Not leaning enough?

L

LotsO’lead

Guest
Hi, as a renter pilot, I try to use many of the tactics necessary for proper operation to help keep costs low. I don’t believe in this “FULL RENTAL POWER” stuff, that’s horrible, horrible advice.

Anyway, I Cherokee Archer with the 180bhp Lycoming at the club. Our house instructor hounds us about leaning it to the hilt on the ground and leaning til the tachometer peaks while in cruise flight. My protocol general is, START (full rich) and right after start-up, I run it to 1000RPM and then pull the mixture back as far as I can possibly go without the engine quitting. Obviously full rich for climb and once I get in cruise flight, I do the lean til peak RPM method taught by our house CFI. Basically once the engine sounds like it’s losing power and the tachometer indicates such, I bring the mixture control forward just enough to smooth it back out and then leave it! Some may call this lean until it stumbles and richen up until it smooths out. Anyway, I put it away, the next guy goes to fly it and it has a bad magneto check. They come back on me and blame me for running it too rich to the point of fouling a plug. I hop in my sedan and dash back over to the flying club to assist in troubleshooting. Pull the top cowl, remove the spark plugs and sure enough, there’s a plug full of lead. Now I’m on the hook to replace it because they claim I don’t lean enough. Question is, does this method that I’m describing not prevent plug fouling? If so, how may I educate our CFI that his teachings are incorrect?
 
Are you leaning on the ground after landing (along with other items in the "clean up the airplane" steps like retracting the flaps)?
 
LotsO’lead said:
Hi, as a renter pilot, I try to use many of the tactics necessary for proper operation to help keep costs low. I don’t believe in this “FULL RENTAL POWER” stuff, that’s horrible, horrible advice.

Anyway, I Cherokee Archer with the 180bhp Lycoming at the club. Our house instructor hounds us about leaning it to the hilt on the ground and leaning til the tachometer peaks while in cruise flight. My protocol general is, START (full rich) and right after start-up, I run it to 1000RPM and then pull the mixture back as far as I can possibly go without the engine quitting. Obviously full rich for climb and once I get in cruise flight, I do the lean til peak RPM method taught by our house CFI. Basically once the engine sounds like it’s losing power and the tachometer indicates such, I bring the mixture control forward just enough to smooth it back out and then leave it! Some may call this lean until it stumbles and richen up until it smooths out. Anyway, I put it away, the next guy goes to fly it and it has a bad magneto check. They come back on me and blame me for running it too rich to the point of fouling a plug. I hop in my sedan and dash back over to the flying club to assist in troubleshooting. Pull the top cowl, remove the spark plugs and sure enough, there’s a plug full of lead. Now I’m on the hook to replace it because they claim I don’t lean enough. Question is, does this method that I’m describing not prevent plug fouling? If so, how may I educate our CFI that his teachings are incorrect?
Click to expand...

At flight schools that operate Warriors and Archers the students never lean. I suspect your club is not performing plug maintenance at regular intervals. Check the engine logs. Unison and Champion recommend 100 hour cleaning and gapping. 70 hours is more realistic value for consistently good run ups.

Also a plug that foaled can be cleaned and gapped, it does no need replacement.
 
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Lycoming recommended shutdown procedure to "clean out unburnt fuel". To prevent fouling after shutdown?

Some advocate, to get rid of the lead, run engine up to 2000ROM, lean aggressively for a minute or two and then shut down. Lead's melting point is 621dF, so once formed on the plugs, it's not likely to be burnt off this way.
Possibly some oil fouled plugs could be cleared doing this.

What is the temperature range of the current plugs?
Might need a hotter plug ex. 40 (range 26-50) or
a different design ex. 40 Y (projected core nose or tip) instead of a 40 E (two electrode massif plug).
Maybe you are running the thing so far LOP that your CHT are running too cold or oil temp under 180 dF :)
 
I just wonder about the type of club that comes after its members for basic things like plug fouling. Education topic for the next meeting, sure, but billing the last member who flew? Back it into the hangar wall or bend the door because you slammed it, sure, bill the member. But fouled plugs??
 
