Does CS prop help in IMC?

I've got a decent amount of hours in IMC behind a FP propeller. At times it results in a lot of throttle jockeying in heavy updrafts and downdrafts.

I have only flown with a CS prop in VMC on basically calm days. Those of you who have flown behind a CS prop in IMC, do you find it makes engine management easier? Can you just "set and forget" the RPM?

JHines said:

I've got a decent amount of hours in IMC behind a FP propeller. At times it results in a lot of throttle jockeying in heavy updrafts and downdrafts.

I have only flown with a CS prop in VMC on basically calm days. Those of you who have flown behind a CS prop in IMC, do you find it makes engine management easier? Can you just "set and forget" the RPM?

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I suppose. But its not really a set and forget, in fact its one more thing to deal with. I could make the argument that a c/s prop under a high workload enviornment like IMC adds to the list of things to deal with. I certianly would not have listed "management in IMC" in the top ten reasons to own a C/S prop. Nor would it be in the top 50 items on my mind for things to deal with IMC. I dont consider it a factor one way or the other.

I agree with Mike - management of RPM wouldn't be anywhere near the top of my list of things to manage in IMC. In fact, after initial climb, I usually set the RPM I like, and don't touch it again until short final.


But then, flying a fixed pitch prop in IMC, I set up cruise power and then don't touch the throttle either - I fly pitch (or let the autopilot do it). Never really thought about playing with the throttle, unless I am managing a descent.

Paul

Ironflight said:

I agree with Mike - management of RPM wouldn't be anywhere near the top of my list of things to manage in IMC. In fact, after initial climb, I usually set the RPM I like, and don't touch it again until short final.

<SNIP>

Paul

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Hi Paul,

I know in extreme situations one should just fly attitude, keep under Va and tell ATC "unable" on the assigned altitude.

I am thinking more of situations such as maintaining altitude +/- 100 feet while transiting 300 to 500 FPM updrafts/downdrafts.

Maybe I'm using some poor piloting techinques, but I've found that in a Skyhawk or similar in such conditions, I would need to pull the throttle to avoid an overspeed or firewall it to maintain altitude.

Ironflight said:

But then, flying a fixed pitch prop in IMC, I set up cruise power and then don't touch the throttle either - I fly pitch (or let the autopilot do it). Never really thought about playing with the throttle, unless I am managing a descent.

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this is what I do in normal conditions.

I would have to disagree with the folks who say it's a hindrance. Having the prop governor control your RPM to prevent overspeeding while fighting up/downdrafts doesn't seem like it would be a problem to me. It's almost like saying that managing an autopilot in IMC is just another thing to increase your workload. Simply not the case! Another possible side benefit of C/S is the ability to shed some prop ice by manipulating the blade pitch.

captainron said:

I would have to disagree with the folks who say it's a hindrance. Having the prop governor control your RPM to prevent overspeeding while fighting up/downdrafts doesn't seem like it would be a problem to me. It's almost like saying that managing an autopilot in IMC is just another thing to increase your workload. Simply not the case! Another possible side benefit of C/S is the ability to shed some prop ice by manipulating the blade pitch.

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Good points Ron. I had not considered the blue lever de-ice function before. Thats a good one.
I personally have zero fixed pitch RV IMC time for any comparison.

Another plus for the CS prop in IMC is that if you screw up and end up in icing conditions, you will have better climb performance to get out of the stuff.

Another advantage for the CS the ability to keep your speed up on the approach and still be in a good position to slow down and land. This worked well for me when on the ILS with jet traffic in trail.

CS prop is less workload in the air... no matter, VFR or IFR.

osxuser said:

CS prop is less workload in the air... no matter, VFR or IFR.

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I agree with that but there are times when you have to pull and push that throttle (or prop control) with either prop type. Today there was pretty strong mountain wave activity along my route and I had to pull the throttle back on my fixed pitch equipped airplane to keep the indicated airspeed to something reasonable in the ups. I would have had to do just the same with a constant speed.

No doubt, but you never have to worry about the overspeed, and if you set to 2500 rpm, never have to worry about the over boost either.

Not a conscious factor

I have a lot of IMC FP time but none in an RV. On rare occasions with a FP I have entered extremely strong down drafts on the downwind side of a mountain ridge and at WOT the rate of descent was 1000+ fpm, I have been been in a heavy ice accumulation situation where the only option was to climb and it was very marginal and I have made high altitude takeoffs that almost weren't where the CS probably would have helped. In my RV with the Hartzell I essentially set it to max for takeoff and pull it back to 2450 for noise abatement shortly after rotation and cross country cruise. I do nothing but check it & tweak it until shortly before arrival at the final approach when I have to jockey the throttle and prop to get it down to final approach speed with the prop in fine pitch (max rpm) where the prop control is out of the management workload. In an RV with its great climb performance, I think you would have a hard time justifying the expense and weight of a CS based on its helping in IMC. I have flown it in ice where it accumulated ~1/4" while I requested lower and it performed normally through that experience - maybe with a FP it may have required more work.

Bob Axsom