Constant Speed Prop

S

SupraPilot

Pre-takeoff checklist
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Apr 9, 2006
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180MPH
Hello,

in a few days i will be starting some lessons for my high perf rating...i will be flying a 182 and the CFI gave me some quick pointers for about 2 mins in the plane on how the prop is used differently and all that, but i just cant figure it ALL out..
I just want someone to explain the basics for adjusting he prop and the mani pressure for different stages of flight.
i try the 182 in MS2004 and thats not really helping..its making me more confused..so if possible just give some normal flight scenarios and how the power and prop are set..i know the basics like prop and power full for takeoff and things liek that...but im not sure about during flight or what different settinmgs do for me on climbout..
i mean i know in ms2004 if i go by the checklist during flight..its like the plane is slower then the 172..and some of the settings on the checklist seem like too low of power settings and the plane wont climb..

Ok if you guys could help out it would be great..i kinda wanna know a little bit about whats going on when i go flying soon..so im not starting off in the dark..

thanx
Ant
 
I just went through this last week. (here is my post...)

Here is the article that I read the night before that helped me out a ton. Give it a read.

http://www.microsoft.com/games/flightsimulator/fs2002_articles_machado_propeller.asp

I'd have to say that it's a lot easier than I thought it would be. Your instructor will give you his version of it, but as long as you remember to "keep the prop on top" (from the article), it's pretty hard to go too wrong.

Most planes will be full forward for startup, taxi, takeoff and landing. In the arrow, we pulled back to "25 squared" on climb out, which means 25" of MP and 2500 RPM. Your maneuvers will vary, but it'll often be something like "23 squared" or maybe 17/22. The CFI will tell you what to do until you get the hang of it.
 
Here's the simplest way to think about it when making adjustments:

Keep the blue knob pushed farther in than the black knob when making power/rpm adjustments.

For me, it's been full throttle, max RPM on takeoff for the constant speeds that I fly. Then at 500' AGL, reduce MP 4-5" or so, and then reduce the prop RPM to 2500. Once in cruise, reduce MP to 23" (of course, if you are too high, you might not get 23" of pressure) and the prop to 2300 or 2400 RPM.

Check the POH for numbers on the 182.
 
Here's the quick version...

Pushing the prop control full forward for take off and just before landing (for the go around) gives you the most power. In cruise climb and cruise, you'll pull it back a tad.

In an engine out, pull it all the way back.

Many people tell you to keep the prop set higher than the manifold pressure. (ie. 22" of MP < 2300 RPM).

After talking with your instructor, let us know if you have more questions! :)
 
Plain and simple, the higher the manifold pressure and the lopwer the RPM, the more efficient you get. It's how Lindbergh crossed the Atlantic which he related to Chenaults Flying Tigers in Burma to get them more mission range and fighting fuel on target. It was then adopted by the entire military aviation sector. If you hear someone use the term "Oversquare" or tell you to never have more manifold pressure than RPM, just politely nod your head as you walk away. Read the specs as to max and min RPM/MP for your power train. There are some crank/prop combos out there that have restricted rpm ranges for harmonic reasons, and that is normaloly placarded on the dash and painted on the ASI.
 
As usual, Henning has got it, although the Harmonic RPM areas with issues are usually a yellow arc on the Tachometer, not the ASI ;)
 
The adivce above is good. I also enjoy studying and playing with the power settings described in the POH. You may be surprised.

For example, it is common practice to change power and prop to a cruise climb setting. On some aircraft this is required and on others it is not. When should you do this, if you have to do so, is in the POH.

Another example is the cruise settings. Perhaps you would like to set cruise based on percent power instead of IAS. See how you can use different MP/RPM settings to get that percent power. How will altitude change that? How much should you lean? Will you lean according to fuel flow, EGT, CHT, or some combination? What does the POH say about this?

Personally, as the POH allows, I like to set the lowest RPM for a given power setting. I get good power with lower noise.
 
spiderweb said:
Personally, as the POH allows, I like to set the lowest RPM for a given power setting. I get good power with lower noise.
Click to expand...

