109 prop pitch (rpm) and the supercharger

[Robo.]

Originally Posted by Crumpp

What he is talking about is doing the same a CSP does automatically, a controllable pitch propeller has to be done manually.

Fine Pitch to maximize rpm and coarsen the pitch to maintain rpm as speed increases.

If you don't lower the pitch, the propeller will begin to drive the engine and you will lose performance.

A given manifold pressure and rpm as listed in the POH will deliver the maximum performance for the condition flight listed. The pilot must maintain that rpm by controlling the pitch.

I have my pitch control set on a slider for the Bf-109 and adjust it constantly to maintain the desired rpm.

You are making the right conclusions. The basics of operating an controllable pitch propeller are given above.

There is another quote in that book, I copy & paste the part from bugtracker where we discussed increasing RPM of the DB 601A : http://www.il2bugtracker.com/issues/211

Quote from 'Spitfire on my tail' by U. Steinhilper, a Bf 109 pilot who has been shot down on 27.10.1940 - before the above document has been issued:

'We had to stay alert if we were to survive that day. Things had started to go wrong as we reached our operational height for the mission. When we flew at that height, the engine only just gave enough pull and we constatnly changed propeller pitch and RPM to improve performance. With a flat pitch we could increase the rpm of the engine and get more pressure from the supercharger. Then, by changing the piitch to a coarser setting, we could make up some speed. (... he then describes some issues with the prop pitch gears, probably from the moisture freezsing up at the altitude)... I decided to set the pitch at its flattest, this way I would be able to run the motor at high revs and gain the benefit from the supercharger. It would mean that the motor would have to be runing well above the maximum recommended RPM, but this had happened before in combat, without total dosaster.' (page 25 of the above book, describing how he got in trouble and got shot down / baled out on that very day)

It's not just about maniaining the optimap pitch and engine RPM...