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MrQBerrt
02-23-2005, 11:07 AM
I'm sorry if you clicked on this looking for an easy to understand guide on Complex Engine Management. I'm not posting one, I'm requesting one.
I have read about 5 guides out there that are commonly linked to (I frequently browse Airwarfare and other sites so I think I've probably hit most of the common guides including Eastern Skies and the one by Vulgar). But I'm looking for something a bit different.

Lets focus on prop-pitch for a second. Say I'm doing a 220 mph flat turn in my F4U and I increase the prop pitch from 100% to 50% while maintaining a constant back pressure on my stick ... what should happen?

I should slow down and my turn should tighten ... more than likely, I'll start to black out. I've read a bunch of guides on prop pitch and I never knew this until I read this (http://www.2gvsap.org/phpBB2/viewtopic.php?t=730).

I've experimented with this some more and found the following:
If my throttle is at idle, increasing the prop pitch (lowering the percentage numbers in IL2) will cause less drag
If my throttle is at maximum, increasing the prop pitch will cause more drag (I'm guessing because it causes the prop to turn slower)
Now these might not always be true, but so far, they seem to be good general guidelines and have helped my flying quite a bit.

Now this is the type of stuff I'm looking for. Hats off to all the guys who have written CEM guides. I've really enjoyed reading them and learned a lot from them. But I think that there is still a gap in the material on CEM. I can read a book on how a clutch works, but still not know that I can slip a clutch in order to get an RPM boost. Similarly, after reading a lot of CEM material out there, I still did not know that increasing prop pitch could tighten a turn.

What I would like is a list of practicle guidlines and tips for prop-pitch and the like. This might just be me who want this, but I imagine a lot of people would benifit from guides written in this manner.

MrQBerrt
02-23-2005, 11:07 AM
I'm sorry if you clicked on this looking for an easy to understand guide on Complex Engine Management. I'm not posting one, I'm requesting one.
I have read about 5 guides out there that are commonly linked to (I frequently browse Airwarfare and other sites so I think I've probably hit most of the common guides including Eastern Skies and the one by Vulgar). But I'm looking for something a bit different.

Lets focus on prop-pitch for a second. Say I'm doing a 220 mph flat turn in my F4U and I increase the prop pitch from 100% to 50% while maintaining a constant back pressure on my stick ... what should happen?

I should slow down and my turn should tighten ... more than likely, I'll start to black out. I've read a bunch of guides on prop pitch and I never knew this until I read this (http://www.2gvsap.org/phpBB2/viewtopic.php?t=730).

I've experimented with this some more and found the following:
If my throttle is at idle, increasing the prop pitch (lowering the percentage numbers in IL2) will cause less drag
If my throttle is at maximum, increasing the prop pitch will cause more drag (I'm guessing because it causes the prop to turn slower)
Now these might not always be true, but so far, they seem to be good general guidelines and have helped my flying quite a bit.

Now this is the type of stuff I'm looking for. Hats off to all the guys who have written CEM guides. I've really enjoyed reading them and learned a lot from them. But I think that there is still a gap in the material on CEM. I can read a book on how a clutch works, but still not know that I can slip a clutch in order to get an RPM boost. Similarly, after reading a lot of CEM material out there, I still did not know that increasing prop pitch could tighten a turn.

What I would like is a list of practicle guidlines and tips for prop-pitch and the like. This might just be me who want this, but I imagine a lot of people would benifit from guides written in this manner.

MrQBerrt
02-23-2005, 11:19 AM
Ok, here's another practicle question or two.

In a dive, if I raise my prop pitch (lower the prop %) then I'll drop my RPM's which can be useful to keep from over-reving. But lets say I'm at full throttle and I do this, should I speed up because I'm up-shifting, or should I slow down because my prop is turning slower?
Now lets say I'm at idle throttle. Should I speed up because the blades are closer to horizontal to the wind causing less drag, or should I slow down (for who knows what reason)?

And just so you don't think all my questions are about the prop here is one re fuel mixture. Say I'm in a DF, down the openent and my engine is overheating. I want to cool down as fast as possible. Should I go 120% fuel mixture and make my engine sputter so that the fuel will have a cooling effect on the engine?

And while we're on the subject of cooling, does a throttle at 50% force more air into an engine than a throttle at idle (with same air-speed)? In other words, can I cool off faster with my throttle paritally open or all the way closed?

whiteladder
02-23-2005, 01:24 PM
Couple of points here, increasing prop pitch does not tighten a turn.

Changing prop pitch from 100 to 50 will drop the RPM of the engine and most likely take it out of the power band (for a lot engines in the game between 2000 to 3000 although some have a very small band of say 2500 to 2800) this will slow the aircraft significantly.