And, if you pay by tach hour, it costs less!!! :D
 
Henning said:
Plain and simple, the higher the manifold pressure and the lopwer the RPM, the more efficient you get. It's how Lindbergh crossed the Atlantic which he related to Chenaults Flying Tigers in Burma to get them more mission range and fighting fuel on target. It was then adopted by the entire military aviation sector. If you hear someone use the term "Oversquare" or tell you to never have more manifold pressure than RPM, just politely nod your head as you walk away. Read the specs as to max and min RPM/MP for your power train. There are some crank/prop combos out there that have restricted rpm ranges for harmonic reasons, and that is normaloly placarded on the dash and painted on the ASI.
Click to expand...
Yup. A Seneca II is almost always "oversquare"!
 
ok this all seems like good info..keep it comin guys..
hopefully when i get in the plane i have some sort of an idea of what i should do..
also i was talkin with another flight instructor and he said that prop management isnt a HUGE issue on a piston engine aircraft but when yoiu transition to turbo prop type of aircraft he said th prop speed and all that are critical because if it is done wrong he said the engine can literally explode..

reason i think i am so confused is that ive been for rides in larger aircraft and it seems that every pilot does it a different way..
i mean i took a quick flight a long time ago with a guy to hop over to a nearby airport and we flew a 182...but i remember i was watching him to see how the CS prop works but he never once touched the prop control..he left it all the way in and just flew the plane (for the short 8 minute flight)like a pixed pitch prop...and ive seen other pilots who almost worship the prop control and they are always adjusting it for different stages of flight...

also from what i am getting from all of this is, that is seems that basically its is BAD if the engine goes faster then the prop...is this correct? or is there other situations where these rules are thrown out the door??

Ant
 
SupraPilot said:
also i was talkin with another flight instructor and he said that prop management isnt a HUGE issue on a piston engine aircraft but when yoiu transition to turbo prop type of aircraft he said th prop speed and all that are critical because if it is done wrong he said the engine can literally explode..
Click to expand...
Don't get your C/S prop training from that instructor, because you can kill a piston engine just as dead (although not as likely cause an uncontained failure) with improper use of the controls of even a non-turbocharged piston engine with C/S prop.

also from what i am getting from all of this is, that is seems that basically its is BAD if the engine goes faster then the prop...is this correct?
Click to expand...
In the direct drive engines that we're talking about here, yes, that would be very bad, since the only way that can happen is if the prop shaft is severed, leaving you in a very noisy glider.
 
Bill Jennings said:
And, if you pay by tach hour, it costs less!!! :D
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But, if you pay by Hobbes hours and rent it wet, max RPM for max speed regardless of fuel flow becomes "best economy" in the renter's mind
 
Ron Levy said:
Don't get your C/S prop training from that instructor, because you can kill a piston engine just as dead (although not as likely cause an uncontained failure) with improper use of the controls of even a non-turbocharged piston engine with C/S prop.
Click to expand...


What condition are you thinking of here Ron? As long as you stay out of detonation, serious short term engine damage due to low (or high) RPM seems pretty unlikely to me on a non-turbo'd engine. Granted that if you get it slow enough, the timing would be way too advanced, but that's likely below the governing range anyway.

I'd be curious as well to hear how anyone could "explode" a turboprop by mis-positioning the "prop" control. (per the original poster's CFI, not Ron).


In the direct drive engines that we're talking about here, yes, that would be very bad, since the only way that can happen is if the prop shaft is severed, leaving you in a very noisy glider.
Click to expand...

Kidding aside, it is considered somewhat detrimental if the prop is driving the engine with direct drive and very detrimental with a geared engine.
 
yeah i didnt really believe the one about the engine exploding...but this wasnt MY CFI ..he was just one that i was talkin to at the airport about it...

also i am trying to get it down on FS2004 before i do the actual flying and i am putting myself in situations and trying to figure out how the prop should be set...
so one thing i cant figure out is how come my cruise speeds are always slow...i set my power and what i think is the correct rpm for the prop and i get ****ty speeds..like the 182 seems like its a waste and the 172 is just as fast but more simple to fly..well as it seems on flight sim at least..idk how accurate it really is..
so what are the proper cruise settings??
also what do you do when transitioning from cruise to climb some more??
If i was level flight and wanted to fly as fast as posible would i just go full power and push the prop all the way in??
It seems that the prop is more of a set it and forget it type of thing..and you just add manifold pressure as needed..

