What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Propeller Performance: F/P vs C/S

9GT

Well Known Member
Patron
Anybody have any performance comparison numbers switching from the Sensenich F/P propeller to a C/S prop on their RV-9 or -9A? My project, RV-9A, came with the Sensenich F/P prop, but the engine, Mattituck IO-320, is capable of C/S by removing the CS plug and adding a governor. I know the benefits of a C/S prop but just trying to figure out if I want to make the switch while the F/P prop is still new in the box. I would love some before and after the swap performance numbers to help me justify the added costs. Thanks! Dave
 
Watch the weight on the nosewheel.

I just finished an RV-9A for a friend. Vertical draft IO-320, Catto 3 blade prop. It does have a backup alternator and mufflers on the exhaust, but otherwise it's not an exceptionally equipped (read: heavy) airplane.

After weighing I was surprised to discover that, while it would be in the CG range for all conceivable loading conditions, the allowable weight on the nosewheel would be exceeded with more than 3/4 fuel unless at least 30 pounds was carried in the baggage compartment. Lighter passengers/pilots requiring more weight.

More info here: http://www.vansaircraft.com/pdf/Nose_gear_service_letter.pdf

Likely paint will move the CG far enough aft that it will cease to be a problem, but meanwhile I have 6 pounds of lead under the empennage fairing.

Point being that there is no way this airplane could be safely equipped with a constant speed prop without a serious diet forward of the current empty CG.
 
Point being that there is no way this airplane could be safely equipped with a constant speed prop without a serious diet forward of the current empty CG.

Move the battery aft of the baggage compartment rear wall, and most of the CG shift that you'll need is accomplished.
 
As for performance numbers, I have never flown my -9 with a CS prop but have flown it with two different engines and FP props.

The only advantage the CS prop gives you is on takeoff acceleration. Cruise speeds can be identical, with often the advantage going to the FP prop. However, to do that, you have to spin your FP prop on the redline, which the engine is designed to do.

If the cost is an issue, you can always install one later.
 
Kitplanes July 2016 Wind Tunnel

Read the Fixed pitch vs. constant speed article in "Wind Tunnel"column from the July 2016 issue of Kitplanes.

I believe that you must be a subscriber to Kitplanes to read the article or any back issue.
 
Last edited:
I have WW200 and a big 25lb battery. I carry some tools, a fly away parts kit and a fireX in the baggage . it's been good.

Empty Weight with oil included, no paint, with anti-splat nose brace and lip skid, firewall insulated with 1" ceramic fibre
Left 389.5 lb
Nose 280.8 lb
Right 411.5 lb

Total 1081.8 lb

IMG_20151103_235956_zpsca7wopon.jpg
 
Last edited:
I haven't flown behind a Sensenich FP but I have over 700 hrs on a 3 blade Catto. Some specs on my airplane.
Total weight 1084 lbs
Right Main 395lbs
Left Main 394lbs
Nose Wheel 295lbs

AeroSport Power O320 D2A, roller tappets, dual Slick Mags, and a backup alternator where the vacuum pump would be attached on the rear of the engine. Climb performance at 100-110 knots is about 1200 to 1300 fpm at moderate weight. (1550lbs or so).

For me, the climb performance and cruise speeds are far better than anything that I flew in the past. I didn't see the need to drop another 8-10K for the prop and governor for what I felt was a minimal increase in performance. Just my thoughts. Good luck on your search.

Steve Koziol
 
If nothing else, i would sell the metal FP sensenich and go with a composite Catto or ground adjustable sensenich or whirlwind. I think the performance increase from the metal FP to a wood or composite FP will be a better value than going to constant speed. I would like a constant speed but as others have said probably only improves the takeoff, which, given the FP performance, probably doesnt justify the added cost, maintenance and weight.
 
My experience

I've got a CS prop on a -9. I tried out several Catto FP props. The Catto gives good performance at a lower cost and less nose weight which is important to the -9a. That's what I would go with if I had a -a model.

In a nut shell, top speed was similar between Catto and CS.
However, takeoff is an entirely different matter. My -9 is off the ground by the time I push the throttle all the way in and I'm at pattern altitude before end of 5000ft runway. Takeoffs are really fun and the -9 wing gives an exciting climb.

That being said, the Catto would be my choice if I wasn't addicted to the climb and the braking action of CS. Especially in a -a model with that toothpick nose gear.

Good luck!!



Anybody have any performance comparison numbers switching from the Sensenich F/P propeller to a C/S prop on their RV-9 or -9A? My project, RV-9A, came with the Sensenich F/P prop, but the engine, Mattituck IO-320, is capable of C/S by removing the CS plug and adding a governor. I know the benefits of a C/S prop but just trying to figure out if I want to make the switch while the F/P prop is still new in the box. I would love some before and after the swap performance numbers to help me justify the added costs. Thanks! Dave
 
I've got a CS prop on a -9. I tried out several Catto FP props. The Catto gives good performance at a lower cost and less nose weight which is important to the -9a. That's what I would go with if I had a -a model.

