Help please! Using Mixture Control

[Frog on Toast 6]

Since I got a throttle quadrant, I've been using mixture control as opposed to letting FSX handle it. Thing is, I'm not sure exactly how it's supposed to be used!

 

If I took in anything from my old air cadet days of learning the principles of flight and propulsion, you have to lean the mixture as you gain altitude? If that's right...

 

...How do I know when I've got it set correctly? Until now I've just been using the engine note, with the intention of getting it sounding smooth as opposed to rough. Is that all there is to it?

 

I know in turboprop aircraft the lever doesn't control mixture, but fuel condition, and TBH I have no idea how to use that either!

 

Any advice would be welcome.

 

Cheers,

 

Mark

[Aircraft Aviation 2]

Hi Mark,

 

Indeed, you do lean the mixture as your altitude increases. Most (GA) people don't lean the mixture below 3,000ft, as the air below 3,000ft is usually sufficiently dense as to provide a good combustion mixture. Furthermore, unnecessary leaning can cause very high CHTs and detonation leading to serious engine damage.

 

Of course, this is the FS world and so these real-world damage considerations are of no concern here!

 

The general idea, once above 3,000ft, is to set your throttle to the desired power setting, and then slowly pull the mixture control back (ie leaning it), whilst simultaneously watching the RPM gauge very closely. If done slowly enough, you should notice that the RPM will slowly rise, then peak, and then slowly fall again. The ideal mixture position is to run rich-of-peak; in other words, you want the RPM to peak, and then you want to push the mixture control in very slightly (ie richening it). If all is done correctly, the aircraft should be running at just slightly lower than peak RPM with the mixture control on the rich side of peak RPM.

 

Alternatively, if the aircraft you're flying has an EGT gauge, you can use the exact same procedure, but this time watching for peak EGT instead of peak RPM (EGT is generally considered to be a slightly more accurate indication). Again, lean the mixture until peak RPM, and then push it in (richen it) a bit.

 

The idea behind running slightly rich of peak is that you get a nice cooling effect from the excess fuel in the cylinders. Some GA operators actually advise you to run lean of peak for a similar effect; I am an advocate for the former, however.

 

I am not sure if FS aircraft (default aircraft, that is) actually respond to mixture adjustment as per the real world, I have never really tried it to be honest! Best of luck!

[allardjd 1,853]

Mixture control is only for piston-engine AC. You can lean by ear and what you describe sounds about right but it's better to use an EGT if you have one. Lean to peak EGT and reset about once a minute when climbing. Reset it after any throttle or altitude change. Go full rich for takeoff, go-around and during descents (when carb heat should be on too). In the RW some engines require 25 or 50 degrees on the rich side of peak EGT to help prevent burnt valves but in the sim the engines aren't that fussy - just lean to the peak.

If taking off or going around at a high-altitude airport, it may require a leaner than full-rich setting to get maximum engine performance.

Jets and turboprops use the other lever for all sorts of things and it can vary from type to type. Most often it's called the "condition lever" and typically has settings like Ground Idle, Flight Idle, Start, Cut-off, etc. Flight Idle is a higher power setting than Ground Idle so you don't blow the fire out with the ram air entering the engine. You pretty much have to read up on the specific AC type.

John

[Quickmarch 488]

The post, above, is an excellent primer on mixture control in the real world.

 

Having said that, FS has no real world results(that I can detect) from leaning Ie: fuel efficiency, temperature efficiency, something else to do with your right hand that impresses the girlfriend, 

 

However, there is an annoying - "Your engine is not working at peak efficiency, yada, yada, yada"  popup that splashes across my screen just about the time I'm trying to clean up the aircraft.

 

My technique: Pull back the throttle to climb power, set the RPM's, yank the red knob out about halfway. That's it. You can ignore the mixture until TOD. Gets rid of the pop-up.

[Frog on Toast 6]

Thanks for the info gents, It does seem to affect flight performance in a small way in FSX, so I'm glad I asked!