LotsO’lead said:
Hi, as a renter pilot, I try to use many of the tactics necessary for proper operation to help keep costs low. I don’t believe in this “FULL RENTAL POWER” stuff, that’s horrible, horrible advice.

Anyway, I Cherokee Archer with the 180bhp Lycoming at the club. Our house instructor hounds us about leaning it to the hilt on the ground and leaning til the tachometer peaks while in cruise flight. My protocol general is, START (full rich) and right after start-up, I run it to 1000RPM and then pull the mixture back as far as I can possibly go without the engine quitting. Obviously full rich for climb and once I get in cruise flight, I do the lean til peak RPM method taught by our house CFI. Basically once the engine sounds like it’s losing power and the tachometer indicates such, I bring the mixture control forward just enough to smooth it back out and then leave it! Some may call this lean until it stumbles and richen up until it smooths out. Anyway, I put it away, the next guy goes to fly it and it has a bad magneto check. They come back on me and blame me for running it too rich to the point of fouling a plug. I hop in my sedan and dash back over to the flying club to assist in troubleshooting. Pull the top cowl, remove the spark plugs and sure enough, there’s a plug full of lead. Now I’m on the hook to replace it because they claim I don’t lean enough. Question is, does this method that I’m describing not prevent plug fouling? If so, how may I educate our CFI that his teachings are incorrect?
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Your procedure did not, by itself, cause the plug to foul. Nor is it likely to have even contributed imo.
 
This isn't you, is your "club" soaking you for everything they can. Your single flight did not cause lead to form in the plug, that happens when the airplane flies. Plus the lead can be picked out if you're careful not to scratch the insulation, I've done it myself. If they're throwing away plugs as soon as there's lead accumulated in them, they're wasting money.

Not a very positive place, they'll run all their pilots off sooner or later. I wouldn't stand for that.
 
Half Fast said:
See https://www.lycoming.com/sites/default/files/SL185B Fuel, Higher Octane Aviation, Use of 100LL for Engines Rated 80_87 Octane (1).pdf

Be sure to follow the recommended shutdown procedure.
Click to expand...

B. Prior to engine shutdown run up to 1800 RPM for one minute to clean out any unburned fuel after taxiing in. (See B, ENGINE GROUND OPERATION.)

Does anyone do that? I sure wouldn't do it in front of my hangar. I just lean after landing just as I do after start and for taxi.
 
Pugs said:
B. Prior to engine shutdown run up to 1800 RPM for one minute to clean out any unburned fuel after taxiing in. (See B, ENGINE GROUND OPERATION.)

Does anyone do that? I sure wouldn't do it in front of my hangar. I just lean after landing just as I do after start and for taxi.
Click to expand...


Sure! I do it in front of my hangar. Why not?

Now, I don’t do it on the ramp with other planes around. I’m sure other owners would not appreciate it.
 
How do they assume that in your one flight you fouled the plug? I would worry more about their procedures than leaning.
 
Have your club bite the bullet and put in iridium plugs in the lower holes. Lean aggressively on the ground. Problem solved. Mag checks will be perfect and your plugs will remain relatively clean. And that's if you never lean in flight.
 
I’ve never heard about that, and I’ve forgotten to lean the airplane several times and never had an issue so I highly doubt that your one flight caused a problem. A spark plug cost what, $35? And that bothered to call you? Sounds like a special place that also overcharges ground time for flight lessons :eek:

Find another place to learn at. Stuff happens and the rental rate should include maintenance and insurance. I’ve heard of students getting a flat tire which a repair on field at another airport easily cost $400. The club I’m at covered that expense. Ridiculous to call you over for a spark plug….
 
Clip4 said:
At flight schools that operate Warriors and Archers the students never lean. I suspect your club is not performing plug maintenance at regular intervals. Check the engine logs. Unison and Champion recommend 100 hour cleaning and gapping. 70 hours is more realistic value for consistently good run ups.

