Why reduce RPM?

[grafspee]

2 hours ago, Nealius said:

It happens in DCS. As stated, I do it frequently and watch my airspeed needle plummet faster than it would if I had not increased the prop pitch. If that's not supposed to happen, then what's the explanation for higher prop pitch causing a dump of airspeed in DCS? It's clearly observable in all the Allied warbirds. 

Then we are playing 2 different games. In my version of dcs if i want to slow down faster i cut throttled and if this not enought increase rpm to max. And if i want to glide as far as possible when my engine gives up i reduce rpm to minimum.

@kablamoman showed you video which explains this topic.

Edited February 14, 2024 by grafspee

[Rene Coulon]

This was Taught to the Pupil Pilots on the SAAF Harvard...T6

Increase power......... 1 set pitch, 2, set MaP,3, set Mixture

Decreasing power.... 1 set MaP, 2 set Pitch, 3 set Mixture

45 minutes ago, grafspee said:

Then we are playing 2 different games. In my version of dcs if i want to slow down faster i cut throttled and if this not enought increase rpm to max. And if i want to glide as far as possible when my engine gives up i reduce rpm to minimum.

@kablamoman showed you video which explains this topic.

 

thats a similar technique used for Flying for Range...or flying for Endurance...

[Art-J]

4 hours ago, Nealius said:

So by going fine pitch at a low power setting, I'm inducing windmilling and that's what causes the speed dump?

Bingo. It's used in real life CSP planes to slow down on approach as well.

It used to work in DCS Mustang too, last time I tested with a stopwatch, but it was a year ago at least. Max RPM vs min RPM deceleration and glide distance difference was noticeable. Unless ED messed up something in the meatime, should still work in current version like Graf says, but I ain't got access to my gaming rig to repeat the test.

[Nealius]

1 hour ago, grafspee said:

In my version of dcs if i want to slow down faster i cut throttled and if this not enought increase rpm to max.

Yes.....that's what I described doing. I increase the prop pitch lever, and slow down.

@Art-J It still does work in the Mustang. I was doing it regularly the past few weeks due to a nasty habit of coming in way too fast in the overhead break.

 

 

[grafspee]

32 minutes ago, Nealius said:

Yes.....that's what I described doing. I increase the prop pitch lever, and slow down.

@Art-J It still does work in the Mustang. I was doing it regularly the past few weeks due to a nasty habit of coming in way too fast in the overhead break.

 

 

By Increasing pitch you reduce rpm.

There is no prop pitch lever in p51.

There is only rpm control lever if you move it full forward governor will lower pitch to maintain 3000. If rpm drops below 3000 while this level is full on this mean that prop pitch is at low pitch stop. Prop pitch in p51 is in the governor hands, pilot can not set pitch directly. You can move rpm lever full back and prop pitch will remain in full fine pitch stop, you can set rpm at max and prop pitch can be very close to coarse pitch stop.

You are saying one thing and doing opposite. I would not start this conversation if you discribe it right.

 

Edited February 14, 2024 by grafspee

[Nealius]

Wait, so by increasing the prop pitch/RPM lever you are also increasing RPM, but decreasing pitch? I see prop pitch lever/RPM lever/prop control lever used interchangeably in DCS communities and in DCS-related documentation (not to mention the levers themselves are labeled "P" and not "R") so I thought "increase" applied consistently to everything.

Edited February 14, 2024 by Nealius

[some1]

It's "P" for propeller, not pitch.

On 2/13/2024 at 10:31 AM, some1 said:

Just to get everyone on the same page, as I have some doubts if you all talk about the same thing.

http://essentialpilot.co.za/wp-content/uploads/2019/02/f0268-01.gif

low pitch = fine pitch. That's high rpm setting. Also higher drag if the engine is windmilling.

high pitch = coarse pitch. That's low rpm setting. Also lower drag if the engine is windmilling.

