Initial Climbout power reduction

wilkersk said:
You accelerate to Vy (in most aircraft) which gets you more cooling air, gets you to cruising altitude faster and therefore gets you to level lean and clean flight. It would seem to me pulling a few RPM off as you lower the nose slightly for Vy is a good thing to do. Why wouldn’t you want to do that?
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In many high performance aircraft, Vy is literally for when you need climb at the fastest rate. Or you are at such a high density altitude that higher airspeeds will not result in much climb. The trade off in many installations is high engine temps.

In these aircraft Vy + 10 to 25 is not uncommon for still good climb rate with adequate cooling. Another reason why pulling back power to some cruise climb is often not a good idea - now you do have to fly Vy for a decent climb rate, but temps suffer even more.
 
wilkersk said:
You accelerate to Vy (in most aircraft) which gets you more cooling air, gets you to cruising altitude faster and therefore gets you to level lean and clean flight. It would seem to me pulling a few RPM off as you lower the nose slightly for Vy is a good thing to do. Why wouldn’t you want to do that?
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Ummm.... So what does your power setting have to do with Vy?? :cool: Now just picking random numbers.... Let's say I have a plane that at max allowable power and at Vy, I climb at 1200ft/min. But if I reduce power, still at Vy, I climb at 800ft/min.

So with your "...gets you to cruising altitude faster and therefore gets you to level lean and clean flight..." which power setting do you want to use? This comment is really the main point of climbing at max allowable power to get to cruise faster. And you said "lean" but for a lot of people when they get to cruise that means "lean of peak" which many will say also has benefits for the life of the engine.
 
Vy is predicated on max available power. It hence changes with altitude.
 
Remember that Normal Ops section are NOT limitations.

Unless the engine is limited (in the Limitations Section) to take off power for some time period (5 minutes), I climb with full power to cruise altitude.

Climb power reductions are from the old days of ROP only power settings.
 
Jaybird180 said:
You're flying behind a Single Engine Constant Speed Prop and the checklist calls for a MP/RPM reduction during the climb. When do you do this and why do you choose that point in time?
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High density altitude and terrain notwithstanding, 1000 AGL.
 
Larry in TN said:
Most of these engines do have a limitation at max power, often indicated by the top of the green arc on the tachometer. Even without that, 2400 or 2500 is a lot quieter than max and should be easier on the engine over the long term.

As far as MP, leave it at full unless limitations require a reduction. Most of the normally aspirated engines do not.

In all cases, the AFM and engine manual are controlling, not some rule-of-thumb that your CFI may have taught you two decades ago.
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This!!!

Stop relying on what your CFI told you that they learned from their CFI that learned from their CFI. Combined those three might have had 1000 hours of total time when they taught you...

In my 310Q, I pull the props back to 2450 at 500' and adjust for a cruise climb. The RPM is never touched again in flight. The MP stays constant.

In my 421C, I pull the props back to 1900 at 500' and adjust for cruise climb. The RPM is then adjusted once in cruise to 1800. The MP is reduced from WOT to 35" at 500' and then to 32.5" at cruise per the RAM guidelines.

Why do I do the 500' reduction? Reduced workload. Because at that time, my gear is up, I'm clear of trees and am at a climb angle that I would allow me to react to an engine issue.
 
Absent a limitation, I am in the leave MP alone and reduce RPM only enough to reduce excess noise and vibration group. Absent a need for maximum performance, that RPM reduction takes place once above traffic pattern altitude.

Side note. FWIW, I think constant speed prop usage (as opposed to theory) is one of those things we tend to overcomplicate. When I do a transition, I teach that there are only three prop settings. Full forward, marginal reduction in climb (optional or required by limitation), and whatever cruise settings you select for that flight. Everything else is throttle, just like with a fixed pitch prop.
 
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midlifeflyer said:
Side note. FWIW, I think constant speed prop usage (as opposed to theory) is one of those things we tend to overcomplicate. When I do a transition, I teach that there are only three prop settings. Full forward, marginal reduction in climb (optional or required by limitation), and whatever cruise settings you select for that flight. Everything else is throttle, just like with a fixed pitch prop.
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just for curiosity’s sake, since I can’t say as I’ve ever heard anything different about CS prop operation, how are people over complicating it?
 
MauleSkinner said:
just for curiosity’s sake, since I can’t say as I’ve ever heard anything different about CS prop operation, how are people over complicating it?
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I don't think it's so much the flight as the ground. We get a lot of pilots who come to our club Diamond DA40s with only 172 experience. They're smart enough to read up in advance or watch videos and manage to get a picture of needing to play with both prop and MP all the time.
 
MauleSkinner said:
just for curiosity’s sake, since I can’t say as I’ve ever heard anything different about CS prop operation, how are people over complicating it?
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My first CS airplane was an Arrow. My instructor way over-complicated the prop operation. It seemed like we were always moving the throttle and prop controls for different phases of flight. And you'd better remember to adjust them in the "right order" or the engine will explode. This cost me lots of brain processor power and certainly lengthened my endorsement training.

