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FM/DM threads Everything about FM/DM in CoD

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  #1  
Old 09-13-2012, 05:23 PM
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Quote:
Originally Posted by JtD View Post
Prop and engine are linked at a fixed gear ratio and if engine rpm changes, prop rpm changes as well. For the DB 601 on the 109E the ratio was 1:1.55, so if the engine is at 2400 rpm, the prop is at 1550 rpm.
Ok..

Quote:
Originally Posted by pstyle View Post
Steinhilper makes it clear that engine RPM is changing with this technique.
Ok..

Quote:
Originally Posted by Crumpp View Post
Geez robo,

Quit being dense on this, I have explained how it works. What I am saying is what the pilots are doing.

Your point is wrong.

Right...by maintain rpm!!!!!
Ok..

So we have

JtD pointing out that a change in engine RPM will result in an change in prop RPM

And we have a conflict between what Crumpp and Steinhilper are saying, i.e.

Steinhilper saying change the RPM
Crumpp saying maintain the RPM

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

Crumpp or Steinhilper
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  #2  
Old 09-14-2012, 10:28 AM
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Quote:
Originally Posted by ACE-OF-ACES View Post
Ok..
Crumpp or Steinhilper
Jeez, stop being so dense. Obviously Crumpp, Steinhilper is just a pilot of the era, he knew nothing about aerodynamic engineering. Duh.......
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  #3  
Old 09-14-2012, 11:18 AM
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Quote:
Steinhilper saying change the RPM
Crumpp saying maintain the RPM
Completely out of context. Silliness like this adds nothing to the discussion and simply an attack.


You change rpm to achieve a given performance. For example, best climb rate is acieved at a specific rpm and manifold pressure.

Steinhilper is changing rpm and manifold pressure in this case to an overboost or combat power rating.

Because his propeller is not constant speed, he must coarsen the pitch to maintain that rpm.

Basic propeller operation....

Only difference is a Constant Speed propeller coarsen's the pitch automatically perfectly timed to the airload.

The German pilots had to do it manually.

Quote:
When increasing power, increase the r.p.m. first, and then the manifold pressure.
• When decreasing power, decrease the manifold pressure first, and then decrease the r.p.m.
http://www.pilotoutlook.com/airplane...ller_operation

Steinhilper and Crumpp are saying the exact same thing.
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  #4  
Old 09-14-2012, 02:50 PM
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Originally Posted by Crumpp View Post
Completely out of context. Silliness like this adds nothing to the discussion and simply an attack.
Attack?

Not at all.. I am simply pionting out that what you said about how to fly a Bf109 is in conflict with what Steinhilper said about how to fly a Bf109

At which point it is up to the reader to choose who they want to belive

Thats all
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Theres a reason for instrumenting a plane for test..
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Last edited by ACE-OF-ACES; 09-14-2012 at 02:52 PM.
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  #5  
Old 09-14-2012, 04:55 PM
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Quote:
Originally Posted by Crumpp View Post
Steinhilper and Crumpp are saying the exact same thing.
Nope. You were saying something completely different and you were wrong. But no worries, that happens to everyone.
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  #6  
Old 09-14-2012, 04:57 PM
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Originally Posted by Robo. View Post
Nope. You were saying something completely different and you were wrong. But no worries, that happens to everyone.
I would have to agree with this assement
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  #7  
Old 09-14-2012, 05:52 PM
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Have anyone thinked about the tehcnology differense what we are having here?

What I'm meaning with this is that in 1940s they where just learning what happens near sonic speeds.
oh look we are losing power because prop is going too fast, maybe we should build bigger one may that gives as more power at the same rpm oh noes its start to lose power at lower rpm than the last one!

Also they did not have many other things what they now about aviation today. I really doubt that they could have calculated every thing in 100% accuracy (how many died because near sonic speed jammed lightnings controls?)

Even the engines where little bit different. For example we have synthetic oils what they did not have back at the days.
--------------------------

I had one more point about the pitch twingling thing in my mind when i remembered all those 2-stroke engines is busted years back.

I burned hole in couple of piston because i drove too "fast" for the engine to cool down. After second engine, I learned when i was driving straight long road and having accelerated to the max i needed to relax the throttle for a couple of moment and accelerate again. This acceleration deceleration cycle gave much better average speed than what speed would have been with the highest possible rpm for not overheating the engine.
What if they did the same with bf109?

Little bit Overrev/overboost which give spike in the temperature and little cool down to minimize the damage? ---> Or maybe they just they had boost and revs to add but cooling could not handle it all and they used that power reserve in short periods not giving enought time for sudden engine failure or over heating?

Quote:
To move between .88 and .92 mach usually takes a change of about 110 to 120 RPM.
If plane would go 400km/h at sea level with prop hitting .88 mach in 2400 rpm would it give even 5km/h hour if pushing rpm to 2500rpm? if the rise would be linear it would be 16km/h

What if they suffling the pitch near this area giving more revs untill engine would start to noise up at .93 mach (believing it would be near braking point) lowering it to near .88 mach then pushing it up untill the noise would go up etc. They just did not know it that day what they where doing.

Aw man... Sorry about huge 'what if' post... And sorry if you just lost 5 minutes of your life with it... Amateur speaking.

Last edited by kohmelo; 09-14-2012 at 05:56 PM. Reason: forgot to put [/i]
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  #8  
Old 09-15-2012, 12:14 AM
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You were saying something completely different and you were wrong
Baloney, read what I wrote.
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  #9  
Old 09-14-2012, 04:01 PM
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Quote:
Originally Posted by Osprey View Post
Jeez, stop being so dense. Obviously Crumpp, Steinhilper is just a pilot of the era, he knew nothing about aerodynamic engineering. Duh.......
You Jest..

But this is a good example IMHO of where 'anecdotal evidence' is useful!

Here we have a WWII pilot telling us how they actually used the equipment..

Which may/can be different from how the engineers intended them to use it..

Again, not enough info to say anything wrt validating a flight model

But from the WWII accounts, we know they did 'something' that seemed to improve the performance..

How much.. We don't know for sure

But as for 'how' they did it

I would be more incline to take this WWII combat pilot's accounts over some civilian pilot's interpretation of the account some 70 years after the fact
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Theres a reason for instrumenting a plane for test..
That being a pilots's 'perception' of what is going on can be very different from what is 'actually' going on.

Last edited by ACE-OF-ACES; 09-14-2012 at 05:07 PM.
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  #10  
Old 09-14-2012, 04:37 PM
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Quote:
If that is true..


If you understood the mechanics of how adjustable pitch propellers work, you would know it is true.
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