Also a plug that foaled can be cleaned and gapped, it does no need replacement.
Click to expand...
I run Tempest plugs, but I swap plugs top/bottom, and clean and gap them, every other oil change. Works well for me
 
21541803 said:
Some advocate, to get rid of the lead, run engine up to 2000ROM, lean aggressively for a minute or two and then shut down. Lead's melting point is 621dF, so once formed on the plugs, it's not likely to be burnt off this way.
Possibly some oil fouled plugs could be cleared doing this.


Might need a hotter plug ex. 40 (range 26-50) or
a different design ex. 40 Y (projected core nose or tip) instead of a 40 E (two electrode massif plug).
Click to expand...
Couple of things:

It's not lead on the plug. The "lead" in the fuel is tetraethyl lead, and when it burns it forms lead salts. The melting point of the salts won't be the same as metallic lead.

The sparkplug's electrodes aren't at the cylinder head temperature. They get much hotter than that, being immersed in repeated combustion flames of 1400°F and more.

The extended electrode plugs are 37BY, not 40Y. UREM37BY or URHM37BY.

Much fouling is just simple carbon from unburned fuel when running rich. Some is carbon from burned oil. Most lead fouling in smaller engines is due to the lead content of 100LL, which is four times as much as the old 80 fuel that those engines were designed for.

The need for more frequent plug cleaning is the result.
 

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Dan Thomas said:
Couple of things:

It's not lead on the plug. The "lead" in the fuel is tetraethyl lead, and when it burns it forms lead salts. The melting point of the salts won't be the same as metallic lead.

The sparkplug's electrodes aren't at the cylinder head temperature. They get much hotter than that, being immersed in repeated combustion flames of 1400°F and more.

The extended electrode plugs are 37BY, not 40Y. UREM37BY or URHM37BY.

Much fouling is just simple carbon from unburned fuel when running rich. Some is carbon from burned oil. Most lead fouling in smaller engines is due to the lead content of 100LL, which is four times as much as the old 80 fuel that those engines were designed for.

The need for more frequent plug cleaning is the result.
Click to expand...

Dan thanks, I stand corrected on multiple fronts.
Seems the UREM is a Tempest plug and REM is a Champion plug.
And there is no 40 plug in the projected nose.

You got me thinking about the melting point of metal lead, so had to do some reading.
Sounds like the combustion process liberates lead oxide (condensation point, where gas turns to a liquid: 1630dF) which can deposit on plugs and valve stems etc.
Ethylene dibromide added to the 100LL converts this lead oxide to lead-oxybromide (1430 dF) and then on to lead-bromide gas (1100 dF) and out the exhaust.

Does this then mean that anytime the spark plug tip is less than 1630dF, some of this lead oxide will deposit on metal and on shutdown cool to solidify?
 
Not a club I’d be a member of, but maybe their aren’t a bunch of other options. If there was I’d be telling where I could make that plug fit. A student needs to learn, but making one sweat over a plug and not concentrating on bigger issues? Grrrr!
 
If the plugs' have got a case of "the clinkers", that bad mag check was in the making long before you last rented it. And, if your "club" is making you pay the full bill for new plugs, that is really not fair, I think I'd protest.
 
What happens when you aggressively lean and a cylinder melts down?

Costlier than fouled plugs (or does it not happen in a lycoming?)
 
I never lean on the ground. Never have in 30 years of flying. Have never been advised to by any of the several dozen CFI's that I have gotten dual, checkouts, or BFR's from. Never been briefed or required to do so from any of the 10+ FBO's and clubs I have rented from. Strangely, I have also never had a problem with plug fouling.

Maybe all those people were using sketchy sources like the Lycoming O-360 Operators Manual section on Ground Running and Warm-up, which says:
Leave mixture in "Full Rich".
Click to expand...

It could also be that all those people have good mechanics who properly adjust the idle mixture setting in the first place.
 
Ed Haywood said:
I never lean on the ground. Never have in 30 years of flying. Have never been advised to by any of the several dozen CFI's that I have gotten dual, checkouts, or BFR's from. Never been briefed or required to do so from any of the 10+ FBO's and clubs I have rented from. Strangely, I have also never had a problem with plug fouling.

