CS vs FP...

[danielhv]

So, are the only advantages to a CS over FP seen during climb & decent? Will they both cruise the same if you have a cruise prop? (assuming two identical airplanes.)

[N941WR]

Dan,

It really depends on the pitch of the FP prop. Some FP props are optimized for cruise and can actually out run a CS prop in level flight. To do that they give up some climb performance.

In the RV's that "degraded climb performance may still be around 1500 FPM depending on the plane, engine, and prop.

One advantage of a FP prop is they are lighter, unless you go with a composite CS prop, then the weight may be a wash.

To toss out some numbers, my old wood prop was around 9 pounds, a FP metal prop can be as much as 40 pounds, and a metal CS prop will be more than that.

Maybe someone who has switch their props can talk about the numbers they have seen with the same airplane/engine combination and list the make, diameter, and pitch of the FP prop involved.

[L.Adamson]

I like the lower sound levels when pulling back to 2300 rpms. Even at full throttle.

I don't have to add some kind of weight at the nose to have decent baggage capacity.

As is known,.... takeoffs are faster, as the engine is allowed to develop full horsepower. The C/S is great for managing deceleration. I even hear it's great for formation flight.............according to some recent threads.

I'd never put an F/P on a 6,7,8,9,10. Perhaps a wooden F/P on a 3. Just a simple lightweight machine. If I wanted an F/P, I'd be flying a Cessna 172.

L.Adamson --- RV6A / Lyc 180 / Hartzell CS

[Finley Atherton]

All other things being equal, for a given HP, fuel consumption will be less at lower rpm (higher MP). So you can bring the revs back on the CS prop to say, 2,000 to 2,200 rpm in the cruise and achieve worthwhile fuel savings compared to a FP prop which will most likely need to operate at higher rpm in the cruise. Plus its great to have another knob to play with!

Fin
9A

[kentb]

I think that it boils down to:
FP - you decide what type of performance you want when you buy the prop.
CS - you decide what type of performance you want while you fly. At a small cost in weight.

Kent

[Jamie]

Another advantage of C/S -- you don't have to worry about overspeeding the prop (unless you're Kevin Horton, of course). Point the nose down for a quick descent and just watch your airspeed. In a FP you'll be watching your airspeed AND your RPM.

One thing that's seldom mentioned and that I was sort of naive about before I made my prop decision -- overhaul cost. Yes, you will pay 2K every five years to overhaul your hartzell. That must be considered into the equation if you plan on keeping your airplane for a while.

[slyfox]

there are so many advantages of a C/s over a f/p prop. for me a max RPM take off with max pull up is one. When I feel a light head I know I've hit it right. Feels great, only way to fly.

[panhandler1956]

Another slight advantage is the braking affect you get from a constant speed prop. Can be great for joining up on someone's wing so you don't overtake - should not be a crutch for good technique however.
Also, on landings you get some braking as the prop flattens out.

Plus it's cool!

[danielhv]

CS it is then. Thanks!

[gasman]

cost of prop after 10 years.........

c/s ................ fixed

prop $6649 $2135
gov 1200
2 oh 4000
__________ _____
total $11,849 $2135


* 2009 prices

It's like a stuffed panel............... What are you going to use the aircraft for?