When to lean mixture?
07-16-2007 | 02:46 AM
#1
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Gets Weekends Off
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From: PA-44 Left
When to lean mixture?
At what altitude do you guys lean out the mixture when flying cross countries? I don't know if it matters from aircraft to aircraft, but I fly a Cessna 172, and I only lean it out if I'm over 3000' AGL. Thanks.
07-16-2007 | 04:04 AM
#4
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From: ATP, CFI etc.
Engines differ and some can be leaned all the time, even on takeoff so there is no hard and fast rule you just have to know an engine and its peculiarities. 3,000' msl would be a good time to do it if it hasn't been done by then. Make sure you have setting the mixture back to full rich before getting into the traffic pattern on your checklist, especially when there is any doubt about how your engine will run leaned out. Back when I did my very first solo cross country I descended to the pattern at the destination without going back to rich and the darned if the engine didn't cut out. I knew what was wrong and managed to airstart it right away, and that airplane was more sensitive than most, but you could get in trouble if you didn't richen the mixture coming back down from altitude.
Last edited by Cubdriver; 07-16-2007 at 11:34 AM.
07-16-2007 | 05:33 AM
#5
Big Poppa
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Engines differ and some can be leaned all the time, even on takeoff so there is no hard and fast rule you just have to know an engine and its peculiarities. 3,000' agl would be a good time to do it if it hasn't been done by then. Make sure you have setting the mixture back to full rich before getting into the traffic pattern on your checklist, especially when there is any doubt about how your engine will run leaned out. Back when I did my very first solo cross country I descended to the pattern at the destination without going back to rich and the darned if the engine didn't cut out. I knew what was wrong and managed to airstart it right away, and that airplane was more sensitive than most, but you could get in trouble if you didn't richen the mixture coming back down from altitude.
07-16-2007 | 06:11 AM
#6
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From: FOD
BINGO! There are many airports (mine included) that are way above 3,000' MSL, so we always lean...we even lean for taxi here and it makes a noticeable difference in how the engine runs just idling around. Not to mention the fact it keeps from fouling plugs as often.
07-16-2007 | 07:39 AM
#8
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From: Engines Turn or People Swim
Unless the POH says otherwise you should lean for taxi at all altitudes...this will keep the plugs from fouling in those engines that are prone to that. A long hold idling at full rich can foul them badly enough that a mechanic will have to remove and clean them.
07-16-2007 | 01:04 PM
#9
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From: JS32 FO
Too true. We lean everything except the DA20s. For some strange reason, they don't foul up. All the other planes will fail a mag check if you don't lean the mixture for taxi. As far as leaning for cruise goes, the POH should give you some advice on that. Check there. 3000 MSL is just a Rule of Thumb.
07-24-2007 | 06:12 PM
#10
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From: BE20/LR-JET Right Seat
i fly Cherokee's and ever since ive started leaning on taxi, ive been having rougher run-ups when i check the magnetos......i end up smoothing it out with the mixture, but wasn't this the reason i leaned for taxi in the first place?
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