Help me crack the mysteries of CEM!

[Pizzicato]

Hey guys,

 

What are the best resources for technically-hopeless incompetents like myself to learn CEM?

 

I've dabbled in CEM ever since the first very first days of Il-2 (12+ years ago?), but I've never managed to wrap my head around it at all. I find it incredibly frustrating because I really, really want to figure it out but it always defeats me. I've tried in Il-2 (in all of its various forms), Cliffs of Dover, DCS: P-51D and A2A's Wings of Power 3 Spitfire, but I never seem to get it. It's not helped by the fact that many descriptions and guides tend to use car engines as a point of reference... but I never bothered learning to drive, so it's all gibberish to me.

 

It's incredibly frustrating to me because I'm usually a full-real sim flyer. The DCS: UH-1, DCS: A-10C and DCS: Ka-50 hold no fears for me, but the nuances of prop-driven WWII aircraft seems to be totally beyond me.

 

I really want to get the best out of Il-2: BoS, so help me out guys! How can I go about learning the impenetrable enigma that is CEM?

 

• Which sites should I be reading?
• Which Youtube videos should I be watching?
• Which sims and/or aircraft should I be using to practice ahead of the launch of BoS?
• What are your top tips for becoming a CEM genius?

 

TL;DR - Heeellllppppp!

[Bearcat]

Read whatever documentation you can find about a given plane as far as specs and learn to fly the plane before you try to fight in it.

[JtD]

I also recommend starting with reading the aircraft manuals. If you then wonder why some things have to be done in certain way, it's probably best to ask specific technical questions.

 

To answer at least one of the four you've asked above: Try Il-2:1946. It is probably simpler and less accurate than BoS will be in the end, but you can fly the exakt same aircraft there that you will get to fly in BoS, and it has the CEM basics.

 

WRT youtube videos, might be good to follow the livestream / updates the BoS crew puts out. At this point still way to go, but it might add up to a complete picture.

[theOden]

CEM in 20 seconds:

PropPitch = GearBox in your car
Mix = less the higher you fly
Radiator = as closed as possible without overheating
Manifold pressure = gas pedal indicator (some people call the gas pedal for throttle, weird huh?)


But I'm sure there are more detailed and correct descriptions out there haha.

[HeavyCavalrySgt]

Hey guys,

 

What are the best resources for technically-hopeless incompetents like myself to learn CEM?

 

I've dabbled in CEM ever since the first very first days of Il-2 (12+ years ago?), but I've never managed to wrap my head around it at all. I find it incredibly frustrating because I really, really want to figure it out but it always defeats me. I've tried in Il-2 (in all of its various forms), Cliffs of Dover, DCS: P-51D and A2A's Wings of Power 3 Spitfire, but I never seem to get it. It's not helped by the fact that many descriptions and guides tend to use car engines as a point of reference... but I never bothered learning to drive, so it's all gibberish to me.

 

It's incredibly frustrating to me because I'm usually a full-real sim flyer. The DCS: UH-1, DCS: A-10C and DCS: Ka-50 hold no fears for me, but the nuances of prop-driven WWII aircraft seems to be totally beyond me.

 

I really want to get the best out of Il-2: BoS, so help me out guys! How can I go about learning the impenetrable enigma that is CEM?

 

• Which sites should I be reading?
• Which Youtube videos should I be watching?
• Which sims and/or aircraft should I be using to practice ahead of the launch of BoS?
• What are your top tips for becoming a CEM genius?

 

TL;DR - Heeellllppppp!

 

Where do you start getting lost?

 

Engine management is complex, partly because it it is not standardized in WW2.  Some planes have a greater degree of automation than others, some engines have complexities that others don't have like superchargers.  In the real world, unless you are Kermit Weeks, you learn how to fly a couple of aircraft (hopefully) well, and spend a long time memorizing things like power settings and emergency procedures, testing yourself and being tested on those items.

 

In a very general sense, in a fixed pitch airplane, power is controlled by the throttle.  You control the engine, the prop speed is controlled by the engine directly. Props aren't good at every environment though.  most of them are compromises.  A prop that gives you a good cruise speed (because it takes big bites out of the air each revolution) isn't going to be great at climbing.  If you have a climb prop, it is going to move less air per revolution because it is designed with more revolutions in mind so you pick a high throttle setting, and climb out cheerfully off the runway with no drama or interrupting the kids playing catch off the departure end of the runway.  Then at cruise you go slower and burn more gas.

