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Propleller Pitch....

PostPosted: Sat Jul 12, 2003 2:36 am
by Moach
how can i EFFICIENTLY use the propeller pitch control?
??? ???
i mean, how does it work, exactly?
i can't seem to use it without losing airspeed, which seems to be the exact opposit of it's supposed to do...

...right?

Re: Propleller Pitch....

PostPosted: Sat Jul 12, 2003 3:31 am
by ozzy72
Adjusting the pitch shouldn't alter the speed too dramatically unless you feather the prop completely!
What it does do is help you increase your range by using less fuel, but you will get a slight decrease in speed.

Ozzy

Re: Propleller Pitch....

PostPosted: Sat Jul 12, 2003 3:58 am
by Fozzer
When you take-off, (and land), the prop should be set to fine. This puts less strain on the engine as the propellor spins faster. (Like first gear on a car).
Once in the cruise adjust the prop to coarse pitch. This takes bigger bites out of the air and the prop spins slower. (Like top gear on a car).
Note that as you increase the pitch the revs on the tachometer will decrease, adjust it 'till the needle in just inside the green arc for maximium efficiency.
I love playing tunes on the propellor control... ;D...!
(Also try reducing the mixture control slightly, (weaker), as well. This will also reduce fuel consumption, and increase efficiency).
When you have done this, and trimmed the aircraft correctly, you will notice a significant increase in air speed... 8)...!

NOTE:...Don't forget to put the prop control to fine pitch and the mixture control to full rich prior to landing, just in case you need full power for a "go around", or "missed approach"... :o...!!
...and make sure "carburettor heat" is off..!

Cheers all... ;D...!
Paul.
(England).

Re: Propleller Pitch....

PostPosted: Sat Jul 12, 2003 4:19 am
by packercolinl
Don't know if it shows in FS but when you pull back on the stick to initiate a climb and don't apply enough throttle you can hear the prop 'chopping' as the angle of attack(the prop is after all a set of wings)changes.
Don't know how I know that ::)

Re: Propleller Pitch....  

PostPosted: Sat Jul 12, 2003 4:21 am
by Calb
Best way to understand the propeller pitch issue is in knowing there are only TWO (yes, 2) pitch settings of any consequence -- CLIMB and CRUISE. Matter of fact, fixed pitch props (usually wooden) typically come in these two varieties (yes, there are "compromise" versions too). The name suggests their intended use.

The climb prop will give the best (shortest) takeoff and rate-of-climb performance because it's pitch is fine which allows the engine to rev higher, thereby developing it's full rated horsepower.

The cruise prop, on the other hand, affords better cruise performance in terms of fuel economy (and therefore range) at a small sacrifice in takeoff distance and rate of climb due to having a coarser pitch and therefore lower engine RPM.

The variable pitch prop has the ability to provide the best of both worlds.  Pitch(RPM) and throttle setting(manifold presure) are interrelated and there is a prescribed sequence when changing each.

Take the default Baron, for example. For take off you have full high RPM, rull rich mixture and full throttle.  You fly it off when speed reaches the top of the white arc and establish the climb.  You pull the gear up and shortly thereafter you reduce throttles for reading of, say, 24 inches of manifold pressure. Then, you reduce RPM to 2400 and continue the climb. As you climb, increase throttle to maintain 24". If you climb high enough you'll find you can't maintain 24" even at full throttle. Not to worry, that's just the way it works.  Let's say you are going to cruise at 5000 ft.  After levelling off, you would reduce throttle so manifold pressure reads 22 inches followed by lowering RPM to 2300.  You can then fiddle with the mixture controls but I find there's very little difference between lean and cut off so I don't often bother.

BTW -- all this "presumes" the air file (whatever aircraft it may be) reacts realistically when the throttle and prop controls of used realistically.

This whole subject comes under the generic heading of "engine management".

Cal
CYXX

Re: Propleller Pitch....

PostPosted: Sat Jul 12, 2003 4:49 am
by packercolinl
Very nice Calb! Thank you!! :)