Propeller Pitch Use

[jollyjack]

Looking at my various Warthog settings i never really bothered with propeller pitch.

With DCS and helicopters the main rotor is something important to adjust constantly. 

For IL2 i now got a little curious what settings, and when or why you use those those actively ... 

 

 

Edited May 7, 2022 by jollyjack

[THERION]

15 minutes ago, jollyjack said:

Looking at my various Warthog settings i never really bothered with propeller pitch.

With DCS and helicopters the main rotor is something important to adjust constantly. 

For IL2 i now got a little curious what settings, and when or why you use those those actively ... 

 

 

 

These two switches are mainly to use with German planes like the BF109, BF110. Although these German planes generally have automatic
propeller pitch, you can in some cases switch to manual prop and change the pitch with this switch. I never do this*.

All other planes, allies mostly and Russian planes, do have a propeller governor lever to change the pitch. These planes need the
manual input, so you can fly in cruise mode and therefore lower consumption and avoid engine stress. 100% propeller pitch is used
for take off, in combat situation and when landing to ensure full power.

 

* There are some Luftwaffe Heinis who do switch to manual prop pitch control and will tell you, that this is the way to go. But historically

   this method is quite questionable. I saw an interview with Günther Rall and some well known other German aces where they were asked

   about manual pitch control in the BF109, BF110 etc. (fighters) - all of them confirmed not to use manual mode at all. Günther Rall even
   confirmed this in his biography, which I have at home.

[Asgar]

2 minutes ago, THERION said:

 

These two switches are mainly to use with German planes like the BF109, BF110. Although these German planes generally have automatic
propeller pitch, you can in some cases switch to manual prop and change the pitch with this switch. I never do this*.

All other planes, allies mostly and Russian planes, do have a propeller governor lever to change the pitch. These planes need the
manual input, so you can fly in cruise mode and therefore lower consumption and avoid engine stress. 100% propeller pitch is used
for take off, in combat situation and when landing to ensure full power.

 

* There are some Luftwaffe Heinis who do switch to manual prop pitch control and will tell you, that this is the way to go. But historically

   this method is quite questionable. I saw an interview with Günther Rall and some well known other German aces where they were asked

   about manual pitch control in the BF109, BF110 etc. (fighters) - all of them confirmed not to use manual mode at all. Günther Rall even
   confirmed this in his biography, which I have at home.

First of all, it's not uncommen to use manual pitch in something like a P-40 as well. It's a back up in case the prop govenor stops operating as it should.

In the case of  DB engines it allows you to nurse your engine, for example when your engine is damaged you can go to 1500RPM and 1.0 ATA to keep it from killing itself too fast. 
Also it is common practive to set your pitch to 12 o'clock when taxing in 109s, cause it makes the plane more responsive on the ground and improves ground handling.

[THERION]

7 minutes ago, Asgar said:

First of all, it's not uncommen to use manual pitch in something like a P-40 as well.

 

Read my post again, mate and you will see that, even not mentioned by name, of course the P-40 and P-39 are included. Especially the P-40,

because if you do not manage trust, mixture and prop correctly you won't even be able to leave your airfield perimeter after take off without

severely damaging and killing your engine.

 

 

[Asgar]

3 minutes ago, THERION said:

 

Read my post again, mate and you will see that, even not mentioned by name, of course the P-40 and P-39 are included. Especially the P-40,

because if you do not manage trust, mixture and prop correctly you won't even be able to leave your airfield perimeter after take off without

severely damaging and killing your engine.

 

 

You're thinking RPM, I'm talking about manual pitch. Disfunctioning RPM govenors aren't really a thing in the sim, but they sure are IRL  

[Weegie]

Do you adjust the pitch in the allied aircraft?

 

I do it all the time after takeoff and only use fine pitch at takeoff, landing or combat.

 

It's just an RPM limiter, the coarser the pitch the lower the RPM will be held at, as @THERION pointed out used to lower engine stress and decrease fuel consumption

 

I'm pretty sure I read somewhere about Lancaster crews being taught to use coarse pitch and high boost to maximize available fuel and they hated it as it sounded like the engines were going to blow up.