[Nealius]

Yes, I'm looking through the ED manuals and the real pilot's handbooks Reflected included in his campaigns. "Propeller control lever" is most often used however the ED manuals are extremely inconsistent, with the Spitfire in particular specifically saying "pitch lever" with high frequency after initially calling it propeller control. Mossie manual also references prop pitch lever friction despite never calling the prop control lever a prop pitch lever. All of this inconsistent labeling of what is essentially the same thing makes it seem like all the terms are interchangeable.

What @some1 clarified (low pitch = fine pitch = lever forward = high RPM; high pitch = coarse pitch = lever aft = lower RPM) isn't discussed in most of the manuals, and may actually be wrong in the P-47 manual? Page 55 says:

Quote

INCREASE RPM. This position is not fixed and increases propeller pitch.

But increasing propeller pitch should DECREASE RPM, correct? The manuals are all over the damn place.

Digressing from the main topic but it should be clear that the documentation the average user gets doesn't enable clear understading of prop pitch; or worse appears to imply the opposite of what is true. 

Edited February 14, 2024 by Nealius

[grafspee]

1 hour ago, Nealius said:

Wait, so by increasing the prop pitch/RPM lever you are also increasing RPM, but decreasing pitch? I see prop pitch lever/RPM lever/prop control lever used interchangeably in DCS communities and in DCS-related documentation (not to mention the levers themselves are labeled "P" and not "R") so I thought "increase" applied consistently to everything.

 

It is called propeller rpm control. By moving it forward or backward you only set target rpm for governor, so when you are on the ground and you are idling engine at 1200rpm, moving this rpm do absolutely nothing, propeller pitch does not change. 

I don't think so that any war time US manual will call it pitch lever.

In order to increase rpm governor will decrease pitch, lower pitch means lower AoA of the prop blades and this mean lower drag and this mean that prop can spin faster with same amount of power. Americans and British call it differently but way that it works is the same. You move this lever forward you get lower/fine pitch if anything else is constant.

Edited February 14, 2024 by grafspee

[Slippa]

Have to thank Sandpatch for posing the question. Contributors too.

For whatever reason I was boring the missus a few days ago and she asked me what I meant by saying “Prop pitch”. I was tangled in knots in no time and admitted it not only being hard to explain easily but that I couldn’t really say I was 100% about it anyway. Then this thread pops up and I’m all ears, or eyes.

One minute I’m thinking I understand it pretty much, the next, I’m tangled up again.

I’ll keep the popcorn nearby.

Good to know I’m not alone in coming in way too hot for an overhead break or trying to squeeze my way down to roll out at silly speeds. 

[Nealius]

20 minutes ago, grafspee said:

It is called propeller rpm control.

That would be a more logical label, but ED and wartime manuals (what I have at least) call it "propeller control," which makes it easy to falsely interpret that as propeller pitch control rather than propeller RPM control, or simply conflate the two and think they're the same (particuarly when the manuals don't explain anything of the mechanics). Which circles me back up to my comment about the ED manuals using various terms interchangeably and erroneously.

Edited February 14, 2024 by Nealius

[kablamoman]

1 hour ago, Nealius said:

That would be a more logical label, but ED and wartime manuals (what I have at least) call it "propeller control," which makes it easy to falsely interpret that as propeller pitch control rather than propeller RPM control [...]

Just to add more fuel to the mixture, I think you could make a strong argument for calling it "Engine RPM Control" as that's what you're selecting with the lever and seeing on the gauge. 

In contrast to this, you can manually set the pitch of the prop blades in the 109 or Anton, and both have a gauge that directly shows you the blade angle. 

[grafspee]

@Nealius

This is from Mosquito manual

Spitfire manual 

Even in British manuals it is always rpm control levers or speed control levers not pitch control.  

This is from DCS mosquito manual

I don't know from where did you get this, because i can't find it neither in DCS or war time manuals.

In every single manual it is depicted very clearly that P stands for propeller, every time it refers to speed control or propeller control or rpm not a single time i could find that manual states that moving this lever forward it increase pitch. Only in this mosquito it refers to pitch that it governs pitch  from 3000 to 1800 rpm. 

