109 prop pitch (rpm) and the supercharger

[Crumpp]

2400 to 2600...

Yep, they were allowed to increase rpm to 2600. In order to maintain that increased rpm overboost condition, they have to manage the pitch just as Steinhilper says!!


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

[kohmelo]

Originally Posted by Crumpp

Yep, they were allowed to increase rpm to 2600. In order to maintain that increased rpm overboost condition, they have to manage the pitch just as Steinhilper says!!


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

Above full pressure height they may be for a short time be increased
from 2400 to 2600...

[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.

[Robo.]

Originally Posted by Crumpp

All done to maintain 2600 rpm!!!

No Crumpp, you're wrong. Please stop arguing.

IvanK that's the (in)famous document, may wonder about the date added by pencil. To me it seems that even if the date is post-BoB, the practice of overreving the engine above FTH was common during the Battle. Steinhilpers quote for example is dated 27.10.1940.

[IvanK]

Agree Robbo

[Crumpp]

It would also appear to be conditional on Auto Prop pitch installation.

No, it says the automatic device has to be modified in order to use the increased rpm.

Until then, a switch to turn off the automatic device is necessary.

In otherwords, if you have an automatic propeller, you must turn it off and use the propeller as the original selectable pitch propeller.



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[ACE-OF-ACES]

Originally Posted by Crumpp

No, it says the automatic device has to be modified in order to use the increased rpm.

Increase..

Not maintain?

Well better late than never!

So.. Is it safe to assume that I can put you down for a vote for Steinhilper over Crumpp?