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Difference between 150hp CS prop and 160hp fix prop

Ralf Schneider

I'm New Here
I´m currently in discussion about two options in a -4
One is 150 hp with CS prop and the other is the 160 hp with fix prop.

What would you prefer and does anyone have experience with it?

What is the difference in performance during take off, climb rate, cruise and top speed?
And what is the fuel consumption when cruising and at top speed?

Which one would be better for aerobatic?

Ralf
 
What is your mission?

I'm assuming you have access to a 150hp engine that is capable of CS and a 160hp engine that is not CS capable, or 2 different flying aircraft you are looking to buy. I built my -4 with a 160hp engine that does not have CS provisions, and run a fixed wood Sterba prop. The 160hp is a perfect fit for an RV-4 and the CS will add weight and complexity. If your mission is mostly long X-country, the CS will be more efficient. If your mission is shorter Sorties, the FP will be simpler and lighter. I have a climb prop on mine, and a buddy has a cruise on his. My T/O and climb are quite a bit better, but at fast cruise I turn about 200RPM more than him. The fuel burn on most O320 RV-4's will be around 8 GPH average. Acro with FP is fine, but I suspect the Pro's would rather be CS..I'm just a play pilot. My motto is simple and light. ALL -4's are great!
 
A friend and i are looking for a cheap 4 or 6.
Most of them with 160hp and fix prop and i would be fine with it.
My friend is always pushing for a CS prop because of performance, fuel consumption and easier to handle in aerobatic.

The mission is to play around after work with gentle aerobatic and xc trips at the weekend. We are in the middle of Germany, so the weekend trips are approx. 200 -300 NM one way.

We did our aerobatic training on a Super Decathlon with 180hp and CS prop. Performance was ok and you only need to touch the throttle for snap rolls and spinning.
After that, i used a Robin 2160 with 160hp and fix prop for some aerobatic lessons.
The performance was not so good. You could do one or two maneuver, then you need to climb again. Furthermore you need to adjust the throttle very often to avoid high rpm.
 
I would not assume a CS will always be faster in cruise. It will vary a fair amount on who you are comparing it to, pitch, and many other factors.

CS will take off quicker, weigh more and cost more to maintain.

FP will weight less, have a longer takeoff roll (or not as fast of cruise), cost less to buy and maintain.
 
This is not a direct answer, but I have a RV6A with a O-360 and FP Sensenich. My son has a RV6A with a O-320. His use to have a FP Sensenich. The two planes performed almost identical except I could out-climb him. He switched to a GA Whirlwind and now he out performers me in every phase of flight.
 
So, what are the parameters?
- Cost?
- availability of all HP at all times?
- Long distance cruise performance?
- Stopping power!?
- operator and/or maintenance complexity?

Over the last 14yrs with our little O320 with a simple constant speed Hartzell that we've put 2400hrs on, there have only been a few times that I really wished I didn't have the additional weight, and one of those was at 16k', way out to sea with the sun getting low without land in sight with the "what-if's" flowing.

Everything has its mission. Mine is with a constant speed prop, no matter the HP.
 
Is the 160hp FP prop a climb prop or a cruise prop? What is the pitch on the blades?

If it's a climb prop, then the 160hp FP will accelerate and climb better than the 150hp CS but will need more fuel to go fast.

If it's a cruise prop, then the 160hp FP will need less fuel to go fast but might not accelerate and climb as well as the 150hp CS.

This is a slight oversimplification, of course ("All other things being equal...") but that's how I'd start thinking about it.

Edit: And for aerobatics, I'd go with the CS prop, definitely. One less thing to worry about.
 
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