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TX-EcoDragon
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« on: March 14, 2003, 08:08:08 pm » |
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First some basic background info about what you should know about CEM in FB
*A couple points about mixture:
As an engine operates at higher and higher altitudes, and air becomes less dense, the mixture of air and fuel that enters the combustion chamber must be kept at a certain optimum ratio for best power, leaning the engine just beyond this point will increase fuel economy, but will also heat the engine which may lead to overheat damage (you can also shut off the engine by leaning too far). Conversely running too rich will cool the engine (unburned fuel carries heat out of the engine), but may foul the spark plugs (if you aren't running full power), decrease performance, and dramatically decrease fuel economy.
In FB, Mixture 100% means full rich, which is the setting to use at low altitudes, and for most takeoffs. You will stay in this setting nearly always if you fly low alt dogfights only (less than 2000 meters). I didnt say 120% because this setting seems useful (and only exists) only in those engines that have a boost effect.
"How do I know if I need to lean my engine out, and how much should I lean it??"
Well, for the most part you can leave it at 100% until you start getting to altitudes around and above about 3000 meters (in the real world it should be much lower). if you lower it from 100% to 80% you can typically climb about 1000 meters more before the engine becomes too rich. etc.
"How can I tell its too rich?"
If externals are enabled you will see a trail of pinkish fuel vapor trailing your aircraft (not realistic method nor effect). If you want to do it more realistically, note any RPM changes as you climb, and when you lean the mixture (in increments of 20% it appears), if the RPMs increase, then you needed to lean it. If you notice a decrease in Engine power (As evidenced by the Manifold Pressure or in the case of fixed pitch props RPM) then you have leaned too far and should go enrich the mixture. You can also lean according to the information provided below as a general guide (this was for the CD version of FB and may change with patches). Generally in FB, take-off at 100% (or 120% in some aircraft for increased performance), go to 80% when passing through around 3000, 60% when passing 5000. These are far from exact values, I only aim to illustrate the concept here. You should take some time to look at your powerplant gauges and learn what they are telling you so that you dont simply have to rely on the info provided below.
There are also blatant exceptions, such as in the Hurricane, it seems that as you climb going to 120% does increase performance, and doesnt cause you to run rich.
"Can I lean too much??"
Yes, in fact that is how pilots shut down their engines, pulling the mixture back to "Idle/Cutoff" Running lean may be useful on a long mission, or when you have to dogfight after you should have landed and need to increase your range as much as possible, as this will reduce your feul burn, however this will also cause your engine to overheat faster.
Please note that the numbers below apply to flights were fuel economy, and cruise performance rank lower on the totem pole. running at a mixture value higher than is needed should suck gas out of your tank at a high rate. . . so keep this in the back of your mind on long sorties.
(these numbers may change slightly with ambient temp and pressure . . . not sure yet though)
As found in the FB readme
I-153 M-62 and I-153P
Fuel mix requires adjustment at altitudes above 4.0 km. At those altitudes, the engine carburetor is incapable of producing optimal mixture with low-density high altitude air. When the engines begins trailing smoke and suffer power loss or RPM instability, adjust the mix level (using Increase Mixture and Decrease Mixture control keys) until the engine returns to the regular output.
I-16 type 18 / 24
Sharing the same engine with the I-153 series, this plane requires the same operations.
La-5 (F, FN) and La-7
Mixture adjustment is required at altitudes above 5000 meters.
LaGG-3 (early series)
. Mixture adjustment is required at altitudes above 4000 meters.
LaGG-3(66 series) and LaGG-3IT
. Mixture adjustment is required at altitudes above 3000 meters.
Yak-9 and Variants (D, K, T)
. Mixture adjustment is required at altitudes above 3000 meters.
Yak (Other Models)
Mixture adjustment is required at altitudes above 4000 meters.
Hurricane
Leave at 100% (auto mix) for most operations, go to 120% for boost in power
P-40M
Same as Hurri
P-40E M-105 (Field mod.)
A Russian modification with the engine found on the LaGG-3 requires the same engine handling.
Mixture adjustment is required at altitudes above 3000 meters.
FW-190s
Mixture corrections may be required above 9000 meters.
My mapping entails pressing these keys in combination:
L+ leans my mixture
L- richens it
AM sets to to auto mixture
*Now, on to Prop Pitch AKA RPM control:
Aircraft with adjustable pitch props act a little like your car's transmission does (this is actually a bad anology but some people get it better when this copmparison is made). You control power output with the throttle, and RPM with the prop control (or gear selector in a car). In this case you want your engine to run at high power, but not be reving too high, so you set power with the throtlle, and then bring down the RPM with the prop pitch. Like first gear in your car, 100% pitch is best for low speed high torque applications. After you level off you will probably need to lower it to around 95% at first, and you should observe an RPM decrease. After your speed builds, you will likely see your RPM increase somewhat, now go to 90% and so on. On a dive to gain speed, you will need to use the prop to control RPM, and can also use it gain increased speed by going to lower numbers. On the other hand, if you need to dive and do not want to accelerate any more than you need to, bring power to idle, and set prop to 100 % (provided you aren't going too fast at the top of the dive) and this will add drag and act as an airbrake. Keep in mind pressing Shift 0 one time in aircraft with auto pitch will take you to climb pitch, pressing again will take you to AUTO mode. If you are at max power and run at climb pitch this is the same as getting on the freeway in first gear. . .and it wont be long before your engine shows its dissapproval.