In effect you are reducing the thrust from the engine It is the slowing that is tightning the turn not the prop pitch. You would have the same effect if you just pulled the throttle back to idle.

This is a very poor way of fighting as it wastes energy. A better way is to reduce the bank in the turn convert some of the speed to height, there by keeping the energy.

You should be using the prop pitch to keep the rpm at the optimal level.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR> But lets say I'm at full throttle and I do this, should I speed up because I'm up-shifting, or should I slow down because my prop is turning slower?
<HR></BLOCKQUOTE>

Well this is a little difficult to answer, what is happening is the two are cancelling each other out. The prop is turning more slowly, but is producing more thrust because it has greater pitch. So you will notice little difference in speed. Again this dependant of the powerband of the engine.

The simple answer is this (not simple really beacuse it is complex engine management after all) you should use the prop pitch to keep the rpm at the optimal level, this will be different for each engine.

A good way to see what is happening is fly something like a Mustang with a constant speed prop. Increase the throttle quickly from say 70% to 100%, watch the tacho the rpm will jump until the constant speed mechanism has had a chance to increase the pitch to bring the rpm back down to the optimal. Now do the reverse 100% to 70% the reverse will happen rpm drop until the pitch has reduce.

It is always trying to "seek" to the correct rpm.

I wouldn't use the fuel mixture to cool the engine, again you should find if you are using the prop pitch correctly your engine is less likely to over heat anyway.

VMF-214_HaVoK
02-23-2005, 02:12 PM
Here ya go http://airwarfare.com/Sims/FB/fb_cem.htm All you need to know should be found here.

MrQBerrt
02-23-2005, 02:33 PM
Whiteladder
Thanks for the answers, those help out. How do I find the powerband of each aircraft in PF? I know there is a lot of that type of info in disk 2 of FB, but what about the F6F, F4F, A6M and so on?

I do know that the prop pitch isn't adding to my lift vector at all, and the increase in G's is caused by the slowing of the plane. However, I still maintain that this is a tactic that has a use. In most cases a high yoyo as you described would be better, but sometimes, you're 2 degrees from a firing solution and changing the pitch gets you a shot into the canopy/engine ending the fight (I've tried the same thing by decreasing the throttle and it doesn't seem to have quite as much effect as decelerating with the pitch. This is subjective I know, but it sure seems like pitch slows you down faster at least in this particular circumstance). I also know that slipping my clutch in my motorcycle doesn't give me more speed when I'm hill climbing. However, it does increase my RPM's getting me back into the powerband and also gives me a nice little boost when I let go of the clutch again. Slipping the clutch can be a practicle way to gain speed given the right settings. Similarly, it seems like changing your prop pitch can tighten your turn given the right settings. I'm not saying there are no consequences, but it sure seems to work great.

Why don't you recommend using the fuel mixture to cool the engine? Because it doesn't work or because it kills the engine or because it doesn't work as well as some other method? I realize that not overheating your engine is a good idea, but sometimes it happens and if it does happen and you're sitting there with no bandits, what is the fastest way to cool it?

Havok
Thanks for your reply as well. If you re-read my first post, you'll see that I specifically mentioned the article on Airwarfare on CEM written by Vulgar, which is the one you linked me to. I'm not saying this is a bad article, it is a very good one. However, after reading though it, I was left with a lot of questions. Some of them I wrote in my previous two posts.

Here is another example of a question I have, but this is on basic flying instead of CEM. I've heard a good ideal turn speed is around 200 mph for a lot of AC. So, if I want to keep a turn speed of 200mph and I'm going 220, I have an oppurtunity to gain some lift and slow back down to 200. Now is lift derived from pulling back farther on my stick better or worse than extra lift gained by adding combat flaps? Or does it matter?

Again, thanks in advance for any answers or links to sites that have answers to these types of questions.

Tallyho1961
02-23-2005, 02:44 PM
I've been looking for the same powerband info since I discovered the joys of CEM about three weeks ago - no luck yet. I posted the same question in Community Help and nobody stepped up to the plate.

I was also temporarily misled by that info about prop pitch helping to tighten a turn. It sounded wonky to me, but I couldn't be sure. Whiteladder's post confirms my suspicion.

Good luck. I'll follow this thread to see if you have better luck than I did.

BTW - I spent a bit of time creating an at-a-glance CEM guide for myself - listing available CEM options and parameters per Allied a/c. It's available here. (http://forums.ubi.com/eve/forums?a=tpc&s=400102&f=49310655&m=2471080482)

whiteladder
02-23-2005, 02:55 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by MrQBerrt:
Whiteladder
Thanks for the answers, those help out. How do I find the powerband of each aircraft in PF? I know there is a lot of that type of info in disk 2 of FB, but what about the F6F, F4F, A6M and so on?

