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Manual Pitch prop

Roarks

Active Member
I'm honestly a low time pilot. I have a hard time wrapping my brain around constant speed propellers for some reason. I've flown aerobatics with one... I understand it helps keep from overspeed doing maneuvers... but adjusting one for cruise flight is something I've never done... thus ignorance. Tried one in flight sim... and seems like I even touch the prop lever I end up lagging the engine and loosing airspeed.

That said... I am a helicopter pilot too... and those make perfect sense to me. Engine RPM is governed or set with throttle, and we control pitch directly.

So while sitting in a Propeller class (A&P) I learned about 2 position props. Sounds amazing. Apparently spitfires were like this and there is a company Hoffman that makes one.

So this all comes down to $$$. a nice CS prop costs what $15k? Now there are oil seals, a prop governor and a whole bunch of other stuff that needs $ maintenance. I'm honestly okay with a fixed pitch prop, but this two speed prop business sounds cool! So thinking about the mechanism... Why not make the pitch infinitely variable so you can tune it in? Seems mechanically simpler than a discrete "two position".

The mechanism is fairly simple. It could be a simple lever in the cockpit... maybe even a collective/throttle like a helicopter... which really is instinct now.

Takeoff and landing would obviously be low pitch... probably even rig up a low throttle+not low pitch=alarm. Apparently some spitfire pilots had issues with this.

I like mechanical simple things. I bet I could make it fairly easily=cheap...This sounds amazing to me what am I missing?
 
I like mechanical simple things. I bet I could make it fairly easily=cheap...This sounds amazing to me what am I missing?

Well, for starters, the hub forces. With a fixed pitch prop, the prop is one piece, and the aluminum prop carries the centrifugal load. Once you want the pitch to vary, you need two separate prop blades, and a hub attachment to keep them from flying off. The force on that hub is measured in TONS. And, while being held against those forces, the blade has to be able to rotate. Not totally simple.

The other stuff (governors, transfer collars, etc) generally go to engine TBO with little or no maintenance.
 
My old I-290d2 was set up for a "controllable pitch propeller". It was neither a constant speed nor a fixed pitch prop.

On the nose of the engine, there was a lever, about where the prop oil line goes in on some engines or where the forward mount goes on others.

From what I understand, and I could be wrong, my O-290d2 came off an agriculture version of the Super Cub. (Think crop duster.)

There was a cable that would run to the cockpit which allowed the pilot to manage the RPM's by adjusting the prop pitch.

When I called Lycoming years ago, they connected me with a gentleman who had experience with this engine (he must have been really close to retirement). He sold me the NOS part I needed to convert the engine to a fixed pitch prop and told me about how the original prop would have worked.

The original props were wood with metal shanks and apparently didn't last very long. Still, it would have been a cool prop to put on my RV.
 
Constant Speeeeeed....

So while sitting in a Propeller class (A&P) I learned about 2 position props. Sounds amazing. Apparently spitfires were like this and there is a company Hoffman that makes one.
I like mechanical simple things. I bet I could make it fairly easily=cheap...This sounds amazing to me what am I missing?

RS,
Great question, one that has been multum disputatum on this site in the past. :) My Dad owned a 65HP 1945 Taylorcraft BC12D and shared a hanger with a 1946 65HP Luscombe 8A. The 8A ragwing was equipped with a Beech Roby manually adjustable wood prop.
https://www.notplanejane.com/beechcraft.htm I flew both aircraft extensively in my youth and was able to compare them it every arena including STOL, formation flying and cross country. The bottom line was the Luscombe has a slight edge but not a huge one yet the Beech Roby always intrigued me.