Power output is indicated on the manifold pressure gauge (MP) which is scalled in units of inches of Mercury (inHg), higher MP=higher power. The Prop control then selects the RPM. In this way you use the RPM control to vary the flight regime that the aircraft is optimized for, highest RPM for climbing (and full power), as you accelerate and level off you will need to bring RPM down to cruise setting (though you may still have fullpower in). etc
Sadly is seems that the way in which constant speed props are modelled is incorrect in FB, so the above applies to FB, and is different from the real world. [In the real world a constant speed prop will very accurately maintain the RPM that you pull the prop to, even when you make dramatic power changes, and dramatic attitude changes (such as aerobatics!) and will prevent the prop from overspeeding under most reasonable instances]
I have mapped this to a rotary, and also use:
Shift 0
p+ increase pitch
p- decrease pitch
FP feathers prop
*Superchargers and boost
Most aircraft in FB have some sort of supercharger control. use the first stage at lower alt, and then the second stage should be engaged when passing through some altitude.
The supercharger acts to compress air that is fed into the engine when at higher altitudes, this will increase power dramatically, and also extend the alt that the engine will operat to.
My mapping entails pressing these keys in combination:
SA Supercharger first stage
SD supercharger second stage
I-153 M-62 and I-153P
When climbing, set the supercharger to stage 2 (Supercharger Next Stage) when passing 2200 meters. When going below 2200 m, one should return the supercharger back to stage 1 (Supercharger Prev. Stage).
I-16 type 18 / 24
Sharing the same engine with the I-153 series, this plane requires the same operations.
La-5 (F, FN) and La-7
The supercharger requires to be set to stage 1 when flying below 3500 meters, and to stage 2 above 3500 meters.
LaGG-3 (early series)
The supercharger requires to be set to stage 1 when flying below 2200 meters, and to stage 2 above 2200 meters.
LaGG-3(66 series) and LaGG-3IT
The supercharger requires to be set to stage 1 when flying below 2200 meters, and to stage 2 above 2200 meters.
Yak-9 and Variants (D, K, T)
The supercharger requires to be set to stage 1 when flying below 2000 meters, and to stage 2 above 2000 meters.
Yak (Other Models)
The supercharger requires to be set to stage 1 when flying below 2000 meters, and to stage 2 above 2000 meters.
Hurricane
The supercharger requires to be set to stage 1 when flying below 2800 meters, and to stage 2 above 2800 meters.
P-40M
The supercharger requires to be set to stage 1 when flying below 2200 meters, and to stage 2 above 2200 meters.
P-40E M-105 (Field mod.)
A Russian modification with the engine found on the LaGG-3 requires the same engine handling. The supercharger requires to be set to stage 1 when flying below 2200 meters, and to stage 2 above 2200 meters.
Bf-109G-6/AS, Bf-109G-10/G-14 and Bf-109K-4
These aircraft are equipped with MW50 injection system. The system operates automatically, giving the engine additional power as you move the throttle control beyond the 100% mark. The system can be switched on and off (using the WEP control key), however, it may only be done when the engine is idle or running on lower throttle to prevent damage. Also, it should be switched off when it runs out of water-methanol mix as it can’t operate properly without external pressure and may lead to engine damage.
FW-190D-9 (1945)
The plane is equipped with MW50 system, similar to the one installed on the Bf-109, and has the same restrictions.
FW-190F-8
The boost is effective only bellow 1,000 meters. It was prohibited for use over 1000 meters altitude.
He-111
The supercharger must be set to stage 1 when flying below 2800 meters, and to stage 2 above 2800 meters.
Ju-87
The supercharger must be set to stage 1 when flying below 2800 meters, and to stage 2 above 2800 meters.
*Now lets talk Multiengine aircraft
engine start is still very simplified dow to just pressing "I", but now you may need to do this on an individual engine basis. You can also control on engine at a time, or one set of engines at a time, etc. I have some mappings that I find I dont forget here they are:
E1 toggles select on engine 1
E2 toggles select on engine 2
and so on
E0 toggles select on all engines
EW toggles select on left engine(s)
ER toggles select on right engines(s)
ET selects all engines
EQ selects no engines
EF fires fire extinguisher on selected engines
the select left bank of engines/righ bank of engines control is nice for when you are on the ground and need to turn a plane like the TB-3 and differential thrust is just the ticket!
Anything else?? Just Ask. I have said, I am more than willing to do this hands on with anyone, and would rather do it that way than via text.
S!
TX-EcoDragon
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