109 prop pitch (rpm) and the supercharger

[ACE-OF-ACES]

Originally Posted by Robo.

So you're saying (again!) that they were constantly changing the rpm to maintain rpm?

You noticed that too?

Talk about trying to have your cake and eat it too! Or put another way, he is just not able to admit he made a mistake!

Simple fact is the 109 pilot accounts clearly show that they were not trying to 'maintain' the RPMs..

They purposely changed the pitch (flatten) to allow the RPM to increase (rev up), even exceed the recommended RPM limit..

Which in turn allowed the supercharger to rev up!

Than the pilot would change the pitch back (course) to convert the excess RPM into a boost in speed and/or climb as the RPM decreased..

This process was not done once, but done over and over, back to back..

Which is what the 109 pilot noted accounted for that 'wa-wa' sound.

The analogy of the manual transmission clutch fits well here!

Back when I raced dirt bikes we called it 'clutch revving'..

In this analogy, the clutch pressure plate is the prop.. and the flywheel is the air, and the clutch lever is the prop pitch adjustment.. As in pulling in or releasing the clutch lever is analogous to adjusting the prop pitch from flat to course..

The way it worked was you would pull in the clutch to let the engine 'rev up'.. Than release the clutch to convert that revved up energy into a boost in speed or torque..

Here too we did this more than once, not all the time mind you, but when ever you needed a little boost..

Notably, this process also produced a 'wa-wa' sound..