 

Think of someone with a multi-speed bike.  Starting out or going up a hill, they might want a lower gear to spread the work they have to do out over more time.  RPMS go up, the bicyclist peddles each revolution with less effort, covering less ground with each rotation, but it is good for getting up the hill.  On level ground again, speed increases, and it doesn't take as much effort to keep the bike going now that it already has some speed.  A higher gear is appropriate, with slower RPM and covering more ground in each revolution.

 

Props have the same sort of effect (did you see my whiny story the other day about getting stuck in an airplane over the Sierras with a cruise prop on it?  I took over with a density altitude of 8200 feet; it was not a good time.)

 

With any form of controllable pitch prop, you are pretty much giving yourself gears.

 

Heavy payload, hot day, high altitude airport and a lot of climbing to do to get over those mountains?  You decrease the pitch and now you have a climb prop.  At altitude, ready to go places?  Increase the pitch to slow the engine down and now you have a fuel efficient cruiser.

 

Early ones were adjustable on the ground.  Someone physically turned the prop blades (hopefully the same amount!) for a particular situation before engine start.  Then there were different systems to allow pilots to control the prop pitch manually or automatically, directly or indirectly, in the air.starting in the early 20s.  It can be done mechanically, electrically or hydraulically. That is another reason for confusion: different airplanes have different controls.

 

The one that was demo'd in the LaGG is not completely different from current systems.  The prop is still connected to the engine more or less directly but the pilot basically picks an RPM that he wants the prop to run at based on what he is going to be doing.  I'm climbing?  I want the prop turning lots of RPM.  I'm in cruise?  Let's slow the prop down and take nice big fuel efficient bites of air.  The adjustment of the prop happens without any more pilot interaction beyond the selection of the RPM.  When the pilot adds throttle, there is a control unit (generally) of some sort that says "Hey wait - the prop is going faster than it should!" and it increases the pitch on the blade to slow the prop - and engine - down again.  If the pilot yanks the power out the control unit flattens the blades to try to maintain RPM by reducing the amount of work the engine has to do each RPM.  Below or, in scary cases, above a certain RPM the prop physically can't adjust the pitch anymore to stay at the selected RPM.  We saw that in the video when the LaGG was at idle throttle, the blades couldn't reduce the pitch enough to maintain whatever prop setting was selected which is fine and normal.  The other situation usually happens when something other than the engine is causing the prop to speed up, usually a full throttle dive.  Not long after that, the engine starts making expensive noises.

 

Now there are basically two controls and indicators for the pilot to be mindful of.  The RPM primarily shows what the prop is doing and we talked about how that works.

 

The other control and indicator is the throttle and the manifold pressure gauge.  The manifold pressure tells us how hard the engine is working.  The more MP, the harder the engine is working.  Race pilots this weekend are thinking a lot about how much MP they can safely get in Reno and for how long.

 

For mere mortals, we have charts that recommend specific RPMs and specific MPs for different situations.  For a climb in a Cessna Cardinal RG, I remember "25 and 25" or, 2500 RPM on the prop, 25 inches of mercury on the throttle.  The reality is that I live at a high elevation, and many times I can't get that much power because the air isn't dense enough -- I never get full power except on a chilly day.

 

That is kind of the problem pilots were having a lot by WW2.  You get to altitude and now your engine isn't making anywhere near as much juice.  In the Cardinal, at 12,000 on a 'standard day' (a largely mythical meteorological benchmark) the absolute most I can get out of the engine is ~59% of its rated power.  That's fine if I am just going somewhere.  I can cruise at about 145 knots or so (166 mph) and do it pretty efficiently.  If I had to mix it up with that guy in the Piper Warrior I am going to be sad I am not making more power, because I am going to be wasting energy trying to out-turn him and get on his tail, and I am going to want to apply a lot of acceleration, but I will be sluggish instead.

 

So designers started sticking turbos and superchargers or both on engines.  This was probably an expensive time for folks that needed to fix engines and an exciting time for the pilots that flew them.  Both work by pressurizing the air coming into the engine to (at first) offset the loss of atmospheric pressure at altitude, then to enhance it.  Some WW2 warbirds could achieve between 45 and 50 inches of mercury in the manifold!  The problem is, with high manifold pressure the engine is working hard and when something breaks it does it dramatically.  Sorta like when a dragster tries to launch its manifold into low earth orbit.