I do know that the prop pitch isn't adding to my lift vector at all, and the increase in G's is caused by the slowing of the plane. However, I still maintain that this is a tactic that has a use. In most cases a high yoyo as you described would be better, but sometimes, you're 2 degrees from a firing solution and changing the pitch gets you a shot into the canopy/engine ending the fight (I've tried the same thing by decreasing the throttle and it doesn't seem to have quite as much effect as decelerating with the pitch. This is subjective I know, but it sure seems like pitch slows you down faster at least in this particular circumstance).

Why don't you recommend using the fuel mixture to cool the engine? Because it doesn't work or because it kills the engine or because it doesn't work as well as some other method? I realize that not overheating your engine is a good idea, but sometimes it happens and if it does happen and you're sitting there with no bandits, what is the fastest way to cool it?

Havok
Thanks for your reply as well. If you re-read my first post, you'll see that I specifically mentioned the article on Airwarfare on CEM written by Vulgar, which is the one you linked me to. I'm not saying this is a bad article, it is a very good one. However, after reading though it, I was left with a lot of questions. Some of them I wrote in my previous two posts.

Here is another example of a question I have, but this is on basic flying instead of CEM. I've heard a good ideal turn speed is around 200 mph for a lot of AC. So, if I want to keep a turn speed of 200mph and I'm going 220, I have an oppurtunity to gain some lift and slow back down to 200. Now is lift derived from pulling back farther on my stick better or worse than extra lift gained by adding combat flaps? Or does it matter?

Again, thanks in advance for any answers or links to sites that have answers to these types of questions. <HR></BLOCKQUOTE>


I wouldn't recommend fuel mixture for cooling (if you are playing online at least) because the cool effect takes longer to act than opening the radiator and you are braodcasting your presence by the smoke trail you leave.

As far as power bands are concerned some aircraft have a mark on the tacho (Stuka for example). for others the information is a little sparse. There is a post over in the general forum about power settings for the zero for example which is about 2500 rpm if I remember correctly. Over on airwarfare there is a pdf with engine setting for most of the original il2 aircraft, not much if any on pacific fighters though.

I agree with you if you are using prop pitch to get the last couple of degrees for a firing solution, but you have make sure that you get the kill. Otherwise all your have got is your self in a regime where( if he was out turning you in the first place) the bandit is happier any way. Otherwise better to accept you have lost the advantage and set up for a better solution.

Tallyho1961
02-23-2005, 04:51 PM
Whiteladder - thank you for the understandable advice. I do, however, have a question to add:

If a given a/c's powerband is, say, 2-3,000 rpm where, if any, is the 'ideal' setting? I have been increasing pitch 985-90% in order to reduce rpm to 1-200 rpm below the maximum, basically as a cooling aid - and it seems to work.

What circumstances would cause me to increase to, say, 30%?

And if I'm cruising at, say, 90%, should I reduce pitch to 100% when combat begins?

ClnlSandersLite
02-23-2005, 06:20 PM
The absolute fastest way to cool an engine? Press the i key and open the radiator http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif. Seriously though, if there are no bandits, set the engine up for economy cruise (try 40%/40% varies by aircraft) with the radiator open. Otherwise, try reducing output to 80%/80% and sadiator pos 4. This too will vary by airplane. In a lightning, I can run full blast (100%/100%) with the radiator closed and I won't overheat. However, if I go to 110%/100% with the radiator closed, I'll overheat in a fef mins. Then all I gotta do is rad 4 95% throttle 100 pitch for a min or so and I'm cool with room to spare.

As for finding powerbands, the way I do it is by ear. Spend some time in an ac you know where the powerband is. Listen to the engine(s) on different settings as they operate. Soon enough, you'll be able to pick out when an engine is working at it's best. Once I got this down, I honestly never look at the tachometer except when trying for a different power output during cruise.

About the dives and decreased rpms. You have to decrease pitch in a dive or you'll overrev. this is because the air blows the prop and makes it move faster. If you chop pitch to 80% in a vertical dive, you're not actually moving away for the powerband. The dive increases your rpms so you'd actually stay right in it without slowing you down.

ZG77_Lignite
02-23-2005, 06:35 PM
An aircraft with a constant speed prop has its best 'powerband' with its RPM Lever fully forward (also known as '100%' in FB/PF). This is an engineered design feature of an aircraft (thats why you can't put a P47 prop on a P51). All of the aircraft you mentioned for PF have constant speed props, so '100%' is your 'powerband'. Lower settings are used for cruising or cooling. FB/PF has reasonably well researched 'numbers' for power settings, so finding out the historical numbers usually translate correctly into FB (Google or Yahoo things like Power Settings, Climb Combat Power, or Cruise Settings followed by your specific aircraft will often return good results).


