Mixture Control Question?

[ColR1948]

I recently bought a Saitek Yoke and Throttle set, I have assigned the RED lever on the throttle for the mixture, I will admit I'm a bit dumb on this bit so when I start the engines I give the full mixture (lever at the top).

 

Now this is my question, when airborne when do I alter the mixture for efficient engine running?

If for example I'm in a Cessna 172 at 2000ft do I leave it or change it?

At 6000? 8000?

 

Or if I'm in a lager aircraft when at what altitude, a few examples please?

[Egsjr1956]

First, make sure you have auto-mixture unchecked. Then you set the mixture according to what the circumstances warrant. There are a few basic rules of thumb that you can follow, but for the overall picture you need to make sure it is correctly set for maximum performance. One thing I have have been studying lately is "density altitude". The link I posted is one of many that covers this.

 

https://www.aopa.org/training-and-safety/active-pilots/safety-and-technique/weather/density-altitude

[lnuss]

That's unfortunately one of the major bugs in FSX (and even in the 'professional training software' P3D).

A lot depends on the specific flight model in FS or P3D, since that can be adjusted in the engine parameters. But in the default 172 (and many other sim aircraft) it is a problem.

 

If you want peak performance you basically need to start leaning immediately once above S.L.!

 

That's mostly true (especially on a warm day) in a real light aircraft, also.

 

You can't even climb to 10000ft with full rich mixture because the engine will die at this altitude.

All this doesn't happen IRL.

The engine might not quite die going to 10K IRL, but it'll not be very happy above 4-5K density altitude.

 

In a real 172, departing from around 2K on a warm (not even hot) day, you're much better off leaning before takeoff, though you can usually get by without it, unless the runway is very short. In the high country (Albuquerque, Denver, etc. --4K plus) leaning before takeoff is a normal part of the runup procedure. And even climbing from low elevation (midwest, east coast -- 500 plus feet) by the time you're at 3,000 feet it's good to lean a bit. This is true whether in a C-172 or a Bonanza or a Baron. There's a very definite performance difference.

 

But to the OP's question, if departing from near sea level I'd lean for max RPM after climbing through 2,000 to 3,000 if you're still in the climb, and after getting leveled off in cruise in any case. With a takeoff from at or above about 2,000 to 3,000 feet elevation, I'd lean during the runup. In either case, I'd then lean again after each 2,000 to 3,000 feet of altitude gain, then again after leveling off in cruise.

 

Or you can leave the sim in auto mixture and it'll take care of that for you.

[lnuss]

Now that's interesting. Where in the air file is this capability?

 

I'm not able to successfully do this, but a friend has, by trial and error, learned to make adjustments to piston engines to reduce the problems (he has MUCH more patience for this than I do). He says this is still trial and error on each aircraft he does, and he doesn't always succeed, so there's no "magic formula" to pass on. But the engine parameters (and sometimes prop parameters) in the aircraft.cfg plus a few in the .air file are the areas he experiments with.

[Sentry_FiveZero]

Push mixture all the way in when your ready to takeoff. If your climbing to 7000 ft, begin to lean a little at a time once you pass 3000, but not too much as the extra fuel helps keep your cylinders cooler. Once you level off, lean to 50 degrees below max power setting temp and you're set!

 

 

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[N33029]

The engine might not quite die going to 10K IRL, but it'll not be very happy above 4-5K density altitude.

 

In a real 172, departing from around 2K on a warm (not even hot) day, you're much better off leaning before takeoff, though you can usually get by without it, unless the runway is very short. In the high country (Albuquerque, Denver, etc. --4K plus) leaning before takeoff is a normal part of the runup procedure. And even climbing from low elevation (midwest, east coast -- 500 plus feet) by the time you're at 3,000 feet it's good to lean a bit. This is true whether in a C-172 or a Bonanza or a Baron. There's a very definite performance difference.

 

But to the OP's question, if departing from near sea level I'd lean for max RPM after climbing through 2,000 to 3,000 if you're still in the climb, and after getting leveled off in cruise in any case. With a takeoff from at or above about 2,000 to 3,000 feet elevation, I'd lean during the runup. In either case, I'd then lean again after each 2,000 to 3,000 feet of altitude gain, then again after leveling off in cruise.

 

Or you can leave the sim in auto mixture and it'll take care of that for you.

 

Back when I had an altimeter in my VW, it could change as much as 800' from the end of one day to the beginning of the next day. I would just correct it to the known altitude of home. I thought in RL, it is important to lean any time at or above 3000' density altitude (the altitude you'd see on the gauge if there was STP at S.L. - 15° C and 29.92").

 

The AOPA made an excellent video called "Lost and Crossed" about those times when your spare GPS batteries are in the cargo compartment, you got lost, and you have a crosswind at destination. They mention the advantage of saving fuel by leaning, especially when you've gone off your intended course.

 

I thought the spark plugs can become fouled with lead when you run the engine too rich.

 

Sean

[Sentry_FiveZero]

 

I thought the spark plugs can become fouled with lead when you run the engine too rich.

 

Sean

 

Only when your running at idle. Cylinder temps at full power are high enough to keep them clean.

 

 

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[PhantomTweak]

Now that's interesting. Where in the air file is this capability?

 

R507. It's a curve, and can be adjusted. If it's not present, it can be added from a plane that has it.

There is a good thread in the FSDev forum about Mixture vs FAR in FSX. You can find it HERE. There are some pretty in-depth mathematics involved, especially on the second page of the thread. Yes, it's about creating an Automixture gauge, but the curves they created could be used in R507 for a manual mixture aircraft, like the C172.

