Prop Pitch speeds

I don't want to start a FM discussion as such but I am just curious if there is a particular explanation behind an observation. It may be because the mechanism is different and I would like to know more about it.

The observation is that when I modify prop pitch from 0 to 100% in a Spit it goes considerably faster than in a bf109 which seems to take an eternity to realize the demanded prop pitch angle. And I am quite sure it is not only the rpm needle but indeed the rpm that changes very considerably slower judging from the engine sound.

Was the mechanism behind the 109 so much different than that of the spit? I would really like to learn about this from an engineering point of view.

EDIT: I chose the wrong forum. It should have gone to the general discussion area. Now I cannot change it.

[Skoshi Tiger]

Which Spitfire are you referring to, the MkIa or MkIIa?

In the sim the MkIa has two settings, coarse and fine. The BF109 has a variable pitch propeller, so the pilot choose any propeller pitch they want between course and fine.

The MkIIa has a constant speed propeller. With the CSU the pilot does not directly set the propeller pitch rather they set the RPM of the engine. A governor on the propeller changes the pitch of the propeller so that the engine stays at a particular RPM.

If the engine at a particular throttle setting is going at a higher RPM then the CSU in make the blade angle coarser so propeller bites more air, does more work and the RPM slows down to the set amount.

If the engine at a particular throttle setting is going at a slower RPM it will make the blade angle finer so that engine RPM increases until it matches the required RPM.

At this stage of the war the German pilots had a higher work load as they would have to manually set the required throttle/Propeller pitch for any given situation.


cheers

[IvanK]

The source of the following is from a DB605 engine re builder and pertains to the DB605A Prop pitch system (not the DB601 but I believe the systems are pretty much the same) when operated in the Manual mode ...i.e. what we have in CLOD.

The Clock instrument 1 Hour represents 6 degrees, 10minutes represents 1 degree of Physical blade movement. The Pitch blade angle can be varied at 1 degree per second.

In the DB605 the propeller range was from 22degrees to 46 degrees.
So to transit the entire range would take 22 seconds.

My comments
Observing in cockpit Hurricane engine run up videos were the pilot exercises the prop from Full fine to coarse then back to fine it would seem that the British systems is very much quicker.

Please provide a link to this video. I would like to see it, I am very curious about it.

[MadBlaster]

Interesting post on 109 prop.

http://marseillegruppe.com/foro/view...f328cb9d3b84f4

Also:

http://www.enginehistory.org/Convent...20Electric.pdf

I like 3 degrees per second better.

[Kurfurst]

Originally Posted by 41Sqn_Stormcrow

Was the mechanism behind the 109 so much different than that of the spit? I would really like to learn about this from an engineering point of view.

The Spitfire had hydraulic propeller pitch change system, the 109 (190) an electric, and it was slow from everything I've read, so its correct.

Electric systems tend to be slower than hydraulic ones, but I guess the advantage is that they are less failure prone or sensitive to battle damage (ie. no leaks as in a hydraulic system, less fire risk). The same is true for example for tank turret traverse solutions.

Thank you, Kur. That is indeed a good explanation. Also why I always get prop pitch failure on the spit

Thanks, Blaster. The last link was really nice. I just love these drawings.