Looking for constant speed operational technique for cruise and descent settings. The best way to operate your engine for life and fuel savings.
Climb, I assume levers forward but if there's discussion on that please do tell!

Kelly

The POH will give you all this info. Everything forward on climb out isn't going to help you in regards to fuel burn. A buddy of mine that has flown in Alaska for years taught me "Five hundred feet: flaps, manifold, prop". Easy for me to remember.

Totally depends on the airplane.

MTV

What you can do is run your plane full throttle at as close to sea lever as is reasonably possible while playing with the rpm. Whatever rpm gives you the best ground speed is theoretically the most efficient rpm for your prop.
Now you know that number, when you are climbing out dial your rpm back to whatever that number is and leave it there, then use whatever MP you want depending on how much gas you want to burn.

River rat wrote:What you can do is run your plane full throttle at as close to sea lever as is reasonably possible while playing with the rpm. Whatever rpm gives you the best ground speed is theoretically the most efficient rpm for your prop.
Now you know that number, when you are climbing out dial your rpm back to whatever that number is and leave it there, then use whatever MP you want depending on how much gas you want to burn.

I might be wrong but I don't this is very accurate. That's like saying take your truck out on the highway and what ever gear lets you go the fastest is the best gear to take off up hill in.

Jeredp wrote:

River rat wrote:What you can do is run your plane full throttle at as close to sea lever as is reasonably possible while playing with the rpm. Whatever rpm gives you the best ground speed is theoretically the most efficient rpm for your prop.
Now you know that number, when you are climbing out dial your rpm back to whatever that number is and leave it there, then use whatever MP you want depending on how much gas you want to burn.

I might be wrong but I don't this is very accurate. That's like saying take your truck out on the highway and what ever gear lets you go the fastest is the best gear to take off up hill in.

The engine develops full power at maximum RPM, dialling the prop back to lower RPM is very unlikely to yield more airspeed as you're shedding horsepower....

Every airframe/engine combination is likely to be slightly different. There are some rather usual "rules", however:

*Take off and climb out will be with full throttle and the prop control all the way in, for highest rpm. Sometimes you'll hear that called "flattening" the prop.
*Some engines require reducing rpm to a climb setting rather than full rpm--check the POH.
*Most engines will handle a somewhat reduced rpm for cruise climb rather than full rpm.
*At lower altitudes, generally it's best to reduce MP (throttle) first, then rpm. At higher altitudes, that won't make any difference, because MP of normally aspirated engines is already pretty low.
*On descent, make up for slower climb by just nosing over and gaining airspeed--leave the prop alone and reduce MP as necessary.

Now with all that, I'll just describe what I do in my airplane (P172D, Lycoming O-360, CS prop):

First, taking off from a low elevation airport and climbing to about 2000' AGL: prop all the way forward, throttle all the way forward. After reaching about 4-500' AGL, throttle back to 25", prop to 2550 rpm. Upon reaching altitude, throttle to 21", prop to 2400 rpm, lean. Results: 9.8 gph.
Second, taking off from a high elevation airport and climbing to about 2000' AGL: prop all the way forward, throttle all the way forward. After reaching about 4-500' AGL, leave throttle full forward (MP is already below 21"), prop to 2550 rpm. Upon reaching altitude, prop to 2400 rpm, lean. Results: 9.8 gph.
Descending: leave both throttle and rpm alone, pitch down. When the MP starts to climb above 21", reduce the throttle to 21", continue to reduce it to maintain 21".
For landing, reduce throttle just as you do with a fixed pitch prop, but once the throttle is below 12" or so, push the prop control all the way forward, in case you need to go around.

All of this stuff, your CFI should be covering, and it won't take you very long to get the hang of it.

Cary

Jeredp wrote:The POH will give you all this info.

Gear, flaps, manifold, prop.

Mister701 wrote:

Jeredp wrote:The POH will give you all this info.

Gear, flaps, manifold, prop.

Yeah i skip the gear part cuz everything that I fly always has the gear down and locked, like it shoud be

I always make sure anyway. I may forget

Cary wrote:Every airframe/engine combination is likely to be slightly different. There are some rather usual "rules", however:

*Take off and climb out will be with full throttle and the prop control all the way in, for highest rpm. Sometimes you'll hear that called "flattening" the prop.
*Some engines require reducing rpm to a climb setting rather than full rpm--check the POH.
*Most engines will handle a somewhat reduced rpm for cruise climb rather than full rpm.
*At lower altitudes, generally it's best to reduce MP (throttle) first, then rpm. At higher altitudes, that won't make any difference, because MP of normally aspirated engines is already pretty low.
*On descent, make up for slower climb by just nosing over and gaining airspeed--leave the prop alone and reduce MP as necessary.

Now with all that, I'll just describe what I do in my airplane (P172D, Lycoming O-360, CS prop):

First, taking off from a low elevation airport and climbing to about 2000' AGL: prop all the way forward, throttle all the way forward. After reaching about 4-500' AGL, throttle back to 25", prop to 2550 rpm. Upon reaching altitude, throttle to 21", prop to 2400 rpm, lean. Results: 9.8 gph.
Second, taking off from a high elevation airport and climbing to about 2000' AGL: prop all the way forward, throttle all the way forward. After reaching about 4-500' AGL, leave throttle full forward (MP is already below 21"), prop to 2550 rpm. Upon reaching altitude, prop to 2400 rpm, lean. Results: 9.8 gph.
Descending: leave both throttle and rpm alone, pitch down. When the MP starts to climb above 21", reduce the throttle to 21", continue to reduce it to maintain 21".
For landing, reduce throttle just as you do with a fixed pitch prop, but once the throttle is below 12" or so, push the prop control all the way forward, in case you need to go around.

