Hammer,
My sentiments exactly! Any money spent on training that causes you to think about process is well worth the money.
I am chagrin to admit that Mike's pointing out this shutdown procedure from Lycoming is new to me
This morning I got the wife & son up at 0530 hrs to return to KPAO (Palo Alto) from Columbia (O22) after having fun yesterday at their 4th of July celebration. I wanted them to enjoy a calm, cool, serene, early morning flight off the mountain to sea level. My wife actually told me to shoosh, so she could take in the peace & quiet. By george I think I've got her hooked!
Just as we entered the SF Bay area we were hit with a barrier of clouds and fog. KPAO was VFR but the approach was not. So I did an abrupt 180 deg turn and headed for KLVK, (Livermoore) and bought breakfast for the passengers. It is all about choices and decisions.
However I must admit some of the mechanical operations don't seem quite as as cut and dried. Although I am learning a lot from you Veteran's of the sky and it is appreciated.
It has come to my attention that I misinterpreted what rjb was communicating and his purpose so I extend my apologies. I am the one who was WRONG ON THE INTERNET! I promise to go to bed on time from now on

I always do run ups after I have restarted. Whether it has been off for an hour, or a week. I do them while rolling if on dirt strips, static or rolling if on asphalt.

However I do use a reduced power setting when doing them. Usually in the 12-1500 rpm range. When cycling the prop, I usually will do it 3 times, but only look for 50-100 drop in rpms.

Seems to work well for me.

Gary

mtv wrote:Hooooo Boy, here we go again!!!!

Hammer, leaning on the ground with the engine at idle does absolutely NOTHING to prevent plug fouling.

In short, your mixture control does not govern the idle jet in your carburetor until you get to idle cutoff, at which point the engine dies.

So, if you lean at less than about 1500 to 1700 rpm, you are accomplishing precisely nothing. The engine is (or should be) running on the idle jet.

The notion of leaning the mixture on the ground is one of those very widespread wives tales that is really difficult to kill.

Give Lycoming a call, and ask them....

If you want to prevent plug fouling, Lycoming has a shut down procedure that works wonders. Run the engine prior to shutdown at 1500 rpm for 20 seconds, then reduce to 1200 and immediately idle cutoff. That procedure (and I've simplified it a bit) can be found in Lycomings "Key Reprints" which can be found on the web, here: http://www.lycoming.com/support/tips-ad ... /index.jsp

This little resource has all sorts of great information on running your Lycoming engine. And, its free.

MTV

Given that, I'm curious as to why the loping engine (due to richness) stops loping when the mixture is pulled out to lean the engine? Beaver, 182, 185, etc. has the same result.

a64,

Nope, sorry. Give Lycoming a call. The mixture control has no effect on the idle circuit UNTIL it reaches idle cutoff. Before that, it has no effect on the mixture, when at or near idle as in below 1500 to 1700 rpm.

I don't know what effect leaning at idle has on a fuel injected engine.

Point is, and Lycoming will verify this: Leaning at idle during taxi in a carbureted engine has precisely NO influence on spark plug fouling.

Give them a call tomorrow morning.

The problem here is that some folks have been known to lean during taxi, then fail to go to full rich prior to takeoff, which can have catastrophic results.

MTV

MTV etal.

I fly out of 6700'. O-520. I usually lean a little prior to take off, then watch temp while climbing. Is it recommended to take off full rich regardless of altitude/density altitude?

Thanks Gary

my Maule....

...has a fuel injected IO-360...210 h.p. Continental engine. Leaning at any rpm, including idle has an effect. In fact the engine runs rough at low elevations and altitudes..... in flight and on the ground at idle. Leaning the mixture makes her run smooth. Fuel injection, carbs, throttle bodies.....different animals.

As to cleaning the plugs....I don't know about that. I do volunteer flying in a turbo-charged Senaca with the same engines. The charity,operator insists on leaning agressively on the ground to keep from "fouling the plugs." What ever they want. It's's their airplane and their maintence people swear by the proceedure.....whatever.

As stated by prior posters..... watch others, listen and evaluate. Keep what works for you and ignore the rest. I have spent a lifetime in cockpits with "experts." My policies and techniques became a blend of the best that I observed over the past 42 years.

Bob

Shortfielder,

Nope, it is HIGHLY recommended to lean the mixture appropriately prior to takeoff when the density altitude is high. The point I was making was at the default sea level or nearly so.

Bob,

Fine--as I said, give Lycoming or Continental a call if you don't believe me. Ask them about CARBURETED engines, which is what I was discussing. They all use the same carburetors, made historically by Marvel, now called Precision. And, leaning at idle does nothing. Ask the experts.

If it makes you or the boss happy to lean for taxi, its fine with me, just remember to select an appropriate position for the mixture control prior to full power. But don't bullshit yourself into thinking that the practice prevents spark plug fouling. The problem is, I've seen too many people miss a checklist item or two prior to takeoff, and I imagine you have as well.

I just went through this same discussion with a major university flight training program. Same deal. I had discussed this with Lycoming previously. The university guys called Lycoming. Lycoming told em it does nothing at all to prevent plug fouling. Their chief of maintenance responded to the effect that "we never have plug fouling, so it must be working". The Lycoming tech rep just rolled his eyes.



MTV

Ha!

Thanks Mike,

Now a procedure taught to me long ago by a flying club I used to belong to makes sense. (All their procedures were well thought out, but this one -- 1500 for 20 seconds, 1200 then ICO -- never had a documented rationale.) Now I got it.

By the way, I haven't actually DONE this since I stopped flying in that club. I reckon a call to both Lycoming and Continental are in my near future.

