Leaning mixture for takeoff, pattern, etc

Pedals2Paddles

Pedals2Paddles

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Pedals2Paddles
To date, training has always been "mixture full rich - check". Lean it out as you climb and in cruise. Then obviously bring it back in as you descend. And full rich for landing. This is all in a C150.

I've been reading about folks who say you should lean the mixture to max RPM at any density altitude, not just the arbitrary 3000ft msl that gets thrown around. This seems logical to me. For the same reason we lean during taxi, screaming around the pattern with the mixture full rich isn't necessarily healthy.

Does anyone else have experience with leaning the mixture prior to takeoff? From what I've read, you would make the last step of the runup going full power, lean for max RPM, enrich by a turn or two, and leave that as your mixture setting for takeoff.

What about landing, still leaned for max rpm or full rich?
 
If you're going to go to full power at sea level (or above X% power, where that number varies a bit), leaning at the same time will not give you maximum power. Detonation robs power and turns it into heat and mechanical distortions. Some people advocate partial leaning at takeoff, but there is a lot of guesswork involved.

Bringing it back in on low throttle descent is not always a good idea, especially if you're landing at high density altitude. It's pretty easy to flood the engine under some circumstances. At high throttle, it's a lot easier to set mixture. Enrichen so it isn't rough, no more.

If you're landing where a full rich takeoff would be called for, going full rich prior to landing is reasonable, as prep for a potential go-around. If you choose not to do that, make sure you enrich BEFORE increasing throttle on a go-around. It's best not to think about that, and just have it done during the pre-landing checklist.
 
To date, training has always been "mixture full rich - check". Lean it out as you climb and in cruise. Then obviously bring it back in as you descend. And full rich for landing. This is all in a C150.

Consult your POH.

I've been reading about folks who say you should lean the mixture to max RPM at any density altitude, not just the arbitrary 3000ft msl that gets thrown around. This seems logical to me. For the same reason we lean during taxi, screaming around the pattern with the mixture full rich isn't necessarily healthy.

You probably can't hurt the engine in your C150 by leaning to full power at a sea level takeoff, but that isn't always the case in other planes.

Does anyone else have experience with leaning the mixture prior to takeoff? From what I've read, you would make the last step of the runup going full power, lean for max RPM, enrich by a turn or two, and leave that as your mixture setting for takeoff.

Look at the limitations for leaning in your POH. For example in my Arrow, they advise against leaning at climbout power below a DA of 5,000 feet. Above that, you need the extra power for maximum climb performance. In a 172 at a high DA airport, would do as you suggest but I wouldn't enrichen past best power.

What about landing, still leaned for max rpm or full rich?

The rationale for landing full rich at sea level is so that you will be full rich if you have to do a go around. I don't personally enrichen the mixture on landing. At a very high DA airport, you can flood the engine by going full rich on landing.
 
Pedals2Paddles said:
To date, training has always been "mixture full rich - check". Lean it out as you climb and in cruise. Then obviously bring it back in as you descend. And full rich for landing. This is all in a C150.

I've been reading about folks who say you should lean the mixture to max RPM at any density altitude, not just the arbitrary 3000ft msl that gets thrown around. This seems logical to me. For the same reason we lean during taxi, screaming around the pattern with the mixture full rich isn't necessarily healthy.

Does anyone else have experience with leaning the mixture prior to takeoff? From what I've read, you would make the last step of the runup going full power, lean for max RPM, enrich by a turn or two, and leave that as your mixture setting for takeoff.

What about landing, still leaned for max rpm or full rich?
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Look more closely at what has been discussed.

Full rich for takeoff and initial climb provides extra cooling and detonation protection. Both good things.

Tooling around the pattern can involve several different things. Descending for a landing involves low power settings and plenty of cooling. Running lean is no problem, is actually good. Doing a go around, T&G, or even a climb back to some altitude requires full power at slower speeds and therefore calls for full rich. What you don't want to do is apply full power and have the engine quit due to being too lean for full power.

YMMV at higher altitude airports.
 
It can be helpful to measure how far out the mixture control is when you lean for best power at take off. In my skyhawk at ~9,000' DA that would be 2 fingers. When its time to land I would use the 2 fingers for correct mixture in case a go-around was needed.
 
What you don't want to do is apply full power and have the engine quit due to being too lean for full power.


my thoughts exactly, screwing around with the mixture when there are way more important things going on isn't worth it to me.
 
MAKG1 said:
If you're going to go to full power at sea level (or above X% power, where that number varies a bit), leaning at the same time will not give you maximum power. Detonation robs power and turns it into heat and mechanical distortions. Some people advocate partial leaning at takeoff, but there is a lot of guesswork involved.
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Not following. How is leaning it while at full power on the ground not going to yield full power or cause detonation?
 
Pedals2Paddles said:
Not following. How is leaning it while at full power on the ground not going to yield full power or cause detonation?
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Gasoline detonates with excessive pressure and temperature. More is not always better. The detonation does not result in nearly as much piston motion as a normal burn. It just breaks stuff and makes it hot.

Full throttle increases temperature and pressure. So does leaning, to a point. Combine them only when the conditions won't let the engine go above recommended power (65% on a 172).