Regarding fuel mixture, I believe in real life they say to enrich the mixture to increase cooling. Whether this effect is coded into FB/PF I don't know, and I agree with WhiteLadder's point that cooling should be controlled through RPM/throttle/radiater settings, instead of mixture, simply due to effectiveness.

Remember, in aircraft with constant speed props you Can Not directly control the blade angle on the prop, it is automatically adjusted for best performance. What you are controlling is the engine RPM.

MrMoonlight
02-24-2005, 04:03 AM
Interesting discussion. While reading it, it occurred to me that one important aspect of CEM is not even modeled in the sim and is probably abused by a lot of players. I'm talking about high manifold pressures at low RPMs with constant speed props.

In FB/PF, you can fly with the throttle wide open with your prop pitch (RPM) at 50% and the engine continues to happily hum along. Try this in real life and you risk detonation or, worse, blowing a cylinder head off.

For each aircraft, there is a certain manifold pressure which should not be exceeded at a given RPM...the figures vary from A/C to A/C but since none of this is documented in the sim, you can use the THROTTLE&lt;=PITCH method as a rule of thumb in the sim if you want to keep it reasonably realistic. That is to say, your throttle setting (in %) should never exceed the prop pitch (in %).

For example: if you're cruising at 60% power, your prop pitch should be set at 60% or higher. In real life, to prevent engine damage when adjusting power settings, you would always increase the RPM upwards before adding throttle (unless you're already at a reasonably high RPM setting). Conversely, when decreasing power such as going into cruise after climbout, you want to decrease MP before decreasing RPM. This ensures that the MP never exceeds the max RPM for the given power setting. Realistically, you should never fly at full throttle with anything less than max RPM (100% prop pitch in the sim).

I'm certain a lot of simmers don't even pay attention to this (I've read posts here where guys describe chopping the prop pitch to 0% while at full throttle to perform some fancy maneuver or slow down quick...which would surely blow the engine IRL)... but this was (and is) an important aspect of engine management and if you're into immersion and "keeping it real", it's something you should pay attention to.

Just some thoughts.

Art-J
02-24-2005, 02:49 PM
Mr Moonlight, You're right. Premature ignition & detonation are not modelled in our sim, so we don't have to cope with right order of adjusting RPM and throttle levers (in CSP planes). I'm not even sure if cooling control via mixture adjustments works (I always use radiator as more effective device). I wonder if BoB will have more sophisticated engine modelling... . That would be fun http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif.

And Mr Qberrt - in CSP planes if You increase prop RPM at idle throttle, You will certainly slow down. Governor adjusts blades angle to meet high RPM requirement, but without power input from the engine, the prop is windmilling and causing a lot of drag. This is what the real pilots use to slow down on final approach AFAIK, and this is what has been improved in one of the latest patches (3.01 or 3.03 - don't remember exactly, check the readme files for "remodelled cylinder compression" or something like that http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif ). I'm not sure about diving with full throttle though. I guess it depends on Your actual speed. There's a certain "speed of balance" I think. If You're below that, You accelerate (full throttle & RPM), but when You go faster - the prop actually begins to "brake" the plane (windmilling again, sort of... this time with full throttle, but prop governor still tries to set as "flat" angle as possible without overrevying) In that, very high speed range, maybe lowering RPMs will cause less drag and speed the plane up a little? Uhm... I'm not sure http://forums.ubi.com/groupee_common/emoticons/icon_rolleyes.gif .

Regards.

P.S. - I wouldn't advice using 'upshifting' and 'downshifting' analogy, since it can only be helpful in understanding how variable pitch props work. Alied CSPs and German default "aeromechanical screws" (adjusted both by air speed and manifold pressure) are both different kind of toys.

Drunken_Moose
02-24-2005, 02:55 PM
I'm only using rudder/pitch/regular throttle while flying, is this why I suck that much online?

EnGaurde
02-24-2005, 08:07 PM
moonlight you may have simply and clearly described how to manage prop pitch.

http://forums.ubi.com/images/smilies/blink.gif

i find myself doing just that, actually, i dont feck round with the pitch settings much and i seem to do ok with the aircraft i fly.

ive always thought that coarse prop pitch (I hate this high and low, i prefer coarse and fine as its intuiative) and high rpm equals immense pressure in the engines.... its just bound to start pinging bits off and follow with a rather loud bang. IVe never lost an engine and ive made some gross mistakes with pitch, but it seems just a mechanically responsible thing to do to not put max load on the engine at max rpm.

i feel its the same as driving thru the.... er.... Mcdonalds drive thru in 5th gear.

who would do that to their cars hmmm? http://forums.ubi.com/groupee_common/emoticons/icon_confused.gif