Lean for taxi

The ground here is at 4500' elevation and in both the 172 and 182 I start full rich, then pull the mixture out about 1" right after starting. At the run-up in the 182, I first go to 2000 rpm and lean to peak rpm which usually means leaner than it was at 1" out. In the 172 I leave it 1" out and it seems to be fine.
 
DesertNomad said:
The ground here is at 4500' elevation and in both the 172 and 182 I start full rich, then pull the mixture out about 1" right after starting.
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Does nothing for idle.
At the run-up in the 182, I first go to 2000 rpm and lean to peak rpm which usually means leaner than it was at 1" out. In the 172 I leave it 1" out and it seems to be fine.
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Umm....at 2000 RPM the mixture control should have NO effect on the RPM in the 182. It has a constant speed prop. We did at BJC lean for peak RPM in the 172 however. Did you get that backwards?
 
One of the techniques I had to use with the Turbo Arrow at high altitude airports (well above 5,000 foot DA's) was to start it in a leaned condition on the ground and run very lean - it wouldn't even run full rich. Then on the takeoff roll, advance the throttle and the mixture at the same time so it's full rich by the time you're at takeoff throttle.
 
flyingron said:
Does nothing for idle.

Umm....at 2000 RPM the mixture control should have NO effect on the RPM in the 182. It has a constant speed prop. We did at BJC lean for peak RPM in the 172 however. Did you get that backwards?
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With the prop full in and 2000 rpm I can get the rpm to move by about 50-75 rpm by adjusting the mixture. My CFI showed me this. Not sure how or why it should work with the constant-speed prop, but I have seen the needle move myself with the throttle locked.

BJC?
 
Sac Arrow said:
One of the techniques I had to use with the Turbo Arrow at high altitude airports (well above 5,000 foot DA's) was to start it in a leaned condition on the ground and run very lean - it wouldn't even run full rich. Then on the takeoff roll, advance the throttle and the mixture at the same time so it's full rich by the time you're at takeoff throttle.
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Wow - same engine in the 'kota and totally different behavior. Start full rich, set throttle at ~1,000 rpm then lean for peak rpm. Mixture to full rich before moving throttle forward for takeoff. Mechanic spent an hour or so getting the fuel pressures as close to spec as possible after installing the new fuel system along with the intercooler.
 
DesertNomad said:
With the prop full in and 2000 rpm I can get the rpm to move by about 50-75 rpm by adjusting the mixture. My CFI showed me this. Not sure how or why it should work with the constant-speed prop, but I have seen the needle move myself with the throttle locked.

BJC?
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At 2,000 rpm you're below controllable speed so mixture can affect the engine speed.

BJC is Rocky Mountain Metro airport - Broomfield, CO - Used to be Jeffco airport. Winds can be just a touch tricky there...
 
steingar said:
Not only do I lean out during taxi, but I lean for max power during my run up, something no CFI ever taught me.
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^bolded above as I think a few missed this^

Leaning until a falloff on a run up gives a much better mag test as a rich mixture can mask some things + the lean mixture also gives a greater RPM drop-off. Easier to see although you still want them to be about equal.

I don't think the OP of this was suggesting leaning for max power during takeoff... just to test the system during runup.

I do it this way, but what I do to prevent inadvertently leaving it too lean is I advance the throttle a 100rpm or so higher then the run up RPM, then I lean it back so it drops 100-200rpm. Then I do my mag test/alternate air test. Then if I forget to go full rich, when I advance the throttle it just stalls out. (this on a Piper Aztec Twin IO540's with constant speed prop)

On my earlier PA32-260, (o540) until I started taxing lean I was constantly getting fouling. All but went away once I started to taxi lean. Highly recommended.
 
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kenjr said:
I'm pretty damn sure this guy forgot more about flying airplanes in the past week than I've learned thus far.
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Don't confuse hours sitting in a seat flying someone elses property with anything more then it is. In fact, sometimes it can be counterproductive if it makes the party think they know more about subjects that have little do with their experience.

The advice Cap'n Ron and others gave here is sound. Leaning for taxi is good advice and on some aircraft almost a requirement to avoid fouling.
 
flyingron said:
Further, if you don't lean enough that the engine stumbles at full power, you probably have done ZERO for leaning at idle. Idle mixture is pretty much unaffected by the red knob until you get near cut-off.
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This is interesting. My schools' checklist has a ground lean step and normally I just give the mixture knob 3 turns counter-clockwise(172N).