Also i am assuming that setting the mixture is the same as a fixed pitch airplane, or is this a totally new thing also??

And finally in general what should i expect from the 182 over a 172 or my usual Warrior?? Is it basically the same with more power and speed..i assume everything just happends a little quicker then im used to..I do have some experience in a 182 actually..I sat right seat,the plane had 4 people, 75% fuel, and i flew it , landed it, and it didnt seem much heavier or anything..was pretty easy actually..BUT i didnt touch the throttle or prop setting..the guy sitting left seat did all that except until short final he gave me the throttle so i could adjust for the flare and stuff on my timing..

sorry for all the questions..but it seems the more i try it on fs2004 the more questions i have

Ant
 
The following is what I usually do with my Comanche - 260 HP. For a normal flight, I don't touch the prop much... full in on take off, 2500 for climb, 2400 for cruise and pattern work until short final, then full. Normal flight, I move it it 3 times. Manifold pressure changes are a lot however. At higher altitudes it's all in after I can't maintain 23", but I always try to limit any change to less than 2 or 3 inches every few minutes to protect fast temperature changes. The variable pitch prop is named correctly in that it varies prop rpm. Many pilots miss the definition and assume it's variable, so they have to vary it all the time. Pick one setting for each phase of flight,and then assume you just swapped out a fixed pitch prop designed for that flight phase and don't change it until you enter another phase.

flight phase MP * RPM

Takeoff full max

Climb 25" 2500

Cruise 23" 2400

Sightseeing 16" 2100 (slow quiet orbiting)

Downwind 13" 2400

Base as required max

ILS at middle marker 17" 2400
ILS at inner maker as required max

* mp's assume you can get that much, otherwise full in.

There are a few other details around mixture and when to use gear and flaps, and while there are lots of ways you "can" use different prop speeds, I've found unless you are setting speed or endurance records, all you need to remember and use is:
max takeoff power,
normal climb power,
cruise power
quiet settings.
short final (ie, ready for max power if you need to go around)
 
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kelly thanx for the reply..

that clarified things a little more...

i guess its not the prop that is directly related to performance...i think i was getting the idea that you can change the pitch of the prop in some cases and leave the power setting alone and you can get different performance...

so for instance, you say 2400 for cruise.. if i needed to get soemwhere asap and had no time to spare, would i still cruise at 2400rpm or would i adjust the prop slightly??

also why such a big difference in the setting for sightseeing??
Does this prop setting help keep the plane moving while the engine barely works?? or is this the setting that the prop is the most quiet in?

haha i almost got the basics understood...only a few more Q's..:D

Ant
 
so for instance, you say 2400 for cruise.. if i needed to get soemwhere asap and had no time to spare, would i still cruise at 2400rpm or would i adjust the prop slightly??
I would go 25" and 2500 for fast. (loud and large full burn).

also why such a big difference in the setting for sightseeing??
Does this prop setting help keep the plane moving while the engine barely works?? or is this the setting that the prop is the most quiet in?
I use the lower prop setting to lower noise since I'm usually taking passengers up over points of interest. I still leave more than minimum power and prop so I'm no where near stall.. the numbers aren't exact, but what I'm looking to get is lower fuel use, lack of vibration and quiet running while we circle and take pictures.
 
SupraPilot said:
also i am trying to get it down on FS2004 before i do the actual flying and i am putting myself in situations and trying to figure out how the prop should be set...
Click to expand...
Don't use FS2004 this way.
SupraPilot said:
so what are the proper cruise settings??
also what do you do when transitioning from cruise to climb some more??
If i was level flight and wanted to fly as fast as posible would i just go full power and push the prop all the way in??
Click to expand...

