E-7 RPM at takeoff

[Roland_HUNter]

Hello everyone!

I'm laic in the prop pitch topic about E-7.

So, please somebody explain me:

With E-7, why I cant have more than ~2100 RPM with 100% throttle/ fine pitch 12:30, while I'm stationary?

The RPM only increasing while the plane getting faster and only reach the 2300 RPM /combat RPM/ around 180 km/h, when we usually taking off.

Why?
Other 109s don't have this "issue".

Thanks in advance for the answers.

[41Sqn_Skipper]

Stationary on the ground it should be 2200-2250 RPM @ 1.35 ata with prop at 12:00.

[Roland_HUNter]

If I lowering the prop pitch to 12:00 from 12:30 the RPM is decreasing aswell.

And sorry , Sadly I can't speak german. there is any description in the report what you uploaded: why only the E-7 has this "unique problem"?

[6./ZG26_Klaus_Mann]

On 5/28/2021 at 5:08 PM, Roland_HUNter said:

If I lowering the prop pitch to 12:00 from 12:30 the RPM is decreasing aswell.

And sorry , Sadly I can't speak german. there is any description in the report what you uploaded: why only the E-7 has this "unique problem"?

It is completely Normal for an early Constant Speed Prop to have a minimum Pitch Angle Large enough not to allow the Engine to Overrev at full Power, it is that Way on many Planes. This Way even if you have a Propeller Failure after Take-Off you still have useful thrust to make a Go-Around.
 

Most old Propellers have very limited Travel, often only something like 20°. In the P-40 you will also not reach full RPM with 45" until you Lift Off.

 

It's not a Problem, or Bug, not even a Feature, just the Way things were done back in the Day, and even today many GA Aircraft have Propellers that will not go to 100% RPM while Static or on Take-Off.

This is a DC-3, it's minimum Prop Pitch is 15°, which is enough to Prevent Max Rev on the Ground:

[Roland_HUNter]

2 hours ago, 6./ZG26_Klaus_Mann said:

It is completely Normal for an early Constant Speed Prop to have a minimum Pitch Angle Large enough not to allow the Engine to Overrev at full Power, it is that Way on many Planes. This Way even if you have a Propeller Failure after Take-Off you still have useful thrust to make a Go-Around.
 

Most old Propellers have very limited Travel, often only something like 20°. In the P-40 you will also not reach full RPM with 45" until you Lift Off.

 

It's not a Problem, or Bug, not even a Feature, just the Way things were done back in the Day, and even today many GA Aircraft have Propellers that will not go to 100% RPM while Static or on Take-Off.

This is a DC-3, it's minimum Prop Pitch is 15°, which is enough to Prevent Max Rev on the Ground:

Thank you for the explanation!

[6./ZG26_Klaus_Mann]

1 hour ago, Roland_HUNter said:

Thank you for the explanation!

Just Consider that the Spitfire, Hurricane and 109 all went from fixed to manually variable to automatic Pitch and that the E-7 still essentially has that Manual Propeller but with an automatic Speed Controller added.
Now, think how tricky already the 109 was to fly, and how making the Propeller in such a way that you would have had to adjust it constantly on take-off for best performance and how much workload it would have added.

Better to just make it so that you wouldn't have to start adjusting until flaps and gear were up and you were in a steady 230km/h climb.