that will have my prop for weeks not months, You seem to have a passion for MT props so you are in the running along with maybe American Propeller.

So are you the full meal deal MT prop shop? Authorized to do any and all service including the blade lag bolts if necessary, erosion strips and refinishing?

Hear is what I want next time.

1. standard hub O/H
2. new erosion strips
3. blade re finish
4. And I want this done without the ferrels being removed if at all possible, this is expensive and they just put them on there last time.

So can this be done and if it?s straight forward what would the cost be? And if we set it up well in advance can you have the parts so you can do the work in short order?

So far getting this prop serviced correctly and in a timely fashion at the same time has proven impossible!!!! I love this prop but I want some good service!!!!

Don?t PM me just answer hear so everyone can hear what you offer at your shop, everyone with an MT will be interested in your answers.

Russ
Click to expand...

Hi Russ,

I get the feeling you have understated the lack of care by the previous owner. I say this, because the repair you describe seems extreme.

The four points you make for overhaul seem very reasonable to do, and is typical for the overhauled propellers I have already completed.

I have an agreement with MT Propeller in Germany to use the USA repair facility they own, MT Propeller USA, for all of the component part overhaul. I say this, because this is the very place you indicated you didn't want to use.
I have developed a very good working relationship with MT Propeller USA, and they have aways provided excellent workmanship with all of my overhauled parts, and provided them in a timely manner.

I had a damaged 3 blade Rocket propeller, MTV-9-B-C/C198-52, returned for overhaul recently. This is a 78" diameter 3 blade MT Propeller with counterweighted blades (the -C/C designation). It came in after 4 years, instead of 6 years. It also came in with only a 72" diameter.
The hub was sent to MT Propeller USA in Florida. The blades were sent to MT Propeller in Germany. By the time the customer had gotten the teardown inspection on the engine completed and the engine installed, he had his overhauled 78" diameter 3 blade propeller back.

I don't see a problem with overhaul time. Worst case, I have a couple propellers that I can loan. If you want to fly down to Oxnard, California. You could leave the same day with your choice of three different (I)O-360 propellers.
However, there is a real risk if you want to borrow the MTV-12-B/183-59b 3 blade MT Propeller. You might not want to give it back to me.
Or, I can ship you one of my 2 blade propellers when you expect to ship me your 2 blade propeller.

Regards,
Jim Ayers
 
Just MT

Brian Vickers said:
Jim,
I am thinking of using a fixed pitch MT on my simple, light weight O320 RV4, currently in the finishing stages of construction. I live in the northwest US. The rain has me desiring the metal edged MT. Plus, it would be interesting to try something different. I'm concerned about spending so much money and possibly ending up with a prop that is pitched too far on either end of the RPM spectrum. Do you have any experience with a set-up like I'm describing?

Sincerely,
Click to expand...

Hi Brian,

I've had 5 different fixed pitch propellers on my O-290 powered RV-3 over the years. I understand what you are saying very well.

The standard MT fixed pitch, MT 170 R 185-3E, propeller for the (I)O-320 powered tandem RV should be very close to, if not exactly, what you need.

MT Propeller has an excellent engineering department. And the company, MT Propeller, stands behind their product. If there were a mismatch between your O-320 RV-4 and their fixed pitch propeller, I have no doubt that MT Propeller would resolve it in a reasonable manner.

Regards,
Jim Ayers
 
Just MT

hydroguy2 said:
I'll be in Hemet next month. What time should I come by?:D:D:D just kidding my -7 doesn't even have a motor yet.

Have you done any testing or gotten any numbers on your 6A. I know of a couple of guys(-7a , -8a) who say their Aluminum MT 2blades are faster than the BA it replaced, but I didn't get their numbers.
Click to expand...

I'm still trying to figure out my RV-6A. I flew it to Oshkosh and back this year. I felt it was a real slug with only a 150 KTAS cruise. Then i go up to get some cylinder head temperature comparison data and I get a solid 160 KTAS cruise. I also had a solid 160 KTAS cruise before I left for Oshkosh.

I know what I changed. I just can't believe it made that much difference. I will try to check it out again Friday.

Then I can work on a MTV-12-B/183-59b vs MTV-15-B/183-402 comparison.

Regards,
Jim Ayers
 
Hi Jim,

I said it was neglected, not at all the fault of MT, he had let it go 10 years and 300+ hours, I thought I could fly it through the summer and then send it in, wrong! All the grease had dried up and hosed the bearings hub and the works, I became aware of a problem when one of the pitch blacks broke on climb out causing one blade to be uncontrolled, this caused a reasonably strong vibration. The work MT USA did was great but it was put on the back burner too many times and too many excuses, so in the end I got a nice prop but the service was not stellar! After they had my prop for about 6 to 8 weeks I had to move my plane and they did send me a prop and told me to fly it wile they had mine but there was no spinner so I flew it for 4 months with no spinner, the loan was nice but it also gave them reason to just keep putting my prop back and back and back tell I finally had had enough and told them it was time they got to my prop, they where or are very under staffed, I would think if you continually have a 6 month back log you should start training more help.

The prop has been in three shops first was American Propeller where they did it no favors at all, it came back slinging grease everywhere and then slinging Teflon plumbers tape that got all wound up around the hub and the paint was peeling off, all in ten hours and it took them 4 months to do the O/H!

The prop then immediately went to MT in Germany where they corrected everything in 6 weeks for free. This was actually good service in my opinion, so MT deserves credit for that.

