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Warpig

RPM Setting vs Prop Pirch

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I've always assumed that a plane either has RPM or Prop pitch but never both. Because of this, I've always combined those controls into one. Is it possible for an aircraft to have both settings?

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Posted (edited)
9 minutes ago, Warpig said:

I've always assumed that a plane either has RPM or Prop pitch but never both. Because of this, I've always combined those controls into one. Is it possible for an aircraft to have both settings?

Most aircraft in the game have an automatic RPM govenor that sets prop pitch for you. An example of an aircraft that has both controls is the 109 where you can turn the automatic govenor off and then chance the propeller pitch manually. 
So yes, basically all aircraft that have RPM settings have prop pitch control. Just depends if you can turn off the automatic govenor of the aircraft.

Edited by Psyrion
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The P-40, P-39 and P-47 have both controls, but in order to manually adjust the pitch you have to deactivate the RPM governor first.

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1 minute ago, -=PHX=-SuperEtendard said:

The P-40, P-39 and P-47 have both controls, but in order to manually adjust the pitch you have to deactivate the RPM governor first.

Is the governor deactivated simply by turning on manual prop pitch?

 

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1 minute ago, Warpig said:

Is the governor deactivated simply by turning on manual prop pitch?

 

Yes, they keybind is called "Switch propeller pitch control mode: manual/auto".

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Think of RPM as your gas pedal when driving a car, and prop pitch as your gear shift.

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Posted (edited)

Okay, makes sense now. I vaguely remember finding a plane that had both, and thinking "everything I know about Prop pitch has been undone".

 

This kind of clears things up for me.

 

 

Edited by Warpig

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Posted (edited)

Requiem has some great vids that cover C.E.M. and explain constant-speed props vs. variable-pitch props.  Constant-speed props are kind of a "set and forget" system where you dial in the RPM you want and the prop hub has controls to automatically vary prop pitch to maintain that RPM, like an automatic transmission in a car.  P47 is a great example.  Variable-pitch props are a slightly cruder system where you dial in the prop pitch you want in order to achieve a desired RPM for the current flight conditions...but put the plane in a climb or dive, and the RPM will speed up or slow down, respectively, with airspeed, so you're frequently adjusting the pitch to stay at a target RPM (manual transmission).  HS129 is a great example. 

 

Like the two different transmission types, you never have both types of control at the same time (do you recall what plane it was that seemed to have both?) so it's ok to bind the same buttons/axis to both actions, at least no ill effects I've seen.

 

Edited by Stoopy
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The earlier Pe-2 series 35 prop governors are, IIRC, controlled by the increase/decrease prop pitch button rather than the increase/decrease RPM button. The series 87 is the other way. Just a little quirk of how they've modeled it.

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1 hour ago, Stoopy said:

Like the two different transmission types, you never have both types of control at the same time (do you recall what plane it was that seemed to have both?) so it's ok to bind the same buttons/axis to both actions, at least no ill effects I've seen.

 

As long as I can keep them both bound to the same control, I'm happy. 😁 That's exactly what I wonted to confirm.

 

 

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Think of an automatic car (some automatics anyway) that shift too soon when you're wanting more torque/revs to climb up a hill.

 

It shifts due to how much gas you're sending through the carburetor, but in that situation you're actually wanting to remain in the power band rather

than shift up.

 

Or imagine wanting to coast down a hill under very little gas, and needing you highest gear.

 

I'm generalizing and some aircraft operate fine like you mention, and are designed to be operated in this way,  but again generalizing,  this is why it's desirable to maintain control over both separately in the appropriate aircraft.

 

 

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Posted (edited)

I think people are getting a little confused.  A constant speed prop is a variable pitch prop.  The write up in the manual doesn't help but see here...

https://en.wikipedia.org/wiki/Constant-speed_propeller

 

Basically you set the speed (constant speed) you want with the Prop Lever and the governor changes the pitch of the Prop (variable pitch)  as required to maintain that.

 

The manual setting on some aircraft is you manually setting the pitch - when you do this the RPM will change depending on the load on the prop - same as a fixed pitch prop - because you've manually set a fixed pitch.  So if you dive the RPM will increase and if you climb it will decrease.

