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...

[Osprey]

Originally Posted by David198502

exactly what i remember....i think im going to read it again in the near future...

.....except miss out all of the bits where he whines about Galland/Radios and mistreatment of his parents. Shouldn't take long to re-read then......

[pstyle]

Originally Posted by Osprey

.....except miss out all of the bits where he whines about Galland/Radios and mistreatment of his parents. Shouldn't take long to re-read then......

Hah! Yeah there is only about 5% flying and combat in the book..

[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.

[Osprey]

Originally Posted by NZtyphoon

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.

I'd like to think that they did, and as the RAF Flyboy gritted his teeth and fired rounds into the terrified Hun he would've yelled things like "Not so fast Fritz!" and "Your number is up Herr Leutnant!"

[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.