What COULD happen if....

orange

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A pilot would lean for taxi and then take off and fly the pattern with the mixture leaned?

Out of curiosity, because I know somebody that it almost happened to.

Thanks
 
It depends on how lean it was. If only slightly leaned, it might even result in increased RPM and better performance. But generally speaking, if the checklist calls for full rich on takeoff, that's what you want.
 
write stuff is correct. But worst case would be low density altitude (~1000ft or less) and fairly lean, then less power, more heat (maybe too much heat) and possibly detonation.

All pretty bad for the engine. But if pressure altitude is high, leaning before TO is a good thing.
 
If properly leaned for taxi, it will probably die. (Don't ask how I know that). Also you don't want to be full rich all of the time. When operating at high altitude airports you will be surprised how lean you are at peak RPM.
 
orange said:
A pilot would lean for taxi and then take off and fly the pattern with the mixture leaned?

Out of curiosity, because I know somebody that it almost happened to.

Thanks
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If he leaned for taxi properly the engine will quit when he adds take off power.
 
You'll probably take off normally and find your temps higher than normal. Full rich fuel at takeoff is for cooling, not power. If you lean really aggressively the engine will stumble as you spool it up. That usually alerts you to correct it before you commit to flying. Ever see an aborted takeoff where the plane exited downfield and taxied back to take right off? It happens.
 
I know a guy who did that at ABQ. When he advanced the throttle for takeoff his next step was to tell the tower there'd be a slight delay while he restarted the engine.
 
I always go full rich for take-off and I my home airport is near Denver. ;);)o_O:rolleyes:
 
That's what checklists are for.

I was under a raised car once and the driveshaft almost fell off and hit me on the head, but thankfully it was attached with bolts. That almost really ruined my day.
 
Yeah, leaned for taxi, and then full power for takeoff you should feel a difference in power - even during the run up. One day I was leaned out a lot at the fuel island, and had to taxi over a slight uphill. Even that slope was enough to make the engine cough until I richened it.
 
orange said:
A pilot would lean for taxi and then take off and fly the pattern with the mixture leaned?

Out of curiosity, because I know somebody that it almost happened to.

Thanks
Click to expand...
There are places that leaning is necessary to do the pattern.
 
If the engine actually developed power when he advanced the throttle for takeoff, he most likely wasn't actually leaned for taxi. At near-idle settings on the throttle, there is a separate enrichment in most carbs. If you actually want to do something effective at those power settings, you need to get it pretty close to idle-cut-off. Most engines will sputter if you try to go WOT at those settings.

I learned to fly at BJC (6000'). Can't say I ever leaned in the pattern. By then it's way too late. We leaned for taxi and then we leaned again for best power at the run up. With my injected engine now, I can set the fuel flow with the gauge rather than having to manually try to peak things. But still it's more important to set it BEFORE THE TAKEOFF RUN. The extra 800-1000' in the pattern is small potatoes.
 
ollopa said:
That's what checklists are for.

I was under a raised car once and the driveshaft almost fell off and hit me on the head, but thankfully it was attached with bolts. That almost really ruined my day.
Click to expand...

Wow. Lucky dog. Who gave you a driveshaft removal checklist? I've always had to just get under there and do it.

Clark1961 said:
No it is not turbo-normalized. :cool:
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Heheh you and your odd-ball plane have too much fun in these threads. :)
 
denverpilot said:
Wow. Lucky dog. Who gave you a driveshaft removal checklist? I've always had to just get under there and do it.
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Obviously lost something in translation, so I'll clarify:
1) Setting mixture before takeoff is a checklist item, so I thought it was a kind of dumb thing to worry about doing accidentally.
2) OP knows somebody it almost happened to. That's like that time the driveshaft almost fell on me, only it entirely didn't. It almost really hurt, only it didn't. And it wasn't being changed, it was just attached to the car that I was standing under. Like how a near miss is a hit and a near hit is a miss. I'm guessing OP's friend ran the checklist and caught the leaned mixture before takeoff, which is almost, but not quite, entirely unlike a big deal.

I think we should start a thread titled "Why is this item on my checklist?" and sticky it.
 
Reminds me of a line from The Money Pit.
Martha: You were almost late.
Anna: Martha, in this country we have an expression for almost late. It's called "on time."
 
Timbeck2 said:
flyingron said:
We leaned for taxi and then we leaned again for best power at the run up.
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That's how I do it. Guess its different for the sea level guys.
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flyingron said:
Most of them never touch the red knob other than to stop the engine.
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That shows absolute lack of training in aircraft systems. If a CFI fails to train a student in the use of "the magic red handle", at least the student should have enough IQ to inquire about its use after reading the chapter on engine power management. But I am making huge assumptions here (about smart student and smart CFI to begin with).

The other day, I flew with an "experienced" pilot. During run-up, I asked him why he didn't check the carb heat. He paused, looked for the handle/knob and having no idea where it was, he simply shrugged and replied that the engine probably didn't have one. After inquiring where his alternate air handle is (assuming that the engine was injected), he shrugged again. Had we been going into clouds that day, I wonder whether I would have exited the airplane and walked home.
 
flyingron said:
Most of them never touch the red knob other than to stop the engine.
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Only if it's a wet rental!

I like the red knob because I'm overly paranoid about running out of gas, not that I ever cut it close enough that full rich settings would cause me to run out.
 
BigBadLou said:
That shows absolute lack of training in aircraft systems. ...
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How so? It's exactly how the checklist tells me to do it. To me it shows excellent training in fuel management and engine health. I for one am not fond of little balls of lead fouling up my spark plugs.
 
I thought about this yesterday. My idle warm-up mixture is too lean to power out of my tie down so when it stumbles I enrich to power up and taxi. I could easily take off at that mixture setting. Believe it or not I've had to go around when I've forgotten to go full rich, too. It worked out fine. Much better than when forgetting to push in carb heat. A guy only does that once on a short strip in tall trees!
 

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Again, I don't go "Full rich" on takeoff. That works at sea level in some planes. At any altitude, you'll want to set the appropriate mixture. Back when flying old 152/172's we'd lean by peaking the RPM at runup. Now with my injected engine, the fuel flow gauge is marked for what power you want to set for takeoff.

Leaning for taxi to the point of stumbling is not only important as it gives you a strong feedback it's overlean when you firewall the throttle to take off, but anything short of that in a carb engine is probably not doing anything to change the mixture when you're running primarily on the idle loop.
 
Idle loop? The only reason to lean for ground ops is to prevent sooting and fouling from overly rich mixtures that happen during inefficient low rpm ops. Its impossible to do any over-lean damage while operating at less than 50% power but that isn't to say there's any requirement to operate at bare minimum mixture. Every plane is different, every op is different. I've worked hard to increase fuel flows in my Cessna and know my own engine well. My description of my operations is factual and aporopriate for my flying. Take it as that, a comment. A pirep. For some of you to try to build an argument about it because it doesn't match what you do or to make stuff up to support what you do is ridiculous. So it goes on the internet.
 
Stewartb said:
Idle loop? The only reason to lean for ground ops is to prevent sooting and fouling from overly rich mixtures that happen during inefficient low rpm ops.
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Exactly.

I wasn't arguing with you, I was just reinforcing something you were saying.
 
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