RV-6 fixed pitch vs constant speed

I don't want to start a war just looking for honest views.
I was in a 6A partnership with an IO-320 constant speed prop. I was very satisfied with the performance.
I am moving so I had to get out of the partnership and am looking to purchase a 6. I am shying away from 0-320's with fixed pitch props. In my mind I feel if it has a fixed pitch prop then I need the extra horsepower of an 0-360.

Am I off base? I don't have experience with a fixed pitch on a RV. My mission will be an occasional form flight and occasionally doing basic aerobatic maneuvers. Other than the occasional flights mentioned above I will getting airborne flying straight and level just for the joy of flying.
Thanks.

You want the Constant Speed (CS) prop and the 360. Look at the Van's factory airplanes. Other than the RV-12, they all have constant speed props.

With over 3,000 hours flying an RV-6 with constant speed hours, the 320 CS will out climb the 360 FP at and below 100 KIAS. From 100 KIAS to about 130 KIAS, they are very close to the same at the same weight. Above 130 KIAS, the 360 FP has a slight edge.

When the 320 CS and 360 FP are flying the same speed, (2,300 RPM on the CS 320) the 320 will burn less fuel than the 360 FP but the 360 CS will burn the same fuel. As you push the power up from there, the 360 CS will burn less fuel then the 320 CS but the FP 360 will burn the same or slightly more. I have over 1,000 Cross Country hours flying with other RVs and that is where this info comes from.

Over 20 years ago, I listened to the late Allen Tolle at an EAA meeting give a talk. He had converted his FP RV-4 to CS and saved over 1-GPH of fuel at the same speed as the FP. If he wanted to burn the same fuel, he was faster with the CS plus had a better CG range. The CS Prop will save enough fuel over 2,000 to pay for the cost of the CS prop.

I am one of those that must have a CS prop on an RV. I would rather not fly an RV with a FP and if I could not have an RV with a CS prop, I would be looking for another airplane.

All props are a compromise. The fixed pitch prop will be better at one RPM / Air Speed than any other props. Since the CS prop changes pitch it is a better compromise but it is still a compromise as the twist of the blade does not change. IF we could change the twist of the CS prop as well as the pitch, we would then have the perfect propeller. The CS is better over a larger range of RPM and air speeds than the FP.

For your reading pleasure:

http://www.vansairforce.com/community/showthread.php?t=125531

Lots of factors to consider.

If properly maintained, the C/S prop will be the most expensive single item to maintain on your aircraft. And will erode your fuel savings.

If your mission is to do a lot of X-country with full baggage...... then C/S.

If most of your flying is local sport.... just for the fun of flying...... then F/P. The weight of an O360 and C/S prop making the nose heavy takes away a lot of the feel that Van worked so hard to create.

If you have never flown an RV that was built as Van had intended to be built.....as RV3.... then you don't know what you are missing.

If you were happy with your Warrior but want to go faster, the load up your RV with leather, extra fuel, O360 and a C/S prop, insulation full carpet three layers of paint 8 ply tires a tool kit and extra parts..... and you will still LOVE the way it flys.

It is EXPERIMENTAL, build what you want....... just understand what the end results will be like to fly.

WISC said:

I don't have experience with a fixed pitch on a RV. My mission will be an occasional form flight and occasionally doing basic aerobatic maneuvers. Other than the occasional flights mentioned above I will getting airborne flying straight and level just for the joy of flying.
Thanks.

Click to expand...

An RV-6 with a C/S is a fine performer. But it sounds as if your mission could be met very nicely with a O-320 FP RV-6.

I've flown my O-320 FP RV-6 for seventeen enjoyable years in spite of many on the forum saying this is impossible...

Sam Buchanan said:

An RV-6 with a C/S is a fine performer. But it sounds as if your mission could be met very nicely with a O-320 FP RV-6.

I've flown my O-320 FP RV-6 for seventeen enjoyable years in spite of many on the forum saying this is impossible...

Click to expand...

+1

I have only been flying my 6A for 8 months and I enjoy it's performance. I have an O-320 (160 HP) with a Catto FP. When solo, I climb at 1400 FPM and cruise at 190 MPH, burning mid 8's GPH, but that is a bit high due to the poor fuel distribution of the carb; a compromise I am reversing. Do some more research on this site. I don't think a C/S will save fuel burn over a F/P at the optimized cruise speed. Sure, I could get a much better climb rate with a C/S, but it wasn't worth the cost and maintenance for me. Formation and aerobatics may benefit from a C/S, but that is not my area.

Larry

My 160hp FP (ground adjustable Sensenich) does perform very well for me 51 weeks out of the year.... the 52nd week when it doesn't perform to my desired level is when I fly it across the Rockies from Texas to Johnson Creek, ID. On those trips, especially when taking off from a high altitude runway loaded up with camping gear is when I really wish I had a CS prop, or an extra 20 horsepower, or both. My plane did get airborne and climbed "good enuff" in that environment, but I sure would've been a lot more comfortable with at least a CS prop in the mountains.

mission & money

I've owned a 200 HP c/s Globe swift, and a couple of different 160 HP f/p RV4s.

Formation work (wing) will seem a bit more difficult with fixed pitch after flying it with c/s. Obviously, climb will suffer a bit, but will still exceed just about every other a/c at the same HP level.

If you've got the money for purchase and maintenance, and can give up the 30-40 lbs of useful load, do the c/s. But RVs fly fine with fixed pitch.

Charlie