 

So those systems are also generally often variable, much like the prop is.  You decide how much pressure you want to pump into the engine at any given time. At the extreme upper limit you have emergency settings where you aren't supposed to operate the engine for long, or you may find that it is no longer available to make any power at all.  The B-29, for example, had an emergency setting (it was a dial labelled 1-10).  The manual says that you can use that 10 setting only for emergencies, and not for more than 2 minutes or bad things happen. no suggestions on how to limit emergencies to 2 minutes or less.

 

The other control some airplanes have is a mixture control.  This is just to change the fuel-air mixture the enters the cylinders to something like optimal.  Too much gas (or not enough oxygen) and you have a mixture that is too rich, and you are wasting gas.  Too lean and you have a mixture that burns hot (because gas helps cool the cylinders) and can seriously break stuff - melt holes in pistons, for example.  I have been there and done that.  Or, more likely, you can cause deposits to form which would otherwise have burned and now your exhaust valve is stuck.  That's no good, because now that cylinder is making much less power.

 

The three things you generally need to know is what power settings to use -- these are documented in the aircraft manuals - and how to achieve those settings.  In modern aircraft when you add power, you set the mixture, set the prop, then set the power.  Decreasing power is the opposite.  The third is what power settings not to use.  The Cardinal doesn't want to be run at below 10 inches of manifold pressure between 1700 and 2400 RPM, for example.  It tends to make the mixture in the cylinders detonate rather than burn, and that is not going to last long before I have to practice my emergency landing skills.

 

Did I help?

[SvAF/F19_Klunk]

Heavy.. they should probably pin that answer down.. best description about this issue i have read in a long time! 

[76SQN-FatherTed]

CEM in 20 seconds:

 

PropPitch = GearBox in your car

Mix = less the higher you fly

Radiator = as closed as possible without overheating

Manifold pressure = gas pedal indicator (some people call the gas pedal for throttle, weird huh?)

 

But I'm sure there are more detailed and correct descriptions out there haha.

 

 

The OP did mention that he didn't know how to drive...

 

The only thing I'd dare add to Heavy's reply above is that it's worth remembering that we're talking about games here.  Whilst it is very useful to be able to apply real-world knowledge, games are usually simplified to some degree.  For instance IL2 1946 has a pretty basic CEM - you can get away with a lot of things that in real life would lose you power, get you told off, or blow your engine.

 

What I'm getting at is that if you want to do well in the game, then it's the game manual you should look at  (and the forums, for "gamey" tips).  Of course "doing well in the game" is not the same as treating it as a proper simulator - it depends on what you want out of it.

[ImPeRaToR]

What you certainly won't see is "ENGINE OVERHEAT" flashing on your screen so you will have to pay attention to your temp gauges yourself

[W1ndy]

Great post HeavyCav. Copy/pasted for reference  

[ImPeRaToR]

W1ndy I think it's time to bring back your windy avatar

[W1ndy]

What you certainly won't see is "ENGINE OVERHEAT" flashing on your screen so you will have to pay attention to your temp gauges yourself 

How about oil splash on the windscreen ?

 

Avatar  - I think all members should sport a dog avatar -

[HeavyCavalrySgt]

Heavy.. they should probably pin that answer down.. best description about this issue i have read in a long time! 

 

 

Great post HeavyCav. Copy/pasted for reference  

 

Thank you both, but I confess I was exhausted when I wrote it.  Should go back and re-read.

[Pizzicato]

That was an utterly fantastic post, HeavyCav. Very, very helpful indeed. Thanks so much for taking the time to write it all up.

 

I'm sure I'll have more questions once I've absorbed all of the idiot-friendly info contained within, so I'll probably post back in this thread in the next day or two.

 

Thanks again for your efforts. Hugely appreciated.

[Capt_Hook]

Great post Heavy, and fun to read.

[Tone71]

Yeah, +1 to Heavy. Very helpful mate.

[J2_Trupobaw]

Great intuitive description, HeavyCavalrySgt. You saved at least me a lot of guesswork and trial by mostly error.

