Prop pitch

If you have a 9A with a 320 and a fixed pitch propeller, 2 or 3 blade, what pitch did you go with and why?
Any performance numbers would help

Catto 3-blade

I went with whatever pitch Craig recommended when I ordered it. He asked model RV, engine and HP, and then said he makes a LOT of props for that combination. Sorry I can't be more specific ... if I had the nameplate data here at home, I'd give you the pitch.

some rough numbers

I have an older 0-320, 7:1 compression, Sensenich metal 2 blade 70" x 77 pitch.
Turns up about 2150 static, so on the takeoff roll, my rough calculations say its making about 85 hp.....so climb of 750 to 1000 fpm is typical.
the prop seems to 'bite' better as you pass thru 85 kts, and it actually climbs better at this speed than at the theoretical 'best' r.o.c. speed of 78 kts.
cruise at 2450 is about 155 kts. at 6000'. ( not calibrated or percent power, just on a calm day the gps groundspeed is about the same).
On a full throttle descent you can nudge up to the 2600 rpm limit.

Overall I am ok with the prop....but wonder why the plane is not a little faster, if it's a bit overpitched, or if it's underpitched, why the low static revs.
If I were buying a new prop, it would likely be the Sensenich adjustable, so that one could dial it in better, or run more pitch in the winter vs summer.

We need speed.

We decided early on, that we wanted the most cruise speed that we could get for our -6A. Craig asked if we minded turning the engine 2750 RPM's and I said that I didn't mind and we ended up with a prop that gave us 201 MPH TAS at 7,500'.

Some guys want better takeoff and climb so they give up some cruise speed for that.

Best,

We have two 9a's, 160hp fixed pitch. One is Sensenich 79" pitch, the other Catto I believe he calls it a 71" pitch, it is his recommended stock 2blade for the 160hp 9a. The Catto is superior in acceleration, climb, and deceleration, and virtually identical in cruise and top end. The Sensenich has 600+ hours and looks like it just came out of the box. The Catto 100+, so far so good (has metal leading edge option), needs more frequent inspection and torque check.
The most noticeable difference is being able to slow down more effectively on descent/landing with the Catto. Both great props, significantly different in operation.

pierre smith said:

We decided early on, that we wanted the most cruise speed that we could get for our -6A. Craig asked if we minded turning the engine 2750 RPM's and I said that I didn't mind and we ended up with a prop that gave us 201 MPH TAS at 7,500'.
Some guys want better takeoff and climb so they give up some cruise speed for that.
Best,

Click to expand...

I've tested a few props for Craig and have found that in many cases, a lower pitched prop, pitched for take-off, will still cruise up there with a cruise prop if you are willing to do it at a higher RPM. Of course, this means a higher fuel burn.

Just to clarify, in cruise, side by side, our 79" Sensenich and 71" Catto are virtually identical in speed and rpm

bforsyth said:

Just to clarify, in cruise, side by side, our 79" Sensenich and 71" Catto are virtually identical in speed and rpm

Click to expand...

Prop pitch is not comparable between different manufacturers. Besides the different methods of measuring pitch is the different planforms, airfoils, and many other parameters involved.

Catto 3-blade performance #s ...

I'm seeing a static RPM of 2280; climb vs cruise seems to be a good combination. In warm weather, climbing at 1500+ is normal; in winter weather it'll do 2000fpm with no problem. Cruise numbers are 2450rpm LOP and 145ktas. To my surprise, full throttle and ROP will spin it to 2750rpm (sometimes 2800!) at any altitude up to 8500'.

flyboy1963 said:

If I were buying a new prop, it would likely be the Sensenich adjustable, so that one could dial it in better, or run more pitch in the winter vs summer.

Click to expand...

It's a great prop. It is very pricey however. The only regrets I have are each month when I make that credit card payment but whenever I pull out onto the runway and push the throttle in, those regrets all go away

BTW, my hangar mate just bought an RV-4 with 150hp O-320 and put his Whirlwind ground-adjustable GA-200 prop on it. It's a very good looking prop but kind of a pain to set the pitch of each blade with a prop protractor whereas the Sensenich has the pitch pins that make the task a breeze. He's still in the process of dialing in his optimum pitch, but we got to fly our planes together in a crude test of "Brand S" vs "Brand W" and the performance is roughly similar. I get better static rpm and initial takeoff climb rpm, and can outrun him pretty easily in level cruise (I've got 10 more horsepower), but in an extended climb up to 8000' he walked off and left me behind. He's got about 75-80 less pounds of weight to carry, though, so that is a factor there. Either way, both of these ground adjustable carbon fiber props are excellent performers and would be a good choice on an RV-9 too.

Consider a Ground Adjustable Prop

Sensenich or WhirlWind Propellers - I fly a WhirlWind behind my IO-320 (165hp) and really like it. You are able to dial in exactly what you'd like.

When I told Craig Catto that I wanted a cruise prop for my 180 HP -9, he suggested we make it 74" long, rather than 72". The idea being that a longer prop helps with initial acceleration / climb.

Since my -9 is a tail dragger, clearance is not an issue.

Some comparison data between Sensenich Metal and Ground Ad.j Composite props that I posted earlier but may be of interest.
Metal prop is Van's recommended Prop for 160hp O-320 prop 79" pitch

Note:Manufacturer Red line 2600RPM on metal prop & engine red line for composite prop.

Test Airframe: RV-9A O-320D2G, Field elevation 1393ft

Sensenich 70CM6S9-79 (Metal)
Density altitude 11700ft 2620 RPM WOT 161ktas (3 run average)
RPM static 2270RPM

Sensenich 2G0M7/C72RG-0 (Composite)
Pin#4
Density altitude 8500ft 2727 RPM WOT 164ktas
Density altitude 10500ft 2705 RPM WOT 164ktas
RPM static 2340 RPM

Pin#5
Density altitude 8500ft 2660 RPM WOT 164ktas
Density altitude 10500ft 2613 RPM WOT 161ktas
RPM static 2271 RPM


YMMV

I have a 9A with a Superior XP-IO-320 which seems to make slightly more than 160hp. It swings an 81" Sensenich at 2240 static rpm and cruise performance numbers are here. The engine has one P-Mag EI which helps at altitude.

numbers are still puzzling

...so for a guy who is trying to decide on a prop, it isn't much help when you see that one guy is going 20 kts faster than another with only 10 more hp, or basically a similar prop/engine combo.
I wish I had this magic prop that climbs at 2000 fpm and does 200 mph.

...maybe I need to wax?

( the plane)