After all this I think the owner could not bear sending it off again so he put it off way to long.

Then I sent it in to MT USA for the service I told you about.

I am just trying to feel out what?s out there for service, I want to send my prop in to a shop on the west coast and get it back in 3or 4 weeks done right, I think that?s reasonable. Maybe you get the service I was not getting from MT USA, maybe my prop was being put on the back burner in favor of service they where giving there shops like you and as such I might get the service I should get by using you or a shop like you in the future.

Russ
 
Adjust fine pitch stop

pvansrv3 said:
Landing is drastically different. The plane is a brick with the throttle closed in the pattern, you have to keep 2000 rpm to make a normal gliding pattern approach. I think there is such a great percentage of airplane in the propwash, and the prop is such a fine windmill sucking energy from the air that the braking effect on a light airplane is enormous. We leave the prop governor set at 2100 rpm and leave power in on approach. You can easily do a go around at that prop setting since the plane is light and powerful.
Peter
Click to expand...
Peter,
You might consider looking into adjusting the fine pitch stop and make it a couple of degrees courser. That works on all the Hartzell's and Whirl Winds I've tried and makes for a more reasonable approach when on an RV. Perhaps Jim Ayers can let us know if it is indeed adjustable on your prop. Call me to further discussion if you like.
 
Just MT

Russ McCutcheon said:
Hi Jim,

(Stuff Cut)

I am just trying to feel out what?s out there for service, I want to send my prop in to a shop on the west coast and get it back in 3or 4 weeks done right, I think that?s reasonable. Maybe you get the service I was not getting from MT USA, maybe my prop was being put on the back burner in favor of service they where giving there shops like you and as such I might get the service I should get by using you or a shop like you in the future.

Russ
Click to expand...

Your suggestion that my companies propeller overhauls are placed ahead of MT Propeller USA's other customers is inappropriate.
As far as I know, MT Propeller USA operates on a "first in, first out" system. The propeller assembly is split into two process lines. One line for the propeller hub, and another line for the propeller blades. When both lines have been completed, the propeller is packed and shipped.

With normal UPS Ground delivery, it would take me about 4 weeks from the time I receive the propeller to complete an overhaul.

It normally takes about two weeks for MT Propeller USA to inspect and overhaul the propeller parts, once they have been started into the process. I have found there is a seasonal backlog of overhauls (especially at the end of the flying season). This backlog can be as much as 6 weeks. Not everyone knows to ask.

My agreement with MT Propeller in Germany allows me to have information about how MT Propeller USA is supposed to operate. I have used this information to be able to work better with MT Propeller USA's system. Basically, to improve my companies working relationship with MT Propeller USA.

I am expecting the return of an overhauled propeller from MT Propeller USA today. It has taken 6 weeks since I received it from the customer. One week was due to my shop. Apparently another week was used MT Propeller USA due to the unusual size of the propeller hub, since this was an early CS propeller from a motor glider.

Regards,
Jim Ayers
 
Jim,

I absolutely did not mean to offend with my observations. And I have first hand knowledge that wile first in first out at MT USA might and should be the norm it is not always the case, When I confronted them about putting my prop on the back burner they admitted they had done that very thing several times and would get it on the front burner straight away and they did. I literally have there confection that they put other work ahead of mine several times.

Now this past work was no normal O/H and I know they could not have done it in 4 weeks because they had to order in a hub and other custom parts from Germany, they needed about 8 to 10 weeks if they had kept it in play.

I was not trying to implicate you in any wrong doing at all, you have no control over how MT processes orders, I was just speculating that shops like yours that regularly do busyness with them and have a good relationship with them might get exceptional service, there?s nothing wrong with that and you should strive for it in order to service your customers the best you can.

Russ
 
Jim
Are the blades in the aerobatic MT rocket prop differenet than the blades in the standard version? I know that they default to the coarse pitch but are the blades themselves different. Thanks
 
Just MT

Tom Martin said:
Jim
Are the blades in the aerobatic MT rocket prop differenet than the blades in the standard version? I know that they default to the coarse pitch but are the blades themselves different. Thanks
Click to expand...

Hi Tom,

Yes and No.

The two Rocket propellers you are asking about are the standard 3 blade MTV-9-B/198-52 and the counterweighted 3 blade MTV-9-B-C/C198-52 propeller.

Aerodynamically, they are identical.

From the propeller model numbers you can see the the propeller diameter and blade design are the same.

However, the blade drive pin on the blade is in a different location for the "standard" blade than the location for the blade drive pin in the counterweighted blade.

This is because increased oil pressure from the governor is always pushing the piston forward in the hub. As the oil pressure increases,
1.) The standard blade starts at a fine pitch and is rotated to a coarse pitch.
2.) The counterweighted blade starts at a coarse pitch and is rotated to a fine pitch.

Bottom line, internally, only the propeller hub and a few of less expensive parts could be used if you wanted to convert a standard blade propeller to a counterweighted propeller.

Regards,
Jim Ayers
 
Overhaul of damaged MT propeller

For the MTV-15-B/183-402 Aluminum 2 blade 72" diameter MT Propeller, the minimum propeller diameter is 68".

For a propeller that has had a propeller strike, each of the aluminum blades from a 72" diameter can be trimmed by up to 2" (68" diameter), and still be serviceable.
There is a required inspection of the propeller hub. Normally, the propeller hub is simply overhauled and returned to service.
This is because the bearings and bearing races are usually the only items damaged in the propeller hub due to a blade strike.

