Spitfire IIa prop pitch

[nakedsquirrel]

The Spitfire IIa prop pitch seems to behave differently than any of the other aircraft in game.

Most aircraft will gain some speed with a slightly coarse pitch, but the Spitfire IIa is fastest with the prop pitch set to fully fine.

Is this unintended, or is there something about the Spitfire IIa prop pitch that makes it different from the other aircraft? (IE is it supposed to be a version of auto-pitch?)

[41Sqn_Banks]

This is because the Spitfire II has a CSP (constant-speed propeller). The lever in the cockpit doesn't set the propeller pitch, it sets the desired engine RPM. The constant-speed unit/governor tries to keep the desired RPM by adjusting the propeller pitch. Of course the constant-speed unit/governor only allows to set RPM values that don't overstress the engine.

So if you set the RPM lever to the forward position the highest possible RPM is maintained. In combination with full throttle this will give you the highest possible engine output power and therefore the highest possible speed*.

*I assume the at highest possible engine RPM the propeller is spinning with an RPM where the propeller has the best efficiency. This is achieved by choosing a suitable propeller reduction gear.

Note that there are other aircraft that have a CSP, e.g. the Hurricane I Rotol and most (if not all) german bombers have a CSP.

[JG53Frankyboy]

flyable palnes with CSP units in the moment are:
-Spitfire II
-Hurricane I_Rotol
-G.50
-Br.20
-Ju87
-He111P&H
-Ju88

Manual pitch, in what you control the propeller anlge directly:
-Bf109
-Bf110

Two speed propeller, actually fixed propellers with two settings (fine and coarse):
-Hurricane I_DeHaviland
-Spitfire I and Ia (weird , but it still is this way :( ) , most propably the heartbreaker too, never flew it
-Blenheim

fixed propeller:
-Tiger Moth



lets hope in one of the future patches at least the Spitfire Ia gets a CSP and the Ju88 a manual one.

[Crumpp]

Spitfire IIa is fastest with the prop pitch set to fully fine.

Vmax occurs at maximum rpm and manifold pressure in any aircraft. Although it is called "course" and "fine" pitch, as the other posters have explained it is really maximum rpm.

The blade pitch will open as velocity increases and maintain rpm. In a selectable pitch propeller, the pilot must open the blade pitch to maintain maximum rpm as the aircraft speed increases.

This the reason for the VDM clock. It gave the pilot a measure of his blade pitch to set to achieve desired performance.

[Crumpp]

Manual pitch, in what you control the propeller anlge directly:
-Bf109
-Bf110

The VDM propellers are constant speed propellers with an electrical manual pitch that is used for emergencies.

I am not the Bf-109 expert but I believe only a small number of purely manual pitch propellers came into service early on in the 109 series development. IIRC, it was during the Battle of France that a handful were delivered "ohne automatik". It was then replaced with the "mit automatik" which is the VDM hydraulic-electric series used throughout the remainder of the war.

http://img683.imageshack.us/img683/9559/109vdmlist.jpg (http://imageshack.us/photo/my-images/683/109vdmlist.jpg/)

[JG53Frankyboy]

During BoB there were A LOT of Bf109s in active service still with manual pitch.

I cant count anymore how often we had this in the forums ;)
here is just one example
http://forum.1cpublishing.eu/showthread.php?t=22204

So , its all do the decission of 1C what propeller system they will give the BoB time 109s - they cant decide wrong !

[Crumpp]

Ok, from December of 1939 it was introduced.

I read that thread.

You have a copy of the Bf-109E Flugzeug handbuch where the automatik propeller is covered and included from December 1939. That means it was in use on the aircraft from December 1939 forward. Probably even sooner as the normal procedure is a Technical bulletin is issued until the POH is republished and updated. It also does not tell us the extent of operational use.

IIRC, VDM did not produce both types concurrently. The automatic propeller superseded the variable pitch only propeller in VDM production and as the propellers were overhauled, they were upgraded.

It also seems the claim is being made the propeller was not introduced until September 1940. That claim introduces a translated OKL document that raises the rpm limit for the engine and instructs that only Mtt and VDM can modify the governor for the new rpm limits. Both companies are working as fast as possible to make the necessary modifications to comply with the new rpm limits.

