High density leaning vs school's leaning

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Jason608

Pre-takeoff checklist
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Jason608
Hi Everyone

The C172 POHs recommends leaning at 3,000'.
On the ground in AZ and similar areas, the density altitude can be 4,500 or higher with a field ALT of 1,400.

The school CFIs instruct leaning on the ground 1/2" during taxi and then high RPMs and lean during run up. Another pilot said that is simply to save fuel for the school and to lean in the air.

Do you lean on the ground with 4,500' density altitude?
If so, do you lean with high RPMs at run up?

Thanks.
 
Yes, I would. If you are in such a situation, give it a try. You will see increased RPMs, which is very useful for reduced take off roll and improved climb.

I flew out of Centennial Airport, near Denver, and leaned as described. It was impressive to a flat-lander like me how much I needed to lean for peak performance.

You would lean anyway at those altitudes, no different if you are sitting the ground.
 
I lean on the ground for taxi as much as I can without stopping the engine.

The engine doesn't know what the elevation is, just how thin the air is, lean accordingly, including for takeoff and landing.

I like to lean based off sound and feel, backing up with my CHT/EGT.

Before takeoff in high and or hot, I like to make sure I'm making full power before I'm anywhere near committed.

In cruise I lean based on my tables for a off the cuff GPH figure, then tune it based on target CHTs primary, EGTs secondary, same deal with cowl flaps if ya got em.
 
I think the current thinking is to lean until it barely runs (that's a lot more than 1/2") until you get to your run up. Yes it saves fuel for the flight school, but it also keeps plugs much cleaner. A recent trip had me at several high DA strips (temps around 100 and DA around 6000-7000) and (after asking around to confirm) right as I started my takeoff roll with a little bit of braking I'd lean to max rpm and then richen a tad with no substantial rpm drop. Worked fine.
 
In the 172 I trained in we would lean on the ground when there was a good bit of DA (usually over 1500, field elev. Only 700) because it would always foul plugs. Just make sure you put it back full rich for run up and takeoff is what I was told. No longer in that plane so it doesn't affect me
 
farmerbrake said:
In the 172 I trained in we would lean on the ground when there was a good bit of DA (usually over 1500, field elev. Only 700) because it would always foul plugs. Just make sure you put it back full rich for run up and takeoff is what I was told. No longer in that plane so it doesn't affect me
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If you're leaning the heck out of it for taxi like you should, you don't need to worry about forgetting to reset the mixture since the engine will die if you goose it with the mixture that far back.
 
At our flight school (elevation 4100 feet, DA's usually 6K+) we always have a LEAN FOR TAXI on the checklist and a full power lean on run-up. The mechanic would go nuts at the amount of spark plugs he had to clean and/or replace from fouling because of people that were just pushing the mixture full rich and leaving it there from start up to shut down.

YMMV
 
Thanks everyone for the replies. The other part of the opinion I received about this topic was not to lean at high temperature, say 110F because the fuel helps to cool the engine. If you are in Colorado with a density altitude of 8,000' lean on the ground but in AZ DA is 5,500' 110F do not lean until after T/O.
 
I remember hearing something about a Pits, I think, comming into land at Vegas, super hot DA day, guy instinctively went full rich on final and the engine guped out, don't recall if it was a dead stick pucker factor, or a "that won't buff out" outcome. Always think of that when I'm landing and it's thin air.


Jason608 said:
Thanks everyone for the replies. The other part of the opinion I received about this topic was not to lean at high temperature, say 110F because the fuel helps to cool the engine. If you are in Colorado with a density altitude of 8,000' lean on the ground but in AZ DA is 5,500' 110F do not lean until after T/O.
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Nonsense. At the power settings you're using to taxi it ain't going to hurt anything. Plus if you're at 5k+ DA conditions your plugs will thank you for leaning on the ground.
 
Find out what the static RPM range is for your airplane...can you achieve that without leaning at 4000' DA or higher?
 
Reasons to lean on the ground:
1. Save fuel.
2. Keep plugs clean.
3. Max power for high density altitude takeoff.

All are valid.
 
For comparison, flying out of an airport at around 4000 feet, I lean it back about an inch after start. That was in the school specific checklist where I received my PPL training.
 
Plenty of take off accidents in the mountains because of people who did not lean appropriately. We had one here and we are not even that high (5K). Bonanza from lower elevation, during taxi witnesses heard snorting and gurgling that comes from an overly rich mixture, on take off he could not climb.
 
Let'sgoflying! said:
Plenty of take off accidents in the mountains because of people who did not lean appropriately. We had one here and we are not even that high (5K). Bonanza from lower elevation, during taxi witnesses heard snorting and gurgling that comes from an overly rich mixture, on take off he could not climb.
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Which is why I really appreciate learning to fly in the mountains. Of course, if I ever fly to the coast I will probably forget to go full rich before landing.