 

The Bf109 and Fw-190 had are fitted with an electro-mechanically automatic pitch regulator.  When the automatic position was selected by the pilot, a governor automatically set the ideal combination of engine boost and revolutions for any throttle position and pitch change. This simplified the pilot’s task and optimized engine life and range.  

Edited by Mikoyan74
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16 minutes ago, Gambit21 said:

Think of an automatic car (some automatics anyway) that shift too soon when you're wanting more torque/revs to climb up a hill.

 

It shifts due to how much gas you're sending through the carburetor, but in that situation you're actually wanting to remain in the power band rather

than shift up.

 

Or imagine wanting to coast down a hill under very little gas, and needing you highest gear.

 

I'm generalizing and some aircraft operate fine like you mention, and are designed to be operated in this way,  but again generalizing,  this is why it's desirable to maintain control over both separately in the appropriate aircraft.


A good analogy Gambit.

As for OP, seems everyone else has covered what I would have said. Just engage manual prop pitch to get the additional control flexibility you seek! Probably the only plane that adjusts rpms with prop pitch is the HS-129b Duck. The JU52 also ties its throttle at below 25% with braking, making it an oddball as well. 

4 minutes ago, Mikoyan74 said:

The Bf109 and Fw-190 had are fitted with an electro-mechanically automatic pitch regulator.  When the automatic position was selected by the pilot, a governor automatically set the ideal combination of engine boost and revolutions for any throttle position and pitch change. This simplified the pilot’s task and optimized engine life and range.  

 

True, however a pilot can squeeze more speed out of an engine in straights using manual prop pitch. So governed is not always the most suitable choice. Though a pilot should not just do these adjustments on the fly without knowledge as over revving the engine can easily destroy the engine entirely.

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Posted (edited)
8 hours ago, Gambit21 said:

Think of RPM as your gas pedal when driving a car, and prop pitch as your gear shift.

 

43 minutes ago, Gambit21 said:

Think of an automatic car (some automatics anyway) that shift too soon when you're wanting more torque/revs to climb up a hill.

 

It shifts due to how much gas you're sending through the carburetor, but in that situation you're actually wanting to remain in the power band rather

than shift up.

 

Or imagine wanting to coast down a hill under very little gas, and needing you highest gear.

 

I'm generalizing and some aircraft operate fine like you mention, and are designed to be operated in this way,  but again generalizing,  this is why it's desirable to maintain control over both separately in the appropriate aircraft.

 

 

 

 

You've really lost me here, Gambit.

 

In my admittedly limited experience with control of propeller pitch, I have only noticed two options:

 

1) Constant-speed propeller: Pilot specifies the desired RPM of the shaft, and the hydraulic or electrical mechanism automatically alters the angle of the blades in the propeller hub to maintain the desired RPM as the "load" on the prop - imposed by manifold pressure of the engine and the aircraft's speed through the air - changes. (Edit: with this system the RPM control is sort of like the "gear" and the throttle controlling the manifold pressure is the "Gas Pedal")

 

2) Non-automated variable pitch propeller: a less advanced system where the pilot only specifies the actual angle of the blades in the propeller hub and the RPM of the shaft varies faster or slower based on the engine's manifold pressure and the aircraft's movement through the air. (edit: constant-speed-prop aircraft with a "manual" control option can also be operated this way).

 

Both achieve the same objective of allowing the pilot to choose how fast the propeller rotates, the first offering more safety from over/underspeed and reducing pilot workload.

 

Are you suggesting in the text that I have bolded above that there are systems where the pilot can specify the desired RPM of the shaft as well as the actual angle of the blades in the hub? Which aircraft allows this and how would that work?

 

Not trying to bust your chops here, I just feel like I've been living in some alternate reality all this time 😂

Edited by Rekt

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Yes it is possible with Manual intervention to gain more power but it will be a trade off  - a newer inexperienced pilot could damage the engine by failing to keep the engine within its limitations - I think this is why the 109 and 190 are quite popular with newer players as only one control to worry about - Rads, Mixture, Prop - all auto as standard.

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17 minutes ago, Rekt said:

 

 

Are you suggesting in the text that I have bolded above that there are systems where the pilot can specify the desired RPM of the shaft as well as the actual angle of the blades in the hub? Which aircraft allows this and how would that work?

 

Not trying to bust your chops here, I just feel like I've been living in some alternate reality all this time 😂

 

LOL

No brain saw "throttle/prop pitch" rather than rpm/prop pitch.