That document does not say a thing about the introduction timeline of the VDM propeller "mit automatik" and does not shed any light on the extent of propellers use operationally.

[nakedsquirrel]

I'm still learning about prop pitch, so bear with me, but I'm still a bit confused because the Hurricane Rotol behaves much differently than the Spit IIa.

While flying the Rotol, I find I get a better cruise / dive speed when I pull the prop pitch lever back to 40-50%.

When I do this, the Boost needle goes up while the RPM gauge drops down. (so, high manifold pressure, low rpms)

This is similar with the Hurri DH, Spit I and Ia except that those Spits have the 2 settings, full fine/ full coarse

In the Spit II, however, when I pull back on the pitch, my RPM drops and my speed drops. Even in a shallow dive, pulling back on the pitch lever still reduced my speed. That's the opposite effect that the control has on the Hurri Rotol.

No comment on the German aircraft because they all seem to make sense to me.

[Blackdog_kt]

First of all, pitch is not the slider's position but the angle of the blades in relation to the oncoming airflow.


In keeping with the analogy of gears in a car, a fixed pitch prop is like having a car with a single gear, the early Hurri and Spit dual-position props are like having two separate fixed pitch props that you can change in flight or like having a car with two gears (one for low speed and initial acceleration and one for high speed and fuel economy).

The manually adjustable props found in 109s and 110s are like a fully manual car transmission, with the added caveat that it's continuous and not in discrete steps: you don't only have 1st, 2nd, 3rd, etc gears, you also have all the in-between settings and this gives slower but finer control.

The car analogy is preferred simply because it exhibits similar use, even though the actual workings of it all are fundamentally different:

If you want to drive uphill or limit your speed when driving downhill you use a lower gear that gives higher RPM for the same position of the gas pedal, you do the same in the aircraft by selecting a finer pitch with higher RPM.

If you want to pick up speed when driving downhill or attain your top speed you switch to a higher gear, RPM drops initially but as you keep accelerating it builds back up, it's the same with selecting a coarser pitch.

And if you try driving uphill on a high gear/low RPM without having enough speed your car can't do it, similar when trying to climb in an aircraft with coarse pitch it only works if you have enough starting airspeed.


A CSP prop is one where the pilot affects the governor state (either through oil pressure/quantity in the governor or a mechanism of flywheels and inertial balancing), each governor configuration corresponds to a certain RPM value and then it's a case of balancing forces:
if the airflow is acting against the prop, pitch changes one way, if the airflow effect is lessened pitch moves the other way.

In this way, depending on forward speed the pitch (the angle of the blades) is constantly changed to maintain steady RPM without intervention from the pilot. The lever might not move, but the blade angle is changing whenever your airspeed or throttle does.

In other words, it's like having all the in-between gears again, but this time it's shifting automatically whenever you exceed or drop below the RPM specified by the governor. If you set a CSP for 2800 RPM, whenever you hit that RPM the blade pitch will coarsen a bit more and this ensures you keep accelerating optimally at all times. If on the the other hand you are climbing and your airspeed drops and RPM drops too, the blade angle will automatically move to a finer pitch to bring the RPM back up.

Imagine driving a car where you can select at exactly which RPM it will shift gears.
If you wanted a responsive drive with lots of speed changes and "nervous", immediate response to your gas pedal (whether accelerating or decelerating), you'd tell it to shift at an RPM range that you know your car behaves with more "nerve". This is like being in a dogfight (sudden speed changes and need for responsiveness) and that's why we select a higher RPM for the prop governor to maintain.
If you just wanted to go on an easy ride without burning a lot of fuel, you'd tell it to shift gears at a lower value. This is similar to cruising in the aircraft and that's why we pull back the lever a bit and have the governor settle the RPMs a bit lower.

Then on top of that, imagine that gears are not discrete steps but a continuous adjustment in the transmission, so that you only have to worry about pressing or releasing the gas pedal to maintain the speed you want and you are automatically shifting gears to ensure optimum usage of your fuel and motor depending on what you want to do. Pretty neat, huh? It's no wonder pilots considered it a big deal ;-)



The auto prop on the 109s is not like that however. The final effects are similar to a CSP but the operating principle is not. Instead of using a governor mechanism, they actually "tied" each throttle position to a certain pitch (or was it RPM?) value and further fine-tuned it by adding instrumentation that measured the amount of load on the engine.