One thing is still unclear to me - the propeller settings adjust how much air blade moves, how about effect of air moving the blade (as in dive)? Do I set the blades for minimal RPM as in cruise (don't want to overrev the engine and minimal RPM is always minimal RPM)? Or do I set it for maximal RPMs and minimal interaction with the air (the blades move and are moved by less air, so the EXTRA RPMs coming from dive are minimalised?). 

My intuition is that climbing setting is correct answer (less revs lost in climb = less revs gained in dive, revs coming from engine can be controlled by throttle), but I'm guessing blindly. Knowing which answer is correct and more importantly  why it's so would help . understand what these levers really do .

How much do I fiddle with prop pitch in combat? When looping? When zooming, do I start at low revs setting and add the revs as I lose the speed, or set it for climb and stick with it? Is continously changing prop with angle of attack in combat practical, or changes are not instantenous enough? 
 

Edited September 14, 2013 by Trupobaw

[JtD]

In a dive, you need low rpm / coarse pitch for minimum drag, and high rpm / fine pitch for maximum drag. Both can be useful.

 

You don't need to fiddle with prop pitch a lot in combat. If you change prop rpm, you also change engine rpm. The engine has a best power rpm, for instance many Rolls Royce Merlin engines generate most of their power at 2850 rpm. So the best idea is to let the engine run at these rpm. You may not have best propeller efficiency under all conditions, but if you optimize the propeller, some of the gains will be lost because the engine is getting worse. Bottom line, you better focus on the combat than on prop pitch.

Essentially, you need a take off/emergency, a combat/climb and cruise setting. Once in combat, you switch to you combat setting and this will take care of 95%+ of the time. It's how most handbooks have it, and it's what works playing Il-2.

[HeavyCavalrySgt]

Thank you gentlemen!

 

Blech, I can't edit my post, and I meant to say "I took off with a density altitude of 8,200 feet."  That is fairly typical for my area, and I have seen density altitudes over 9,000 feet fairly regularly, meaning sitting on the ramp I am at the atmospheric equivalent of 9,000+  feet above sea level.  I have questions about why there is an airplane with a cruise prop here.

Great intuitive description, HeavyCavalrySgt. You saved at least me a lot of guesswork and trial by mostly error.

One thing is still unclear to me - the propeller settings adjust how much air blade moves, how about effect of air moving the blade (as in dive)? Do I set the blades for minimal RPM as in cruise (don't want to overrev the engine and minimal RPM is always minimal RPM)? Or do I set it for maximal RPMs and minimal interaction with the air (the blades move and are moved by less air, so the EXTRA RPMs coming from dive are minimalised?).   In dive of any significance where you might overspeed your prop, You would probably want to pull the prop control and the power back

My intuition is that climbing setting is correct answer (less revs lost in climb = less revs gained in dive, revs coming from engine can be controlled by throttle), but I'm guessing blindly. Knowing which answer is correct and more importantly  why it's so would help . understand what these levers really do .

How much do I fiddle with prop pitch in combat? When looping? When zooming, do I start at low revs setting and add the revs as I lose the speed, or set it for climb and stick with it? Is continously changing prop with angle of attack in combat practical, or changes are not instantenous enough? 
 

 

 

The propeller control typical sets RPM - I'm talking about constant speed systems here - and they typically are not very smart systems, generally being driven at that time by simple hydraulic pressure.  They don't really care why engine RPM is going up or down, they just try to compensate to get back to the selected RPM.  

 

In a long dive (or maybe a dive bombing attack?  I have not received instruction on those so I am guessing here)  you might pull power, then pull the prop back to keep the engine from overspeeding.  The rest of the time in combat, you probably want something at or close to the climb setting because acceleration is what you want unless you have to chase down someone who just remembered an appointment elsewhere and is trying to exit the fight.  Did you notice how the plane accelerated and decelerated dramatically in formation with the AI plane when the prop control was tweaked in the last livestream?

 

You probably would mess with the prop control when you needed to in combat but for the most part I suspect your attention would be elsewhere - set it and forget it unless you really are changing your strategies like trying to get away from that swarm of FWs that just came out of the clouds.

[BMA_West]

Thx Heavy, copied it to a BOS desktop folder but bookmarked it just the same - buckle strap and suspenders is the way to go here

[Crow]

Hey guys,

 

What are the best resources for technically-hopeless incompetents like myself to learn CEM?