Like I said above, READ THE POH. If you want to know about your bird, that's what you do. Prepare for your checkout like it is a checkride in that bird, by studying the POH.
SupraPilot said:
And finally in general what should i expect from the 182 over a 172 or my usual Warrior??
Click to expand...
Slightly faster speeds, more room, heavier controls. It is an overgrown Skyhawk.
 
SupraPilot said:
Does this prop setting help keep the plane moving while the engine barely works?? or is this the setting that the prop is the most quiet in?

haha i almost got the basics understood...only a few more Q's..:D

Ant
Click to expand...

STOP RIGHT NOW. I am not trying to be a jerk, but seriously--read the POH. That is how best to prepare and understand what will happen.
 
SupraPilot said:
kelly thanx for the reply..

that clarified things a little more...

i guess its not the prop that is directly related to performance...i think i was getting the idea that you can change the pitch of the prop in some cases and leave the power setting alone and you can get different performance...

so for instance, you say 2400 for cruise.. if i needed to get soemwhere asap and had no time to spare, would i still cruise at 2400rpm or would i adjust the prop slightly??

also why such a big difference in the setting for sightseeing??
Does this prop setting help keep the plane moving while the engine barely works?? or is this the setting that the prop is the most quiet in?

haha i almost got the basics understood...only a few more Q's..:D

Ant
Click to expand...

Its just like an automatic transmission in your car. Think about downshifting to pass someone (Prop full forward). Just like being in a lower gear, it's easier to go uphill in 1st, than in 3rd right?

However you don't go screaming all over town in 1st gear. You've got a lot of power, but that would just wear on the moving parts a lot.

When you pull the prop back, the speed of the prop is forced to be held constant and the blades change pitch to keep that prop speed.

If you had to go somewhere fast, you could push that prop controll all the way in and run at your max continuous power. Might not be a good idea, but you 'could'. (ie my disclaimer, read the POH...) Some turbo engines only let you run MAX power for a short period of time.


For me, I'll dial the prop back a tad right after takeoff for noise issues at my home base. In cruise climb, I set it at 2500 RPM and full MP. After passing through 5k feet, you're at 25/25 roughly and I leave it WOT and 2500 rpm until I level off.


Also don't confuse a variable pitch prop with a constant speed prop. :)
 
lancefisher said:
What condition are you thinking of here Ron? As long as you stay out of detonation, serious short term engine damage due to low (or high) RPM seems pretty unlikely to me on a non-turbo'd engine.
Click to expand...
Oh, say, slamming full throttle at sea level in a 182 with the prop in the governed range at maybe 1900 RPM. You will hurt the engine doing that.

I'd be curious as well to hear how anyone could "explode" a turboprop by mis-positioning the "prop" control. (per the original poster's CFI, not Ron).
Click to expand...
I'm sure that there are ways to cause the gear box to come apart if you overdrive the prop.
 
spiderweb said:
STOP RIGHT NOW. I am not trying to be a jerk, but seriously--read the POH. That is how best to prepare and understand what will happen.
Click to expand...

i know your not tryin to be a jerk but i do not have the POH for this specific airplane, and i DO NOT trust generic ones( i have already had bad experience with a generic checklist/POH for the warrior)..i wouldnt waste my time writing here if i could just read it and be done with it..also liek i said..the more i read about this subject the more questions i have..i am doing this so i dont overload my instructor with stupid questions..i wanna know as much as possible so i can learn even more from the intructor....also the POH isnt gonna give me specific details..it just suggests power setting and prop setting for different stages of flight...

also why should i not practice with fs2004?? isnt it a simulator .i mean i practice other things like IFR procedures and things like that..are you saying the flight model in fs2004 isnt THAT good??..becasue i think this sometimes myself...

Ant
 
also Air Baker i see that you say you pull the prop back slightly after takeoff for noise reasons...I am assuming from this that pulling the prop back doesnt really effect the performance..What i mean is, that by making it quieter (pulling prop back) your not sacrificing climb performance or anything like that since your still at full power right??

also i didnt even think there was a difference between constant speed and variable pitch props..i thought it was just 2 different names for same thing...

hehe if you guys didnt already figure this out..i am ALL about performance wether it be in an airplane, a car, a boat, or whatever..im always lookin for ways to get the most out of it...