So I sort of responded to a different query.

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53 minutes ago, Mikoyan74 said:

Yes it is possible with Manual intervention to gain more power but it will be a trade off  - a newer inexperienced pilot could damage the engine by failing to keep the engine within its limitations - I think this is why the 109 and 190 are quite popular with newer players as only one control to worry about - Rads, Mixture, Prop - all auto as standard.

 

That, and the amount of power increase is so negligible that it's just not worth the bother. 

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Posted (edited)

Prop Pitch is what changes in order to achieve RPM

 

That is, any plane with a powerful engine should have a variable pitch propeller. Such a propeller can turn its blades so they bite deeper into the air, thus providing more power without having to spin so fast that the tips would break the speed of sound (loud and inefficient) 

 

That is what the "prop pitch" control does - it directly changes the pitch of the blades.

 

However, managing this by hand requires the pilot to constantly check his RPM as the airplane speeds up or down. That's a chunk of your attention span you may not wanna spend when people are behind you shooting guns in your general direction.

 

 

So enter the constant-speed propeller, and with it the "RPM" control.

 

A CS Prop has a built-in governor, (not a politician) a mechanical device that detects engine rpm and affects some output (usually oil pressure) to cause the propeller to automatically change the pitch of its blades.  In consequence, with increasing RPM,  the propeller is made to bite harder, which in turn causes the engine to slow down, satisfying the governor by returning it to the speed the pilot has selected (by way of the RPM control setting)

 

 

As to the original question:  It's perfectly ok to set both RPM and Prop Pitch controls to the same inputs on your joystick or keyboard - in 99% of situations, you would not have the two options on a single plane

 

exception:

 

the P40 has an override switch that allows you to disconnect the electric governor and take manual control of prop pitch. This is mainly used in emergencies however, and in any case, you would not be able to use the RPM control with the override on. So you can still have the same buttons for the two "flavours" of propeller control and never run into any problems in the sim.

 

 

IL2-Specific Note:

 

Planes like the Pe-2 that have an electric switch instead of a lever on the cockpit to set the governor target RPM usually respond only to the "prop pitch" controls - this is done so to better represent the  indirect non-axis operation in the real cockpit. (that is: it requires you to push and hold the switch until you get the setting you want, rather than just move the lever and leave it there) 

 

It does not mean the Pe2 does not have a CS prop. It's just a workaround taken by the IL2 devs to make it more realistic without making a mess out of their input logic.

 

 

 

 

 

 

 

 

 

 

 

 

Edited by 19//Moach
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17 hours ago, Mikoyan74 said:

Yes it is possible with Manual intervention to gain more power but it will be a trade off  - a newer inexperienced pilot could damage the engine by failing to keep the engine within its limitations - I think this is why the 109 and 190 are quite popular with newer players as only one control to worry about - Rads, Mixture, Prop - all auto as standard.

for example where is usefule to turn of auto i think that on 109g2, where you dont have emergancy power, abow 6km you can gain 20kmh and better climb if you turn off auto prop and increse rpm manualy to simulate same but better emergancy power you get for 109G4 on auto, and for up to 2min is ok, and will not brake engine, on lower alts it dosent make any differance. Also on P-47 abow 8km you can also turn off auto rpm and go to 3000rpm and gain climb and speed you could not on auto, also on lower alts doesent make any differance.

This is type of aditional key pressing that can mather in flying combat game, unlike aditional repetative, boring, no dexterity needed and totaly unnecesary key pressing that they added with last patch on starting the airplane for no reason what so ever exept to frustrate players that spend time playing the game more then 1 time a month 😄

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3 hours ago, 77.CountZero said:

 

This is type of aditional key pressing that can mather in flying combat game, unlike aditional repetative, boring, no dexterity needed and totaly unnecesary key pressing that they added with last patch on starting the airplane for no reason what so ever exept to frustrate players that spend time playing the game more then 1 time a month 😄

Some day, I have faith that you will heal from this horrible trauma.

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20 minutes ago, RedKestrel said:

Some day, I have faith that you will heal from this horrible trauma.

already had to replace one parrot, money could go elswere but now i have to buy new parrot every few weeks, oh the tragedy 😄

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Just had to check. At 3 keystrokes per engine start per month (including spaces), that was just shy of 9 years and 4 months' worth of engine starts.

 

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