I can only find only one in DCS spitfire during start tu procedure player is instructed to move pitch lever all the way forward, but still does not saying that increase pitch, only move pitch lever all the way forward.

And spitfire pilot's notes are saying that this is propeller control. Till now i found only one spot where name changed, in any other instances lever is named properly. Hundreds instances where speed control / propeller control is used and single one case where someone made mistake and name lever in wrong way.

And on top of that DCS manuals are not free from wrong data.

Ofc someone can say set pitch for take off, climb , cruise but by no means this does not mean that moving this lever forward increases pitch actually it is quite opposite. 

Edited February 14, 2024 by grafspee

[DD_Fenrir]

Frankly it’s semantics - RPM is governed by the pitch of the blades whether it’s controlled automatically or manually.

 

 

Edited February 14, 2024 by DD_Fenrir

[Art-J]

Even Dave Hadfield in his latest cool Spitfire onboard vid posted on his YT channel calls the prop lever a "pitch" one, even though I'm sure he knows how CSPs work in warbirds he flies .

I suppose for RL pilots this thing is so basic and "obvious" that they don't give a funk about nomenclature, 'cause they know what they mean anyway. It can, however, cause confusion amongst less experienced enthusiasts who want to learn about it.

Game manuals should describe it correct though, that's for sure.

[grafspee]

5 hours ago, Art-J said:

Even Dave Hadfield in his latest cool Spitfire onboard vid posted on his YT channel calls the prop lever a "pitch" one, even though I'm sure he knows how CSPs work in warbirds he flies .

I suppose for RL pilots this thing is so basic and "obvious" that they don't give a funk about nomenclature, 'cause they know what they mean anyway. It can, however, cause confusion amongst less experienced enthusiasts who want to learn about it.

Game manuals should describe it correct though, that's for sure.

Nomenclature may originate from early planes which were equipped with pitch lever and name stick to this since then.

Similar situation could be with throttle, in early planes pilot controlled throttle valve directly later throttle valve is controlled by automatic boost regulator.

Edited February 15, 2024 by grafspee

[Nealius]

@grafspee This is the source of my confusion, and I'm frankly tired of being invalidated; worse gaslighted by saying the confusing usage of terminology in the manuals doesn't exist.

The Spitfire--my first warbird module--references "pitch lever" 7 times. It also says:

With the P-51 and P-47 manuals not specifying P is for "propeller," the above first-contact knowledge led me to assume P is for "pitch" as the manual says the lever controls propeller pitch. Though it does often say "set RPM with pitch lever" nowhere is there an explanation of how the prop pitch itself relates to RPM.

P-47 manual pages 55-56 are clearly wrong, indicating correspondence between low pitch and low RPM, high pitch and high RPM.

The Mosquito manual also throws in "pitch lever" when talking about the friction adjustment:

 

All of this combined easily leads the average end-user to believe that propeller control, RPM control, propeller pitch control are all the same, the control lever controls pitch rather than RPM, and that increasing/decreasing prop pitch increases/decreases RPM respectively, not the inverse (high pitch=low rpm, etc.). 

I have searched all the DCS warbird manuals from ED for a description of the inverse relation between prop pitch and RPM, and there is none. The closest is the above pictured excerpt from the P-47 manual, and it's claiming a direct relation (high pitch=high rpm), not an inverse relation (high pitch=low rpm).

It should be abundantly clear that the documentation is anything but clear.

Edited February 17, 2024 by Nealius

[Slippa]

It’s unclear to me.

Only thing I can make sense of is the English vs Americans using different terminology for essentially the same things?

[some1]

It's not, ED manuals are simply wrong. The only difference here is that the English call propeller an airscrew.

 

6 hours ago, Nealius said:

I have searched all the DCS warbird manuals from ED for a description of the inverse relation between prop pitch and RPM, and there is none

You won't find that even in the real period manuals. This is not the kind of knowledge that a WWII pilot needs to be concerned with, as he only really needs to know which way to push the lever to increase rpm. Even the backup manual pitch control switch in p47 is still labelled "increase rpm".