With primacy being what it is, it took a long time for me to realize it was really quite simple, and to teach my students that way. I operate the same way @midlifeflyer does. Keep it simple.
 
The guys who really believe that the throttle must be reduced before the prop would mess themselves if they saw MP vs RPM on takeoff with a fixed-pitch prop. Use the power setting tables. A few inches “oversquare” is almost always acceptable. Heck, they were pulling 45” at 2600 RPM on Constellations, and going 3,000 hours between overhauls.
 
ateamer said:
The guys who really believe that the throttle must be reduced before the prop would mess themselves if they saw MP vs RPM on takeoff with a fixed-pitch prop. Use the power setting tables. A few inches “oversquare” is almost always acceptable. Heck, they were pulling 45” at 2600 RPM on Constellations, and going 3,000 hours between overhauls.
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My Maule had a cruise prop…static RPM was about 2250, so substantially over square.
 
midlifeflyer said:
Side note. FWIW, I think constant speed prop usage (as opposed to theory) is one of those things we tend to overcomplicate. When I do a transition, I teach that there are only three prop settings. Full forward, marginal reduction in climb (optional or required by limitation), and whatever cruise settings you select for that flight. Everything else is throttle, just like with a fixed pitch prop.
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MauleSkinner said:
just for curiosity’s sake, since I can’t say as I’ve ever heard anything different about CS prop operation, how are people over complicating it?
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Probably the fallacious oversquare rule? Some people undercomplicate it by leaving it full forward the whole flight. "If you do that, it's just like a fixed pitch" is the argument I've heard.
 
dmspilot said:
Probably the fallacious oversquare rule? Some people undercomplicate it by leaving it full forward the whole flight. "If you do that, it's just like a fixed pitch" is the argument I've heard.
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who doesn’t like hearing “eeeeeeeeeeee” for the rest of their lives ha ha
 
midlifeflyer said:
I teach that there are only three prop settings. Full forward, marginal reduction in climb (optional or required by limitation), and whatever cruise settings you select for that flight.
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You don't go to the bottom of the green arc for cruise-descent?
 
asicer said:
You don't go to the bottom of the green arc for cruise-descent?
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Green arc for RPM or Airspeed??? And NO, at least not in my Mooney (TSIO-360) as I only have a Red Line to worry about for the RPMs. There really is no shroud of secrecy about a CS prop. And as @midlifeflyer said, you only really need to adjust it a few times.

For descent, I don't change much of anything for descent in smooth air. This lets me gain back a lot of the energy I used in the initial climb with some really nice speeds in the descent. In rougher air I'll bring the throttle/power back as I start down to keep the Airspeed in the green. If the end of my descent will have me going right into the airport environment, I will start pulling the throttle/power back as I'm coming down in the descent to make sure I will be slowed down in time. But if ATC brings me down away from the airport, I'll leave the power in to keep the speed up for when I level off.
 
I fly out of small grass strips and back yards. So it’s pretty standard to roll back the prop immediately after lifting off. In a Husky it hardly affects the climb.

If I were flying a Cessna 185 out of these places, I’d shoot for pulling the prob back even sooner.
 
dmspilot said:
Some people undercomplicate it by leaving it full forward the whole flight. "If you do that, it's just like a fixed pitch" is the argument I've heard.
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I’ve seen that one. It’s doable but tends to be noisy. And inefficient. The one place I have seen the technique work is in the traffic pattern. Prop full forward and target RPM rather than MP

You can see something similar with leaning. I was flying as a passenger. Familiar airplane. Cruising at 4500’, I noticed the fuel flow was 12 GPH. I asked the pilot about leaning and the response was, “the POH says 5000’.”

I asked for permission, then pulled the red knob back to 9 GPH.

We gained 8 KTS.
 
midlifeflyer said:
Nope. I keep the cruise prop setting all the way until it’s time to go full forward again.

What do you see as the necessity, purpose, or operational advantage of prop reduction for descent?
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Same here....cruise settings until 'GUMPFS".
 
midlifeflyer said:
Nope. I keep the cruise prop setting all the way until it’s time to go full forward again.

What do you see as the necessity, purpose, or operational advantage of prop reduction for descent?
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The AFM says so:
Descent:
- Set RPM to 2000 - 2200 RPM in order to prevent shock cooling of the engine. Manifold pressure as necessary, observe engine temperatures.
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asicer said:
The AFM says so:
Descent:
- Set RPM to 2000 - 2200 RPM in order to prevent shock cooling of the engine. Manifold pressure as necessary, observe engine temperatures.
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POH power recommendations* aside, I have not flown an airplane - normally aspirated or turbo - where that has been an issue. I don't discount the possible negative effects of excessively rapid cooling, but planned "manifold pressure as necessary" takes care of descent very nicely. Now, if one waits until the last minute to reduce power, I can see a need for making changes to both RPM and MP, but not when staying ahead of the airplane.

