Prop Pitch/Engine RPM Question (possibly stupid question)

[fogster]

In the manual the lever is labelled "Propeller pitch lever", however in DCS the lever is labelled "Engine RPM lever". Are these two the same thing or is one of the labels incorrect. Also is this the lever that is referred to when they talk about proper pitch?

[fjacobsen]

In the manual the lever is labelled "Propeller pitch lever", however in DCS the lever is labelled "Engine RPM lever". Are these two the same thing or is one of the labels incorrect. Also is this the lever that is referred to when they talk about proper pitch?

 

 

Yes - it´s the same.

[bbrz]

In the manual the lever is labelled "Propeller pitch lever", however in DCS the lever is labelled "Engine RPM lever". Are these two the same thing or is one of the labels incorrect. Also is this the lever that is referred to when they talk about proper pitch?

Further info; Increasing propeller pitch decreases engine RPM and vice versa. 'Proper' (whatever this means) pitch usually refers to the pitch attitude of the airplane, not propeller blade pitch.

[lmp]

Engine RPM lever is technically more correct cause that's what you're controlling with it - the change in prop pitch is just the "mean to an end". But calling it the prop pitch lever is really no worse than calling the engine control lever of a modern jet the throttle lever.

[fjacobsen]

Further info; Increasing propeller pitch decreases engine RPM and vice versa. 'Proper' (whatever this means) pitch usually refers to the pitch attitude of the airplane, not propeller blade pitch.

 

 

Normally the angle of the propeller blades are also refered to as pitch and the lever simply called prop lever.

 

 

Calling it Engine RPM is somewhat wrong, since it only sets the engine rpm to a certain value if the propeller governor has something to work with i.e if the throttle is set near idle and the airspeed is low, then engine rpm will drop regardless of the prop lever setting.

 

 

With the prop lever You essentially tell the prop governor which prop rpm You would like it to spin at, and the governor will adjust the propeller pitch accordingly, though within limits. So the prop lever does not set propeller pitch directly.

 

 

All this offcourse only holds true for constant speed props.

 

 

There are also variable pitch propellers, where the prop lever will set propeller pitch directly and thus calling it prop pitch lever is right.

[bbrz]

The point is that you don't set a certain pitch, e.g. 15° with the prop lever, you set a certain RPM!

 

Your example with idle throttle and low speed doesn't make any sense, since you would never try to set a certain RPM with the propeller not being within the governing range.

Edited August 9, 2018 by bbrz

[fjacobsen]

The point is that you don't set a certain pitch, e.g. 15° with the prop lever, you set a certain RPM!

 

Your example with idle throttle and low speed doesn't make any sense, since you would never try to set a certain RPM with the propeller not being within the governing range.

 

And what rpm do You get with prp lever full forward (high rpm / fine pitch) throttle at idle standing still on the ground ?

Definitly You don' t get high rpm.

[lmp]

What does the lever do? It controls the RPM governor. What does the pilot want when he moves it? To set the RPM. Thus - RPM lever.

 

At idle/low throttle moving the lever forward (beyond the RPM the engine can achieve) will not change the RPM... nor the prop pitch! The prop pitch will be at the fine stop. As soon as you pull it back to the point where you are changing pitch with it you are also changing RPM. So if that argument makes it not the RPM lever, it also makes it not the prop pitch lever. I don't know what do you want to call it at this point ;).

[bbrz]

+1

 

 

And what rpm do You get with prp lever full forward (high rpm / fine pitch) throttle at idle standing still on the ground ?

Well, this example is even worse then your approach example. And what RPM do you get with the engine shut down?:lol:

Edited August 10, 2018 by bbrz

[fjacobsen]

Please read my initial post once again.

 

 

I guess we all can agree on this posted by bbrz: "The point is that you don't set a certain pitch, e.g. 15° with the prop lever, you set a certain RPM!"

 

 

Only caveat ist that You don´t set a certain RPM, but set a desired RPM, and the prop governor will adjust the prop pitch to achieve that RPM, but it can only achive this within certain limits (low and high stops of the prop pitch).

Generally for such constant speed props, You might see rpm drop with low throttle setting and low speed (f.ex during approach, standing still and offcourse with the engine stopped ), cause there is not sufficient airflow to windmill the prop to the set desired rpm. Also on the extreme, going into a steep dive, the govenor will lower prop pitch, but once reaching it´s low stop, prop RPM will start to increase.

 

So in most conditions the prop lever might be refered to as engine rpm lever, cause thats what it will do, but still only within certain limits.

 

 

A better and also most used name for it is Prop control lever, cause that's universally usable for the different kind of propeller systems i.e Constant speed, variable pitch or two state props (as used on the very early Spitfires f.ex).

The BF-109 and FW-190 f.ex did not have constant speed props, but variable pitch props, where the throttle and prop levers where combined into one lever (called Kommandogerät on the FW-190).

[fogster]

Soooo, keep the lever all the way forward for maximum thrust?

[bbrz]

Yes. But there's a 5min time limit for max power!

 

Max continuous power requires an RPM reduction to 82% (and 855mmHg at Sea Level and 15°C)

[fogster]

Yes. But there's a 5min time limit for max power!

 

Max continuous power requires an RPM reduction to 82% (and 855mmHg at Sea Level and 15°C)

 

that explains the engine dying with fuel still left in the tanks. I figured it had to do with keeping it at full power.