For the MTV-12-B/183-59b "Natural Composite" 3 blade 72" diameter MT Propeller:

THe blade length is 1/2 the propeller diameter minus 3". So for a 72" diameter propeller, the blade length is 36" minus 3", or 33".
Up to 15% of the "Natural Composite" blade tip can be replaced by a factory overhaul of the blades.
The 72" diameter propeller can be reduced to about a 62 1/8" diameter, and the blades can still be overhauled back to be a 72" diameter propeller.
It normally takes about two weeks for the MT Propeller factory in Germany to overhaul the blades.
There is no life limit on the "Natural Composite" blades. There is no limit to the number of times that they can be overhauled.
Normally, the stainless steel leading edge is replaced and the blades are repainted.
Again, the propeller hub is inspected and overhauled for return to service. Any internal damage is normally limited to the bearing races and bearings.

Since Lycoming requires a tear down inspection of their engine, after a propeller strike, the propeller can usually be returned in about he same time as the engine is reinstalled. Assuming they are both started at the same time.
It does take about 4 weeks to replace the spinner, if this is damaged. (Been there, done that. Obviously, the blades weren't usable in this instance.)

Regards,
Jim Ayers
 
Custom Aircraft Propeller

I am in the process of building a Harmon Rocket II type aircraft. I plan to use this aircraft for higher altitude cross country trips, in addition to the other normal uses.
The 4 blade propeller theoretically has the best efficiency for this upper VFR altitude flight use.

MT Propeller designed a 4 blade propeller for my engine and aircraft. It has been flown on a F-1 rocket that normally had the 3 blade MT propeller. I was informed that the 4 blade propeller was 2 knots slower a 4,000'. A little less than I expected for this low altitude. Also, the 4 blade propeller seemed to perform better than a 3 blade propeller above 9,000'. (Unfortunately, there are no numbers available.)
Apparently, the performance cross over between a 3 blade and the 4 blade is a little lower than I expected. (It probably helps that the 4 blade propeller efficiency is 0.3% better than the 3 blade propeller.)

I have a customer, Bud, with a Lycoming 360 engine in his single aircraft. (Piranha) His son bought a 3 blade MT Propeller for his HR2. And Bud's aircraft is just a little faster than his son's HR2.
Bud felt he needed to replace his original 2 blade with a 3 blade MT Propeller. However, he wanted too still be a little faster than his son's HR2.
Bud really likes how smooth the 3 blade propeller operates. (Although there were apparently some issues with the original 2 blade propeller.)
And Bud's aircraft is still a little faster than his son's HR2.
(I still am amazed at the reported 120 mph stall speed of the Piranha.)

Regards,
Jim Ayers
 
Counter weight? EI survey? OH cost? Fly off?

Tom Martin said:
Jim Are the blades in the aerobatic MT rocket prop different than the blades in the standard version?
Click to expand...
Aerobatic propellers have counterweights on the blades and use oil pressure to decrease pitch. Any momentary oil pressure loss (common with hard acro maneuvers) causes the engine to go to a high pitch and the engine slows down. Aerobatic propellers are heavier due to the counterweights. With standard props (pressure for high pitch) you can get the engine to Rev if you lose oil pressure. Not sure why Jim pushes the acro prop. We do acro but not Pitts/Extra acro. If you have done acro and lost oil pressure you do get a RPM surge, but not gentlemans RV acro. If you are doing wild ultimate acro maneuvers like a Lomcevak, yea, get a acro prop, but you are not doing Lomcevak in a RV or Rocket.

Some say its better for engine out guide even for a non hardcore Acro plane? May be? Course pitch would give less drag than fine pitch, which is what standard props go to when RPM/oil pressure drops. Is that really a reason to buy a prop on a single sport plane? Why by a light weight MT prop and add the weight back? Jim whats your reason for pushing Acro props on planes that really are not for aggressive acro (like the Rocket).

RVjim said:
For the MTV-15-B/183-402 Aluminum 2 blade 72" diameter MT Propeller, the minimum propeller diameter is 68".

For a propeller that has had a propeller strike, each of the aluminum blades from a 72" diameter can be trimmed by up to 2" (68" diameter), and still be serviceable.
Click to expand...
Jim has MT ever done Vibration surveys for Lycs with electronic ignition? If so do you have proof in writing. This question applies to both the metal and "natural composite' bladed props.

For the MTV-12-B/183-59b "Natural Composite" 3 blade 72" diameter MT Propeller:

THe blade length is 1/2 the propeller diameter minus 3". So for a 72" diameter propeller, the blade length is 36" minus 3", or 33". Up to 15% of the "Natural Composite" blade tip can be replaced by a factory overhaul of the blades.

It normally takes about two weeks for the MT Propeller factory in Germany to overhaul the blades.
There is no life limit on the "Natural Composite" blades. There is no limit to the number of times that they can be overhauled.
Click to expand...
What does it cost? What is a full standard overhaul for both the metal two blade and wood/fiberglass three blade props. I assume shipping cost to Germany of a prop is not cheap? I heard the cost to OH a MT is almost as much as a new Hartzell? I doubt that but what is the real cost, with shipping, the full meal deal cost.

Why do you call the blade "natural composite"? Its WOOD right, wood wrapped in fiberglass. I don't know any material called natural composite.

Normally, the stainless steel leading edge is replaced and the blades are repainted.
Click to expand...
How often do those leading edge erosion shield become de-laminated? I assume a repair means taking to prop off and shipping it, verses just blending the a nick out of a Hartzell with a file.