Twenty years later my first sport-plane, a Van's RV4 was and still is a marvel of aviation prowess. It had ALL the qualities I required in a personal aircraft. At 925 pounds with a Wood Sterba prop and salvaged 0-320 I could take off from my 400 meter rough turf strip, clearing 50' pine trees on a hot, muggy FL day, climb at 1500 FPM and cruise at 180 MPH at 8500'. I could perform aerobatics, fly formation with and dog-fight my F16 bros in their RV's and travel from Idaho to FL in one (albeit long) summer day. I didn't want to add weight or cost so I kept it as is for many years. However comma, I kept my eye out for a lower cost, albeit lighter weight alternative CS propeller. My search yielded nothing I could either afford or wanted to compromise in additional weight.

Several years ago I flew a Lancair 235 on a pre-purchase inspection. It was equipped with an MT electric constant speed 3 blade prop.
https://www.mt-propeller.com/en/entw/pro_elec.htm
It had a three position setting, needed no oil pressure or assorted lines and was light. I was very impressed at how well the little LA performed with only 118HP and how fast it cruised with the MT electric. The owner informed me that Hoffman also made a similar prop. MT had a service center near where I lived in FL so I flew in for a visit. Not only did they show me an electric CS prop, they allowed me to test a FP MT 2 blade prop on my RV4. That prop still sports the nose of "The Bandit" and the new owner (an F18 pilot) tells me it still performs well against any equally or even higher equipped adversary!
Worth a look...


Bottom line, over the past 25 years I have now flown all the RV models, many with CS props of all the varieties. My own take is a FP prop works well and helps it retain a lighter nose, lower EW and cost with less complexity.
The beauty is like Burger King, you can have it your way...

V/R
Smokey

PS: Another option might be ground adjustable. I have also flown both the Sensy and the Whirlwind. Smooth, capable and not a bad compromise.
https://whirlwindpropellers.com/aircraft/
 
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Adjusting a CS prop for cruise is easy - Select a desired rpm with the prop control and tach, and select manifold pressure with the throttle and manifold pressure indicator. Done.

The manifold pressure is limited by your altitude on normally-aspirated (non turbo/supercharged engines). At many cruising altitudes, full throttle is an option, since the cruising altitude controls that.

Descents can be interesting. As you descend, the outside air pressure increases and so does the manifold pressure. So you need to reduce throttle appropriately. If you don't, you may find that the manifold pressure has increased to the point that you are no longer descending. It's a form of automatic altitude stability, kind of.

Dave
 
RS,
Great question, one that has been multum disputatum on this site in the past. :) My Dad owned a 65HP 1945 Taylorcraft BC12D and shared a hanger with a 1946 65HP Luscombe 8A. The 8A ragwing was equipped with a Beech Roby manually adjustable wood prop.
https://www.notplanejane.com/beechcraft.htm I flew both aircraft extensively in my youth and was able to compare them it every arena including STOL, formation flying and cross country. The bottom line was the Luscombe has a slight edge but not a huge one yet the Beech Roby always intrigued me.

Twenty years later my first sport-plane, a Van's RV4 was and still is a marvel of aviation prowess. It had ALL the qualities I required in a personal aircraft. At 925 pounds with a Wood Sterba prop and salvaged 0-320 I could take off from my 400 meter rough turf strip, clearing 50' pine trees on a hot, muggy FL day, climb at 1500 FPM and cruise at 180 MPH at 8500'. I could perform aerobatics, fly formation with and dog-fight my F16 bros in their RV's and travel from Idaho to FL in one (albeit long) summer day. I didn't want to add weight or cost so I kept it as is for many years. However comma, I kept my eye out for a lower cost, albeit lighter weight alternative CS propeller. My search yielded nothing I could either afford or wanted to compromise in additional weight.

Several years ago I flew a Lancair 235 on a pre-purchase inspection. It was equipped with an MT electric constant speed 3 blade prop.
https://www.mt-propeller.com/en/entw/pro_elec.htm
It had a three position setting, needed no oil pressure or assorted lines and was light. I was very impressed at how well the little LA performed with only 118HP and how fast it cruised with the MT electric. The owner informed me that Hoffman also made a similar prop. MT had a service center near where I lived in FL so I flew in for a visit. Not only did they show me an electric CS prop, they allowed me to test a FP MT 2 blade prop on my RV4. That prop still sports the nose of "The Bandit" and the new owner (an F18 pilot) tells me it still performs well against any equally or even higher equipped adversary!
Worth a look...


