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View Full Version : Usage of prop pitch in combat/cruising.



PanzerAce
08-31-2008, 03:10 PM
So now that I have it mapped, I'm trying to figure out how to use prop pitch to maximize speed/cooling of the engine. But I don't have *any* idea of how to use it. Sometimes it seems like lowering the pitch reduces my acceleration, sometimes it raises it. Is there a guide to using pitch on various planes anywhere?

DKoor
08-31-2008, 05:54 PM
I never heard that you can improve your performance by lowering pp in any way, other than in dive, and that too is doubtful somewhat or at least you wont gain some super-duper advantage.

Cooling? Yes, lowering pp should help a lot... and you can still go very fast at level.
But that will probably aircraft turn into a beaten dog if you climb with low pp.

One can see on tracks how people sometimes lower their pp and stuff, but if you really are not sure what to do and when to do it, then it is probable that you'll do more harm than good by fiddling with pp.
Much better idea for a start would be to fly on lower throttle and in fast cruise then firewall it if necessary in combat and to experiment with your fav type over the time, so once when in combat you'll know exactly what to do and when to do it.

Go in QMB and measure some times of climb, dive and level flight on same throttle and different pp. Record tracks for easier checking (you have timer on tracks). Then change throttle value and repeat... etc. Best way to check it all out if you like.

K_Freddie
08-31-2008, 06:03 PM
The best explanation I came across..

Think of PP as gears of a car..
The lower the gear (Prop-Pitch) ratio (higher gears 4th and 5th), the lower your engine has to rev for the same speed.

There is a power limit for each a/c, which you have to work out.
And there's fuel mixture to consider as well, but this is dependent on altitude.

http://forums.ubi.com/groupee_common/emoticons/icon_cool.gif

WTE_Galway
08-31-2008, 06:06 PM
Originally posted by DKoor:
I never heard that you can improve your performance by lowering pp in any way, other than in dive, and that too is doubtful somewhat or at least you wont gain some super-duper advantage.

Cooling? Yes, lowering pp should help a lot... and you can still go very fast at level.
But that will probably aircraft turn into a beaten dog if you climb with low pp.

One can see on tracks how people sometimes lower their pp and stuff, but if you really are not sure what to do and when to do it, then it is probable that you'll do more harm than good by fiddling with pp.
Much better idea for a start would be to fly on lower throttle and in fast cruise then firewall it if necessary in combat and to experiment with your fav type over the time, so once when in combat you'll know exactly what to do and when to do it.

Go in QMB and measure some times of climb, dive and level flight on same throttle and different pp. Record tracks for easier checking (you have timer on tracks). Then change throttle value and repeat... etc. Best way to check it all out if you like.

I stick to auto though I fiddled around a few years back and seemed to be getting slightly higher straight and level speeds in a 109 by fiddling with pitch and redlining the engine but never bothered trying to test it properly and confirm whether it was just my imagination because the engine didn't last long enough to make it useful.

Janus1980
08-31-2008, 06:26 PM
I don't know for absolutely sure that i am right to do this , but my experience in the P-39 taught me to use 100% prop pitch to climb or when in level flight until 450-480km/h in order to reach combat speed quicker , but then switch to 90%prop pitch and close rad to reach my top speed over 500km/h , helps me to reach top speed quicker than if i leave it to 100% prop pitch , at least i often had this impression , especially when in very shallow dive during combats when you follow a fast plane trying to flee (for instance above 600 km/h , i always set 80% or lower to maintain that speed the best i can , as long as i am in shallow dive , cause i noticed that with 100% prop pitch , you lose your speed quicker when over 600km/h than with a lower prop pitch setting which would help me to maintain the high speed longer during a chase i noticed ) .

When i am in a dive , i noticed i pick up speed quicker when i lower prop pitch once i am over 480-500km/h , my aircraft then picks speed quicker (at max throttle )if i set 80% or lower than if i dive with 100% prop pitch (which seems like it acts as a brake in a dive ) , i use 100% prop pitch only for climbing , landing ( in order to lose speed quicker , throttle to 0 , prop pitch 100% , rad open , and still have possiibility to accelerate fast by throttling if something goes wrong) or for accelerating the fastest i can from 0 to approx 460-480 km/h in level flight on this plane , i change prop pitch depending on my speed (over 480 to approx 580kmh i use 90% , over 580 kmh 80% and lower ) , like said K_Freddie , as it were gears of a car , but from plane to plane , the speed at which it is best to change prop pitch might vary

M_Gunz
08-31-2008, 07:20 PM
Originally posted by PanzerAce:
So now that I have it mapped, I'm trying to figure out how to use prop pitch to maximize speed/cooling of the engine. But I don't have *any* idea of how to use it. Sometimes it seems like lowering the pitch reduces my acceleration, sometimes it raises it. Is there a guide to using pitch on various planes anywhere?