RVjim said:
The 4 blade propeller theoretically has the best efficiency for this upper VFR altitude flight use.

MT Propeller designed a 4 blade propeller for my engine and aircraft. It has been flown on a F-1 rocket that normally had the 3 blade MT propeller. I was informed that the 4 blade propeller was 2 knots slower a 4,000'. A little less than I expected for this low altitude. Also, the 4 blade propeller seemed to perform better than a 3 blade propeller above 9,000'. (Unfortunately, there are no numbers available.)
Click to expand...
Well I heard just going from a two bladed Hartzell to a three bladed MT causes loss of 6-9 mph, which seems to be shown over and over by independent sources. I also heard the Four blade was worse than the three blade by more than 2 kts. Van did one of these prop comparison fly-offs, and it showed the MT's where slower, significantly. It would be good to give the MT a fair shake. May be we should have another independent Prop Round-up, fly-off comparison with all the MT's verses other props.
 
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I guess if I am going to be quoted I should clarify why I wanted to know if there was a difference between the standard and aerobatic blade. I was curious to know whether there would be a top speed difference between the different versions. I have been in three races where my MT standard prop rocket was faster than some other aerobatic blade MT props. Jim answered that aerodynamically the blades are the same. The differences are all in the hub. Thus I would conclude that there should be no difference in speed between an aerobatic and standard MT prop. I have owned both versions and prefer the lighter weight standard prop.
 
Tom Martin said:
I guess if I am going to be quoted I should clarify why I wanted to know if there was a difference between the standard and aerobatic blade. I was curious to know whether there would be a top speed difference between the different versions. I have been in three races where my MT standard prop rocket was faster than some other aerobatic blade MT props. Jim answered that aerodynamically the blades are the same. The differences are all in the hub. Thus I would conclude that there should be no difference in speed between an aerobatic and standard MT prop. I have owned both versions and prefer the lighter weight standard prop.
Click to expand...

Hi Tom,

I guess I'm not the only one that resents being misquoted. :)

Just as a clarification, the counterweights are mounted at the base of the blade hub. (There are two hubs on the MT Propeller, the propeller hub and the blade hub.)

The counterweights weigh around 4 pounds each. This is 12 pounds on the three blade propeller. There is a CG change with this weight increase.

There is also a 12 pounds different between the aluminum 2 blade propeller and the 3 blade propeller. When I do testing on my RV-6A with the extra 12 pounds of the Aluminum propeller on the front, I place 16 pounds in the baggage compartment to maintain the CG location, and burn off an extra 5 gallons of fuel before I start the test.

The counterweighted blade propeller could just be shifting the CG forward with a resultant increase in pitching moment, and additional elevator trim drag. Or it could just be the differences in the aircraft.

Regards,
Jim Ayers
 
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Natural Composite

MT Propeller refers to the core of the propeller blade as "Natural Composite". They manufacture their own blade core from the selection of the Beechwood and Spruce to the completed blade.

The initial Beechwood and Spruce are dried to a 6% relative humitity. While most of the blade is Spruce, the blade hub is Beechwood.
These two materials are bonded together in a press, which causes the wood fibers to become impregnated with resin, like any other composite product.

Since this process starts with a natural fiber, you get a "Natural Composite" blade laminate that becomes the core for the MT Propeller.

The two layers of fiberglass are used as a moisture barrier to maintain the 6% relative humitity of the core.

Regards,
Jim Ayers
 
Hello Jim,
Does MT publish mass moment of inertia values for their propellers, in particular the MT7(?) as used on Eggenfellner Subaru packages? If so, can I get a copy?
 
Some stuff I've heard

DanH said:
Hello Jim,
Does MT publish mass moment of inertia values for their propellers, in particular the MT7(?) as used on Eggenfellner Subaru packages? If so, can I get a copy?
Click to expand...

The first place to look for this type of information is www.mt-propeller.com

The following is information I remember that I may have just heard and not seen written down.

The polar moment of inertia of the 3 blade MT propeller is 40% of that for an Aluminum 2 blade propeller.

A feathered propeller has 7/8ths less drag than the same propeller in low pitch.

A counterweighted blade propeller with the loss of oil pressure has 5/8ths less drag than the same propeller at low pitch.

Zero G maneuvers are most likely to cause the loose of oil pressure to the governor and propeller. Even with an inverted oil system.

I had the opportunity to disassembly a 2 blade MT Propeller that had been flying off of rock strips in Iceland. (I was attended the MT Propeller certification class in Germany, at that time.) The stainless steel leading edges were badly dented on both blades. However, they were still serviceable and the propeller had only been sent in due to the required overhaul time. The blades were serviceable because there were no cracks in the stainless steel leading edge. Only dents.

The two layers of fiberglass on the ?Natural Composite? core are not a structural part of the blade assembly. However, this layer acts as a moisture barrier for the core, and this surface must be kept sealed. The Installation and Operation manual that comes with the propeller identifies typical repairs (and repair limits) that can be done.

A Velocity landing at Sun-N-Fun had to make a go-around, and in the process over rotated and trimmed ?? off of each blade. The blade tips were trimmed to equal lengths and sealed with 5 minute Epoxy. The owner was only cautioned to make certain when the propeller was overhauled that the original blade length was emphasized to the repair station when it was time to overhaul the propeller. That way he could get the overhauled propeller back with the original blade length.