All of this stuff, your CFI should be covering, and it won't take you very long to get the hang of it.

This is good general info, thanks Cary! Wish this would have been posted a year ago when I was teaching myself how to fly with a constant speed prop.

I suggest reading the articles from Mike Busch and John Deakin. Excellent info. Here is one to get you started.

http://www.avweb.com/news/pelican/182179-1.html?redirected=1

Not all aircraft have a POH for the engine and prop they are currently running.

River rat wrote:Not all aircraft have a POH for the engine and prop they are currently running.

Especially experimentals but that is part of the fun.

The Bearhawk I was flying had an O360 with a 78"Mac C214 prop. After much fooling around I found that it seemed to like 2400-2450rpm for cruise and I usually just left it WOT because I was operating at highish altitudes. Fuel burn was around 9gph.

The governor was turned up a little so it would pull about 2750rpm on takeoff and I'd leave it there till pattern altitude. Then I'd dial it back to about 2600 for climb then to 2400 in cruise. From there I didn't mess with the prop till turning base when I reduced throttle to the point that rpm dropped. Then I shoved the prop all the way in incase I had to go around. As I said before I left the throttle all the way in with resulted in 20-21" mp.

There is a good chance I was doing a lot of things wrong. Learning how to operate a CS prop by chatting with a neighbor while out mowing the lawn likely won't result in the best technique.

Jeredp wrote:

Mister701 wrote:

Jeredp wrote:The POH will give you all this info.

Gear, flaps, manifold, prop.

Yeah i skip the gear part cuz everything that I fly always has the gear down and locked, like it shoud be

Many years ago I heard a controller at a large airport, telling a fixed gear on final " cleared to land, check gear down" in which the pilot retorted, "Roger cleared to land, gear down and welded" That one made the conversations circles for months.

whee wrote:

River rat wrote:Not all aircraft have a POH for the engine and prop they are currently running.

Especially experimentals but that is part of the fun.

The Bearhawk I was flying had an O360 with a 78"Mac C214 prop. After much fooling around I found that it seemed to like 2400-2450rpm for cruise and I usually just left it WOT because I was operating at highish altitudes. Fuel burn was around 9gph.

Mine seems to like running at 2300 rpm / 22", also burning 8-9gph for cruise LOP (IO-540 with 82"Mac).

For cruise climb, I leave it as is and simply enrich ROP to increase power.
For performance climb, 2500 and WOT as required unless I need to cool the engine (I like to run cool as much as possible). I reserve redline 2700 for takeoff & tight spots, just to save stressing the cam lobes unnecessarily.

For descent, I sometimes like to reduce RPM a bit and maintain MAP, just to reduce stress on the engine. I descend LOP, and enrich only when it starts to run ever so slightly rough. There is no training or science behind that, but I am interested to hear what others do.

These engines are detuned as it is. Why not takeoff at 2700? Is there evidence to show that can lobes are being stressed at 2700 rpm?

Zzz wrote:These engines are detuned as it is. Why not takeoff at 2700? Is there evidence to show that can lobes are being stressed at 2700 rpm?

I agree Zane, I've talked to the Continental rep a handful of times regarding different issues, each time I come away with the impression that these engines are a lot more resilient than we think. It seems like most engine issues seem to be cylinder related and can often be linked to cooling issues. One of the last reps I talked to (regarding my O300) told me that flattening the pitch on my prop, increasing rpm, would reduce manifold pressure and would actually be easier on the engine. Made sense after I thought about it.

From reading the articles I mentioned above, here is how i rin my IO470.

Takeoff - WOT, max RPM, 1000' AGL, note EGT, lean to maintain same EGT until reaching desired altitude.

Cruise - upon reaching desired altitude, reduce throttle 1/4 to 1/2 inch MP (I'm usually already at or below 22" MP due to altitude. If not, reduce below planned RPM setting, then increase to 1/4 - 1/2 less than max after setting RPMs. It helps with fuel distribution for running LOP w/ Gammis), reduce to 2200 RPM (lower RPMs = lower fuel flow & slightly slower TAS), close cowl flaps. After giving the engine a couple of minutes to stabilize, I reduce mixture to LOP (roughly 65 degrees LOP). It will run at 9.3 gph but I have found that 10.0-10.3 helps keep my #5 CHT from hanging out in the 280-290 range.

Descent - I dont touch a thing other than throttle unless the engine starts to run rough. Then enrichen only enough to keep it smooth. Abeam the numbers in the pattern, mixture goes ROP for a go around, and on base prop goes to full RPM, also for a go around.

The only thing I'll add that seems to be particular to my airplane/engine combination is that I have to RPM up from 2300 to 2500 during descent to keep from going too fast. If not, I have to pull the power out too much too quick. I cruise close to the top of the green already and if I simply nose it over with pitch my airspeed will climb 10+ knots into the yellow. Descent and arrival has proven to be the most difficult phase for me to figure out in the 206 with IO-550. As GUMP stated about power management in cold climates, I have to plan my descent well before I reach TOC so I've already reduced power.

Brett