In a nut shell, top speed was similar between Catto and CS.
However, takeoff is an entirely different matter. My -9 is off the ground by the time I push the throttle all the way in and I'm at pattern altitude before end of 5000ft runway. Takeoffs are really fun and the -9 wing gives an exciting climb.

That being said, the Catto would be my choice if I wasn't addicted to the climb and the braking action of CS. Especially in a -a model with that toothpick nose gear.

Good luck!!

I agree with this sentiment. Now that is resolved, where's the beer tent?
 
Last edited:
9A Nose Gear

...the Catto would be my choice if I wasn't addicted to the climb and the braking action of CS. Especially in a -A model with that toothpick nose gear...

So how does the 9A "toothpick" nose gear differ from that on the 7A? Since the fuselage's are the same, I always assumed the two were the same nose strut...

Doug Lomheim
RV-9A Mazda 13B/FWF
RV-3A sold
 
So how does the 9A "toothpick" nose gear differ from that on the 7A? Since the fuselage's are the same, I always assumed the two were the same nose strut...

Doug Lomheim
RV-9A Mazda 13B/FWF
RV-3A sold

Excellent, we are ending the never ending debate on f/p vs c/s with starting a never ending debate on nose wheel vs tail wheel.
 
The only advantage the CS prop gives you is on takeoff acceleration. Cruise speeds can be identical, with often the advantage going to the FP prop. However, to do that, you have to spin your FP prop on the redline, which the engine is designed to do.

Bill, I'd like to comment and add a bit.

Takeoff. True
Cruise speed. Can be true (often? Hmm) but by definition of prop design the FP climb will be anemic compared to CS in that situation.
Spin to redline. Yes you can. However, if one reviews the Lyc engine performance documents, you can see lower RPM improves fuel economy because of differences in frictional horsepower and the theta P timing effects. As a side note, this is one reason I have not jumped to EI yet.
Decent. A CS prop can leave an FP in the dust on decent with the ability to run high power levels without overspeeding the engine.
Deceleration. While I do not use it, the CS can give temporary braking in the pattern by a sudden shift to fine pitch.
 
Last edited:
The Sensenich that came with my project has a 2600 rpm limitation also and the engine is rated 160hp @ 2700 rpm. An extra 100 rpm can be noticeable on take offs so whether I go to C/S or stay with F/P, I think I want to change out the prop. I've noticed just moving the plane around in the hanger that the nose wheel strut does seem a bit "flimsy" as compared to my old -10 so I definitely want to keep the FWF as light as possible. I am not looking to debate whether a F/P or C/S prop is better or not, I am just looking for some actual performance numbers from people who have made the switch, or even some numbers from folks who have switched from the F/P Sensenich to another brand of F/P such as a Catto or other brand.
 
I'm on my third prop

My -9A started life with the Sensenich metal prop on my IO-320 (rated at 170HP - high compression, flowed and balanced w/ P-Mags). After about 20 hrs I decide that the RPM limit didn't allow me to get the performance i wanted. I switched to a Whirlwind GA200 ground adjustable prop. I really liked that prop - when dialed in correctly (after 3 attempts) i found a setting that gave me excellent climb and cruise performance. I used that prop for 300 hrs, then came upon a great deal on a WhirlWind WW151 - 3 bladed CS prop. I installed that this winter and now have about 20 hrs on it. Take off and climb is like a different plane - top end cruise is similar, maybe slightly better. This CS only weights 28 lbs - so it is the same weight as the FP Sensenich. Granted, i would not have changed out the prop unless the economics worked - likely would not have paid full retail ($10K+) for the 151. However i am very happy i have it.

Did a re-weight last week with the WW151 - here are my numbers:

NOSE - 250
LEFT MAIN - 451
RIGHT MAIN - 455
 
Last edited:
vote for CS prop on a 9A

On my 9A I tried a wood that was too flat a pitch (climb prop) causing 2700 RPM with a max speed of 180 mph and 1700fpm max climb- weight from W&B 417#, 403# and 237#. Eventually switched to a Hartzell CS with max 2000 fpm climb and 195mph at 2650 or 2700- weight 418#,408# and front at 273#. 42# also included Nav radio and ILS and nose wheel, strut upgrade and anti-splat. Loved the climb, ability to select cruise on MP and RPM and the braking effect. No CG problem ever with any loading with CS. Slightly biased to front means that unlike a light fixed pitch you could never get aft CG or too forward with any loading combination. Wish I had a CS in the 12 much more than more speed or power. If you don't like a CS for a 9 then you have never flown with one. More than other RVs I think it is a perfect match with the lower horsepower 0-320 and the high lift longer wing.
 
Back
Top