Ant
 
SupraPilot said:
also Air Baker i see that you say you pull the prop back slightly after takeoff for noise reasons...I am assuming from this that pulling the prop back doesnt really effect the performance..What i mean is, that by making it quieter (pulling prop back) your not sacrificing climb performance or anything like that since your still at full power right??

also i didnt even think there was a difference between constant speed and variable pitch props..i thought it was just 2 different names for same thing...

hehe if you guys didnt already figure this out..i am ALL about performance wether it be in an airplane, a car, a boat, or whatever..im always lookin for ways to get the most out of it...


Ant
Click to expand...

- For the first part, you do lose some performance by pulling the prop back. The general rule is that you don't make any power changes until 1000' AGL in case you have a problem. With the noise sensitive neighbors, I try to be a little nicer and dial it back 50-100 rpm. It makes a huge difference in noise reduction on a 2 blade prop and I don't have any trees to dodge at the end of the runway. (For your checkout, don't do this...) :)

- They're similar but some aircraft, including the early Bonanzas had an electric prop control. The constant speed prop is a variable pitch prop that has a mechanical governor that holds the prop at a specifc speed. (at least that is the short version).
 
Kelly said:
so for instance, you say 2400 for cruise.. if i needed to get soemwhere asap and had no time to spare, would i still cruise at 2400rpm or would i adjust the prop slightly??
I would go 25" and 2500 for fast. (loud and large full burn).
Click to expand...

Any engine will make more power at a higher RPM and the same throttle setting or MP. There are infinite combinations of RPM and MP that yield the same thrust HP (power delivered by the prop) and therefore the same airspeed all else being equal. Typically the higher the RPM the worse the economy for the same airspeed because the efficiency of the prop drops pretty dramatically with RPM increases. Noise (inside and out) also increases with RPM and both noise and efficiency are noticeably worse when the prop tips reach transonic speeds (around 1100 fps). Most engines have limitations on the extremes of low RPM and high MP but below 60% power it's hard to hurt a normally aspirated engine by running RPM too low (but still in the green on the tach).

I typically cruise with the throttle wide open above about 5000 DA and use the prop and mixture to set the power (yes the red knob is very effective at controlling power on a fuel injected engine), and will normally use the lowest RPM that produces the power and TAS I want. Since my engines are normally aspirated, the higher I go the more RPM I need to achieve the same TAS, so up high I might run 2400-2500 and at lower altitudes it might be 2200-2300. For max range (approx 120 KIAS vs 150-175 KIAS for normal cruise) I'd use 2100 RPM (bottom of the green arc) unless I was so high that didn't give me enough power (like above about 15000 MSL).


also why such a big difference in the setting for sightseeing??
Click to expand...

Normally for sightseeing you want to go slow and burn as little gas as possible. That means minimum RPM and reduced MP.

Does this prop setting help keep the plane moving while the engine barely works?? or is this the setting that the prop is the most quiet in?
Click to expand...

As explained above, the answer is both. The prop is more efficient and produces less noise at the lowest RPM.
 
AirBaker said:
- For the first part, you do lose some performance by pulling the prop back. The general rule is that you don't make any power changes until 1000' AGL in case you have a problem.
Click to expand...
And just to clear the air on that, the reason is because full RPM will gain altitude and/or airspeed more rapidly than less than full RPM. You will often hear pilots quoting the OWT that an engine failure is most likely to occur during the first power reduction, but there is no data to support that at all.

With the noise sensitive neighbors, I try to be a little nicer and dial it back 50-100 rpm. It makes a huge difference in noise reduction on a 2 blade prop and I don't have any trees to dodge at the end of the runway. (For your checkout, don't do this...) :)
Click to expand...


The idea is to get the prop tip speed below the transonic region where they can get really loud. On large engines (>200 HP) a two blade prop large enough to absorb that power efficiently will likely go transonic between 2500 and 2600 RPM. A three blade prop for the same engine is usually enough smaller in diameter that this problem is avoided until you get upwards of 300 HP.
 
