Mixture when on the ground

[chadryan]

I noticed something interesting about the Bonanza that is different than the other A2A GA planes. When on the ground at or near sea level I can pull the mixture almost all the way out and when I do this the RPM actually increases a bit. With the other GA planes if I pull the mixture out this much the engine would die or run very rough and the RPM definitely wouldn’t increase. I was wondering why this is.


Sent from my iPhone using Tapatalk

[AKar]

Slight increase in idling RPM when leaning is something that is present in reality...or, is adjusted to be present. Idle mixture adjustment is done so that a slight but just noticeable increase in RPM should happen when leaning the mixture towards cutoff with throttle at idle position. Too noticeable increase in RPM on the other hand indicates too rich idle mixture that may result in problems such as fouling plugs or even poor idling when warming up. Obviously, there are other variables as well which dictate the proper settings for an individual airplane.

-Esa

[Oracle427]

On an O-470 I use regualrly, I can lean out right up to about the very last 1/4" of travel on the mixture while at idle power. Not the same engine and not fuel injected, but similar in behavior. When leaning for idle ops on the ground, I can get a 100 RPM rise. When I pull the mixture knob that last 1/4" inch from full idle the engine will show a very slightly increase in RPM and then die. Always make note of that to make sure I have a properly adjusted mixture control.

I think this behavior is fairly realistic.