Leaning the Mixture is bad?

[denverpilot]

I have friends that will not trust with my money or car keys.

Dang it. That explains why you wouldn't lend me $20.

LOL!

(I know... The next post is going to say, "Who said you're my friend!?" I'm setting myself up...)

 

[Tom-D]

Any one think that if the idle mixture was set correctly it would not load up?

And if it was, why would you lean at idle?

 

[zaitcev]

Simple solution: fly a Rotax powered airplane. Or a jet. In both cases you'll need a new mechanic and you never need to manage the mixture.

 

[mondtster]

Any one think that if the idle mixture was set correctly it would not load up?

And if it was, why would you lean at idle?

I've always wondered about that. People always harp about leaning on the ground but it doesn't seem like it is necessary if the idle mixture is set right. The local flight school planes I've serviced never get leaned and frequently idle for extended periods of time yet they have little to no deposits on the plugs when we pull them for inspection at oil change time. I can't remember the last time we had a complaint of a fouled plug either.

 

[denverpilot]

I've always wondered about that. People always harp about leaning on the ground but it doesn't seem like it is necessary if the idle mixture is set right. The local flight school planes I've serviced never get leaned and frequently idle for extended periods of time yet they have little to no deposits on the plugs when we pull them for inspection at oil change time. I can't remember the last time we had a complaint of a fouled plug either.

So you guys have those fancy new carbs that auto-lean the idle mixture on hot days and when you visit Leadville?

 

[PilotAlan]

Dang it. That explains why you wouldn't lend me $20.
(I know... The next post is going to say, "Who said you're my friend!?" I'm setting myself up...)

[Biting tongue... Biting tongue]

Just kidding. I would loan you $20.... Thats low enough that I don't care if I get it back

 

[mondtster]

So you guys have those fancy new carbs that auto-lean the idle mixture on hot days and when you visit Leadville?

The same can be said going the other way. If your idle mixture was set in Denver and you went to sea level what will happen?

In general, carburetors are just dumb fuel metering devices that won't compensate for environmental changes. Typically, the changes are small enough that idle mixture doesn't seem to be affected much if it is set right to begin with. Of course you'd want to lean on the ground up at Leadville or any other higher elevation airport but if you're typically operating out of airports with similar field elevations to the one where you set the mixture at how much change are you really going to see?

One thing I've noticed is that the float type carburetors seem less finicky with mixture settings than my PS-5C pressure carb is. I've spent a lot more time messing around with making sure this pressure carb is set right than I have ever bothered to spend on the other ones.

 

[Tom-D]

If your idle mixture was set in Denver and you went to sea level what will happen?

On the MA3SPA ….. Nothing.

Remember the mixture adjustment on a MA3SPA is an air bleed adjustment not a fuel metering oriface.

 

[mondtster]

On the MA3SPA ….. Nothing.

Remember the mixture adjustment on a MA3SPA is an air bleed adjustment not a fuel metering oriface.

Interesting, I didn't realize that. Good to know.

 

[Hank S]

The success of leaning on the ground will vary between models. I routinely pull the red knob out about halfway on the ground (O-360), bur when I did that recently in an O-320-powered 172 on rollout, the engine died . . . . Know your plane.

Ground leaning won't hurt anything, just push the red knob in for runup and takeoff.

 

[Skylane81E]

I've always wondered about that. People always harp about leaning on the ground but it doesn't seem like it is necessary if the idle mixture is set right. The local flight school planes I've serviced never get leaned and frequently idle for extended periods of time yet they have little to no deposits on the plugs when we pull them for inspection at oil change time. I can't remember the last time we had a complaint of a fouled plug either.

Depends, on an 80/87 octane engine running 100LL leaning is more important. Also need to remember that the idle mixture isn't set for prolonged idling, it is set for best performance of the engine and too rich or too lean can cause an off idle stumble.

 

[bluerooster]

Most folks I know that routinely do high alt ops, lean at startup for peak rpm, then enrichen just a tad, leave it there untill climbing through 1000agl. Yes even with O-320s and 360s with the MA3spa.
Also interesting note, on those with constant speed prop, there's no need to reduce MP, prior to reducing RPM, after takeoff.