Do you lean for take off ?

txflyer

txflyer

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Fly it like you STOL it ♦
Departing KHRX this morning, I did my runup and leaned it to clear the right mag because it was running a little rough. The engine sounded so good I just left it leaned out and took off. Keep in mind, I normally operate from 300 ASL.

Elevation there is ~4000. It was cold so DA wasn't much a factor, but the engine liked it better leaned out.

Did I commit a no-no? :dunno:
 
Depends...what does your POH say on the matter?
 
Cold temps already leaned your engine more than normal. In winter I struggle to get enough fuel into the engine.
 
At 4k, if you leaned for best power at less than full throttle, and then took off at full throttle, you are fine. The mixture enrichment circuit was activated. -Skip
 
Stewartb said:
Cold temps already leaned your engine more than normal. In winter I struggle to get enough fuel into the engine.
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Man I'm all discombobulated.

I thought cold air was more dense, thus more fuel/air mixture.

When you pull carb heat, you can lean the snot out of it. :confused:
 
Cold air is dense but your fuel flow doesn't adjust for it so the mixture is leaner with colder temps.
 
txflyer said:
That's the thing. It says full rich on take off in all applications... :dunno:
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That seems kind of bizarre... I operate out of 4200 ft, and leaning gives you an extra 100-200 rpm.
 
txflyer said:
That's the thing. It says full rich on take off in all applications... :dunno:
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So you invented something new that departed from your POH and you're asking us if it's OK?

:confused::)
 
txflyer said:
Man I'm all discombobulated.

I thought cold air was more dense, thus more fuel/air mixture.

When you pull carb heat, you can lean the snot out of it. :confused:
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Carb heat introduces hot air into the mixture, and hot air is less dense, i.e. fewer molecules per unit volume, all with the same fuel component, so the mixture becomes richer. If you know you'll need to apply carb heat for a prolonged operation (e.g. carb icing conditions that can't be avoided), you'll need to lean the mixture appropriately.
 
Stewartb said:
Cold air is dense but your fuel flow doesn't adjust for it so the mixture is leaner with colder temps.
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Okie dokey. I guess I better keep it full on rich.

Another weird thing was my generator light stayed on even during the runup to 1700RPM but when I took off, it started working.

I was hoping it would start working because I wanted out of there and it's Sunday ... no mechanic ... but I was prepared to circle back and stay another night if it didn't.
 
woodchucker said:
That seems kind of bizarre... I operate out of 4200 ft, and leaning gives you an extra 100-200 rpm.
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Right. That's it. When I checked the mags full rich she ran like puke.

When I leaned it out, she started to purr. :yesnod:
 
Of course you lean for TO if elevation and/or conditions warrant it, "full rich" for to/ldg is not something a CFI with NO experince teaches.
 
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txflyer said:
Man I'm all discombobulated.

I thought cold air was more dense, thus more fuel/air mixture.

When you pull carb heat, you can lean the snot out of it. :confused:
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txflyer said:
Right. That's it. When I checked the mags full rich she ran like puke.

When I leaned it out, she started to purr. :yesnod:
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puke and snot ain't good.....:no:
 
James331 said:
Of course you lean for TO if elevation and/or conditions warrant it, "full rich" for to/ldg is not something any CFI with experince teaches.
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Unless you train at 300 ASL.

Landing checklist says full rich, prop in, carb heat on, but I don't do any of it.

I don't shove the prop in until I'm in the pattern and have pulled the throttle back until RPM drop below the green. I'll pull carb heat on the decent to clear any ice, but then it goes back in for the pattern.
 
txflyer said:
Unless you train at 300 ASL.

Landing checklist says full rich, prop in, carb heat on, but I don't do any of it.

I don't shove the prop in until I'm in the pattern and have pulled the throttle back until RPM drop below the green. I'll pull carb heat on the decent to clear any ice, but then it goes back in for the pattern.
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You need a new checklist, go somewhere higher or hotter and that rote action will kill ya.

Mine says, mixture for takeoff.

I also am a fan of carb heat off on short final
 
James331 said:
You need a new checklist, go somewhere higher or hotter and that rote action will kill ya.

Mine says, mixture for takeoff.

I also am a fan of carb heat off on short final
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I was taught carb heat robs power. So it stays off on T/O and landings.

I have a carb temp gauge, but you know, I've never had a carb icing encounter even with it reading on the cold end of the yellow for an extended period.

But after a long cruise, I'll pull the carb heat out when I start down just to be sure.
 
txflyer said:
That's the thing. It says full rich on take off in all applications... :dunno:
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What type aircraft? And are those the exact words in the manual, or is there some other context ... ? :skeptical:

On account of because, with a normally-aspirated engine at higher density altitudes, you're getting significantly less than full available power if the red knob is all the way forward.

More information is needed.
 
My POH for takeoff says Mixture-FULL RICH (or as required by field elevation) Carb Heat (set cold for takeoff) for landing Carb heat as required and mixture FULL RICH (or as required by field elevation)
 
If you don't pull throttle to descend, you won't need to add carb heat. Depend that fuel in climb, get it back as extra speed in descent. Your block time will be reduced, but fuel use will stay quite similar.