Edited February 17, 2024 by some1

[Slippa]

3 hours ago, some1 said:

the English call propeller an airscrew.

Maybe? I’d say we say ‘prop’ and ‘prop pitch’ too but anyway, it’s something else then.

[grafspee]

@Nealius It is outrageous to have so errorus manuals. This is why i stopped reading them. It is obvious that person who creates them has no knowledge about stuff he or she is working on.

And now you had very good explenation how this thing works by couple ppl from this topic so there is no need for further arguments about it. 

[Art-J]

20 hours ago, Slippa said:

Maybe? I’d say we say ‘prop’ and ‘prop pitch’ too but anyway, it’s something else then.

"Airscrew" term seems to be the norm in your manuals, docs and videos from '30s and '40s. You chaps don't use it anymore in "modern" times? Just curious.

[Skewgear]

On 2/17/2024 at 1:24 AM, Nealius said:

@grafspee This is the source of my confusion, and I'm frankly tired of being invalidated; worse gaslighted by saying the confusing usage of terminology in the manuals doesn't exist.

The Spitfire--my first warbird module--references "pitch lever" 7 times. It also says:

With the P-51 and P-47 manuals not specifying P is for "propeller," the above first-contact knowledge led me to assume P is for "pitch" as the manual says the lever controls propeller pitch. Though it does often say "set RPM with pitch lever" nowhere is there an explanation of how the prop pitch itself relates to RPM.

P-47 manual pages 55-56 are clearly wrong, indicating correspondence between low pitch and low RPM, high pitch and high RPM.

The Mosquito manual also throws in "pitch lever" when talking about the friction adjustment:

 

All of this combined easily leads the average end-user to believe that propeller control, RPM control, propeller pitch control are all the same, the control lever controls pitch rather than RPM, and that increasing/decreasing prop pitch increases/decreases RPM respectively, not the inverse (high pitch=low rpm, etc.). 

I have searched all the DCS warbird manuals from ED for a description of the inverse relation between prop pitch and RPM, and there is none. The closest is the above pictured excerpt from the P-47 manual, and it's claiming a direct relation (high pitch=high rpm), not an inverse relation (high pitch=low rpm).

It should be abundantly clear that the documentation is anything but clear.

 

It's been deeply frustrating reading this thread two weeks after the block-headed wilful idiocy being displayed towards someone asking a reasonable question. No wonder users shy away from posting on these forums.

Nealius. Ignore the oddball who was constantly telling you you're wrong and your understanding was invalid. He is not worth engaging with in good faith because he has been giving you bad faith answers throughout this thread.

In English the terms prop pitch, prop RPM selector and prop lever are mostly interchangeable even when this is technically incorrect. The terms are widely understood to refer to levers that, when pushed forward, make the propeller spin faster. In that context "increasing" refers to higher RPM.

This post is a great and simple explanation, including the relationship between propeller pitch setting and RPM:

[Slippa]

On 2/18/2024 at 7:44 AM, Art-J said:

"Airscrew" term seems to be the norm in your manuals, docs and videos from '30s and '40s. You chaps don't use it anymore in "modern" times? Just curious.

I’m not a pilot but have spent countless hours on a grass strip that still operate Spits, Tiger Moths, Harvards/Texans, Stampes and many ‘prop’ driven aircraft. I still hear “Clear prop” a fair bit. Also, I speak to pilots now and then, hear a lot of chatter and often hear all kinds of fascinating stuff. Mostly, stuff I know little or nothing about personally. Technically speaking, I’m just as interested as the rest of us to understand it better. If I remember to, come better health and better weather I’ll be bending the ears of the next pilot I bump into at the airfield.  - Poor sod, I can talk the hind legs off a Donkey.

Come to think of it, I’m still owed a flight in a Tiger but doubt I’ll be having this conversation in the cockpit. 

I’m curious to get their take on it now, I know that much.

[jaylw314]

To add more fuel to the fire, there have been aircraft the have pitch control for the prop, rather than a propeller governor controller, so it's not for someone to conflate pitch control with prop control.  Come to think of it, the Me-109 was one of them, IIRC.