It has to do with your power and speed together, which is testable if you fly at less than full
or in steep dives.

Props are wings and wings have drag, the parasitic drag squares with speed. The prop also has
induced drag that your CSP rpm-setting (called pitch) can affect.

The speed of the prop blade is by rotation and forward speed of the plane and it varies along
the length of the blade. The speed of the blade tip you can find as the third side of a right
triangle where side one is the speed of the plane in m/sec (or ft/sec) and side two is the
radius of the prop x 2 x Pi x rpm / 60. At 2500 rpm the tips of a 2 meter prop will be going
about 262 m/s just turning around. That's about 942 kph without any forward speed at all and
not a little bit of drag even without the induced drag from lift.

With CSP (Constant Speed Prop):
As long as your engine is making enough power to overcome the drag it's fine but once it is
not the prop turns to a finer pitch to allow the rpm's to be held and that means less than
optimum thrust.

So when you're cruising at 70% power you should find that too high an rpm will get you less
speed than you can get at about 70% rpm with best match depending on the plane and altitude
since power at altitude and power vs prop vary plane to plane.

But I find that matching rpm % to power is generally a good start point in setting up cruise.

Note that a slower turning prop also makes less torque and related effects, I run less rpms
in high speed (relative to target) gunnery passes and seem to have an easier time correcting
my aim, there's less jiggle.

Running high rpm and low power is a great way to control your landing approach speed too.

Bearcat99
09-01-2008, 12:17 AM
Originally posted by PanzerAce:
So now that I have it mapped, I'm trying to figure out how to use prop pitch to maximize speed/cooling of the engine. But I don't have *any* idea of how to use it. Sometimes it seems like lowering the pitch reduces my acceleration, sometimes it raises it. Is there a guide to using pitch on various planes anywhere?

Depending on the plane... The 109s at least (I don't know if there are others) have manual prop pitch and you have to be careful. I am not good at managing it.. I overheat my engine 7 times out of 10... on the American planes though... The Mustang in particular.. the 90/90 rule applies. If you apply 90% throttle and 90%PP you will wind up going faster than just 99% throttle & 100% pitch. Experiment between 90 & 100 for both... with different planes.

Janus1980
09-01-2008, 09:24 AM
I'm not convinced it is worth touching manual prop pitch in the 109 anymore though , i remember a few years back when AEP got out , it was still very efficient to use manual prop pitch in order to climb faster , you had to be careful to not go above a certain rpm limit depending which version of 109 ,but it defintely helped you to climb faster than on auto , since PF (don't remember which patch ) , 109 does not seem to benefit from manual prop change anymore .

Also in what i read , real pilots rarely used manual prop pitch in 109 , only rare times for landing , i always use Auto in game , only Axis plane i use manual prop pitch is on the Fw-190 (to climb faster) .

For Allied planes in game however (Soviet , American mainly ) , IMHO , changing rpm at the right moment (well it's also called prop pitch in game ) can really give better performances in my experience , i think it is important to manage well this aspect in planes like Yaks , P-51 , P-47 , Lavochkin , P-39 etc.. for better speed , energy retention and cooling the engine

Altamov_Steppes
09-02-2008, 08:10 PM
Originally posted by Janus1980:
I'm not convinced it is worth touching manual prop pitch in the 109 anymore though , i remember a few years back when AEP got out , it was still very efficient to use manual prop pitch in order to climb faster , you had to be careful to not go above a certain rpm limit depending which version of 109 ,but it defintely helped you to climb faster than on auto , since PF (don't remember which patch ) , 109 does not seem to benefit from manual prop change anymore...

Also in what i read , real pilots rarely used manual prop pitch in 109 , only rare times for landing , i always use Auto in game , only Axis plane i use manual prop pitch is on the Fw-190 (to climb faster) .



The DB engine in the 109 was such a step forward that it needs 'auto-prop'. The majority of propellors in WW2 eventually were similar Constant Speed Propellors on a powerful engine).

The 109 cannot take a swith to PP easily. One can test PP out on the 109 (shift 0) by nose up a little then cutting the RPM and then reduce PP to 0.
It is from there that a feel can be developed for how the DB handles manual PP changes. There's little room at medium to high speed.

Using co**** PP on landing is also a frequent practice in high-performance pistons today. Some military trainers come to mind.

M_Gunz
09-03-2008, 01:43 AM
109 auto manages engine as well as prop and does so IMO better than simple linked levers like
used in later P-39's.

I wonder how close the 109 system was to Kommandogerat used by FW? I bet Kurfurst knows!
Probably Crumpp too from museum work but then it goes to 20-30 pages of "did so"-"did-not"
and the lock after pile-up with no goal by either side.

The electric prop control mechanism has been shown here, very similar to Curtiss electric prop
though where the whole electric prop control originated is probably debatable.