Bottom line, over the past 25 years I have now flown all the RV models, many with CS props of all the varieties. My own take is a FP prop works well and helps it retain a lighter nose, lower EW and cost with less complexity.
The beauty is like Burger King, you can have it your way...

V/R
Smokey

PS: Another option might be ground adjustable. I have also flown both the Sensy and the Whirlwind. Smooth, capable and not a bad compromise.
https://whirlwindpropellers.com/aircraft/

WOW! Roby huh. THAT'S AWESOME! Thanks for sharing

I'm designing an engine for my RV8 and Great lakes... probably for a friends acroduster too... I'm out at the prop... stub/flange. I don't want to fool with prop governor and all that and started thinking of alternatives. I'll have to see if I can get my hands on one of those. I've been eyeballing how Spitfire blades are made... should be a good fit.
 
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Aeromatic

Roark,

It looks like what you may be interested in is an aeromatic. There is a company in Nevada making new ones ($5350 and up according to their web site at www.aeromatic.com). There have been other discussions here at VAF regarding these props. Good luck.

Note, these are not controllable by the pilot. If that is what your looking for, the electric variable pitch and hydraulic CS props are really the only two options available currently. You could buy the aeromatic hub and blades and adapt or build a helicopter Swash-plate pitch control that could be controlled from the cockpit. It would be an interesting engineering challenge (like putting retractable gear on an RV), but I think it would end up costing more than an off-the-shelf CS prop/engine combination and you may have a hard time getting the plane insured.
 
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Interesting for sure. But the average Aeromatic blade is a bit clubby. This soaks up much of the prop's potential.

A modern carbon or refined wood/composite blade would make a big difference. I have flown behind Aeromatics for years. Nice. I would be standing in line for an improved and certified blades though.

Ron
 
I put Whirlwind W-530 blades on my Yak-55. These are direct replacement carbon fiber blades made for the Russian V-530 hub.
Whirlwind or Catto or (?) could certainly make blades for Aeromatic or other self adjusting propellers... if there was a market for it...for experimental aircraft.
 
Ptops

The Aeromatics were by far the most popular of the early variable pitch props. Early on they were mostly seen on Stinson 108 and Swift .Somewhat later they were seen on many aerobatic airplanes. Many of the Warner powered airplanes used Aeromatic. Examples are modified Great Lakes and Monocoupe. They were also commonly used on the PJ260/Senior Aero Sport.The standard Aeromatic was completely automatic. There was a fairly rare Aeromatic that had a cockpit control. I believe all this did was lock the pitch into cruise mode. The standard Aeromatic did not have enough pitch range for anything much faster than the 140 m/h Swift.
Sensenich built a Skyblade prop which was two position. This was pilot controlled and is what the control arm on the front of some of the 0 290D's was for. A few 0 235's were also configured for this prop. There were some relatively expensive recurring AD's that pretty much spelled the end of this prop.
The Beech Roby was manufactured by Beech Aircraft. There may have been earlier history but by the first Bonanza in 1947 a variant was factory standard on the Bonanza for a relatively short time.
 
Tons of great information Thanks!

A Roby style prop really has my attention. Now that I've seen how they did it... and that it can be done I'll probably aim that direction.

I'm convinced I can make something Pretty light.
 
Props

Couple more points: the Beech Roby for the small Continental engines was mechanically controlled. A straight shaft from the panel to a gear behind the prop. I think all the Bonanza props were electrically controlled.
Flottorp also made a prop which was very similar to the Roby for the four cylinder.
Over the years there have been many attempts at electrically controlled props for homebuilts. None that I know have ever become popular.
 