 

I've dabbled in CEM ever since the first very first days of Il-2 (12+ years ago?), but I've never managed to wrap my head around it at all. I find it incredibly frustrating because I really, really want to figure it out but it always defeats me. I've tried in Il-2 (in all of its various forms), Cliffs of Dover, DCS: P-51D and A2A's Wings of Power 3 Spitfire, but I never seem to get it. It's not helped by the fact that many descriptions and guides tend to use car engines as a point of reference... but I never bothered learning to drive, so it's all gibberish to me.

 

It's incredibly frustrating to me because I'm usually a full-real sim flyer. The DCS: UH-1, DCS: A-10C and DCS: Ka-50 hold no fears for me, but the nuances of prop-driven WWII aircraft seems to be totally beyond me.

 

I really want to get the best out of Il-2: BoS, so help me out guys! How can I go about learning the impenetrable enigma that is CEM?

 

• Which sites should I be reading?
• Which Youtube videos should I be watching?
• Which sims and/or aircraft should I be using to practice ahead of the launch of BoS?
• What are your top tips for becoming a CEM genius?

 

TL;DR - Heeellllppppp!

Do you want to know how to do it in real life or just how to fly adequately in a flight sim? They are very different things. Aircraft are highly technical beasts with complex parts. If you aren't able to comprehend the reasons why you run an aircraft engine the way you do, it will always seem like magic and nonsense.

 

This is the real FAA handbook on learning to fly an airplane: http://www.faa.gov/regulations_policies/handbooks_manuals/aviation/pilot_handbook/

Chapter 6 is all about aircraft systems. If you want to know how to do it for real, read that. Read the whole book if you really want to know how to fly an airplane.

 

Here is some advanced reading:

"Manifold Pressure Sucks!" http://www.avweb.com/news/pelican/182081-1.html?redirected=1

"Mixture Magic" http://www.avweb.com/news/pelican/182084-1.html?redirected=1

"Those Marvelous Props" http://www.avweb.com/news/pelican/182082-1.html?redirected=1

 

If you have any specific questions about this reading feel free to ask.

Edited September 14, 2013 by Crow

[Dutch]

• What are your top tips for becoming a CEM genius?

 

 

Hmmm. Don't take any notice of the people who want to fly at maximum boost (manifold pressure), maximum revs, maximum rate of climb and maximum speed, all of the time. You know who you are.

 

Treat your virtual aircraft engine like you'd treat your car. In the main, fly it at low revs, low power. Only thrash it through the gears with the rev counter on the red line when you need to. Metaphorically speaking that is.

[dkoor]

Concentrate on one plane only (best to choose some large family like Bf-109, Yak or LaGG).

Always best to put focus on.

[theOden]

..

Here is some advanced reading:

"Manifold Pressure Sucks!" http://www.avweb.com/news/pelican/182081-1.html?redirected=1

"Mixture Magic" http://www.avweb.com/news/pelican/182084-1.html?redirected=1

"Those Marvelous Props" http://www.avweb.com/news/pelican/182082-1.html?redirected=1

 

If you have any specific questions about this reading feel free to ask.

 

Very nice and educational reading.

I wonder if the "singles go fine and twins go coarse" applies to wartime birds such as Bf110 and Pe-2 too?

Time will tell (since I get shotdown very often )

[Uufflakke]

A basic CEM guide can be found here.

That is the way I learned to 'fly' in IL2.

 

http://www.mission4today.com/index.php?name=Knowledge_Base&op=show&kid=249

[Crow]

Very nice and educational reading.

I wonder if the "singles go fine and twins go coarse" applies to wartime birds such as Bf110 and Pe-2 too?

Time will tell (since I get shotdown very often )

It's not a 100% perfect rule (the Cessna 208 Caravan feathers rather than going fine for example), but in general that's how the systems are designed to fail because it is the safest method. I don't know if early WWII-era twins all failed to feather though. Some twins fail to the max RPM position and then require some intervention on the part of  the pilot to feather it.

[RAF74_Winger]

It's not a 100% perfect rule (the Cessna 208 Caravan feathers rather than going fine for example), but in general that's how the systems are designed to fail because it is the safest method. I don't know if early WWII-era twins all failed to feather though. Some twins fail to the max RPM position and then require some intervention on the part of  the pilot to feather it.

 

Props designed for aerobatics are counterweighted to feather on loss of oil pressure to prevent dangerous overspeeding, so that's another exception to the rule.