In other words, the 109's auto-prop is much like having an early analog computer operating the prop in the same manner that the pilot manually would: by directly influencing the blade angles through motors and not by indirectly commanding a certain RPM via a governor mechanism.

Here's a pretty good link explaining how it works (i got it from the other thread linked a few posts above): http://marseillegruppe.com/foro/viewtopic.php?p=2954&sid=3591268e7829c1e00ff328cb9d3b84f4

[Crumpp]

The auto prop on the 109s is not like that however.

NO...You have confused automatic devices.

The VDM hydraulic electric propellers are CSP in hydraulic mode and variable pitch in electric mode.

Schwarz-man, whom I know and he is correct in his explanation of how the SYSTEM works.

He is describing the interaction of the CSP PROPELLER with MANIFOLD PRESSURE of the ENGINE!!

This eliminated the pilot from having to adjust PROPELLER RPM as with ANY CSP and then have to adjust ENGINE MANIFOLD PRESSURE. It reduced his workload when compared to a using a CSP on regular aircraft engine with manual controls.

[CaptainDoggles]

Regardless of what it was in real life, in game on the 109E-1 and E-3 the propeller behaves as a variable-pitch prop. There's no auto mode.

[Kurfürst]

NO...You have confused automatic devices.

The VDM hydraulic electric propellers are CSP in hydraulic mode and variable pitch in electric mode.

Schwarz-man, whom I know and he is correct in his explanation of how the SYSTEM works.

He is describing the interaction of the CSP PROPELLER with MANIFOLD PRESSURE of the ENGINE!!

This eliminated the pilot from having to adjust PROPELLER RPM as with ANY CSP and then have to adjust ENGINE MANIFOLD PRESSURE. It reduced his workload when compared to a using a CSP on regular aircraft engine with manual controls.

Yup, my understanding is that effectively the 109 Automatik is just the manifold pressure throttle linked to certain RPM, it keeps the

It wasn't fixed-pitch-to-certain-MAP since if you think about it - if *pitch* would be fixed, rpm would increase/decrease all the time as speed - and load on the propeller blades - would decrease/increase.

In essence its just a single lever CSP where you can set the rpm/map correctly quickly and convinient. You did not have to mind much how to set up the engine.

On Allied planes with CSP, you set the desired RPM and MAP seperately, and the system would keep the RPM constant, by adjusting the pitch as needed. You still had to set the optimal RPM/MAP combination manually, by using two seperate levers, and there was a bit of a backside, since you had to do this in correct order , IIRC/AFAIK for example when increasing power, first RPM needed to be increased with the RPM lever, then boost, otherwise you would run the engine at low rpm / high boost which would stress the engine. The downside was that it required more attention from the pilot, and a bit of extra work.*

This was not modelled correctly in old Il2, and I as I recall it still isn't in COD.

* later it seems that a simplistic mechanical "system" was introduced, according to later Spitfire manuals for example that mention interconnected control. This however I believe was fitted only the some later Mark batches - impossible to tell which ones and how many - and not all planes, and the system was merely a metal rod that ensured that if MAP was increased, the MAP lever grabbed the RPM lever and pushed it forward, too. But unlike on the 109, it did not give optimal rpm/map combinations on most of the lever movement range, it just enabled the pilot firewall the throttle quickly and push both rpm/map the maximum regime.

[JG53Frankyboy]

...................................The auto prop on the 109s is not like that however. The final effects are similar to a CSP but the operating principle is not. Instead of using a governor mechanism, they actually "tied" each throttle position to a certain pitch (or was it RPM?) value and further fine-tuned it by adding instrumentation that measured the amount of load on the engine.

..............]

it was RPM..............
a pilot in a german one lever system had to set a specific "Leistungszustand" -
just read the link you self posted. If the ATA would be fixed to a certain pitch....that would be senseless.

[TomcatViP]

NO...You have confused automatic devices.

The VDM hydraulic electric propellers are CSP in hydraulic mode and variable pitch in electric mode.

Schwarz-man, whom I know and he is correct in his explanation of how the SYSTEM works.

He is describing the interaction of the CSP PROPELLER with MANIFOLD PRESSURE of the ENGINE!!