It also depends on whether your engine is configured for a hydraulic CS prop. If it is not, consider MT or Airmaster. Airmaster tends to be a bit cheaper than MT, and people say they are bullet proof and much cheaper to service, and unlike MT they actually encourage you to service your own.

If it fails to maintain rpm in flight, you can still ferry the plane home by turning the controller off (fixed pitch).
 
Aeromatic

Post #13: "The standard Aeromatic did not have enough pitch range for anything much faster than the 140 m/h Swift"

Not accurate. The Aeromatic has been the go to prop for the Monocoupe 110 and 110 Specials (clip wings). The Warner 185 hp powered clip wings can easily cruise at 160 to 180 mph. Just needs to be set up correctly.

BTW, Tarver, the shop in Nevada is no longer making the Aeromatic props, but the last time I spoke with them were able to refurbish blades.

My Aeromatic:

Aeromatic99.jpg
 
49clipper

funny, no one even mentioned the all electric Airmaster prop currently built in New Zealand. I am putting on one my new homebuilt this next spring. they finally got them designed and built for 320's and 360 lycomings. a little pricey at 13500 but competitive. Uses whirlwind blades.
 
Monocoupe

I specifically mentioned the Monocoupe in post #13. I believe the reason the Aeromatic works well on the Warner is the relatively low rated r/m for the Warner. The numbers I find are 2050 max r/m for the 145 and 2175 for the 185. So these engines operate in a relatively small r/m range which favors the Aeromatic.
The PJ260 and Lycoming powered Chipmunks used geared Lycomings which also helped the Aeromatic work better.
Am I correct that the Warners are not set up for modern constant speed props and therefor the Aeromatic is the best of limited prop options???
 
PROPELLERS The First, and Final Explanation by Jack Norris . It's difficult reading the way he wrote it but the math is great. He mentions WirlWind and their RV 200 prop several times. WirlWind is building the prop for my project ( not an RV200) they seem willing to " work outside of the box"
 
I'm honestly a low time pilot. I have a hard time wrapping my brain around constant speed propellers for some reason. I've flown aerobatics with one... I understand it helps keep from overspeed doing maneuvers... but adjusting one for cruise flight is something I've never done... thus ignorance. Tried one in flight sim... and seems like I even touch the prop lever I end up lagging the engine and loosing airspeed.

That said... I am a helicopter pilot too... and those make perfect sense to me. Engine RPM is governed or set with throttle, and we control pitch directly.

So while sitting in a Propeller class (A&P) I learned about 2 position props. Sounds amazing. Apparently spitfires were like this and there is a company Hoffman that makes one.

So this all comes down to $$$. a nice CS prop costs what $15k? Now there are oil seals, a prop governor and a whole bunch of other stuff that needs $ maintenance. I'm honestly okay with a fixed pitch prop, but this two speed prop business sounds cool! So thinking about the mechanism... Why not make the pitch infinitely variable so you can tune it in? Seems mechanically simpler than a discrete "two position".

The mechanism is fairly simple. It could be a simple lever in the cockpit... maybe even a collective/throttle like a helicopter... which really is instinct now.

Takeoff and landing would obviously be low pitch... probably even rig up a low throttle+not low pitch=alarm. Apparently some spitfire pilots had issues with this.

I like mechanical simple things. I bet I could make it fairly easily=cheap...This sounds amazing to me what am I missing?
Well I dare say almost everything under the sun has been tried with props, but maybe you have a better idea. However the standard is hydraulically controlled "constant speed" prop with a prop governor. This is not new, been around for a half century. There are variable pitch props both in flight and on ground but those have given way for the most part to either "constant speed" or fixed props. Not to say having the ability to vary the pitch of your prop does not have benefit, but I am saying go all the way to constant speed. If you love simplicity and lower cost than FIX prop is an excellent compromise.