[* if yours is a limitation, different story]
 
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My IO-540 is derated in the Commander 114A so there is no max power limit. I usually just leave the power forward and pull the prop back to 2500 rpm at about 1000 ft as I turn off the fuel pump and switch from both tanks to the right or left depending on the time of day, then just fly max continuous power at 2500 RPM to cruise. Then I look at the POH cruise table and pick the best combo of MAP, and Prop speed, and then use the engine monitor to lean to best power. I feel that 400 ft is too low to be making any power changes.

(The Commander will not feed equally from both tanks, so treating it as a left/ right fuel system keeps the wing balanced. On the left side of the hour, I fly the left tank, and so on...)
 
midlifeflyer said:
POH power recommendations* aside, I have not flown an airplane - normally aspirated or turbo - where that has been an issue.
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I figure if it's in there, it's worth considering and not immediately discarded just because "it's only a recommendation".

midlifeflyer said:
I can see a need for making changes to both RPM and MP, but not when staying ahead of the airplane ATC.
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FTFY.

"Approach, Cessna 123 direct FIXIT 9000MSL"
"Cessna 123, 5 miles from FIXIT, cross FIXIT at 3000, cleared for the approach"
 
asicer said:
I figure if it's in there, it's worth considering and not immediately discarded just because "it's only a recommendation".


FTFY.

"Approach, Cessna 123 direct FIXIT 9000MSL"
"Cessna 123, 5 miles from FIXIT, cross FIXIT at 3000, cleared for the approach"
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I doubt this was a real clearance (especially since FIXIT is not an approach fix), but your point about ATC-delayed descent is taken.

Obviously steep descents do happen, but if ATC kept you 6000 feet high until 5 nm from an approach fix, you probably shouldn't be accepting that clearance. "Unable, I'll need vectors for descent".

Of course, being ahead of the airplane would have meant you'd have seen this starting to happen miles ago, and should have slowed the airplane in advance to prepare for the upcoming descent.
 
RussR said:
I doubt this was a real clearance (especially since FIXIT is not an approach fix), but your point about ATC-delayed descent is taken.

Obviously steep descents do happen, but if ATC kept you 6000 feet high until 5 nm from an approach fix, you probably shouldn't be accepting that clearance. "Unable, I'll need vectors for descent".

Of course, being ahead of the airplane would have meant you'd have seen this starting to happen miles ago, and should have slowed the airplane in advance to prepare for the upcoming descent.
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Yup. Staying ahead of ATC. :)
 
My POH says to limit MP to 26”, when clear of obstacles, 26” is full power at about 3000’ or reduction of 90% full power.
During certification process they run these engines for 50 hours at full power.
I always keep the RPMs below max.
 
M20K said:
Green arc for RPM or Airspeed??? And NO, at least not in my Mooney (TSIO-360) as I only have a Red Line to worry about for the RPMs. There really is no shroud of secrecy about a CS prop. And as @midlifeflyer said, you only really need to adjust it a few times.

For descent, I don't change much of anything for descent in smooth air. This lets me gain back a lot of the energy I used in the initial climb with some really nice speeds in the descent. In rougher air I'll bring the throttle/power back as I start down to keep the Airspeed in the green. If the end of my descent will have me going right into the airport environment, I will start pulling the throttle/power back as I'm coming down in the descent to make sure I will be slowed down in time. But if ATC brings me down away from the airport, I'll leave the power in to keep the speed up for when I level off.
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I am the same in my M20K 252. Full forward for take off and climb (2600 RPM). Accelerate to cruise speed, set cruise RPM (2300 typically).

For descent, push nose over and enjoy 220+ KTAS speeds. Push in prop control on downwind or approaching FAF after RPM is less than set point to avoid noise.
 
For whatever it's worth, my O-470 equipped Cessna 182P, the POH states increased engine wear occurs at higher power settings and to reduce power "whenever possible".
1740011981361.png
 
Lower wear per time, but longer at climb power to get to altitude.

And remember, these POHs for most planes we are flying were written 40 - 60 YEARS ago. Knowledge of engine operation has changed a LOT in that time.
 
robertb said:
For whatever it's worth, my O-470 equipped Cessna 182P, the POH states increased engine wear occurs at higher power settings and to reduce power "whenever possible".
View attachment 138293
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And yet I've run TSIO-520s, a different big bore Continental, to 2300+ hours with no decrease in oil pressure. Running at 26-27" MP continuously, which an O-470 can't maintain much past 4000'. Sure, one set of cylinders was changed along the way, but those are bolt on disposable parts anyhow. Climb was at 28" MP or so.
 
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