Learn use of constant speed propeller

Mohamed Ahmed

Mohamed Ahmed

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MAH
Hello,

As a new PPL holder (less than 100 hours), with all my training and experience around C172 & piper Cherokee 140/160, I wanted to learn how to use the fixed speed propeller as a step up.

I plan to learn first on my xplane, then start renting C182.

I’ve looked over the internet, there are many educational materials on the engineering concepts, but couldn’t find a resource for practically how to use it, manifold pressure and RPM values that should be maintained during different phases of flight (takeoff, cruse, and landing).

Any guide or reference is highly appreciated...



Thank you
Mohamed
 
Mohamed Ahmed said:
I’ve looked over the internet, there are many educational materials on the engineering concepts, but couldn’t find a resource for practically how to use it, manifold pressure and RPM values that should be maintained during different phases of flight (takeoff, cruse, and landing).
Click to expand...
That's aircraft specific - go to the POH as said above. They may be similar, but you aren't going to run the same numbers in a C177RG as you might in a Bonanza or a Mooney. Most of those aircraft will have different options for manifold and RPM that can achieve different things - like longer range, faster speed, staying aloft longer.
 
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And as far as what settings for power and RPM, the PoH of the different aircraft is a good start.

A CFI who is very experienced that airframe can help

A modern engine monitor can help

Articles and webinars from Mike Busch can help. Including his recent "Over square" ones.
 
Or just get a Cirrus and enjoy being able to enjoy flight without the blue knob.
 
AggieMike88 said:
  1. Airplane Flying Handbook, starting at page 11-4
  2. www.Boldmethod.com, https://www.boldmethod.com/learn-to-fly/aircraft-systems/how-a-constant-speed-prop-works/
  3. AvWeb's John Deakin and Pelican's Perch #16, Those Marvelous Props. https://www.avweb.com/news/pelican/Pelicans-Perch-16-Those-Marvelous-Props-182082-1.html
Click to expand...

I rate the FAA's materials on the subject a solid "Meh". They give a description that, while accurate, does not really teach you anything worthwhile if you're just starting out.

Deakin's Those Marvelous Props, IMO, should be the second stop on your journey to learn this subject. The first stop should be the column preceding it, entitled "Manifold Pressure Sucks!"

Read those two, and you might not need to do anything else... They're that good.
 
You are going to find the adjustable speed prop quite easy to use. Just think:

1. Just a bit more to pre-flight (look for leaks, make sure they aren't twisting by hand)
2. Just a bit more during the run-up (cycle 1..2 times to ensure oil flow and operation)
3. During taxi and takeoff its gonna be full forward (maximum rpm), easy to catch because you have time to checklist.
4. Flight
5. During landing its gonna be full forward (maximum rpm) see 'B'

...so its really #4 -during flight that you will be "adjusting" or tweaking it. And for that you have (2) things. The POH which lists various MP vs RPM settings for cruise. However, for our 182 the POH also indicates to adjust it for the smoothest operation. Guess what - that is what works best. You get up to cruise. Make slow smooth changes (Vernier'd) until its nice and smooth. That will be paired with a small range of valid MP's for your cruise altitude.

I would say there are two things to watch out for:

A.) As you let down you will learn to back off the throttle (MP) and then start bringing the prop back in (higher RPM). If you do the reverse (prop in then throttle) it will overs-peed for a bit...you should be avoiding that that.

B.) Make sure it is full forward at sometime in the pattern so when you are on final you will have full prop rpm available for a go around. I bet everyone flying constant speed props has left it in on final at least once (I have). Its easy to miss as the amount you have pulled it out during cruise may not be much. And you are usually slowly bringing it back in during the pattern sometime around the base turn. So at that point you are not looking at checklists...you are watching for traffic and flying.

I think the CS prop is also taught differently. My CFI taught to to gradually letdown more and more power during the pattern entry, downwind and base. So I might be at 15"-20" MP and 2200rpm during the downwind. As I turn base I bring the MP down to 15" or a bit lower and then bring the prop the rest of the way in. My wife on the other hand will reach downwind, reduce MP fairly low and as the RPM starts to come down and no longer governed she will bring the prop in and fly the entire pattern at 1700 rpm (throttle only, not governed) until close on final. Both work. Neither overspeed. She moves through the pattern a nice fixed speed and is very stable. Mine leaves me a little more speed during the downwind and out at the turn to base. Mine has a few more steps where hers is more simple. I learned it in the 182. She learned it in a T-34 (envy that one!)

Re: Simulator

If you already find value in the simulator it should be good for some of it. But you will not "feel" and "hear" the shudder, smoothness or over-speeding. And the knob is verniered and rather stiff vs a simulator knob or pressing a keyboard key. I would think the simulator would be great for simulating a go around with the prop out a bit and learning the letdown and pattern entry. Definitely will show the effects of cruise speed vs prop.
 
