Constant speed propellars

Terry

Terry

Line Up and Wait
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Terry
Hi All,

Is there a good book on constant speed propellers and how they intricately work?

I mean a book that shows the hydraulic fluid flow, and the actual mechanics of the propeller system.

Thanks,

Terry :confused:
 
Don't really need a book, they are very simple. Here's a good pic of the control system:
propweb.jpg


As for the prop itself:
Cutaway_constant_speed_propeller_hub.JPG

Any specific Questions? It's just oil pressure moves a piston inside the hub fore and aft, and that piston is connected to the prop blade ends at the edge which rotates the blade in the pitch dimension. In the governor end, the speed of the engine effects a set of fly weights which move a spool valve back an forth to add or release oil pressure.
 
Last edited:
Thanks for posting the picture of that cutaway, Henning. I haven't found a high resolution photo of a constant speed prop cutaway like that to use when teaching the system to students 'til now. :)
 
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No worries. Oh yeah, on last thing, so, the oil goes from the governor through the nose bearing and into the core of the end of the crankshafr where the prop is bolted, and then it fills that entire cavity of the prop.
 
Henning said:
No worries. Oh yeah, on last thing, so, the oil goes from the governor through the nose bearing and into the core of the end of the crankshafr where the prop is bolted, and then it fills that entire cavity of the prop.
Click to expand...

Only on 2 of the manufacturers. several use a squash plate behind the prop bolted to the nose of the case.
 
McCauley has the dope. For the typical constant-speed prop on a single:

http://www.mccauley.textron.com/von_klip_tip_cs_propeller.pdf

For the typical constant-speed setup on a twin:

http://www.mccauley.textron.com/von_klip_tip_ff_constant_speed_propeller.pdf

The difference is in the blade movement under hydraulic pressure. In the single, increasing oil pressure move the blades to a coarser (low RPM) setting. In the multi, oil pressure moves them to a finer (high RPM) setting so that if the oil pressure fails in flight (which usually means that the engine has quit) the blades will go through the coarse setting and into feather position.

Dan
 
McC used to put out a small booklet with color diagrams - it was pretty helpful.
 
Let'sgoflying! said:
McC used to put out a small booklet with color diagrams - it was pretty helpful.
Click to expand...

I have a couple of those. They also used to be on their website, but they were replaced by the ones I posted.

Dan
 
Somewhere, I have also seen an animation depicting a cross section of prop/hub and governor as it is coarsened/feathered/made fine again...shows control movement, oil pressure, blade actuation.
 
There are a couple more resources you might try. You can follow this link to the Hartzell website:

http://www.hartzellprop.com/service_support.php?id=69

Find Manual 115N (Full Document) and click on it. This is Hartzell's Owner's Manual for most GA type propellers. It will download or open the manual. If you go to the "Description and Operation" section, there are cutaways and operational descriptions of the various propellers covered by that manual. You can also follow this link to the AOPA site:
http://www.aopa.org/asf/online_courses/

Find the "Engine & Propeller" course. It has some moving animations of a propeller and how RPM & MP are influenced by the cockpit control settings.
 
Henning said:
Don't really need a book, they are very simple. Here's a good pic of the control system:
propweb.jpg


As for the prop itself:
View attachment 23212

Any specific Questions? It's just oil pressure moves a piston inside the hub fore and aft, and that piston is connected to the prop blade ends at the edge which rotates the blade in the pitch dimension. In the governor end, the speed of the engine effects a set of fly weights which move a spool valve back an forth to add or release oil pressure.
Click to expand...

Maybe I haven't had enough caffeine this morning, but those cutaways look to have the prop 90° to the crank shaft...
 
EdFred said:
Maybe I haven't had enough caffeine this morning, but those cutaways look to have the prop 90° to the crank shaft...
Click to expand...

I think they did that for illustrative purposes. What's missing for clarity is the actuator piston and linkage that moves the prop blade.
 
EdFred said:
Maybe I haven't had enough caffeine this morning, but those cutaways look to have the prop 90° to the crank shaft...
Click to expand...

Well, not really for two reasons. First, I think they are simply showing oil flow, and 2nd the governor is often perpendicular to the crankshaft.
 
Henning said:
Well, not really for two reasons. First, I think they are simply showing oil flow, and 2nd the governor is often perpendicular to the crankshaft.
Click to expand...

But the prop isn't. And that picture makes it look like the crankshaft is spinning around an axis that is vertical and the prop around one that is horizontal.
 
EdFred said:
But the prop isn't. And that picture makes it look like the crankshaft is spinning around an axis that is vertical and the prop around one that is horizontal.
Click to expand...

That's not the crankshaft, that is the governor shaft spinning the flyweights.
 
Henning said:
That's not the crankshaft, that is the governor shaft spinning the flyweights.
Click to expand...

But the note "connects to crankshaft" should be on the left of the drawing, not the bottom. 12 years of drafting and design drawings says this is a bad schematic.
 
EdFred said:
But the note "connects to crankshaft" should be on the left of the drawing, not the bottom. 12 years of drafting and design drawings says this is a bad schematic.
Click to expand...


Yeah, but it was there and relatively clear. they could have said, "Connects to crank through gear"
 
Look in one of the A&P advisory circulars (AC65-??). I'm sure they talk about them at length.
 
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