Don't confuse full power with maximum power. They are not always the same. Full power is a throttle position. Maximum power (or near maximum power) is what you really want for a takeoff, and it also involves prop RPM and mixture. Even fixed pitch.
 
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The answers vary too much by aircraft type (engine, prop, induction system, etc) to give any hard-and-fast rules on point. Also, what you can do safely varies with available instrumentation -- you can do a lot more leaning safely with an all-cylinder engine analyzer than you can with nothing but a tach and oil temp. So...

Read the book for your plane. Learn the book for your plane. Fly the book for your plane.
 
You are talking about staying out of the "red box", as described in John Deakin's AvWeb articles, aren't you?

The way i understood Deakin is -- stay OUT of the danger zone (right around peak EGT and RPM) while climbing to 7K or so, at which point it does not matter where the mixture lever is for NA engine. Staying out of the "danger" zone could be accomplished by being either ROP or LOP, but the latter is not practical without GAMI injectors, engine analyzer and constant fiddling with mixture, as during LOP richer is hotter. According to Deakin keeping mixture full rich during climb out does not hurt anything. I believe he used skydiving operations for an example of full rich engine regimen that (according to him) does not negatively affect the TBO times.

182536mixture_example_chart_2.jpg
 
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Pedals2Paddles said:
This is all in a C150.
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I think some of the replies missed this, so gave generic "see Operating Handbook" answers. You aren't likely to have EGT or CHT instrumentation in such a plane.

I often fly a C152 from near sea level airports to ones up to 4000 ft. Of course it has a different engine from C150 and I cobbled together my procedures from various flying guides and the POH for the C152. Also, I am a relatively low time pilot so what I say on this should be taken with caution. So far it seems to work:

Before takeoff, apply full throttle and lean to maximum RPM. (The Mountain Flying Bible suggests doing the leaning during the takeoff roll if no suitable place to do it without risk of kicking up debris into the blades!)

When approaching for landing and to set up for possible go-arounds, while nearing pattern altitude and before throttle reduction from cruise, I lean to maximum RPM at that throttle setting. I have not found any great advantage to applying full throttle before leaning - cruise setting seems fine (but I've only checked a couple times.) By the way, I periodically adjust lean on descent - I no longer just shove it to full rich and forget it. (Unless I'm under 3000 MSL.)

It would be interesting to see what others who fly in similar situations think of my procedures, or what they do.
 
Which article is that chart from?
 
It is VERY hard to set mixture correctly while descending at low throttle. You will almost certainly be too rich at full throttle when it looks good at low throttle. If it's rough, you know it's too lean, and can enrich it just enough to keep it smooth. If it's not rough, leave it alone.

I've had an engine quit on short final due to this at a high altitude airport, and fail to restart due to the flooded condition. Fortunately, the runway was made and there was no damage whatsoever -- in fact, the landing was a really nice greaser. I did block a runway for a while, though.
 
Pedals2Paddles said:
screaming around the pattern with the mixture full rich isn't necessarily healthy.
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I have a funny feeling that this officially marks the first time that someone said "C150" and "screaming around the pattern" in the same post.


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Jim Logajan said:
When approaching for landing and to set up for possible go-arounds, while nearing pattern altitude and before throttle reduction from cruise, I lean to maximum RPM at that throttle setting....
By the way, I periodically adjust lean on descent - I no longer just shove it to full rich and forget it. (Unless I'm under 3000 MSL.)
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So if you're landing above 3000msl, you leave it at the leaned-for-cruise setting just before pulling the power back? Is that 1000-15000ft difference between that and the runway enough to make a difference if you have to punch it and go around?

For landing below 3000msl, are you saying you do go full rich?


NJP_MAN said:
I have a funny feeling that this officially marks the first time that someone said "C150" and "screaming around the pattern" in the same post.
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HA! What I really meant was screaming "Just make it to pattern altitude before abeam! You're almost there, YOU CAN DO IT!!".
 
Full rich, takeoff landing. Taught that way. Always done it that way, no problems, 4000 hrs. Always warned not to screw with the mixture after approaching the pattern or on take off. Full rich.
 
I don't go full rich before landing. I have practiced the go around and can push both the throttle and mixture in together for max power. I lean agressively no matter the altitude.
I don't know your engine but for me pattern work is done at less than 65% power after getting to PA. Below 65% you really can't hurt the engine by leaning too much. You can foul the plugs by not leaning.
 
Jimmy cooper said:
Full rich, takeoff landing. Taught that way. Always done it that way, no problems, 4000 hrs. Always warned not to screw with the mixture after approaching the pattern or on take off. Full rich.
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I once got a case of fouled plugs when taking off full rich from a 2120 MSL airport. (Density altitude was about 3000 at the time.)
 
Pedals2Paddles said:
So if you're landing above 3000msl, you leave it at the leaned-for-cruise setting just before pulling the power back?
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Yes.

Is that 1000-15000ft difference between that and the runway enough to make a difference if you have to punch it and go around?
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There is no doubt some difference - but not enough (I think) for me to fiddle with the mixture on final!