This eliminated the pilot from having to adjust PROPELLER RPM as with ANY CSP and then have to adjust ENGINE MANIFOLD PRESSURE. It reduced his workload when compared to a using a CSP on regular aircraft engine with manual controls.

+1

I hve eard of that also since long.

Two set of pitch ctrl mechanisms from early design : hydro and elec (that's why the pitch adjust itself slower when eng is off).

The manual pitch crtl was selected only at T.O and landing (11h45 and 11h30 are the value standing in my memory)

The system auto adjust the best pitch value in fonction of eng boost, speed (my guess - not sure ) and barometric alt leading to a given rpm.

It's a primitive version of the system found in the 190 but seemingly working fine as it was installed even on latte war versions.

That wld be interesting to dig into that ;).

Regarding the Merlin CSP, it was a demanding arrangement. You can found trace of this in the Merlin's mustang evaluation report that clearly say that despite increased workload for the pilot the new perfs achievable was a fair price to pay.

[Blackdog_kt]

Yup, my understanding is that effectively the 109 Automatik is just the manifold pressure throttle linked to certain RPM, it keeps the

It wasn't fixed-pitch-to-certain-MAP since if you think about it - if *pitch* would be fixed, rpm would increase/decrease all the time as speed - and load on the propeller blades - would decrease/increase.

In essence its just a single lever CSP where you can set the rpm/map correctly quickly and convinient. You did not have to mind much how to set up the engine.

On Allied planes with CSP, you set the desired RPM and MAP seperately, and the system would keep the RPM constant, by adjusting the pitch as needed. You still had to set the optimal RPM/MAP combination manually, by using two seperate levers, and there was a bit of a backside, since you had to do this in correct order , IIRC/AFAIK for example when increasing power, first RPM needed to be increased with the RPM lever, then boost, otherwise you would run the engine at low rpm / high boost which would stress the engine. The downside was that it required more attention from the pilot, and a bit of extra work.*

This was not modelled correctly in old Il2, and I as I recall it still isn't in COD.

* later it seems that a simplistic mechanical "system" was introduced, according to later Spitfire manuals for example that mention interconnected control. This however I believe was fitted only the some later Mark batches - impossible to tell which ones and how many - and not all planes, and the system was merely a metal rod that ensured that if MAP was increased, the MAP lever grabbed the RPM lever and pushed it forward, too. But unlike on the 109, it did not give optimal rpm/map combinations on most of the lever movement range, it just enabled the pilot firewall the throttle quickly and push both rpm/map the maximum regime.

Yes, you' right. I guess it tied RPM values to MAP values (which means changing pitch to maintain RPM). Well, that's what i get for typing posts about technical things late at night :-P

Also, very interesting what Crumpp has to say. I read that link a while ago and always had the impression those props were only electric and the auto-system just changed pitch to maintain the MAP-RPM relations specified. So they were actually electric in manual mode and hydraylic in auto mode? Very interesting system.

[Crumpp]

http://img705.imageshack.us/img705/2913/vdmhydraulicelectric.jpg (http://imageshack.us/photo/my-images/705/vdmhydraulicelectric.jpg/)

I think the confusion comes from the fact the propeller is electric. An electric motor is what changes the blade pitch.

The motor is operated by a hydraulic switch in normal operations and functions as a CSP. The hydraulic's reads the engine rpm and converts it hydraulic pressure with a regulator. That pressure then operates the electric motor to adjust the blade pitch to maintain the calibrated rpm. This way, both engine and propeller can be operated with a single lever in normal operations.

In an emergency, the pilot can manually operate the electric motor to change the blade pitch to maintain rpm or feather the propeller should he lose hydraulic pressure.

[wallydog69]

I was curious about how the Boost Gauge worked in relation to the changing the prop pitch in the Spitfire IIa. I've noticed that when increasing/decreasing my RPM setting that my manifold pressure will adjust accordingly... is this correct operation? I'm not changing my throttle at all. I'm typically used to seeing the MP stay consistent with the throttle applied so this is a bit confusing for me. Any response greatly appreciated.

[SEE]

All the accounts that I have read from BoB vets flying Spits during the BoB with CSP suggest that it was common practice to set PP for a combat RPM figure of 2650. This would be increased to around 2800 when engaging boost.

