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Do I have the right propeller pitch?

M

mlwynn

Well Known Member
Hi folks,

I am in the early part of phase I testing. I am trying to figure out if I have the correct pitch. Here's the data:
RV 8
IO 360 M1B with 9.5 pistons, dual Plasma III ignition, 185 HP printed on the plate
Catto 3 blade prop 66 inch diameter, 75" pitch. I requested a cruise pitch when I ordered it.

When I take off with full power, showing about 29 inches MP, I turn about 2300 RPM. Cruise climb at 110 kts is about the same. Level off at 4500 feet and I have to throttle back to about 21 inches to keep the RPM at 2500. Any more throttle than that and I am overspeeding the 2700 RPM that I think of as redline.

A knowledgeable EAA guy here told me that the old rule of thumb was to go to 7500 feet and open it up. If you were about 100 RPM over redline, the pitch was correct. I did that operation and the engine went to about 2800 RPM (2780 to be exact).

So the question is, do I have the correct pitch?
 
That's Craigs main test he'll have you do as well.

The design RPM of my prop is 2750 (listed on prop placard), so leaned out at 7500' that's what Craig wanted to see. I could get about 2830-2840, so Craig repitched mine. Now it's about 2740 at 7500'. It sounds like yours is pretty close assuming it too is designed for 2750.
 
mlwynn said:
Catto 3 blade prop 66 inch diameter, 75" pitch
Click to expand...

What "version" of Catto 3 blade do you have?

Mine says 3-B at the top of the sticker on the hub, I think indicating the B or gen 2 version of the 3 blade prop (build date Feb 2014). Mine is a 68x76 and I'm running a Aerosport 0-360 carb 180HP dual P-MAG.

At 1700ft I turn 2760 for 185KTS TAS
at 7000ft I turn 2705 for 180KTS TAS
at 10000ft I turn 2650 for 175KTS TAS

This is all with wheel pants & faired gear legs, without intersection fairings top or bottom.
 
Catto

My says red line 3200 RPM. Date of manufacture was Oct 2008 so it is probably not a B model.

Should I not worry about running the engine at 2700 RPM for a prolonged period of time?

I have all my fairings in place. Airplane sure does scoot. Just not sure how to optimize the power settings. I'm used to constant speed props on fast planes and fixed props on puddle jumpers. New territory for me.
 
I've had a similar experience witha 2013 catto two blade on MY O-320. Catto said it should run 2700 rpm at wot at 8,000 ft..... I was seeing 2800 rpm at 10,500' DA at wot. This was a 70x70 They said if it exceeds red line rpm by 100 or more rpm at 8000' DA it needs to be re pitched.... Who's got time for that?:rolleyes:
 
Numbers?

Dbro172 said:
I've had a similar experience witha 2013 catto two blade on MY O-320. Catto said it should run 2700 rpm at wot at 8,000 ft..... I was seeing 2800 rpm at 10,500' DA at wot. This was a 70x70 They said if it exceeds red line rpm by 100 or more rpm at 8000' DA it needs to be re pitched.... Who's got time for that?:rolleyes:
Click to expand...

....for what they're worth, I'm curious what speed resulted in all those revs? I can't imagine what it would sound like at 27-2800! Can't get my ol' -320 FP sensi to get that excited...maybe 2450.
I'm pretty happy with 152 kts. at 5000 or so (gps groundspeed) but always curious what it would be like to optimize the performance.
 
Not as good as you'd think

It's like being geared too low. Maybe get 157-160 ktas with that prop. If you're only turning 2450 I think you could really benefit from a new Catto or one of the ground adjustable variations from Sensi or whirlwind You'd still see that 150kts at 2450 rpm, with a couple hundred rpm left in the tank I'd bet.
 
akarmy said:
What "version" of Catto 3 blade do you have?

Mine says 3-B at the top of the sticker on the hub, I think indicating the B or gen 2 version of the 3 blade prop (build date Feb 2014). Mine is a 68x76 and I'm running a Aerosport 0-360 carb 180HP dual P-MAG.

At 1700ft I turn 2760 for 185KTS TAS
at 7000ft I turn 2705 for 180KTS TAS
at 10000ft I turn 2650 for 175KTS TAS
Click to expand...

I'd say my my -9A is exactly the same as your 8 (minus 20kts):eek:
 
It's fantastic!

flyboy1963 said:
....for what they're worth, I'm curious what speed resulted in all those revs? I can't imagine what it would sound like at 27-2800! Can't get my ol' -320 FP sensi to get that excited...maybe 2450.
I'm pretty happy with 152 kts. at 5000 or so (gps groundspeed) but always curious what it would be like to optimize the performance.
Click to expand...

Perry:

I bought Derek's Catto for my 0-320, 160 hp 9a because I couldn't get my FP Sensenich that excited either.

As for what the prop sounds like, I don't know; all I hear is me saying "wheeeeeeeee!"
 
Just my two cents

mlwynn said:
Hi folks,

I am in the early part of phase I testing. I am trying to figure out if I have the correct pitch. Here's the data:
RV 8
IO 360 M1B with 9.5 pistons, dual Plasma III ignition, 185 HP printed on the plate
Catto 3 blade prop 66 inch diameter, 75" pitch. I requested a cruise pitch when I ordered it.

When I take off with full power, showing about 29 inches MP, I turn about 2300 RPM. Cruise climb at 110 kts is about the same. Level off at 4500 feet and I have to throttle back to about 21 inches to keep the RPM at 2500. Any more throttle than that and I am overspeeding the 2700 RPM that I think of as redline.

A knowledgeable EAA guy here told me that the old rule of thumb was to go to 7500 feet and open it up. If you were about 100 RPM over redline, the pitch was correct. I did that operation and the engine went to about 2800 RPM (2780 to be exact).

So the question is, do I have the correct pitch?
Click to expand...

I think you have it pretty close to perfect. Try it at about 10,000 density altitude. If you can get it to near 2700 then you are at your best cruise at an allowable-all-day power. Your climb numbers are almost exactly the same as mine, too. If you went for lower RPM at the top you would hurt your climb, obviously. Notwithstanding all the old-time rules of thumb, an RV doing around 200 mph is well above 75% at 2700 rpm and 8,000 feet.
 
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