Regards,
Jim Ayers
 
MT on an XIO-390

Jim,

I am building an RV-8, and plan to put an XIO-390 on it. Does the 3 blade MT prop work with this engine? I realize there is a speed loss with the 3 blade, but I really don't care. My Pratt powered 195 has one(Hartzell), and so will my RV-8(MT), if it works with the engine.

Thanks,
 
RVjim said:
My purpose in starting this thread is to provide a place for the exchange of information in the form of an interactive discuss about MT Propellers.

Since I am more than a little concerned about off topic comments,

Regards,
Jim Ayers
Click to expand...

George, did you happen to read the above in the first post in this thread??

I think pretty much everyone knows that the MT is a bit slower, and there may be other issues also.

But there is a lot I do not know about the MT, and I am interested in finding out what I can about these props.

Good, and bad.

Your questions about service availability, and cost are valid, but your way of presenting them comes off as confrontational, not informative.

I happen to have a MT 3 blade sitting on the floor, waiting to go on the nose of my 10. It came with the project, part of the package. I did not do any research on props, so I am a bit behind the power curve in knowledge here.

Therefore, I am watching this thread pretty close------to learn what I can to help me with my future usage of this prop.
 
gmcjetpilot said:
Excuse me but you have no right and these are open forums. I asked GOOD questions. Your post is arrogant and disrespectful. I think KNOWING what the cost of an overhaul is, how reliable are the bonded erosion strips, if vibration analysis was done on metal props and getting good performance data on speed is relevant. very relevant. If you have a problem I'm sorry, you joy was diminished. I follow the rules of the forum, I'd appreciate if you would also. You can complain to Doug. You can email me in private if you want to tell me what you think, but to do this on the thread is ridiculous. Have a happy holidays and great new years.
Click to expand...

I am not sure how relavent this response is but I have an MT-7 3 blade electric prop and just had it overhauled.

I learned a few things about the MT in that I was permitted - with their help - to disassemble the unit to save shipping and crating costs from this end. That was fun and seeing how the blades are held in the hub reinforced my confidence in the prop. The unit is of suberb design in my opinion.

The total cost to overhaul was $1820.15 plus $200 for a dynamic balance. The actual overhaul cost was $1170, the rest crating and shipping. If one lives close enough to haul it in and pick it up, it is worth doing it. It is my understanding the next OH won't be due for 1500 hours but I don't have paper to back it up, yet. This unit was overhauled in Florida.

I don't know how this compares to a Hartzel OH or any other American made prop.

The prime advantage of this particular propeller is its weight and it is a true constant speed prop, very easy to install and operate. I weighed the thing before install some time ago and it came in at 31 pounds plus an electric controller on the panel that might weigh 10 ounces. It comes with a predrilled spinner that fits perfectly. Annual maintenance is minimal in that it does not require lubrication (it is sealed) and about all you do is check the blades for damage.

The prime disadvantage is that this unit is suited ONLY for the Subaru engine as far as I know. I specifically asked MT about using it with a 0320 or 0360 and they said no. I do know it is certified with the 0235 but that version has different, shorter blades. Also, this unit is not adequate for hard core aerobatics, 2 or 3 G gentleman stuff is OK I am sure. I fly the thing out of a grass strip so there is occassional light leading edge damage due to killing bugs and/or clipping high weeds, but none of it seems to be serious. A good cleaning after each flight and it looks very good.

The comparitive performance of the unit is well known. It does very well at the low end, like take off and climb, but falls off at the top end. I have heard this story at OSH forums by people who seem to know their stuff so I believe it. One guy got into some deep blade design stuff to explain why this is so. Plus we know Vans did an extensive survey of various props with published results of top end numbers. The MT was not the winner. If they had had a 2 blade in the race, it may have come in better.

I think we all would like everything to be perfect, but it just is not possible. This unit has advantages and disadvantages. Also, there are MT versions suitable for just about any flight activity with any engine. The company has been around a long time and they do seem to know their stuff.
 
390 engine & MT Propeller

CE196 said:
Jim,

I am building an RV-8, and plan to put an XIO-390 on it. Does the 3 blade MT prop work with this engine? I realize there is a speed loss with the 3 blade, but I really don't care. My Pratt powered 195 has one(Hartzell), and so will my RV-8(MT), if it works with the engine.

Thanks,
Click to expand...

Hi Calvin,

The MTV-12-B/183-59b propeller may be the only propeller available without RPM restrictions. MT propeller engineering has said that this 3 blade propeller with the 183-59b blades is a good match for your engine.

I wouldn?t count on this 3 blade propeller being any slower than an Aluminum 2 blade propeller. The complete text of propeller theory says that the greater the horsepower and altitude, a greater number of blades become the most efficient.

Neither Van?s Aircraft, nor I, have published any performance data on the MTV-12-B/183-59b propeller. Or on other propellers that have become available since Van?s Aircraft data published years ago.

A RV-6A with a 180 hp Lycoming O-360-A1A showed an efficiency crossover altitude between the 2 blade propeller and the 3 blade propeller of around 7,500?. Your higher horsepower should decrease the altitude at which this occurs.

I have heard of some tests performed in Australia between the MTV-12-B/183-59b propeller and a 2 blade (aluminum) propeller. Basically the same top speed performance from both.

If you are planning to be doing aerobatics, especially zero G maneuvers, then you might consider the counterweighted blade MTV-12-B-C/C183-59b propeller. It is the same weight as an Aluminum 2 blade propeller.