From what you're saying, I should be leaning much more?

I'm not worried about taking off lean as my lights/camera/action includes pushing in on the mixture knob to ensure it's full rich, not to mention the step is on my pre-takeoff checklist.
 
flyingron said:
I thought the Mac would do better than that.
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My governor loses it by then - haven't paid enough attention in my few 182 rides to know what is really typical in them so maybe I'm making a bad assumption.
 
Clark1961 said:
Wow - same engine in the 'kota and totally different behavior. Start full rich, set throttle at ~1,000 rpm then lean for peak rpm. Mixture to full rich before moving throttle forward for takeoff. Mechanic spent an hour or so getting the fuel pressures as close to spec as possible after installing the new fuel system along with the intercooler.
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It would start full rich, but you had to lean it out pretty quickly or it would sputter and die. Depending on how high the DA is of course.
 
flyingron said:
Does nothing for idle.

Umm....at 2000 RPM the mixture control should have NO effect on the RPM in the 182. It has a constant speed prop. We did at BJC lean for peak RPM in the 172 however. Did you get that backwards?
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During run up, the prop is set to max. If it is doing 2000 RPM, a conventional 182 run-up speed, the pitch is against the fine stop and mixture WILL affect it. At cruise or full throttle, it won't. However, the POH (182Q) tells you to use the EGT gauge or "lean 'till rough, enrich 'till smooth" method.
 
fiveoboy01 said:
This is interesting. My schools' checklist has a ground lean step and normally I just give the mixture knob 3 turns counter-clockwise(172N).

From what you're saying, I should be leaning much more?

I'm not worried about taking off lean as my lights/camera/action includes pushing in on the mixture knob to ensure it's full rich, not to mention the step is on my pre-takeoff checklist.
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Yeah, 3 turns is nothing. You should lean it to just rich enough not to miss (run rough). How much that is will vary with aircraft and density altitude, but it's usually a bit more than an inch out at sea level in a 172.

And, while checklists and mnemonics are really important, if that's all you do, you WILL forget it at some point.

Especially since "lights, camera, action" is no longer correct, at least at towered airports. See AIM 4-1-20(a)(3).
 
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MAKG1 said:
Especially since "lights, camera, action" is no longer correct, at least at towered airports. See AIM 4-1-20(a)(3).
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I don't follow. I turn the transponder to ON while on the ground, then to ALT before takeoff. So the CAMERA part of my check is turning it ON to ALT. Is this correct?
 
Lights camera action is separate and happens AFTER my checklist while taxiing onto the runway and immediately before advancing the throttle for takeoff. All the steps in that procedure are done on the checklist, it's a quick confirmation that nothing was missed.
 
asechrest said:
I don't follow. I turn the transponder to ON while on the ground, then to ALT before takeoff. So the CAMERA part of my check is turning it ON to ALT. Is this correct?
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The AIM is ambiguous about whether ALT or ON should be used. If you use ON, there is still something to do.

The old procedure was that it should be on STBY on the ground.
 
MAKG1 said:
During run up, the prop is set to max. If it is doing 2000 RPM, a conventional 182 run-up speed, the pitch is against the fine stop and mixture WILL affect it. At cruise or full throttle, it won't. However, the POH (182Q) tells you to use the EGT gauge or "lean 'till rough, enrich 'till smooth" method.
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My POH calls for 1700. Don't know where the 2000 comes from. Perhaps the O-470U engine in some Q models.

Correct on the governing range... You have the prop control full forward for the run up and governing won't kick in until RPM redline in that configuration.

Which is, 2600, with no time limitations on our O-470S, but they decided to mark the tach top of the green arc at 2450 which is the recommended cruise-climb setting.

Making mixture changes below 2600 with the prop forward, will affect RPM just as if it weren't a constant speed prop. The blades won't come off the low pitch stops until you reach 2600.
 
Geico266 said:
None, only benefits. You cannot over lean on the ground, meaning you cannot hurt anything.
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Not true.

If you over lean, you can burn valves on a garden tractor, much less a plane.

However, for all practical purposes, you're right.

