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| IL-2 Sturmovik The famous combat flight simulator. |
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#2
12-13-2007, 01:23 PM
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It's something like the transmission on your car in effect, but not really. The pitch on the propeller is the angle at which the blades meet the air, the greater the angle (or pitch) the more air the prop "grabs". Most of the aircraft in IL2 that have adjustable pitch have a constant speed prop, where you set the engine speed you want and the propeller automatically turns the blades to keep the engine at that RPM, the theory is that you are applying the power directly to the air at the RPM you set rather than reving the engine higher. More like traction control than a transmission in that respect. So when you set the "prop pitch" in game, you are setting the engine RPM. If max RPM on a given plane is 3000, then 66% will be 2000, etc. That said, the aircraft in the game are all quite different, and like different settings for different purposes. In general, 95-100% will be for max power, eg. takeoff, climbing, fighting. (experiment, most planes make best power at 100%, some, esp japanese planes run better at slightly less RPM, and many planes overheat less at lower RPM) 60-80% will be for cruising, diving, limping home, etc. lower rpm settings will keep the engine cooler,use less fuel and ease wear and tear on the engine. Many planes dive much better at lower rpm settings, dont forget to throttle back! you can over-rev your engine. One big thing, always land at 100%, if you need power for an abort, you need it fast! Oh, BTW some planes like the 109, 190 and many spitties are fully auto, controlling even the rpm automatically. Have fun. 
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#3
12-14-2007, 07:59 AM
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Of course 95-100% PP will achieve the most power .... but not speed. It's much like you push the pedal to the metal in first gear in a car. You will accelerate very fast with very high RPM's, but if you want to accelerate further, you have to swith to second/third ... gear. In other sims - like BoB:WoV for example - you have to adjust the proppitch according to your speed, like the transmission in a car. You DON'T achieve the highest speeds with 100% PP. If you cruise in the 109 for example with 300 kph and decrease PP accordingly, you can actually see the speed increase dramatically. (Which seems logical, because the prop blades grip more air). In IL2 you actually loose speed when decreasing PP in level flight - which I find kinda strange. Last edited by Therion_Prime; 12-14-2007 at 08:04 AM.
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#4
12-14-2007, 08:20 AM
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Thats wrong. Your comparison with a manual transmission in a car is only valid when having a manual pitch control, but not for constant speed. A csp is a car with automatic transmission where 100% rpm is for "sporty" driving and everything below 100% rpm is for economical driving.
Top Speed is at maximum rpm and maximum boost, just look at historic performance tests, for top speed they always were at maximum rpm and maximum boost. Why would they do this when there was more speed at lower rpm 
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#5
12-14-2007, 10:07 AM
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Have read here: http://people.ee.ethz.ch/~chapman/il.../proppitch.htm
Be patient with it, read it over a few times if you have to...you'll get it eventually.
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#6
12-14-2007, 11:51 AM
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need a bit of help on this
I think I understand a little of the prop pitch article, but I'm not all that clear on it as I think I should be. Someone check me out, please. I'm thinking of altitude, and speed situations where I need to adjust prop pitch to either achieve, or maintain performance. For instance:
* I think I need more pitch at higher altitude for biting into the thinner air, and less drag on the airfoils (wings, and propeller blades), especially if speed has fallen off like during a long climb. * I think I need to decrease prop pitch when I dive from high altitude, as speed builds up, and engine rpm rises ( I'd have to watch, and adjust pitch to keep rpms from over-reving the engine). * I think I don't need as much "bite", in general, from the prop at lower altitudes where the air is more dense. * I think all of the above are dependant on tactical power requiremens. That is, whatever it takes to keep the engine in the desired performance regime: Max aircraft speed at low altitude versus max aircraft speed at high altitude: increasing diving speed: takeoff: landing: cruising. I guess it all depends on the individual aircraft, and knowing your plane, or watching the engine revs. Anyway, that's my thinking. Am I on the right track anywhere here? thanks! Flyby out
__________________
the warrior creed: crap happens to the other guy!
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#7
12-14-2007, 03:33 PM
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CEM is so messed up in this game, I mean, he never really had it modeled. I believe you got things mixed up a bit. Manual pitch control and constant speed propellers are the same thing. When you set a RPM with your prop lever you are doing two things, changing the angle of the blade AND setting a particular RPM. Neither change with power (manifold pressure) inputs. If you're confused in game about how to use these things, its understandable since it isn't modeled correctly. Each aircraft has a chart in the pilot operating handbook that shows manifold pressure and prop settings for different phases of flight ie; takeoff, climb, cruise climb, cruise, decent, approach and landing. For full power and speed its always full MP and full Prop. Again, this game doesn't model it correctly and the little tricks learned to do different things in here (concerning CEM) would not work in a real plane, it would destroy the engine. I fly aircraft with constant speed propellers daily for work, turbines included. My boss would kill me if I pulled my pp back to 50% (as it is in game) and had full power. lol Here's an example that explains a bit of what you shouldn't do, generally. It puts it into words better than I can. "For any given RPM, there is a manifold pressure that should not be exceeded. Manifold pressure is excessive for a given RPM when the cylinder design pressure is exceeded, placing undue stress on them. If repeated or extended, the stress would weaken the cylinder components and eventually cause engine failure." http://www.coryat.com/faa-pp-written/index11.html Read the Q & A there. It should help explain things a bit. The short answer to someone about pulling your PP back for more speed isn't correct. Again, before you even begin to pull your prop back you have to pull your throttle back or you will damage your engine, just not in game because it isn't modeled. One last thing, that info is for real world aircraft/flying. In game you can do whatever and have different results, none of which are correct in the real world. Last edited by BSS_Sniper; 12-14-2007 at 03:36 PM.
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#8
12-14-2007, 04:49 PM
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With CSP, inside the CS governor limits, the blade angle WILL change with speed and attitude variations. Since Speed and attitude will change il you change power (manifold pressure), then blade angle WILL change.... and same if you use elevator input to climb or dive. Manual pitch control is different: The pitch angle is directly controlled by the pitch lever. With IL2, almost all planes are CSP equiped when they don't have fixed pitch. Only Bf109 (and maybe Bf110... don't remenber...) use manual prop pitch when automatized control is off. Even FW190 never use manual controlled pitch, but CSP when Kommandogerät is off.
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#9
12-14-2007, 08:16 AM
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thank you for your details, I am no mechanic (ie; dont even know how a transmission works) and I am finding the concept a little ambiguous...
This is how I see it...can you please correct my thinking where need be... If I set the prop pitch to 66% (in a plane with a constant speed prop) this will: adjust the pitch of the blades to have less of an angle therefore making the prop spin easier and faster...increasing the RPM of the engine?? Another thing , you say "when diving use 60-80% prop pitch, and also to throttle back". Does this mean that the increasing air speed (which your plane encounters during a dive) can and will increase the speed of your planes prop, which is what causes over revving? Therefore as a precaution you should throttle off and change blade pitch?
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