 

Unless you allow the engine to rev to its max you will not get full power (power=torque * Revs)

 

With the German aircraft, I do the same as @Asgar putting the pitch to manual in the 109s and some of the 190s. This makes them easier to taxi and takeoff because the prop pitch (or bite if you like) isn't constantly adjusting, I place at 12 or 12:30.

 

It's not so much of a problem in IL2 but in DCS the 109 swings much more when the pitch is left in Auto at takeoff.

 

Guess this is due to the large power changes at takeoff and the slow response time of the Kommandgerat.

 

I can't remember where I heard it but there was alleged cases of axis pilots ocassionally deystroying their engines when they had the pitch in manual for takeoff and forgot to switch it back to auto.

[Asgar]

55 minutes ago, Weegie said:

Unless you allow the engine to rev to its max you will not get full power (power=torque * Revs)

That is a very basic understanding of what's happening. At some point when you rev to high, piston speed is higher than the burnspeed of your fuel and you will lose torque, leading to reduced power. So no, max revs =/= max power. you can see that on pretty much all engine power charts.

Coming back to allied aircraft. You do not adjust Pitch in normal operation. You adujst RPM. It's not an RPM limiter, it's an RPM govenor. You can switch to manual pitch control, but that is not usually in normal operation.

[dannytherat]

1 hour ago, Weegie said:

I'm pretty sure I read somewhere about Lancaster crews being taught to use coarse pitch and high boost to maximize available fuel and they hated it as it sounded like the engines were going to blow up.

 

 

I've read a few of the old Air Ministry Pilots' Notes for some of the British aircraft (Hurricane, Typhoon, Spitfire and the eagerly awaited Mosquito) and the implication in these documents is that the aircraft are best cruised at a high (possibly full) throttle setting but with the rpm set to achieve the appropriate indicated airspeed.

 

This doesn't actually imply a high boost setting, as the reduction in the engine speed (via the increased propeller pitch introduced by the rpm governor) also means that the mechanically connected supercharger also spins more slowly, which reduces the boost, preferably to a point where the engines are running at a boost setting which the manuals indicate as being appropriately "lean" for cruise (at least in most of the British engines).

 

As an example, the notes indicate that the Typhoon should cruise with no more than +3lb boost, but the most efficient way to do that is to set the throttle to full, then reduce the revs so the boost also drops to the required level as the engine (and consequently the supercharger) spins slower, reducing the boost.

 

I've been quite enjoying trying to fly the aircraft fairly efficiently recently by trying to fly them more or less as per the pilots' notes. I don't know if many others do this but I wouldn't be surprised if they didn't. I find it quite satisfying though!

[Asgar]

First guess would be they did that to reduce throttling losses, but i guess you can do that with just any engine, Most US plane manual state, increase RPM first then throttle, when reducing power the reverse, reduce thorttle, then RPM to avoid overboosting the engine.

Edited May 7, 2022 by Asgar

[dureyo]

I use manual pitch in 109s/190s if the engine goes out and i want to increase my glide ratio, it does help quite a bit to reduce pitch. 

[Weegie]

20 minutes ago, Asgar said:

That is a very basic understanding of what's happening. At some point when you rev to high, piston speed is higher than the burnspeed of your fuel and you will lose torque, leading to reduced power. So no, max revs =/= max power. you can see that on pretty much all engine power charts.

Coming back to allied aircraft. You do not adjust Pitch in normal operation. You adujst RPM. It's not an RPM limiter, it's an RPM govenor. You can switch to manual pitch control, but that is not usually in normal operation.

Interesting @Asgar

 

I was endeavouring to simplify the functions of the pitch lever & RPM/Power relationship.

 

There isn't any function similar to pitch/RPM lever, for example automobiles, or other IC engines people have experience with.

 

In allied aircraft the pitch lever sets a limit on the maximum revolutions the engine can run to

 

Regarding RPM vs Power, I have never worked on an aircraft engine or used one IRL.

 

Looking at typical Dyno graphs engine power rises linearly with rpm, peaks then drops off sharply. Torque is generally flat but does reduce at higher rpm, inidcating other factors coming into play.

 

I've seen many many threads on the DCS forum on prop pitch/rpm lever topic.