As I understand it you want a mechanical link to prop pitch that is simple but allows you to set the prop pitch in flight for low pitch (high RPM) for high pitch (low RPM) and maybe something in between... like shifting a 3 speed manual transmission. There have been variable pitch non-constant speed in-flight adjustable pitch props. Navion and Bonanza have had them. The Navion used hydraulics I recall and the Bonanza electric. These would not be cheaper today and most owners have converted their Navion or Bonanza to hydraulic constant speed props.

Moving blade pitch to a mechanical control in the cockpit (no electrical or hydraulics) on a spinning prop requires some kind of swash plate and linkage (like a helicopter). I don't know of anyone accusing helicopters of being simple. Again hydraulic is the standard because it has proven to be the best design.

ELECTRICALLY controlled both available pitch and constant speed props have been done from the early days to present. You can buy electric props but cheap they are not. A slip ring and brushes provides power to the electric pitch motor in the hub. Again hydraulic is the standard and has replaced electric exclusively for certified planes. If low cost and simplicity is your goal while having control over blade pitch, the path of least resistance is hydraulic constant speed prop.

The compromise is a fixed prop. This is a very good compromise giving good TO and climb and efficient cruise. In general fixed pitch props are cheaper, lighter and smoother and can't get more simple. For the experimental plane builder/owner having one or two spare fixed props for STOL or Speed or general purposes is doable. To swap a prop is about an hour or two. Wood fixed props are wonderfully smooth. If you love simple FIXED PITCH is the way to go.

There are also fixed pitch ground adjustable props but I don't care for them for high powered Lycomings, based on poor history from some manufactures in the past. Things may have changed. Ground adjustable props are fine for small engines on ultralights, and in the past ground adjustable props didn't do well on the Lycoming with strong power pulse. I'm not up on the latest greatest props. I much prefer a fixed prop as mentioned above. Simple, reliable, cheap, light. If you want a different prop it's pretty straight forward swap.

Cost? You can find a serviceable used Hartzall CS Props for $4000 and a governor for $1000.
 
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...
Moving blade pitch to a mechanical control in the cockpit (no electrical or hydraulics) on a spinning prop requires some kind of swash plate and linkage (like a helicopter). I don't know of anyone accusing helicopters of being simple. Again hydraulic is the standard because it has proven to be the best design.
...

Lycoming used to have a manually controlled prop, see my post above.

While I never flew with it, I am familiar with it.

The problem, as I understand it, is that the pilot needs to he careful not to over speed the engine. In flight, you essentially have a fixed pitch prop but depending on where it is set, it could be a climb or cruise prop, or anything in between. The blade angle did not change with RPM and/or manifold pressure.
 
Lycoming used to have a manually controlled prop, see my post above.

While I never flew with it, I am familiar with it.

The problem, as I understand it, is that the pilot needs to he careful not to over speed the engine. In flight, you essentially have a fixed pitch prop but depending on where it is set, it could be a climb or cruise prop, or anything in between. The blade angle did not change with RPM and/or manifold pressure.
I just can't picture the mechanism. I know it has been done. The old Navions had a diaphragm behind the prop and it expanded and contracted moving mechanism to move the blades. It was variable pitch not constant speed. I can't picture the design....
 
I just can't picture the mechanism. I know it has been done. The old Navions had a diaphragm behind the prop and it expanded and contracted moving mechanism to move the blades. It was variable pitch not constant speed. I can't picture the design....

These are on old spline shaft engines. E-225 -( ). The pilot selects the position of the blade angles by sending oil to and from the propeller via the bladder and transfer collar. Baldder should be changed every two years.
Old Hartzell... If still flown should be modified to "MV" conversion to the existing blade shanks, new clamps and new hub depending what you have. Existing props have several AD's against them. Rarely maintained correctly. Transfer collar has a large expensive bearing. We won't let them in our shop. We send them to Hartzell for even creating such a ******* child contraption. The factory, I'm sure would like these to go away...
Most people install O-470's with a flanged modern crank and propeller.
More reading here:
http://www.navioneer.org/riprelay/The Navion Files/hartzell_propeller.htm
 
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