Lean for takeoff at high(er) altitude. Full throttle, lean for max RPM, release brakes and go.
 
At high DA airports you can hear many stories of low-altitude pilots running off the end of the runway because they took off full rich. Many POH's do not adequately address the importance of leaning for the airport elevation.



txflyer said:
Departing KHRX this morning, I did my runup and leaned it to clear the right mag because it was running a little rough. The engine sounded so good I just left it leaned out and took off. Keep in mind, I normally operate from 300 ASL.

Elevation there is ~4000. It was cold so DA wasn't much a factor, but the engine liked it better leaned out.

Did I commit a no-no? :dunno:
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Pilawt said:
What type aircraft? And are those the exact words in the manual, or is there some other context ... ? :skeptical:

On account of because, with a normally-aspirated engine at higher density altitudes, you're getting significantly less than full available power if the red knob is all the way forward.

More information is needed.
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I'll pull the POH out tomorrow and check the exact wording.

Cessna 180G.
 
Operating at altitude, you do need to lean for max rpm during run-up. Even immediately after start up it's not a bad idea to pull the mixture out about an inch until run-up.
 
Pilawt said:
What type aircraft? And are those the exact words in the manual, or is there some other context ... ? :skeptical:

On account of because, with a normally-aspirated engine at higher density altitudes, you're getting significantly less than full available power if the red knob is all the way forward.

More information is needed.
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Ether way its wrong. Full rich in ANY conditions = not going to have a good time.
 
A pilot needs to know the DA in order to operate the airplane correctly.

My local DA right now is about -5,500'. What's full rich normalized for?
 
Cessna POHs generally say to lean over 3000 [DA]. If the engine ran like crap full rich, DA WAS a factor, or your carb has a problem.

If the former, there was no no-no. Leaning for best power is SOP. If the latter, that could have ended badly.
 
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txflyer said:
That's the thing. It says full rich on take off in all applications... :dunno:
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What airplane, what engine? The early piper AFM has very little to say about anything so I use the Lycoming manual as reference.
Unless you're flying a Jabiru with Jabiru engine, the airframe manufacturer probably only copies the engine manufacturer info. So go find the engine manual, you'll find details there.
 
murphey said:
Do you often TO from higher elevation airports?
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Maybe, maybe not. There are a few high D-Alt airports in the western part of North Carolina where leaning will be necessary in the summer to get good performance ("underground" compared to even the flatland airports in the Denver area). But it is common among lowland pilots to forget what they learned about density altitude. We tend to remember what we use and forget what we don't. You can't imagine what I have had to learn and relearn about instrument flying when I moved here from Denver.

Of course, while I read more than my share of accounts of serious accidents due to an attempt to take off too rich, most of the time I've seen it has involved the engine quitting while still sitting on the ground.

Besides, most of the POH I have seen do call for leaning above a certain altitude - at least for normally-aspirated engines that do not have some type of automatic compensation mechanism - and that is definitely density altitude although the POH might not say it in those words.
 
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Back to the OP. If the run-up identified a rough engine that rough condition should have been cleared up prior to flight. It may have needed to be leaned for ground ops. It's impossible to over-lean when operating at taxi power. At those power settings the engine will stop running before it'll damage anything. I'd have leaned it to clear the 1700rpm run-up but I wouldn't have assumed that made a leaned 2700 rpm take-off the correct action. Get schooled about leaning for best power and figure out what your plane needs. No two 180s are identical for fuel flows and leaning. What somebody tells you on the Internet may not be accurate for your plane.
 
At our club, with a 2120" high runway, and 90s in summer, it is recommend to lean. Over 3500" DA mandatory per local regulations
 
I managed the airport in Leadville, CO for a year...you better believe there was some leaning of the mixture taking place for take-off there! In the summer, our DA regularly was +14,000 ft. I learned to fly in the flat lands of Indiana where we could only speculate what DA was all about. You want an education? Go find a CFI that regularly operates in and out of Rocky Mountain airstrips.
 
Normally the only time you wouldn't lean for takeoff at a high DA is with a turbo. Taking off at near 10,000 foot DA's in the Turbo Arrow, I would lean aggressively on the ground to keep the engine running, and then go full rich as I advanced the throttle. Otherwise, I'm leaning for best power.

The Deb I used to fly had this neat feature, which was a best power per altitude setting on the fuel flow gauge. You could go full power, and set the mixture at the field DA marked on the gauge and be close enough.
 
177s and some 182s also have fuel flow specs as a function of elevation, but the fuel flow gauge is actually a fuel pressure gauge labeled in lb/hr, and is best cross-checked with the EGT gauge. Even better, with an engine analyzer (and those are fairly common to find on 182s) You use those fuel flow specs for takeoff only. At altitude, you use the more standard methods (except max RPM is not available with a CS prop). In practice, they are usually pretty close to the spec at high throttle.

The definition of "high DA" has some variation with model. Cessna 172/177/182 seem to all like 3000 feet. PA28s like 5000.
 
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