Spitfire IIa prop pitch

[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.