Regards,
Jim Ayers
 
<<first place to look for this type of information is www.mt-propeller.com>>

Thank you Jim. Yes, it is in the type sheet for each prop, 0.5 kgm^2 for the MT7.
 
RV-10 MT Propeller testing request

Mike S said:
(Stuff Cut)
I happen to have a MT 3 blade sitting on the floor, waiting to go on the nose of my 10. It came with the project, part of the package. I did not do any research on props, so I am a bit behind the power curve in knowledge here.

Therefore, I am watching this thread pretty close------to learn what I can to help me with my future usage of this prop.
Click to expand...

Van?s Aircraft uses a single data point for their flight testing. They use an 8,000? density altitude, full throttle and 2500 RPM. I haven?t heard what mixer setting they use.
This is their standard ?Cruise? performance test point.

I have done some propeller comparison flight testing with two different RV-6a?s each having the 180 hp Lycoming O-360-A1A engine.
I have also chosen to use an 8,000? density altitude and full throttle for this testing. This is not ?Cruise? performance testing, since I varied the RPM from 2000 to 2700 RPM in 100 RPM steps. The engine was leaned to 50 degrees rich of peak for each data point setting. Basic physics of the airframe and engine allows this method to provide very repeatable data with total disregard to an actual power setting.

Using this test methodology and some new insight into engine/propeller performance characteristics, I asked a MT Propeller customer with a RV-10 to obtain some very basic performance data.

He ran the Van?s Aircraft data point at 8,000? density altitude, full throttle and 2500 RPM leaned to peak EGT. He also ran data points at 2300 and 2100 RPM.

2500 RPM used 20 gallons per hour (GPH).
2300 RPM used 15 GPH and was 1 knot faster.
2100 RPM used 12 GPH and was 6 knots slower.

He chooses to fly at 2100 RPM because he really likes the 12 GPH fuel flow with only a minor decrease in airspeed.

Another MT Propeller customer with a RV-10 reduced his cruise RPM to 2350. He claims a 5 knot speed increase with a 2 GPH fuel flow decrease.

Obviously, this is very incomplete data.
So the real point is this. I own a MT Propeller for a Lycoming IO-540 powered RV-10. However, I don?t have a RV-10.
Does someone have a Lycoming 540 powered RV-10 currently flying with an Aluminum 2 blade propeller? And would like to do some very interesting propeller performance comparison testing in the Southern California area?
If you like the performance with the MT Propeller, I can make you a real good deal on it. I?m also certain that there will be a market for your used Aluminum 2 blade propeller.

Regards,
Jim Ayers
 
Custom Aircraft Propeller

CE196 said:
Thanks Jim, next question do you sell them?
Click to expand...

Yes. I sell MT Propellers. Check the propeller page on my website, www.ca-propeller.com

I was looking for a replacement propeller on my RV-3 at Oshkosh 2002. In visiting all of the propeller booths at the airshow, I found what I felt was an excellent propeller manufacturer. One thing lead to another, and I became certified by MT Propeller and then created a new FAA certified repair station, Less Drag Products, Inc. Custom Aircraft Propeller is the sales division of Less Drag Products, Inc.

Regards,
Jim Ayers
 
electric CS MT Propeller

mark manda said:
can you guys talk about governors and electric controllers and "true constant speed prop...." ? thx
Click to expand...

The experts on the hydraulic governor at off for a two week company holiday. I would like to pick up a discussion on the hydraulic governor then.

At Oshkosh 2002 I ordered an electric constant speed propeller from MT Propeller for the LOM engine in my RV-3.
The short version of the story is that I was at MT Propeller in Germany and was able to do the original propeller assembly of my propeller. Then I disassembled it for shipment to myself. When I got home, I assembled my propeller again, and installed it on my RV-3. I have the P-120-U controller.

There is a description of the electric CS propeller on the electric propeller page of the products page on www.mt-propeller.com

The electric controller has a 3 ?? wide face plate that is 1 1/8? tall. The controller mounts from the front of the panel through a 1? tall by 3? wide slot.

There is a toggle switch on each side with a rotary knob in the center.
The left side toggle switch selects Automatic mode or Manual mode.
The rotary knob in the center selects the RPM when the unit is in the automatic mode.
The right side toggle switch changes the blade pitch up or down when the unit is in the manual mode.
There is also a self test light and a low pitch light on the face plate. The self test light comes on when power is applied. The low pitch light is on anytime the propeller blades are at their low pitch position. (Like when the engine is idling while the controller is in the automatic mode.)

The P-120-U on my RV-3 has a maximum RPM of 2700. The center knob is marked from 1700 to 2700 RPM.
I modified my normal Mag check at 1800 RPM to include rotating the RPM knob to 1700 RPM. (When the RPM decreases from 1800 RPM and the low pitch light goes out, this indications that the full controller/propeller system is functioning properly.) The rotary knob is then returned to the 2700 RPM take off position.

The electric CS propeller responds much slower than the hydraulic CS propeller, at about 1/5 the pitch change speed.
In all of my normal flight operations with the electric CS propeller, the controller has been able to maintain the set RPM. However, one time I was reminded why the electric controller isn?t recommended for aerobatics when I made a descending ?RV-3 standard rate turn?. The controller couldn?t maintain the cruise RPM, and allowed an increase from 2400 to 2500 RPM in the 180 degree turn. (A ?RV-3 standard rate turn? is at least 3 G?s. No passengers changes ones perception.)