Here is a good example of a Power Setting Table (word doc) for a 180 HP lycoming engine, similar to what would be in PA28R-180 Arrow. You'll see that all things being equal (altitude and temperature) you can get the exact same power by going "over square" and running a high MP with the prop at a slower RPM.

(Here is the same graph in HTML if you don't want to open it in Word...it just isn't formated as well)
 
SupraPilot said:
i know your not tryin to be a jerk but i do not have the POH for this specific airplane, and i DO NOT trust generic ones( i have already had bad experience with a generic checklist/POH for the warrior)..i wouldnt waste my time writing here if i could just read it and be done with it..
Click to expand...

Then, the very first thing you need to do is to get a copy of the POH for your specific airplane. Still, the "generic" ones should still be very accurate from an operational standpoint, unless the specific airplane has had an different engine put in.
SupraPilot said:
also liek i said..the more i read about this subject the more questions i have..i am doing this so i dont overload my instructor with stupid questions..i wanna know as much as possible so i can learn even more from the intructor....also the POH isnt gonna give me specific details..it just suggests power setting and prop setting for different stages of flight...
Click to expand...
The POH *will* give you very specific details--so many details, in fact, that you can sit there at a desk for over an hour working out different cruise/climb/descent scenarios. The POH will also have recommendations on handling the mixture in different regimes. If you don't want to have to ask your instructor stupid questions, have the POH down pat. Personally, I don't think there are any stupid questions, but the more you know from the POH, the more probing your questions will be.

[/QUOTE]
SupraPilot said:
also why should i not practice with fs2004??
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It is not accurate for what you want--prop/MP settings and practice. It may even confuse you.
SupraPilot said:
isnt it a simulator .
Click to expand...
No.
SupraPilot said:
i mean i practice other things like IFR procedures and things like that..are you saying the flight model in fs2004 isnt THAT good??..becasue i think this sometimes myself...

Ant
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That's what I'm saying.

Read up, and have fun!
 
yeah ben ..i guess it might be fs2004 thats confusing me...
ya know they advertise as the most realistic flying EVER and blah blah..and when i fly in fs2004 i ALWAYS think that the flight models and speeds arent even close...especially the power and prop settings...
idk i thought i was missing something becasue i flew in a aircraft with a CS prop and it was nothing like it seemed in fs2004...

i guess i wont trust that game much anymore..
Ant
 
I think the biggest problem (or benefit) with flight sims, is that you can do things in the Sim that you just shouldn't do in real life.
 
I do enjoy FS2004 for the computer gaming fun it gives me, and I do use it to refresh IFR procedures (though I'd caution using it to train IFR, except under CFII guidance).
 
SupraPilot said:
ok this all seems like good info..keep it comin guys..
hopefully when i get in the plane i have some sort of an idea of what i should do..
also i was talkin with another flight instructor and he said that prop management isnt a HUGE issue on a piston engine aircraft but when yoiu transition to turbo prop type of aircraft he said th prop speed and all that are critical because if it is done wrong he said the engine can literally explode..
Click to expand...

Nahhhh, you're trollin now, no one is stupid enough to say or believe that. Turbo prop engines are specifically designed so trained monkeys can operate them. Once started and spun up, a turbine is nearly impervious to any operator input. Where handle management is most critical is in geared high performance engines. GTSIO, GO, TGIO... all designate geared engines. It's no great trick to operate them properly, you just have to be aware that the geared down prop carries great inertia and to make your adjustments smoothly. The most critical is power reduction. I am of the school that once the manifold pressure is back to max continuous that power reduction should be done first through the prop until you need to reduce power below the level of minimum RPM. Once you get there then you start pulling back the throttle (or if I'm at altitude in a turbo with manual waste gates, turn down the turbo). Typical profile for me in a plane like my Travel Air which had manual control turbos. Take off :28"MP 2700 RPM redline rotate, come off, positive rate gear up keep the nose down and plane in ground effect until blue line (110kts) then start climbing at 110 to 500 ft then bring the props back to 2500 pitch down for 125-130 at 1000, bring the props back to 2425 and trim throttles to 25" and manage that power with the throttles and wastegates until I could no longer make it (full throttle/turbo) or I hit top of climb. Top of climb I have to decide how fast I want to go. I wasn't exactly rich so I went for the fuel economy option most of the time I was paying for the fuel. That had me around 2160 ish and 24.5" MP. The engine had a real sweet spot there where she got smooth and comfy. Always remember, no matter what a book says about a power setting, if she don't sound and feel happy, it's not good, change something, typically RPM. Usually 15 or 20 RPM will get it out of its unhappiness. Just listen, she'll let you know. But don't be afraid to put her under a load either. The higher the mean effective cylinder pressure you can achieve without going into detonation, the better off you and the engine are.