I tend to stick with those settings and they seem to work well in CloD in terms of engine management and reliability/performance though I do tweak if necessary to squeeze a bit more out of the Merlin.

[VO101_Tom]

I think the confusion comes from the fact the propeller is electric. An electric motor is what changes the blade pitch.
...

Hi.
The 109 had no hydraulic prop pitch, just a simple electric rpm regulator and motor. That was the point, is that hydraulic failure does not cause an failure of PP. Fw-190 has elektro-hydraulic combined system. I think this verstellgerät, which showed that belongs to 190's BMW engine.

http://iaro.3dmax.hu/images/2011/11/07/abb2.jpg

http://iaro.3dmax.hu/images/2011/11/07/s3.jpg

http://iaro.3dmax.hu/images/2011/11/07/s16.jpg

http://iaro.3dmax.hu/images/2011/11/07/einheitsverstellgerat1.jpg

http://iaro.3dmax.hu/images/2011/11/07/einheitsverstellgerat2.jpg

http://iaro.3dmax.hu/images/2011/11/07/drehzahlregler9-9518.jpg

[TomcatViP]

Thx Tom

It seems I mixed both the 109 & 190 system.

[Crumpp]

The 109 had no hydraulic prop pitch, just a simple electric rpm regulator and motor.

I am confused, are you thinking what I told you was wrong? It is not. The FW-190 and the Bf-109 have the same basic system. An electric propeller controlled by a hydraulic switch. The picture I posted is the BMW 801's system which basically combines many of the separate components of the 109 system into a single unit.

The motor is operated by a hydraulic switch in normal operations and functions as a CSP. The hydraulic's reads the engine rpm and converts it hydraulic pressure with a regulator. That pressure then operates the electric motor to adjust the blade pitch to maintain the calibrated rpm. This way, both engine and propeller can be operated with a single lever in normal operations.

That is the function of the Drehzahlregular. If you look at the diagram, you can see where it is mounted to the engine pad and connects with a splined shaft. It requires an oil filter because the engines oil circulates through it and it reads the pressure to meter the amount of current to control propeller rpm, ie...blade pitch.

It seems I mixed both the 109 & 190 system.

No you haven't mixed them up. They work exactly the same. The propellers are ELECTRIC but are controlled by a hydraulic switch. I think there is confustion over the hydraulic switch. That hydraulic switch is an ELECTRICAL Switch that meters electrical energy based on hydraulic pressure. It changes the electrical current going to the propeller based on the engines oil pressure.

:)

[VO101_Tom]

I am confused, are you thinking what I told you was wrong? It is not. The FW-190 and the Bf-109 have the same basic system. An electric propeller controlled by a hydraulic switch. The picture I posted is the BMW 801's system which basically combines many of the separate components of the 109 system into a single unit.

The basic principles can be the same, can not argue with this, but the BMW Commadogerät is a bit different device than the 109 VDM auto PP. The only hydraulic equipment in the 109 the landing gear.

190's Commandogerät:
http://iaro.3dmax.hu/images/2011/11/07/commandogerat.jpg

[Crumpp]

The basic principles can be the same, can not argue with this, but the BMW Commadogerät is a bit different device than the 109 VDM auto PP. The only hydraulic equipment in the 109 the landing gear.

190's Commandogerät:


We are not talking about the Kommandogerät, we are discussing VDM hydraulic electric propellers. The KG is a completely seperate device and no, it is not the same as the system found on the Bf-109 and nobody ever said it was either. Both the FW-190 AND the Bf-109 use the same type of VDM hydraulic electric propeller. That is a fact. I am not telling you this out of a passing interest. I happen to know what I am talking about because I deal with the real thing.

Crumpp says:
The propellers are ELECTRIC but are controlled by a hydraulic switch. I think there is confusion over the hydraulic switch. That hydraulic switch is an ELECTRICAL Switch that meters electrical energy based on hydraulic pressure. It changes the electrical current going to the propeller based on the engines oil pressure.


Crumpp says:
That is the function of the Drehzahlregular. If you look at the diagram, you can see where it is mounted to the engine pad and connects with a splined shaft. It requires an oil filter because the engines oil circulates through it and it reads the pressure to meter the amount of current to control propeller rpm, ie...blade pitch.

