fixed pitch vs. constant speed

[meloosifah]

Originally Posted by plehrke

To really pull all the debates into one big ball, I have never heard any one with glass voluntarily trade it in for steam. Nor have I heard of some one that primed decide they wanted to un-prime. Sunk cost.
The debate is not if primed constant speed glass is better, the point is if unprimed fixed pitch steam is good enough for me the builder or buyer. That is an individual decision and one of the big perks of Experimental Amateur Built.

I agree. But that is not what the OP asked. He essentially asked which is better. And the tribal village of VAF, by and large, has uniformly stated that they would never trade back to FP, given the option of CS. One is not BETTER, but you are making my point. The VAST majority of people, given a choice where price and effort are not an issue, will choose to put in glass and CS. The very few that diverge, do so, typically, for a VERY specific reason.

So, to the OP, if you can, buy CS. You won't ever wish you hadn't. Or buy a 152 and then an RV with a pair of rowboat paddles will seem to be a rocket ship.

[brad walton]

"Vast majority"? Maybe your just reading every other post.

[Bill Dicus]

Thanks Bill. I sure do love that strong initial acceleration!

[StuBob]

Deviating even more from the OP, what about complexity of installation? To install a FP prop, all I'd need is a spacer, a prop, and about a dozen bolts.

I'm a big fan of CS props, but is the added work for installation significant?

[airguy]

Originally Posted by StuBob

Deviating even more from the OP, what about complexity of installation? To install a FP prop, all I'd need is a spacer, a prop, and about a dozen bolts.

I'm a big fan of CS props, but is the added work for installation significant?

Up front at the prop, it's the same - spacer, prop, bolts just like a FP. I added maybe 2 hours hanging the governor and running the lines forward, and maybe 2 hours running the cable to the panel.

Where I added a whole BUNCH of time was at my office, earning the dollars to pay for the constant speed - but it's so worth it!!

[rightrudder]

Originally Posted by meloosifah

I agree. But that is not what the OP asked. He essentially asked which is better.

Better. There's that word again. I consider my FP Catto to be better because of lighter weight, lower cost, less complexity and very little maintenance (wiping the bugs off the nickel leading edge and retorquing the hub bolts occasionally).

Better can vary greatly according to your mission profile. I don't need to be pinned back in my seat on the takeoff roll. I land at paved strips that probably average 3000', so I don't need prop braking to clear 50' trees and a kamikaze dive down to a 1200' grass strip. Climb performance is still excellent compared to the rental bug-smashers I've flown, and to tell you the truth, I prefer a climb rate of less than 1000 fpm most of the time so I have improved visibility over the nose and increased airflow over the cylinders. Less workload in the cockpit is always a good thing, to maximize eyes-outside time.

A CS prop in an engine-out scenario goes to high-drag configuration, right? I'd rather have an FP's better gliding distance for more landing options in an emergency. As for increased float on landings, I'm learning to manage the energy better, and becoming more comfortable with a slight lower over-the-fence speed that allows me to hit my mark.

So, better depends...

[StuBob]

Originally Posted by airguy

Up front at the prop, it's the same - spacer, prop, bolts just like a FP. I added maybe 2 hours hanging the governor and running the lines forward, and maybe 2 hours running the cable to the panel.

Really? That's hardly worth talking about in the big picture.

Where I added a whole BUNCH of time was at my office, earning the dollars to pay for the constant speed - but it's so worth it!!

There is that part.....

[mlwynn]

Hi all,

I recently converted my RV 8, IO360M1B from a three blade Catto to a Hartzell composite. There have been a number of pluses and and number of minuses.

On the plus side, markedly better acceleration. Much shorter take off run. About 20 kts improvement in top speed (I would overspeed the prop with much more than 19" MP at cruise). Aerobatics work better as it climbs better and the flat prop also provides a little more wind resistance in the down line. I can make substantially shorter landings now with a giant air brake in the front.

On the minus side: Definitely louder, especially at cruise speeds. More vibration although not uncomfortably so. My CG moved quite a bit forward, which sometimes a plus and sometimes a minus. I usually keep #25 ballast in the rear luggage compartment if I don't have a passenger or baggage.

In general, I thought the airplane was more ladylike with the FP prop: smooth, maneuverable, easy to land and take off. With the CS, it is much more of a tiger. More torque on take off to adjust the rudder for, need much more care in landing as I can't tell how much power I have by listening to the engine--the RPM is pretty high until the throttle is way reduced. Also, if you come completely off the throttle at speed, there is kind of a backfiring that goes on. Doesn't sound like it could possibly be good for the engine. Glide ratio was better with FP.

In the final analysis, I am glad I made the transition. I think the overall performance improvement was worth the time and expense to make the change. The actual installation with pretty simple and straightforward.

[sglynn]

I just purchased my engine and prop. I currently drive a Piper Dakota with an O540 engine and CS prop. I use the CS prop per pilot handbook. But benefit is marginal, if detectable. Weight is high. Maintenance is high. Doesn't seem worth it. So I was definitely going Fixed Pitch on my RV-7A. I've been building since 2008 and no way am I using CS prop. Dah. . .

So at Sun-n-Fun I filled in my engine order form and left prop type blank.
Then Van's called me and asked which prop?

I buckled and ordered the Constant Speed. Why? Weird. Because . . .


1. If cost were no object, CS does give a little performance improvement.
2. Cost at this point is mute. I'm building a new plane. Might as well put in the type of prop future buyer will want.
3. Weight of CS for RV-7A is actually beneficial because it needs forward weight.
4. I want a plane configured like most everybody else

Good luck deciding. No remorse.

[plehrke]

Originally Posted by sglynn

I buckled and ordered the Constant Speed. Why? Weird. Because . . .

1. If cost were no object, CS does give a little performance improvement.
2. Cost at this point is mute. I'm building a new plane. Might as well put in the type of prop future buyer will want.
3. Weight of CS for RV-7A is actually beneficial because it needs forward weight.
4. I want a plane configured like most everybody else

Good luck deciding. No remorse.

You have the freedom to make the choice and use what ever reason you want BUT I would have thought 1 of the 4 reasons would have been "it is what you wanted" instead of 2 of the 4 being about what others would want.

Best advise I ever got is that I should build what I wanted.