The propeller blades, propeller blade retention and propeller hub are identical between the hydraulic and electric CS MT Propellers. I have had the occasion to convert between them more than once.
The point is that MT Propeller recommends that aerobatics not be performed with the electric CS propeller because the controller can not change the blade pitch fast enough to control the engine and propeller RPM.
My suggestion is to place the controller in the manual mode at a reasonable RPM and to control the engine/propeller RPM with the throttle, like any other fixed pitch propeller.

I hope this is a good start on a discussion about the electric CS propeller.

Regards,
Jim Ayers
 
RVjim said:
I hope this is a good start on a discussion about the electric CS propeller.
Click to expand...

The only thing I can add is last winter, for reasons I can't remember, I went flying one day when the temp was in the 12-14F range. The prop worked going to an airplort, about 20 minutes, but on the return would not reset to a course pitch. It worked to a finer pitch but not the other way...figured the whole thing was just too cold soaked. There really was not a good reason to fly that day and I wondered why I was there doing it.

Also, if going into a high speed dive at altitude, sometimes the air load becomes so great the electric motor can not move the blades and the system goes into some sort of lock up - nothing works, the blades are in fixed pitch. The fix is to remove power for a moment and turn it back on - the system works again. There is a factory fix for this event, I think it involves a different resistor in the controller.
 
electric CS controller

David-aviator said:
The only thing I can add is last winter, for reasons I can't remember, I went flying one day when the temp was in the 12-14F range. The prop worked going to an airplort, about 20 minutes, but on the return would not reset to a course pitch. It worked to a finer pitch but not the other way...figured the whole thing was just too cold soaked. There really was not a good reason to fly that day and I wondered why I was there doing it.

Also, if going into a high speed dive at altitude, sometimes the air load becomes so great the electric motor can not move the blades and the system goes into some sort of lock up - nothing works, the blades are in fixed pitch. The fix is to remove power for a moment and turn it back on - the system works again. There is a factory fix for this event, I think it involves a different resistor in the controller.
Click to expand...

Hi David,

What is the RPM range (1700 to 2700 RPM?) on your controller, and your aircraft voltage (12 or 24 volts).

Your symptoms sound to me like a controller issue. Unfortunately, MT Propeller has gone on a two week company holiday.

Normally, the CS controller is internally limited to 2.7 amps output on a 12 volt system. I remember hearing about a controller change that increased the output to 3.0 amps. And I bellieve it was for the Subaru installation.
Unfortunately, I wouldn't be able to confirm this right away.

Regards,
Jim Ayers
 
RVjim said:
Hi David,

What is the RPM range (1700 to 2700 RPM?) on your controller, and your aircraft voltage (12 or 24 volts).

Your symptoms sound to me like a controller issue. Unfortunately, MT Propeller has gone on a two week company holiday.

Normally, the CS controller is internally limited to 2.7 amps output on a 12 volt system. I remember hearing about a controller change that increased the output to 3.0 amps. And I bellieve it was for the Subaru installation.
Unfortunately, I wouldn't be able to confirm this right away.

Regards,
Jim Ayers
Click to expand...

Jim,

All of the above correct. I just have not gotten around to sending the controller in for the modification. I can deal with the problem since it has not happened since finishing phase one testing. The lock up occurred taking the airplane up to the red line.

It is 12 volts, rpm range 1700-2700.
 
Electric CS propeller

Just a quick update on myself. I am an advocate for MT Propeller. I started this thread to introduce some of the unique features of the propeller assemblies that MT Propeller manufacture. And to be available to answer whatever relevant questions that might be brought up.

MT Propeller?s electric CS propeller is a fairly unique propeller assembly.

The propeller hub, blade retention and blade design are identical to their hydraulic CS propeller design. Just the front cover and central drive mechanism is different between the hydraulic CS propeller and the electric CS propeller.

The electronic controller and slip ring are what allow the electric CS propeller to be functional.
The slip ring and brush design appears to be the same design as the brushes and slip ring used to provide power for the electric de-ice boots on blades so equipped. However, the electric CS propeller requires a maximum of 3 amps of power on a 12 volt system, while the de-ice boots could require as much as 20 amps through the same brush/slip ring assembly.
The normal electronic controller uses an automatic mode to hold the specified RPM. And it has a manual mode in the event that the automatic mode fails and can not be reset.

When the electric CS propeller is assembled at the factory, or assembly facility, there are a pair of high and low pitch stops set. The mechanical high and low pitch stops. And the electric high and low pitch stops. The electric stops are set 2 degrees before the mechanical stops. (There are other stop configurations, but this is typical for what is usually installed on an RV.)

There is a set up procedure for the electric CS propeller that is supposed to happen before the first flight. The details are in the installation and operation manual that comes with the propeller.

Briefly, as an overview:
With the spinner assembly and spinner filler plates removed, a full power static RPM run up should be made.
For an engine with a 2700 RPM maximum RPM, this static RPM run should provide 2600 to 2650 RPM. The electronic controller has a low pitch stop light to show when the propeller is on the low pitch stop.
Again, the actual adjustment is made per the instructions of the Installation and Operation Manual.

IMHO, it is a safety of flight issue to make certain that the low pitch stop on any CS propeller is set at, or below, the maximum engine/propeller RPM in a static run up.
(If someone wanted to exceed the maximum recommended RPM in flight, in the hopes of increasing their maximum speed, this can be set with the low pitch (high RPM) governor adjustment alone.)