 

It always ended up in the minutae and the more esoteric workings of engines, making it difficult for the OP who asked the question to understand the function of the control

 

I apologise for trying to keep it simple to answer the question

 

Gregg who is waaaaay more knowledgable and eloquent than I could ever be explains prop technology starting around 8:00 minutes onwards

 

 

[Asgar]

21 minutes ago, Weegie said:

In allied aircraft the pitch lever sets a limit on the maximum revolutions the engine can run to

that's only true if you're throttle setting is to low. again, not a limiter, a govenor. And I like to think that I know what I'm talking about since i'm an EASA licensed aircraft engine mechanic ?

They're constant speed props, you set the RPM (prop speed) and the govenor will hold that speed by adjusting pitch an thus the counter torque produced by air resistens that works against the engine torque. If your engine isn't putting out enough power (too little throttle) the RPM will drop below that yes, but that's just because the govenor can't reduce the torque acting against the prop through pitch change. It doesn't just limit your RPM, it also makes sure your RPM doesn't drop when flight attitude or other circumstances change. 

 

Quote

Looking at typical Dyno graphs engine power rises linearly with rpm, peaks then drops off sharply. Torque is generally flat but does reduce at higher rpm, inidcating other factors coming into play.

That is exactly what I'm talking about the torque drops because the piston is so fast the burning fuel mixture can't impart all it's energy on the piston before it reaches dead center. thus the torque drops which results in less power even though you have high RPM

Edited May 7, 2022 by Asgar

[jollyjack]

Pfff, no wonder i like a Sopwith Camel ...

With a heavy loaded Heinkel H6 (Liz Lemon's torpedoes f.i.), is there a pitch setting for increasing ground speed faster for take off?

Sometimes a runway is too short.

Edited May 7, 2022 by jollyjack

[Weegie]

@Asgar

 

I agree the pitch/rpm lever adjusts the prop pitch throughout the range to hold a set number of revolutions, so it's a Governer or controller rather than limiter

 

@dannytherat

 

The high boost reference was from a RR Heritage book Historical Series No2 by Alec Harvey Bailey, page 27, where he quotes crew room dogma in the bomber squadrons. This came after Nuremberg raids where a 125mph headwind forced a number of aircraft to ditch in the North Sea after running out of fuel

 

"Don't fly at night either fast or slow,

With your revs too high or your boost too low,

Or you will run out of gas with a long way to go,

and you won't get home in the morning"

 

[RyanR]

Engines have a sweet spot(s), for power and economy. Just like a car engine, there's peak torque at a given RPM (peak torque is never at the max RPM).... which isn't the same place where fuel economy is.

 

Propellers have their own sweet spot. Automatic prop pitch adjusts the prop not to just to maintain RPM, but to grab air as the plane moves faster.

 

German planes aren't great examples, as most of their planes in the sim have these relationships baked into the throttle, and you're only really adjusting pitch for ground handling. American planes like the P-38 use slightly higher RPM's for combat power.

 

-Ryan

[Traffic]

As far as the P39 and P40, I found it most efficient to run the throttle and pitch up together as one. It gives you total control, 74% max continuous on the deck at around 305mph, and ~330mph, at a high combat setting, 78% pitch/78% throttle, depending on summer/winter map. 75% starts combat mode, up to about 80%, which changes with altitude. Mapping both pitch/rpm and throttle together as one with these Allisons is the best solution, for me. 75% pitch/rpm/throttle on take off, then back down to 74% max continuous. 

 

Early Allisons didnt have manifold pressure regulators and the later models, like the most produced N model did, with stronger internals and a better intake manifold. 

 

With these settings run up together, the P40 is good for 390mph on the deck before the engine burns out after 15 seconds or so from over speeding the prop. 

 

Fly it offline, turn on unbreakable, and see what it really can do. It's just too bad it's built like glass in this sim, but is workable. 

 

I think, unless we see, if ever, a later model like an N, or Merlin model, we're stuck with a capable aircraft where we can only really use 75% of the available engine power. 

 

I fly the P47 the same way. I use turbo, throttle and pitch all together as one and it works just fine. 

[[CPT]Crunch]

With a prop governor your only getting a vote by moving the lever, there are other mechanical features like RPM inputs and fly wheel weights that may over ride your current selection, there's built in safety limiters.  With a selectable electromechanical servo you are directly choosing your blade angle.  That one has the real potential to break things or blow stuff up if improperly used, but not so much in a game.