109 prop pitch (rpm) and the supercharger

[JtD]

Originally Posted by Crumpp

Absolutely NOTHING about changing rpm constantly......

Originally Posted by Steinhilper

we constantly changed propeller pitch and RPM

I highlighted the important bit.

[Crumpp]

I highlighted the important bit.

I did the same for you!!

Unfortunately, you don't have any experience operating a variable pitch propeller to know how it works in the air.

Here is how to get extra performance from the Bf-109....

Increase rpm to....

To increase the performance of the Me 109 an increase in the revs for a short time at heights over 5.5 km. will be in future be
permissable. For the DB 601 A engine the normal maximum revs are 2400.
Above full pressure height they may be for a short time be increased
from 2400 to 2600...

And maintain it by:

Ulrich Steinhilper, in his auto-biography (chapter 16) , talks about managing the prop-pitch on the early (E3 and E4 variant) 109s during the Battle of Britain. He states that, in order to achieve max climb rate and airspeed (particularly at higher altitudes) one had to constantly increase and decrease the propeller pitch. Increasing the pitch would engage the supercharger, which would be run for a short period (i.e. a second or less?) to force more air into the cylinders, then the pitch would be dropped back down again to disengage the supercharger and convert the power gained into airspeed, and allowing the engine/ supercharger to rest.

All done to maintain 2600 rpm!!!

...the excess revs can only be obtained by
means of the thumb switch after switching off the automatic device.
In doing this the danger of an additional impermissable increase in
the revs must be watched.

Given that we know how a variable pitch propeller is operated and the physics of how it transfers power to the air we know this quote:

we constantly changed propeller pitch and RPM

Is a general statement without context of time line for rpm.

Not a stumbling block though as I said, we know the physics!!

Since propellers are optimal at a specific speed and rpm....

We know what the RLM meant in the their instructions and what Ulrich Steinhilper is telling us both fit together without contradiction!!

[bongodriver]

Originally Posted by Crumpp

I did the same for you!!

Unfortunately, you don't have any experience operating a variable pitch propeller to know how it works in the air.

But I do, and I can say he has the right idea....

Originally Posted by Crumpp

Here is how to get extra performance from the Bf-109....

Unfortunately, you don't have any experience operating a Bf-109

Originally Posted by Crumpp

Increase rpm to....

increase RPM you say.....but I thought you said there was no RPM changing?

Originally Posted by Crumpp

And maintain it by:....

1. one had to constantly increase and decrease the propeller pitch.....which makes the RPM change

2. Increasing the pitch would engage the supercharger, which would be run for a short period (i.e. a second or less?)......a second or less he says....hmmm doesn't sound like it's maintained for long then....but then that would make sense as 2600 RPM was only acceptable for a short period.

Originally Posted by Crumpp

All done to maintain 2600 rpm!!!

Oh wait!....were you not paying attention? 2600 RPM was for a 'short period' only....like a second or less.

Originally Posted by Crumpp

Given that we know how a variable pitch propeller is operated and the physics of how it transfers power to the air we know this quote:

Is a general statement without context of time line for rpm.

Not a stumbling block though as I said, we know the physics!!

Since propellers are optimal at a specific speed and rpm....

A general statement without timeline for RPM?....how about a second or less from your own quote?

Originally Posted by Crumpp

We know what the RLM meant in the their instructions and what Ulrich Steinhilper is telling us both fit together without contradiction!!

But sadly not a skill you are blessed with.

[JtD]

Originally Posted by Crumpp

Is a general statement without context of time line for rpm.

No, it's a word for word quote. Context can be found left and right of it.

[Crumpp]

'short period' only

Which is where your confusion lies about "constantly changing rpm". If the setting was only allowed for one minute, they you reduce pitch to reach 2600 rpm and coarsen it as speed increases to maintain 2600rpm for ONE MINUTE or a SHORT TIME!!

Given that we know how a variable pitch propeller is operated and the physics of how it transfers power....

Since propellers are optimal at a specific speed and rpm....

We know what the RLM meant in the their instructions and what Ulrich Steinhilper is telling us both fit together without contradiction!!

It is a fact that you operate a selectable pitch propeller by managing pitch to maitain the a constant rpm at a desired setting....in this case 2600U/min.

Round and round the mulberry bush, mulberry bush....

round and round

[ACE-OF-ACES]

Originally Posted by Crumpp

Absolutely NOTHING about changing rpm constantly......

Actully that is not correct either..

Allow me..

Originally Posted by Ulrich Steinhilper

When we flew at that height, the engine only just gave enough pull and we constantly changed the propeller pitch and RPM to improve the performance. With a flat pitch we could increase the RPM of the engine and get more pressure from the super-charger. Then, by changing the pitch to a coarser setting, we could make up some speed.

Hope that helps you see your errors..

Only question left to answer is if you can admit your errors..

[SlipBall]

Originally Posted by ACE-OF-ACES

Actully that is not correct either..

Allow me..



Hope that helps you see your errors..

Only question left to answer is if you can admit your errors..

So what are you saying here?... Are you saying that the throttle came into play with what the author is describing. Because when the pitch is adjusted, it also adjusts the RPM in the same motion.

[ACE-OF-ACES]

Originally Posted by SlipBall

So what are you saying here?...

Ah, I see where you are confused..

Note that is not a quote of something I said.. That is a quote of what an actual Bf109 pilot from WWII said

Hope that helps!

[SlipBall]

Originally Posted by Crumpp

Which is where your confusion lies about "constantly changing rpm". If the setting was only allowed for one minute, they you reduce pitch to reach 2600 rpm and coarsen it as speed increases to maintain 2600rpm for ONE MINUTE or a SHORT TIME!!

Given that we know how a variable pitch propeller is operated and the physics of how it transfers power....

Since propellers are optimal at a specific speed and rpm....

We know what the RLM meant in the their instructions and what Ulrich Steinhilper is telling us both fit together without contradiction!!

It is a fact that you operate a selectable pitch propeller by managing pitch to maitain the a constant rpm at a desired setting....in this case 2600U/min.

Round and round the mulberry bush, mulberry bush....

round and round

Very helpful for others who may visit, don't pull all your hair out

[ACE-OF-ACES]

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.

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.

Ok..

So on one had we have Crumpp telling us that is how it works, that the 109 pilots coarsen the pitch to maintain the RPM..

So we have an opinion of a modern day civilian trained pilot some 70 years after the fact as to how the 109 pilots did it..

But we also have the following..

Originally Posted by Ulrich Steinhilper

When we flew at that height, the engine only just gave enough pull and we constantly changed the propeller pitch and RPM to improve the performance. With a flat pitch we could increase the RPM of the engine and get more pressure from the super-charger. Then, by changing the pitch to a coarser setting, we could make up some speed.

Ok..

So we have Ulrich Steinhilper telling us that is how it works, that the 109 pilots constantly changed the propeller pitch and RPM to improve the performance..

So we have the opinion of an actual WWII military trained pilot as to how the 109 pilots did it..

Which is in conflict of how Crumpp said 109 pilots did it..

So at this point there is no need for any further discussion or debate..

Both sides have spoken!

A) Crumpp a modern civilian trained pilot
B) Steinhilper an actual WWII military trained pilot

Thus the only thing left to do is decide who do you want to belive

Crumpp or Steinhilper

For me the choice is simple

Steinhilper hands down!