SupraPilot said:
reason i think i am so confused is that ive been for rides in larger aircraft and it seems that every pilot does it a different way..
i mean i took a quick flight a long time ago with a guy to hop over to a nearby airport and we flew a 182...but i remember i was watching him to see how the CS prop works but he never once touched the prop control..he left it all the way in and just flew the plane (for the short 8 minute flight)like a pixed pitch prop...and ive seen other pilots who almost worship the prop control and they are always adjusting it for different stages of flight...

also from what i am getting from all of this is, that is seems that basically its is BAD if the engine goes faster then the prop...is this correct? or is there other situations where these rules are thrown out the door??

Ant
Click to expand...

If the engine on a 182 goes faster than the prop, yes, that would be a bad thing. This feels like something under the bridge....
 
SupraPilot said:
also i am trying to get it down on FS2004 before i do the actual flying
Click to expand...

Don't bother. The flight model in FS2004 is simply not realistic. FS2004 is not a simulator, it's a game.

If you want a much more realistic flight simulator, try X-Plane. http://www.x-plane.com/ X-Plane is good enough that it's FAA-approved for several different things, if combined with the right hardware.

As for your original question, here's the basic gist of constant-speed props: The prop control varies your RPM (but you knew that). The amount of power varies the actual pitch. So, if you stay at a constant prop setting but you push the throttle in, the prop will simply take a bigger bite of the air so that it remains at the same RPM. If you leave the throttle the same but change the prop setting, the blade pitch will vary to match. (Lower RPM = bigger bite of the air, higher RPM = "flatter" pitch)

Read the links Ron posted, Deakin's articles are great. "Manifold pressure sucks!" :D

Hope this helps,
 
spiderweb said:
Slightly faster speeds, more room, heavier controls. It is an overgrown Skyhawk.
Click to expand...

Well... Yes and no. It's faster, wider, and can carry more. However, it really doesn't fly anything like a Skyhawk. It definitely demands more respect.

Two things about the 182 for the transitioning 172 pilot:

1) Tendency to porpoise (The nose is heavier with the bigger engine.) If you bounce, add a little power (1000 RPM or so). If you bounce again, GO AROUND. If you bounce a third time, you will have a prop strike.

2) On the 182 I fly, Vx = Vs1. That means that if you're climbing out at Vx and your engine fails, you'd better get that nose pushed over NOW or you'll stall.

Definitely read the POH. Get one for the specific year of 182 you'll be flying at http://www.esscoaircraft.com/ and that'll give you good info.

As for what I do (1971 182N, max RPM 2600): Wide open throttle. Prop full forward for takeoff, back to 2500 when practicable for noise abatement and used for cruise climb throughout the flight, and down to 2200 (bottom of green arc) for cruise. Pitch over for descent, pulling throttle a bit if I get too fast. Descent from TPA at 12" and put the prop back full.

Don't forget the cowl flaps too...
 
flyingcheesehead said:
Well... Yes and no. It's faster, wider, and can carry more. However, it really doesn't fly anything like a Skyhawk. It definitely demands more respect.
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A 182 also moves you into the category of airplane where the flying characteristics (besides climb rate) can change dramatically with different legal loads. A fully loaded 182 can get so far behind the power curve on descent that you can't dig your way out by just opening the throttle a bit as inertia and wing loading can be much higher. This occasionally comes as a surprise to a newbie 182 pilot or two.
 