My 2nd cfi mentioned to me that she had forgotten to enrich for landing once. The engine died coming over the threshold.
 
In my Dakota I lean for max rpm, then a tad more rich while doing my run up. Yesterday I flew from Reno (DA about 6500') and landed at South Lake Tahoe (DA 9000'). After taxiing back to depart, I ran the engine up to 2000 rpm like a normal run up, and leaned again for max rpm, plus a tad to the richer side.
 
Let'sgoflying! said:
Plenty of take off accidents in the mountains because of people who did not lean appropriately. We had one here and we are not even that high (5K). Bonanza from lower elevation, during taxi witnesses heard snorting and gurgling that comes from an overly rich mixture, on take off he could not climb.
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I was at KAPA (5885 msl) on a warm summer day when I saw a Cherokee (a transient) with all the seats filled taxi up and do a very abbreviated runup. I just knew there was no way he had leaned the engine. Fortunately for the pilot and his family, when the Tower cleared him to line up a wait, he pushed the throttle forward and the engine died from the overly rich mixture. The pilot reported the conk-out to Tower.

I keyed the mike and said, "Tower, you might ask the Cherokee if they leaned for density altitude." Before Tower's response, came "Ooh. I forgot about that."
 
Jason608 said:
Hi Everyone

The C172 POHs recommends leaning at 3,000'.
On the ground in AZ and similar areas, the density altitude can be 4,500 or higher with a field ALT of 1,400.

The school CFIs instruct leaning on the ground 1/2" during taxi and then high RPMs and lean during run up. Another pilot said that is simply to save fuel for the school and to lean in the air.

Do you lean on the ground with 4,500' density altitude?
If so, do you lean with high RPMs at run up?

Thanks.
Click to expand...

I wonder how many aircraft get grounded for uncleanable fouled plugs, after that pilot flies them.

At high density altitude, the ONLY time you should ever consider having the mixture all the way in is for priming a fuel injected engine, and perhaps for engine start in a carbureted engine. Everything else should be done leaned.

You taxi leaned even at sea level. You can tell which rental aircraft were leaned by the previous pilot.
 
woodchucker said:
Which is why I really appreciate learning to fly in the mountains. Of course, if I ever fly to the coast I will probably forget to go full rich before landing.

My 2nd cfi mentioned to me that she had forgotten to enrich for landing once. The engine died coming over the threshold.
Click to expand...

The only time you should have issues with an excessive lean condition is if you were leaned out aggressively at a high altitude (e.g. lean of peak) and descend lower without enrichening. But normally, a power reduction will have the result of enrichening the mixture. I never go full rich on landing, even at sea level.
 
That's why "set mixture" before T/O or during GUMPS check should not be taught as "full rich". A good POH says "set mixture for best power" and a good CFI/school will teach the same. If a school is teaching otherwise, I would leave.

There have been many incidents/accidents with excuse "but I was always taught mixture full fwd". :dunno:
THAT is where understanding aircraft systems pays off. There is no guesswork, only useful knowledge.
 
FastEddieB said:
Hence the need for checklists, and adherence to them.
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DO NOT put "mixture full rich" on a checklist, mixture set, or mixture for field DA or whatever, but not a carte blanche "full rich"
 
BigBadLou said:
That's why "set mixture" before T/O or during GUMPS check should not be taught as "full rich". A good POH says "set mixture for best power" and a good CFI/school will teach the same. If a school is teaching otherwise, I would leave.

There have been many incidents/accidents with excuse "but I was always taught mixture full fwd". :dunno:
THAT is where understanding aircraft systems pays off. There is no guesswork, only useful knowledge.
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But, but, but, my 'kota does require full rich for full power regardless of DA. :D
 
Maybe we can convince the FAA or congress to make FADEC a regulatory requirement and take engine management out of our hands. It shouldn't cost us all too much should it? It is all about keeping us all safe and keeping us from coming through someone's roof. You know, the common good. :idea:

:D:goofy::rofl: :lol:
 
James331 said:
DO NOT put "mixture full rich" on a checklist, mixture set, or mixture for field DA or whatever, but not a carte blanche "full rich"
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I use the medical shorthand PRN for mixture (and a bunch of other items). But really, assuming one knows how to operate an aircraft, the setting side of the standard checklist [Item] ....... [SETTING] is often superfluous (not that I don't do it myself). Far more important to have a reminder that you have to do something with the mixture than what that something is (at least I home nobody here would think the Mixture item in the cruise checklist means Idle /cutoff" :eek::yikes:
 
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