Regards,
Jim Ayers
 
Prop oil system

I have a standard 2 blade MT prop and governor. I have a couple of questions which are in fact common to other setups.

1. Since, particularly with a tail dragger, the prop is the highest part of the oil system, how does the air escape when the prop is bolted on and the engine started.

2. Since the prop is a dead end for the oil system, presumably cycling the prop governor changes the pressure inside the prop hub, but apart from the compression of the trapped air, there is no real flow. So what is the point of doing it.

I must be missing something. Can someone please explain.

Thanks.
 
Propeller & governor

Steve Sampson said:
I have a standard 2 blade MT prop and governor. I have a couple of questions which are in fact common to other setups.

1. Since, particularly with a tail dragger, the prop is the highest part of the oil system, how does the air escape when the prop is bolted on and the engine started.

2. Since the prop is a dead end for the oil system, presumably cycling the prop governor changes the pressure inside the prop hub, but apart from the compression of the trapped air, there is no real flow. So what is the point of doing it.

I must be missing something. Can someone please explain.

Thanks.
Click to expand...

Perhaps someone else can explain it better than I for question 1.
I believe there are two flow paths for oil to return to the engine sump.
a.) leakage from the crankshaft bearing between the governor case inlet to the crankshaft and the crankshaft.
b.) the pressure return valve on the governor.

For question 2.)
Integral in the governor is a 375 psi oil pump capable of flowing 8 quarts per minute. It's not exactly a "no real flow" system.

As you have identified, the propeller hub is at the top of the oil system. While the aircraft is parked, the oil will drain out of this area and eventually just leave air in the propeller hub/crankshaft.

Cycling the propeller as part of the pre-flight check is done to remove the entrapped air in the propeller hub/crankshaft. If this isn't done adequately, the governor has difficulty controlled the propeller properly (due to a "soft" air bubble (compressible), instead of the "hard" oil (incompressible)).
This would be noticeable as an RPM variation, or engine surge, in flight. At least, this is one of the ways that engine surge can occur.

I have been told that the typical oil pressure in the propeller hub is around 150 psi.
Varing the oil pressure between almost zero pressure to 375 psi is how the governor changes the blade position to maintain a constant RPM. The 8 quart per minute capacity is needed to allow the governor to change the blade position quickly enough to maintain a set RPM.

The numbers I have given are for MT Governors only. I guess that's why I started this thread as being Just MT Propellers. That's what I know.

Regards,
Jim Ayers
 
The oil/air has no way to return from the prop.

Jim, I cant be explaining myself very well. Your mental model of how this all works just does not match up with mine.

In my model there is only one path from the crank shaft to the prop. The oil moves forward through the hole that is covered by the orange plastic plug in the centre of the flywheel in this picture. There is no return path from the prop. The pump may be capable of flowing '8 quarts per minute' but once oil goes into the prop that will soon get full and then all the pump can do surely, is increase/decrease the pressure with no flow. The two return paths you mention are both behind the prop/crank shaft interface so the air is trapped.

http://gikonhome.blogspot.com/2007/11/engine-cowls.html#links See the second picture down, double click it for more detail.

To me ,this means that there is no flow in and out of the prop, because the oil has nowhere to go. Similarly I cant see the trapped air has anywhere to go. I accept I must be missing something but I dont begin to understand what!

PS I have been sitting thinking about this and I have just one idea, but I struggle to believe it is possible. Because of the rotation of the crank shaft there will be a slightly higher pressure in the oil close to the edge of the tube compared with that on the central axis. Is the oil actually flowing two ways at once? There is a tube running across the centre of the crank shaft if you look back into it, with a hole that could be collecting returning oil/air. Surely this cant be right. Help, someone must know!
 
Governor oil flow

Hi Steve,

With the propeller installed on the crankshaft, there is a (fixed) cavity in the crankshaft, a (fixed) cavity in the propeller hub and a moving piston (variable cavity) in the propeller hub.

Cycling a standard CS propeller does th following:

Pulling the governor lever back to low RPM causes the governor to flow OIL into the propeller hub at up to 375 psi.
Pushing the governor lever forward to high RPM releases the AIR & OIL mixture out through the governor return valve into the engine sump.

Cycling the propeller two or three times usually results in the flow of oil in both directions. That is, there may be an insignificant amount of air in the cavity.

I hope this helps.
Jim Ayers
 
gmcjetpilot said:
Really for a fixed pitch prop consider the Sensenich, which is made for RV's. A prop is not designed as a stand alone component, it must match the airframe and engine to get the most efficiency. For props one size does NOT fit all. Yes it weighs more but maintence and rain wise, its a no brainier. Also a RV-4 needs weight on the nose with a O320 to get full pass and bag weights, while not exceeding aft CG. Metal also can be re-pitched. Lets say a few years from now you do some plane mods and reduce your RV's drag, with new wheel pants, cowl and other clean ups. YOU CAN REPITCH the Sensenich. Also the performance of a metal props and their thinner blades are better than thicker wood blades. Van tested 8 props, all constant speed props except one, a Sensenich. It came in 2nd behind the Hartzell BA prop!


(Note: the Sensenich if allowed to over speed was faster in this typical cruise condition at 8,000'. Van estimated 2,500 rpm cruise would be about 207.9 mph (from 210.0 mph at 2730 rpm). I believe that est is a little high. Regardless the Sensenich is an efficient prop you can bolt on and forget about.)
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THEN WHERE DID THE MT RATE ? ? ?. Allen B
 
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