I did use that leaning procedure prior to several go-arounds due to gusty cross-winds at a 4053 ft airport (4S7) last year. Climb was anemic even after flaps retracted, but since I didn't try comparing with several mixture permutations I don't know if it could have been improved.

For landing below 3000msl, are you saying you do go full rich?
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In the C152 or C172 I rent - generally yes.
 
Jimmy cooper said:
Very doubtful.
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A number of them have been with instructors in the right seat. They fly up from sea-level together. If its a 4 cylinder like a 172 and they are departing up hill they will be lucky to get out of the pattern. A 182 recently made it over 5 miles before impacting 9,000' terrain. Full rich and too dumb to turn back when they fail to outclimb the terrain. If leaned for best power the 182 could clear that 9,000' pass by 2,000'
 
If flying behind a continental or a lycoming you need to lean for best power here or your performance will be horrid.

Now I have a Rotax 912ULS with self leaning carbs ( they only lean below 92% throttle and I fly at WOT which is full rich ) and the 912 is happy full rich. Even at 14,000' the Rotax works great full rich.
 
I fly out of KRNO (4415' and 90° on a typical late-spring to early-fall day).

For a 172 I start full rich and immediately pull the mixture knob about 1" out. It stays in that position for most local flights (up to about 8000' MSL)… if I go higher, I'll lean it out more for cruise.

I've only flown at sea level a couple times. At sea level I gather I'd start full rich, then lean (how far?) for taxi. For the run-up, should I be doing this full-rich, or at the level I leaned for taxi?

Up here at KRNO in a 182, after starting full rich, I'll pull it back an inch, then before the mag/carb check at runup, I'll run it up to 2000rpm and lean for max rpm, then turn the mixture two turns toward rich. It'll stay there for local flights same as in the 172.

I never go full rich to land up here - just to the same 1" out I used for t/o.
 
Sac Arrow said:
I can vouch for that. Goes for several of the higher elevation airports like KTVL as well.
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Yes of course. You neglected to mention the altitude of your airport. I'm at sea level most of the time or 1000 feet above it on take off- landing. I never screw with a throttle setting much on landing ( unless I've got the runway made) or mixture control at low altitude, especially on takeoff. Risky. In my circumstances, full rich taxi, full rich takeoff and in some aircraft full rich below 5000 feet. AOPA has excellent easy to read articles on this subject. Lots of myths out there.
 
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Jimmy cooper said:
Full rich, takeoff landing. Taught that way. Always done it that way, no problems, 4000 hrs. Always warned not to screw with the mixture after approaching the pattern or on take off. Full rich.
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All works till it doesn't.

Guessing your 4k hours are all around the same type of places??
 
Jimmy cooper said:
Yes of course. You neglected to mention the altitude of your airport. I'm at sea level most of the time or 1000 feet above it on take off- landing. I never screw with a throttle setting at low altitude. Risky.
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TVL is about 6,300 feet and density altitudes can exceed 10,000 in the Summer. I fly out of a sea level airport but frequently fly to Sierra airports.
 
Jimmy cooper said:
Yes of course. You neglected to mention the altitude of your airport. I'm at sea level most of the time or 1000 feet above it on take off- landing. I never screw with a throttle setting much on landing ( unless I've got the runway made) or mixture control at low altitude, especially on takeoff. Risky.
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The point is a hard and fast rule of full rich (your post is easily interpreted this way) is the most common cause of crashes in locations with very high density altitude and therefore isn't a great hard and fast rule.

BTW it isn't a throttle setting issue.
 
But throttle settings, constantly f$&@ing with them down low is every bit as dangerous as screwing with the mixture control. As I mentioned , above 5000 feet things become different. Very common knowledge . As I mentioned your altitude on take off was not mentioned. It set meup for a " gotcha". ( my fault , I should have seen it coming) Again, AOPA has great article on this as do many others.
 
MAKG1 said:
What's screaming? The airplane or the poor schmuck in the right seat?
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Usually it's tower screaming at you because you are 200' lower than TPA by the time you are abeam and pulling power back for the next touch and go.
 
Yup. It's kind if a joke in mid august. Hey, we made it to 850agl this time around!


<< Sent from my mobile device at 0agl >>
 
This one time "read the POH" is not going to be much help. The typical "lean above 3000'" for takeoff is pretty useless and few POHs (if any) say a single word about leaning on the ground for taxi or for

Having spent 20 years in Colorado where we are almost never "full rich," I can count the times on one hand when I have followed the Cessna 172 POH's, "the mixture should be leaned to give maximum RPM in a full throttle, static runup" guidance. And have never followed the landing checklist Mixture-RICH" command (yeah, I know; some would say "Mixture-RICH" doesn't necessarily mean "full" rich, but there is nothing in the expanded procedures to explain that).

My favorite leaning for taxi story: I was in LA on business and ended up as an assisting passenger on an Angel Flight. The pilot owner a gorgeous 182 and leaned aggressive for taxi on the ground at KSMO. As he explained, many of his 182 friends have told him it's completely unnecessary. OTOH, he also explained, he's the only one of his friends who has never had fouled plugs showing up on the runup.
 
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