One other thing. RPM = noise. Please be a good neighbor.

Also, low MP + high RPM = drag. Might want to take that into account when you are on short final or doing a power-off glide/landing.
 
As said before:

Taxi/takeoff, full forward. I usually bring back the prop after takeoff just a smidgen to reduce noise.

The POH will give you power settings, but most non turbo engines will be similar. For cruise usually squaring the MP to RPM works out, 23/2300, 24/2400, etc.

Descending I leave the prop alone, just reduce MP as necessary for rate and speed. Once you slow down in the pattern and you decelerate, the RPM will decrease when the prop hits the stops. Then prop lever in. Even if you forget to push it in before landing, not a big deal unless you go around. I always teach on a go-around, mixture, props, throttles anyway, just like "The Drill".
 
Distilled, a CS prop gives you an efficient climb prop for climbing and an efficient cruise prop for cruise. That's really what it's all about.
 
Find an instructor to teach you what you need for a high performance sign-off.
 
Bill Jennings said:
Distilled, a CS prop gives you an efficient climb prop for climbing and an efficient cruise prop for cruise. That's really what it's all about.
Click to expand...
Other than understanding the mechanics of how it works, that really is just about it. When I do transition training, I point out that there are really just two prop positions for most of us in piston singles most of the time. Max forward, which is for takeoff, climb, and landing (actually, for the go-around) and cruise.

Despite the number of possible combinations to get equivalent cruise power, most of us tend to settle on one which provides us the most "comfortable" performance in terms of noise and vibration. Cruise can be further subdivided into low altitude and high altitude - increasing RPM as available MP tapers off) but not everyone does that.
 
AggieMike88 said:
Do you mean "constant speed" instead of "fixed speed"?

To learn about constant speed propellers, try these resources...

  1. Airplane Flying Handbook, starting at page 11-4
  2. www.Boldmethod.com, https://www.boldmethod.com/learn-to-fly/aircraft-systems/how-a-constant-speed-prop-works/
  3. AvWeb's John Deakin and Pelican's Perch #16, Those Marvelous Props. https://www.avweb.com/news/pelican/Pelicans-Perch-16-Those-Marvelous-Props-182082-1.html
Click to expand...

This really is it. I'd add the Pelicans Perch article 15 Manifold Pressure Sucks as well once you've got a better handle on the concept. The Airplane Flying Handbook is also a fantastic reference and is where I would start. Don't start with the POH in my opinion if you don't have a strong understanding of the concepts behind what make a constant speed prop work. Otherwise, it's just rote numbers on a page.
 
Stewartb said:
Find an instructor to teach you what you need for a high performance sign-off.
Click to expand...
This!

I was just like you and tried to study up all I needed to know before climbing into the Toga with the blue knob.

In reality. Just go fly the plane with a CFI. It’ll make sense in the air much more than on paper. Of course have your power settings handy but most good CFI’s would be able to educate you without looking anything up.
 
Just remember when adding power to enrichen, increase RPM, then increase throttle. When decreasing power decrease decrease power, adjust RPM, then adjust mixture. There are some variations but that will get you started.
 
Sinistar said:
You are going to find the adjustable speed prop quite easy to use. Just think:

1. Just a bit more to pre-flight (look for leaks, make sure they aren't twisting by hand)
2. Just a bit more during the run-up (cycle 1..2 times to ensure oil flow and operation)
3. During taxi and takeoff its gonna be full forward (maximum rpm), easy to catch because you have time to checklist.
4. Flight
5. During landing its gonna be full forward (maximum rpm) see 'B'

...so its really #4 -during flight that you will be "adjusting" or tweaking it. And for that you have (2) things. The POH which lists various MP vs RPM settings for cruise. However, for our 182 the POH also indicates to adjust it for the smoothest operation. Guess what - that is what works best. You get up to cruise. Make slow smooth changes (Vernier'd) until its nice and smooth. That will be paired with a small range of valid MP's for your cruise altitude.

I would say there are two things to watch out for:

A.) As you let down you will learn to back off the throttle (MP) and then start bringing the prop back in (higher RPM). If you do the reverse (prop in then throttle) it will overs-peed for a bit...you should be avoiding that that.

B.) Make sure it is full forward at sometime in the pattern so when you are on final you will have full prop rpm available for a go around. I bet everyone flying constant speed props has left it in on final at least once (I have). Its easy to miss as the amount you have pulled it out during cruise may not be much. And you are usually slowly bringing it back in during the pattern sometime around the base turn. So at that point you are not looking at checklists...you are watching for traffic and flying.