SupraPilot said:
kelly thanx for the reply..

that clarified things a little more...

i guess its not the prop that is directly related to performance...i think i was getting the idea that you can change the pitch of the prop in some cases and leave the power setting alone and you can get different performance...
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We are not talking turbines here. The Power Setting is the combination of throttle and prop. The Prop governs the top end of the RPM thereby limiting the maximum power produceable. It does not come into effect until the engine tries to turn faster than the specified RPM. This is why it doesn't make a difference if you pull back the handle during an engine out or not, a windmilling engine isn't turning enough RPM for the governor to bring the prop pitch down. By limiting RPM, you limit the amount of air that can flow through the engine. The fuel system meters the air coming through the engine and the carb/fuel servo adjusts the amount of fuel being put in accordingly. If you pull back the throttle, you restrict the air/fuel going into the engine and the governor reacts by decreasing pitch to maintain the RPM you are requesting by flattening the pitch on the prop and reducing the load for the reduced power output. Now, lets say we set power for 70% (the following is using arbitrary but reasonably accurate numbers). We can achieve 70% by a range of prop and throttle settings. Lets use 2500 RPM and 22 inches or 2100 RPM and 25 inches. Power is directly related to the amount of fuel you put through the engine so the 70% power is going to use 10 gph regardless which method you use. Here's the catch, drag goes up by the cube of speed on everything involved from the reciprocating revolving assembly to the propeller, so the hp required to turn the assembly at the higher RPM setting is higher. This means more of your 70% of power is absorbed turning the engine/ prop leaving less excess to pull on the plane.
SupraPilot said:
so for instance, you say 2400 for cruise.. if i needed to get soemwhere asap and had no time to spare, would i still cruise at 2400rpm or would i adjust the prop slightly??

also why such a big difference in the setting for sightseeing??
Does this prop setting help keep the plane moving while the engine barely works?? or is this the setting that the prop is the most quiet in?

haha i almost got the basics understood...only a few more Q's..:D

Ant
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If you need Max speed, everything goes to the firewall (or max continuous) and you lean to 50* rich of prime. You hope it holds together or you'll be real late, and you pay for the fuel.
 
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Henning said:
This is why it doesn't make a difference if you pull back the handle during an engine out or not, a windmilling engine isn't turning enough RPM for the governor to bring the prop pitch down....

...If you need Max speed, everything goes to the firewall (or max continuous) and you lean to 50* rich of prime. You hope it holds together or you'll be real late, and you pay for the fuel.
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Henning these two small excerpts from your otherwise factual and informative post are a bit in error.

First, pulling back the {prop} handle during an engine out does make a difference on every single I've tried it on. It itsn't that you are significantly reducing the RPM, but rather that you are getting the prop off the fine pitch stops that decreases the drag of the windmilling prop enough to almost double your glide range on a slippery airframe.

Second, if it's max speed you want (and efficiency isn't a concern), you need to be about 100°F ROP not 50.

Granted these are nits, but such errors are not up to your usual standards.
 
lancefisher said:
Henning these two small excerpts from your otherwise factual and informative post are a bit in error.

First, pulling back the {prop} handle during an engine out does make a difference on every single I've tried it on. It itsn't that you are significantly reducing the RPM, but rather that you are getting the prop off the fine pitch stops that decreases the drag of the windmilling prop enough to almost double your glide range on a slippery airframe.

Second, if it's max speed you want (and efficiency isn't a concern), you need to be about 100°F ROP not 50.

Granted these are nits, but such errors are not up to your usual standards.
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As to the windmilling prop, It didn't do a thing for me in a Cardinal or a 210. At best glide neither engine was turning over 1700 RPM so the governor had nowhere to seek. Ever since I've reasoned for any next plane will have a feathering prop, preferably reversable. You get to like having that especially if you consider floats.

As to the 50*, that was 50*C;) . Really, how do you work out 100 rather than 50?
 
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