Maybe all those people were using sketchy sources like the Lycoming O-360 Operators Manual section on Ground Running and Warm-up, which says:


It could also be that all those people have good mechanics who properly adjust the idle mixture setting in the first place.
Click to expand...


See the Lycoming SB I linked above. The original manual was written for 80 octane fuel which had much less lead than 100ll. Lycoming changed their guidance when 100ll became necessary.
 
Shortly after the right brothers taught me to fly. I learned in a 172. We never leaned unless over 3000 feet and even then not so much. We rarely if ever had fouled plugs. Ifn I am being honest in my current 172 I rarely (never) lean on the ground (usually a very short taxi to the run up area) I lean in the air to save fuel more than worry about fouled plugs. The guys in your club sound like jerks. You didn't foul plugs in one flight. Use a plug cleaner and a fine pick if there are any stubborn bits of lead. New plugs are for rich people.
 
Half Fast said:
See the Lycoming SB I linked above. The original manual was written for 80 octane fuel which had much less lead than 100ll. Lycoming changed their guidance when 100ll became necessary.
Click to expand...

I am not referring to your post about shutdown procedures. I am referring to advice to lean during ground operations.
 
21541803 said:
Does this then mean that anytime the spark plug tip is less than 1630dF, some of this lead oxide will deposit on metal and on shutdown cool to solidify?
Click to expand...
Most likely. That plug will not reach 1630°F, ever. Iron begins to glow at around 1100 degrees, IIRC, and a glowing plug causes preignition.

Its temperature will be somewhere between CHT and 1100, I'd think. And that would be just the electrodes themselves. The plug well, where deposits tend to pile up, will be cooler, closer to CHT.
 
Half Fast said:
Same SB discusses ground ops.
Click to expand...

Yes it does. But it does NOT say to lean during ground ops. It says that proper adjustment of the idle speed fuel mixture and operating at 1000-1200 RPM is sufficient to prevent plug deposits. Idle speed fuel mixture is a mechanical setting, not the pilot adjusting the mixture control.

idle mixture.PNG
 
In the flight school we didn't lean much during taxi and warm-up, either. But we cleaned those plugs every 50 hours, usually. And we ran the engines hard. And we leaned during cruise. And we leaned, as per POH, in short-field takeoffs. That tends to keep plugs clean.

Cleaning the plugs every 50 hours sounds stupid to some, until you factor in the downtime and lost revenue and annoyed students and instructors when a runup finds a big mag drop. And the extra work of taking the cowl off once more to clean those plugs that could have been cleaned at the oil change.
 
Dan Thomas said:
In the flight school we didn't lean much during taxi and warm-up, either. But we cleaned those plugs every 50 hours, usually. And we ran the engines hard. And we leaned during cruise. And we leaned, as per POH, in short-field takeoffs. That tends to keep plugs clean.

Cleaning the plugs every 50 hours sounds stupid to some, until you factor in the downtime and lost revenue and annoyed students and instructors when a runup finds a big mag drop. And the extra work of taking the cowl off once more to clean those plugs that could have been cleaned at the oil change.
Click to expand...

There is a Lycoming SB advising the use of ground leaning in certain variants of the O-360 used in the 172S in intensive training operations. But the fact that they felt it necessary to spell it out for that limited population of aircraft highlights that they do not view it as a normal operating procedure for most engines.
 
LotsO’lead said:
Obviously full rich for climb and once I get in cruise flight, I
Click to expand...

Depending on where you are this isn’t always “obvious”. I’m at 2700’ take off elevation. I lean for taxi after start up and again during the run up. Then I don’t touch it again until I’m at 5000’ and then again at cruise altitude.
 
I lean aggressively on any ground operations and when flying I pull till engine stumbles than I twist in just enough to make it run smooth.

Mike Bush has a great YouTube video about leaning procedures. I recommend watching
 
Ed Haywood said:
Yes it does. But it does NOT say to lean during ground ops. It says that proper adjustment of the idle speed fuel mixture and operating at 1000-1200 RPM is sufficient to prevent plug deposits. Idle speed fuel mixture is a mechanical setting, not the pilot adjusting the mixture control.