Do you know who I work for?

http://www.white1foundation.org/

Here is OUR Kommandogerät....

http://www.white1foundation.org/parts/kommandogerat1.jpg

YES IT WORKS..

We are also the North American distributor for Motobende. Do you know who they are?? He specializes in Diamler Benz inverted V's. Schwarze-man works for Dirk.

The seven-cylinder Bramo Siemens SH-14 radial engine was stripped,
overhauled, and rebuilt by Dirk Bende of Motobende Gmbh. This company,
based at Köningswinter-Sassenberg near Bonn, specializes in the overhaul of
German-built World War II-era engines and the remanufacturing of engine parts.

http://quax-flieger.de/sites/default/files/VintageSept2011.pdf

[Crumpp]

Here is OUR VDM hydraulic electric propeller:

http://www.white1foundation.org/parts/prop_assemb2.jpg

It functions the same as all VDM hydraulic electric propellers. It functions the same in both the FW-190 and the Bf-109 series.

The only hydraulic equipment in the 109 the landing gear.

Negative Ghost rider.....

The propeller is a VDM hydraulic electric propeller. It functions as a CSP in hydraulic mode (don't get confused, hydraulic mode is when the hydraulic switch is turned on) and as a variable pitch propeller with the switch turned off.

[VO101_Tom]

Here is OUR VDM hydraulic electric propeller:

http://www.white1foundation.org/parts/prop_assemb2.jpg

It functions the same as all VDM hydraulic electric propellers. It functions the same in both the FW-190 and the Bf-109 series.

Negative Ghost rider.....

The propeller is a VDM hydraulic electric propeller. It functions as a CSP in hydraulic mode (don't get confused, hydraulic mode is when the hydraulic switch is turned on) and as a variable pitch propeller with the switch turned off.

Congratulations to the Foundation, will be a very nice aircraft. It will be good to see a bird fly again.

So you are saying that the base of the propeller feather is hydraulic mechanism? I'm sure, it does not have a separate hydraulic system (for example, is something that the landing gear, or (later) the oil/water radiator). The "hydraulic systems" is in a separate chapter of the manuals, and there is no VDM parts. But this means, that it get the pressure directly from the engine? The lubricating oil used as "hydraulic fluid"? It is also true that the air compressor is doing the same way... :rolleyes: I did not know this.

[Crumpp]

So you are saying that the base of the propeller feather is hydraulic mechanism?

The propeller itself is electric but the system uses a hydraulic switch to read engine oil pressure and meter electric current to the propeller.

The lubricating oil used as "hydraulic fluid"?

No hydraulic propeller system AFAIK uses hydraulic fluid, they all use engine oil. That is also why you cycle a CSP several times during your ground run up, to ensure it is filled with engine oil.

http://img851.imageshack.us/img851/4483/drehzahlregularexplaine.jpg (http://imageshack.us/photo/my-images/851/drehzahlregularexplaine.jpg/)

[TomcatViP]

Really fascinating Crumpp.

Took me a lot of time to browse the website.

If I can be of any help :rolleyes:

[Crumpp]

If I can be of any help

Thank you. Buy stuff from us in the gift shop, LOL...donate, it is tax deductible! Get a membership!

Come on down and start drilling rivets! We welcome any help in the project.

If you are interested in the FW-190 or WWII aircraft in general, there is some pretty good stuff in our members website. Lots of never before published pictures too.

[Crumpp]

Congratulations to the Foundation, will be a very nice aircraft. It will be good to see a bird fly again.

Yes it will and thank you. The confusion on VDM propellers is very understandable and is much clearer when you have one, LOL.

[TomcatViP]

Oh well... I am just en engineer with all the top end stuff that comes with. But as I never had to handle a riveting machine by myself It cld be interesting.

[Flanker35M]

S!

Tomcat..our engineers sit in the office for a reason ;) Just kidding, I bet working on a real WW2 bird would be a real adventure :) Crumpp..Has the pilot of White 1 seen the plane lately? I think he would be very happy to see it fly again after so many years..:)

[Crumpp]

Has the pilot of White 1 seen the plane lately?

Unfortunately Heinz flew west a few years ago.

http://www.white1foundation.org/history_orlowski.htm

[TomcatViP]

S!

..our engineers sit in the office for a reason ;)


:grin: