Spitfire IIa prop pitch

[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]

Originally Posted by Crumpp

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]

Originally Posted by Blackdog_kt

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

Originally Posted by Crumpp

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]

Originally Posted by Kurfürst

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

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]

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]

Originally Posted by Crumpp

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.

[TomcatViP]

Thx Tom

It seems I mixed both the 109 & 190 system.