I think the CS prop is also taught differently. My CFI taught to to gradually letdown more and more power during the pattern entry, downwind and base. So I might be at 15"-20" MP and 2200rpm during the downwind. As I turn base I bring the MP down to 15" or a bit lower and then bring the prop the rest of the way in. My wife on the other hand will reach downwind, reduce MP fairly low and as the RPM starts to come down and no longer governed she will bring the prop in and fly the entire pattern at 1700 rpm (throttle only, not governed) until close on final. Both work. Neither overspeed. She moves through the pattern a nice fixed speed and is very stable. Mine leaves me a little more speed during the downwind and out at the turn to base. Mine has a few more steps where hers is more simple. I learned it in the 182. She learned it in a T-34 (envy that one!)

Re: Simulator

If you already find value in the simulator it should be good for some of it. But you will not "feel" and "hear" the shudder, smoothness or over-speeding. And the knob is verniered and rather stiff vs a simulator knob or pressing a keyboard key. I would think the simulator would be great for simulating a go around with the prop out a bit and learning the letdown and pattern entry. Definitely will show the effects of cruise speed vs prop.
Click to expand...

Appreciate your response Sinistar. It is exactly what not told in the books and I was missing...

Also many thanks for everyone contributed to this thread...


Thank you
Mohamed
 
If you get a Cirrus, the throttle lever will take care of that for you! ;)
 
You can study ahead of time, that's a good thing, but you will still require to get checked out and a sign-off.
 
Stewartb said:
Find an instructor to teach you what you need for a high performance sign-off.
Click to expand...

Plenty of constant speed props on planes with 200 hp or less. Also plenty without retractable gear.

My point is that a constant speed prop does need some pilot education, but doesn't ALWAYS need an endorsement.
 
Ravioli said:
Plenty of constant speed props on planes with 200 hp or less. Also plenty without retractable gear.

My point is that a constant speed prop does need some pilot education, but doesn't ALWAYS need an endorsement.
Click to expand...

Maybe not an FAA signoff, but the renting FBO most likely will require their person to sign off on you.
 
PaulS said:
Maybe not an FAA signoff, but the renting FBO most likely will require their person to sign off on you.
Click to expand...

I was replying to the suggestion to get a High Performance endorsement.
 
Ravioli said:
Plenty of constant speed props on planes with 200 hp or less. Also plenty without retractable gear.

My point is that a constant speed prop does need some pilot education, but doesn't ALWAYS need an endorsement.
Click to expand...

The OP specifically said he was going to rent a 182. I'm guessing the owner will require a logbook endorsement.
 
Stewartb said:
The OP specifically said he was going to rent a 182. I'm guessing the owner will require a logbook endorsement.
Click to expand...

Point taken. All 182's are High Performance. Thus your advice was on track and mine was not.

But for OP, don't learn it on your sim... do what Stewartb said and do it right.
 
Basically the prop is like the stick shift in a car
The throttle is like the gas pedal
 
Stewartb said:
The OP specifically said he was going to rent a 182. I'm guessing the owner will require a logbook endorsement.
Click to expand...

Yes Stewartb. The plan is to rent it with CFI to get training, transition and high performance endorsement.

I don’t even switch different plane as c172 and PA28A without proper transition training.



Thank you
Mohamed
 
midlifeflyer said:
Other than understanding the mechanics of how it works, that really is just about it. When I do transition training, I point out that there are really just two prop positions for most of us in piston singles most of the time. Max forward, which is for takeoff, climb, and landing (actually, for the go-around) and cruise.

Despite the number of possible combinations to get equivalent cruise power, most of us tend to settle on one which provides us the most "comfortable" performance in terms of noise and vibration. Cruise can be further subdivided into low altitude and high altitude - increasing RPM as available MP tapers off) but not everyone does that.
Click to expand...

Yes to Paragraph #1.

For cruise, I have mostly settles on three (3) power settings based on altitude:
--Low altitude, 23/2300
--Mid Level, 22/2400
--High Cruise, 20/2500
This keeps power in the safe zone, 65-70%, and greatly reduces workload when ATC gives step-ups and step-downs. For this, mid-level is ~4000-7000 msl. Check your Performance Tables; took me a few years' page flipping to settle on these. Oh, they are all smooth. Dynamic propeller bakancing is a good thing!

My normal descent is 500 fpm, trimmed hands off, and as altitude unwinds, MP and EGT both rise, so I reduce throttle and enrichen mixture to my cruise settings every few thousand feet.

Just go Full RPM somewhere in the pattern, I do on downwind.
 
Read the POH and the limitations for the prop/engine combination. an O-540 has a pretty big range of MP/RPM you can operate in safely.
 
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