The determining factor there is how hard you work the engine. At taxi RPM, you're highly unlikely to damage an engine from being too lean -- it will simply run crummy, and if you lean enough it will stop running.
 
asechrest said:
A big con I assume is failing to go full rich for takeoff. But I've got that on my checklist and on my lights-camera-action check.
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Take it OFF your checklist, unless you always fly from low airports.

If you are at a high airport (I'm at 4620 MSL here), full rich will, at best, cause you to use more runway. Depending on the runway length and material, density altitude and acft weight, it might call for an abort.

Set your mixture during taxi, fine-tune it during runup, and leave it there through takeoff.
 
denverpilot said:
My POH calls for 1700. Don't know where the 2000 comes from. Perhaps the O-470U engine in some Q models.
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I've seen light piston plane run-up RPM's listed in their books from 1700 to 2000. Varies with the engine/prop combination, and generally seems to be lower with fixed pitch props and higher with c/s props.
 
SoloEqs said:
Take it OFF your checklist, unless you always fly from low airports.

If you are at a high airport (I'm at 4620 MSL here), full rich will, at best, cause you to use more runway. Depending on the runway length and material, density altitude and acft weight, it might call for an abort.

Set your mixture during taxi, fine-tune it during runup, and leave it there through takeoff.
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I always fly at low airports. But what I could do is change the checklist item from full rich to something that reminds me to set the mixture for the airport's altitude.

I went up two days ago by myself as my first flight as a private pilot. For taxi I leaned until rough and then pushed in slightly. Went to full rich for takeoff. No fouling.
 
Honestly, that's really minor. I have altitude qualfiers in my checklists, like "mixture rich (alt <3000)" in the 172 takeoff checklist (it's 5000 for almost everything else).

At altitude, you simply must be aware of it. Vy is lower, expect less climb performance, etc. While the mixture being set incorrectly full rich is probably the biggest mistake, there are a number of others to watch for. Pitching for 750 FPM will almost certainly result in a departure stall.
 
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Ron Levy said:
I've seen light piston plane run-up RPM's listed in their books from 1700 to 2000. Varies with the engine/prop combination, and generally seems to be lower with fixed pitch props and higher with c/s props.
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That's nice. He was specifically talking about a 182. Thus my question for him.

Don't really care what two hundred other types say in their POHs. But thanks for sharing.
 
nddons said:
Congratulations!! Isn't that an awesome feeling?
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Thanks. Yes, it was amazing. The whole time I'm thinking "it's crazy they let regular people do this stuff." :D

My brother will be my first passenger, this Wednesday if weather permits.
 
Ron Levy said:
Varies with 182 models, too, depending on older with Continental or newer with Lycoming (1800 vs 2000, IIRC).
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Isn't that what I surmised in my question? ;) Heh. I only mentioned the O-470U since the Lycs are usually too rich for my blood. Heh. The rental places are usually way too proud of them for what they are. G1000 being spiffy and all, but not worth the premium most of the time. ;)
 
Leaded gas is bad for living things - and spark plugs.
On the ground lean it till it shakes like a wet dog. There is no way you can take off by accident as it will quit cold the instant you push the throttle.
If you are a student you have to do it the CFI's way.
If you are a renter - do you want to be AOG at another airport with a fouled plug?
 
MAKG1 said:
Fuel injected auto engines aren't the same. Not even the mechanical injection systems like VW CIS. All it means for aircraft is that fuel is forced through an orifice at each intake stroke, instead of through a venturi.

There is no lambda sensor, no air charge temp sensor, no air flow sensor, no manifold pressure sensor (sometimes, there is a gauge, but that's for the pilot, not the engine) and most importantly no PCM.

Really rich is still really rich, and plugs foul just the same.
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If by that you mean that it constantly squirts fuel at the intake port, yes. The stroke has no effect on when the fuel is flowing.
 
flyingron said:
Does nothing for idle.

Umm....at 2000 RPM the mixture control should have NO effect on the RPM in the 182. It has a constant speed prop. We did at BJC lean for peak RPM in the 172 however. Did you get that backwards?
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If you are still in the upswing at 2000rpm with the prop pitched for fine, then indeed leaning will allow for a rise in RPM as one isn't into the governor yet.
 
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