 

Does that answer your question?

Pat☺

[ColR1948]

You frightened me now when you said, "pretty in-depth mathematics" I have discalculia so I find a lot of things with numbers hard.

 

If you have an Automixture gauge as you said above why not just select it in the settings?

[PhantomTweak]

If you have an Automixture gauge as you said above why not just select it in the settings?

There are several planes designed with automixture built in. The F7F-3, the F8f-2, and so on. The real planes actually do have it built in.

Many ways for it to be accomplished in FSX. There is a setting in the aircraft.cfg file, the [Piston_Engine] section, that you can select to have FSX do the mixture for you, or, for a more accurate way, they can make an .xml file to control the mixture, dependant on the various variables involved. Now THAT is a confusing phrase...:rolleyes:

Sorry. There are automixture gauges that permit you to select, just as in the real plane, Full Rich, if the system fails somehow and you want manual control, Auto-Rich, for take-off, climb, even for fast cruise. Auto-Lean for economy cruise, and Idle Cut-Off, for shutting engines down. Automixture gauges permit this, whereas the aircraft.cfg entry only sets the mixture to automatic all the time, whatever the conditions.

That thread I mentioned was a discussion of such a gauge, and how they were going to use mathematics in the .xml gauge to make the different settings give the proper mixture for the differing conditions.

I did find that if you select the automixture in the aircraft.cfg file, there is a curve in the plane's .air file you can alter to change the mixture at various altitudes. Say you either prove mathematically, or just guess, even, that the FSX automixture is too rich for a given altitude. Then, you get into R507 in the .air file and alter the curve slightly, and see what happens under the desired flight conditions.

 

There are even automixture gauges you can " steal" from a plane and add on to a different plane, like a C172 for example. BUT, are the mathematics in the .xml guage correct for the C172's engine, as opposed to the plane it was designed for? Only way to tell for sure is to fly it and see. SAFEST way to select automixture is to either put it in the aircraft.cfg file, OR select Automixture in the game's master menu. But, if you do, ALL your planes will have it, and most prefer the "realism" of controlling the mixture manually.

 

Of course, not all planes need or use mixture control. Jets, turbo-props, etc.

 

Does all that babbling like a brook answer your question? Not answer it? Confuse you as much a it did me? :p

 

Have fun!

Pat☺

[ColR1948]

@Phantom Tweak, That was a good explanation of what the guage does, I thought at first it was just an on/off switch.

 

The reason I first asked in my above posts is I recently got the Saitek Yoke and Throttle Quad and I wanted to make proper use of the quad, plus I have the Air Hauler program and in that if you don't know you buy fuel for the trip.

So to economise and also have the engine/s run smooth I wanted to see and know what difference this made.

[ColR1948]

Just had something of interest, I was flying the Cessna 172 at 2500ft, I set the mixture on the throttle quad to 25, after a few minutes flying I got a popup saying, "Your Engine is losing power because the mixture is not leaned correctly - To complete press Ctrl = X"

 

I didn't press Ctrl+X I set the mixture up to 50 on the quad and that cured it, so according to that does that mean leaning too much I lose power, having said that I didn't notice the speed dropping, perhaps I didn't wait long enough?

[Sentry_FiveZero]

That's why I exclusively fly A2A planes when I fly in the GA category. Their software makes the gauges and such react in a much more realistic manner than other publishers. When you adjust mixture, it takes about 15-30 seconds to see the reaction in the EGT gauge.

 

 

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[Sentry_FiveZero]

Just had something of interest, I was flying the Cessna 172 at 2500ft, I set the mixture on the throttle quad to 25, after a few minutes flying I got a popup saying, "Your Engine is losing power because the mixture is not leaned correctly - To complete press Ctrl = X"

 

I didn't press Ctrl+X I set the mixture up to 50 on the quad and that cured it, so according to that does that mean leaning too much I lose power, having said that I didn't notice the speed dropping, perhaps I didn't wait long enough?

 

I suggest you go online and read about leaning. Also look at a POH for your particular type of aircraft and see what they recommend. That's how I learned it! Plus I talked to a few pilots to get their ideas on it.

 

 

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[ColR1948]

Yes, bbrz above is a pilot and his advice has helped a lot, as for A2A I posted about them in another thread.

[Sentry_FiveZero]

Still reluctant to do so because the FDEs of their Spitfire and the T-6 aren't exactly impressive.

Concerning the 172, I've read numerous times that it has a rather strong throttle lag, very much unlike the real one.

 

Each to his own. I like them because they are alot better than any default or Carenado plane.

 

 

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[il88pp]

Yes, he should go online and read about leaning.:) He should have done before starting the thread.:) Google: lean mixture aircraft

would have done the trick.:)

 

Anyway.

The mixture should be ok. Mixture. Yes? means two things are mixed. Mixed together.

In this case air and fuel.

Air and fuel are mixed before being injected into the engine.

They should be mixed in the right ratio.

Right ratio is: explosive mixture.

Not the right ratio is:

too much fuel--> does not combust completely. And no powerful explosion, but more a slow burn.

To much air--> does combust, but could have added more fuel for more power. Also not full explosive power.

 

 

Air is 20% oxygen.

Altitude-->low pressure. Means fewer molecules per liter. (you learned that in school.)

Low pressure therefore means also less molecules of oxygen per liter.

------>>>add less fuel to mixture, or it won't all burn.

 

Higher up-->lean more.