109 prop pitch (rpm) and the supercharger

[NZtyphoon]

Originally Posted by Robo.

Quote from 'Spitfire on my tail' by U. Steinhilper, a Bf 109 pilot who has been shot down on 27.10.1940

A question, and waaay OT - just how often did German pilots yell "Achtung Spitfire!!!" and did they ever yell "Spitfire!!" - I have long taken this to be an urban myth peddled by old British comics (a few years ago I flipped through an olde collection of Victor and Commando comics - every time a German pilot got bounced he yelled "ACHTUNG, SCHPITFUERER!!" or a variation thereof, then "AAARGH!!" as their 109 or 190 was torn apart...)

Did German pilots and aircrew actually use the British "Spitfire", or were they more likely to use the German equivalent Hitzkopf or Feuerkopf?. Just a question and pardon my ignorance.

[Crumpp]

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

It is all about maintaining optimum pitch and rpm.

As you coarsen the pitch to reacquire the rpm, you will notice an increase in performance.

In the quoted cases, they are setting the engine to a limited over boost and coarsening the pitch to maintain rpm.

That is how it works.

The experienced pilots you are quoting are coarsening pitch before rpm drops. If you know the approximate performance for a given setting, then coarsening the pitch at rpm will cause an increase in performance within limits.
It will also cause a subsequent manifold pressure drop and the performance will suffer as a result if outside of a narrow range.

[kohmelo]

How am i getting the feeling about those quotes that they "kick the clutch" to acquire better rpm powerband?

Like with those insane 80s turbocharged cars they used clutch slip to keep engine at better rpm (in the narrow maxpower area). Even without charger it would give technically short boost --> In car you kick the clutch for so long that you can rise RPM to best rpm usually the power from engine and momentun in driveshafts makes your car "burn rubber," or go "slowly sideways"

Technically would it be the same thing with prop pitch? "feather" prop to add rpm and then kick in the more coarser? pitch to force that engine power and momentum to movement for that narrow timeline.
I really don't think that pitch would change fast enough for that have any kind off use.

As for milling pitch up down in narrow area there might be some advantages if doing this at point where engine starts to lose RPM.

Well working or not i'll might test this for my own amusement.

[Crumpp]

"feather" prop to add rpm

You would not feather the prop to add rpm. Feathering is where you coarsen the blade pitch to the point the chord is parallel to the relative wind.

A feathered propeller produces no thrust at all and minimal drag. It would be very poor practice to run the engine with a feathered propeller and the engine is shut down when the propeller is feathered.

It is done to keep the shut down engine propeller from windmilling and causing loss of control.

http://www.youtube.com/watch?v=E7x8iAjFtzI

You are right about the Bf-109 pilots doing the aerial equivilent of "popping the clutch". That is exactly what they are doing so to speak. It is an advantage of a controllable pitch propeller. It is something that would take experience to do. The pilot must understand the principles of propeller operation regarding pitch and the relationship of manifold pressure and rpm.

[kohmelo]

Originally Posted by Crumpp

You would not feather the prop to add rpm. Feathering is where you coarsen the blade pitch to the point the chord is parallel to the relative wind.

Sorry about that, I really do did'nt know the exact terms in english. So term would be quite opposite what i meant.
Still you did understand what i meant. Great!

[Crumpp]

Still you did understand what i meant. Great!

I knew exactly what you meant! You expressed it well.

[Robo.]

Originally Posted by Crumpp

It is all about maintaining optimum pitch and rpm.

As you coarsen the pitch to reacquire the rpm, you will notice an increase in performance.

That is how it works.

I understand how it works, no need for bold writing mate. My point was that it's not all about setting your engine for certain (optimal) rpm and keeping it that way - but especially at the altitudes, you would need to work with it constantly to get more speed. This is all relevant to the thread title which is about supercharger and rpm in 109s.

Originally Posted by Crumpp

In the quoted cases, they are setting the engine to a limited over boost and coarsening the pitch to maintain rpm.

To mainatin speed / performance. Not rpm... it's all explained in detail in the above quote...

[Crumpp]

Geez robo,

Quit being dense on this, I have explained how it works. What I am saying is what the pilots are doing.

that it's not all about setting your engine for certain (optimal) rpm and keeping it that way

Your point is wrong.

To mainatin speed / performance.

Right...by maintain rpm!!!!!

If you lived close by, I would take you and show you how it all works. My plane has a very accurate Engine Monitoring System.

Manifold pressure, rpm, and mixture are all interelated to produce a given performance.

[JtD]

Steinhilper explains how he's constantly changing pitch and rpm to improve speed performance. It would be interesting to know if the perceived increase in speed was placebo or not, but that doesn't change the method.

[Robo.]

Originally Posted by Crumpp

Geez robo,

Quit being dense on this, I have explained how it works. What I am saying is what the pilots are doing.

Thank you, I appreciate how you're trying prove you're right at all times, especially when you happen to be wrong.

Again - 'to maintain rpm' in my book means keeping it constant. That is possible and desirable for optimal performance of a 109 (even in CloD), but it is clearly not the case with the practice described in Steinhilper's quote, he was actually changing (changing is the word here) rpm up and down to maintain his speed = he would be slower without doing that = he would be in more danger with all those Spitfires around. I thought that quote would be interesting for virtual pilots in here and it is on topic with this thread (especially for supercharger part), but you obviously assumed that I don't know how things work because it is soo complicated. I am so glad to have you on this forums so thank you again for your kind offer.