View attachment 110484
Click to expand...


It says:
“Proper adjustment of the idle speed (600 to 650 RPM) fuel mixture and maintenance of the induction air
system will ensure smooth engine operation and eliminate excessively rich fuel/air mixtures at idle speeds.”


I typically taxi about 200 to 250 rpm above idle. Therefore, I lean for ground ops. Certainly there is no harm in doing so, and likely some benefit.
 
I was not thought to lean on the ground

but once not longer after my PPL checkride, I was on a short cross county flight in the school's 172N...controlled airport, long taxi to the active....I don't really remember but there was probably some wait at the end before takeoff too....
something like maybe 200 ft up the engine stumbled hard.... lost most power. Quickly pushed the nose and pulled the power, landing straight ahead...thankful for the 8,000 ft runway!
Engine seemed fine taxiing back to the ramp
The school sent an instructor down in another airplane to get us home. Later a mechanic checked the plane and found nothing. theory fouled plugs and my theory was because of the long ground run.
That event got me into the habit of leaning on the ground.

I've later felt bad about the way it went down though. The school lost a lot of money on my flight that time! In hind site, I probably should have done an extended run-up on the ground and had I known I might have suspected fouled plugs.
 
LotsO’lead said:
Hi, as a renter pilot, I try to use many of the tactics necessary for proper operation to help keep costs low. I don’t believe in this “FULL RENTAL POWER” stuff, that’s horrible, horrible advice.

Anyway, I Cherokee Archer with the 180bhp Lycoming at the club. Our house instructor hounds us about leaning it to the hilt on the ground and leaning til the tachometer peaks while in cruise flight. My protocol general is, START (full rich) and right after start-up, I run it to 1000RPM and then pull the mixture back as far as I can possibly go without the engine quitting. Obviously full rich for climb and once I get in cruise flight, I do the lean til peak RPM method taught by our house CFI. Basically once the engine sounds like it’s losing power and the tachometer indicates such, I bring the mixture control forward just enough to smooth it back out and then leave it! Some may call this lean until it stumbles and richen up until it smooths out. Anyway, I put it away, the next guy goes to fly it and it has a bad magneto check. They come back on me and blame me for running it too rich to the point of fouling a plug. I hop in my sedan and dash back over to the flying club to assist in troubleshooting. Pull the top cowl, remove the spark plugs and sure enough, there’s a plug full of lead. Now I’m on the hook to replace it because they claim I don’t lean enough. Question is, does this method that I’m describing not prevent plug fouling? If so, how may I educate our CFI that his teachings are incorrect?
Click to expand...


That's lots of BS, tell them no, you run it as they tell you to run it, it's not your problem. Sounds like pseudo-science morons making stuff up. I would make a stink about it.
 
Brad W said:
I was not thought to lean on the ground

but once not longer after my PPL checkride, I was on a short cross county flight in the school's 172N...controlled airport, long taxi to the active....I don't really remember but there was probably some wait at the end before takeoff too....
something like maybe 200 ft up the engine stumbled hard.... lost most power. Quickly pushed the nose and pulled the power, landing straight ahead...thankful for the 8,000 ft runway!
Engine seemed fine taxiing back to the ramp
The school sent an instructor down in another airplane to get us home. Later a mechanic checked the plane and found nothing. theory fouled plugs and my theory was because of the long ground run.
That event got me into the habit of leaning on the ground.

I've later felt bad about the way it went down though. The school lost a lot of money on my flight that time! In hind site, I probably should have done an extended run-up on the ground and had I known I might have suspected fouled plugs.
Click to expand...
Sounds more like carb ice than any fouling. Ice can accumulate in a long taxi, then start melting with the throttle wide open. Pieces break off and cause hiccups like that.

Lycomings can and do get carb ice.
 
Randomskylane said:
What happens when you aggressively lean and a cylinder melts down?

Costlier than fouled plugs (or does it not happen in a lycoming?)
Click to expand...

Leaning really aggressively LOWERS temperatures. The only place you do no want to lean at all is for take off and climb, until you reduce power.
 
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