--Tony

MTV,
Thank for the info about leaning. Despite Jeremy's push to study the
Lycoming manual, this didn't sink in, and thanks, Bill, for starting this
thread.

-Dick

Mike,

Reread my post! "Fuel injection, carbs. throttle bodies, different animals." In no way did I disagree with you. You are absolutely right concerning carbureted engines. I never suggested otherwise. Simple experience is evidence in and of itself.

Nor did I imply that I believed leaning the turbo-charged, fuel injected engines on the Senaca kept the plugs from fouling. I simply stated that the charity for which I volunteer insists on doing it that way and their mechanics swear by it. As you know....when flying for an operator, you do it their way.....at least when they are giving a check ride.

I stated that I don't do it on my(injected)engine either, except to smooth out the roughness.

By the way my 1937 Buick has a Marvel carburetor on it's straight eight engine. One of the smoothest running engines ever. Maybe we should stick one of those in our airplanes. Might be kind of nose heavy though.

Happy flying!

Bob

Maybe a new thread should be started about old-wives-tales, like never running over squared or never turning into a dead engine on a twin, or never cycling the prop? What???.

I would like to know the history of this crap. Who makes this stuff up and gets it to stick throughout time???

I'm not disputing that leaning on the ground at idle does nothing to reduce plug fouling. It does however have an effect on fuel flow. There being no return line on a carbureted engine, what goes through the carb goes through the engine. You can not "over lean" to the point of engine damage when operating at idle power. My fuel flow reduces from 2.4 gph to 1.6 gph at idle. Sitting there waiting for the oil temp to warm up prior to departure why not save a little fuel, over the long run it adds up. Leaned to this point the engine will not run smoothly when the RPM is increased to do the run up or to take off so there's not much of a chance of forgetting to reset the mixture control.

While I'm not sure about little engines, 1340's will foul plugs while idleing waiting for the oil to warm up. The idle time can be extended on these engines. These engines will lean out at low power. I'm sure they don't lead foul, because you can usually burn off the fouling during the run-up. I don't think you can burn off lead fouling. Perhaps it's lead fouling as opposed to carbon you speak of Mike?
The only other carburated aircraft I fly has a C-85 with the Marvel carburator, which doesn't lean much at low power settings. You can't kill this engine at idle with the mixture. So I'm not much on carbs.
If you chose to lean on the ground, lean it so much that it won't take throttle. If your human you will eventually try to take off leaned out, just like you will eventually take off on one mag .
Call it whatever you want to, but the IO's that I fly will sometimes either foul a plug or maybe just "load up" if run full rich at taxi power. Lycoming knows this and their shutdown procedure is designed to elevate the temp of the center electrode and nose of the ceramic insulator to burn off the fouling prior to shutdown.
The best thing I ever did as far as fouling, easy starting etc. was to install fine wire plugs. I haven't had a rough mag check in a coiple of hundred hours with the fine wires.

a64,

Yes, it's lead fouling I'm referring to. As you note, the round engines tend to load up while warming some, but I don't think that's lead fouling.

You should be able to shut down that C-85 with idle cutoff, though.

MTV

mtv wrote:If you want to prevent plug fouling, Lycoming has a shut down procedure that works wonders. Run the engine prior to shutdown at 1500 rpm for 20 seconds, then reduce to 1200 and immediately idle cutoff.

MTV

Thanks for posting the link to the Lycoming tips. It's a good read.

Not to be a nitpicker, but their procedure reads as follows:

"Prior to engine shutdown, the engine speed should be maintained between 1000 and 1200 RPM until the operating temperatures have stabilized. At this time the engine speed should be increased to approximately 1800 RPM [not the 1500 rpm described above] for 15 to 20 seconds, then reduced to 1000 to 1200 rpm and shut down immediately using the mixture control."

Eric

Man oh man, this thread has got a lot of attention in the last 6 days or so! I just read it all, spellbound by god!, even though I fly behind a fixed-pitch prop.
FWIW my new airplane had a vernier (aka verneer) throttle on it when I bought it. I didn't like it, but figured I'd get used to it. Not! The main problem was landing, too slow to dial in a power increase or decrease, and damn near impossible to push the button in with my palm while pulling the knob out with my fingers for a power decrease. Too jerky to hold the knob with my fingers & push the throttle in or out. So I gave up and bought a regular friction lock type throttle assembly.
If anyone wants it, I'll sell the vernier throttle assembly for half the new price. I can get the Spruce part number & length if anyone's interested.

Eric

PA 12 pilot,

Thanks for clarifying the procedure. It's been a while since I read the procedures, but even at the lower rpm it really helps to scavenge the lead.

Key Reprints should be read by EVERY Lycoming pilot. And a few Continental types as well.

MTV

"And, leaning at idle does nothing. Ask the experts. "

Actually, that's not quite true in a Marvel Schebler...... when the idle circuit is in use, the idle cutoff valve becomes the main metering valve.... so yes, you can lean at idle... in fact I do all the time. If your carb is set up right, as per the instructions, you'll see a 25-50 rpm increase at idle cutoff...and if you're careful, you can indeed "lean" the carb to that mixture, and have it running there for an extended period of time.
The most likely reason the C-85 isn't cutting off with the mixture is that normally it has a Stromberg carburetor, and that has a "back suction" style mixture circuit, so at idle it doesn't produce enough low pressure to make the mixture effective. There is an STC to run a Marvel/Precision MA3-SPA carb, which has a positive mixture control... and if yours is modified as per that STC, you've got a problem somewhere.

John

Ok, I'm confused. I've got whatever carb the C-85 on a little Cessna came with. You can't kill it at low speeds with the mixture, your not supposed to be able to, most people for some reason disconnect it. Small matter really, the point is that some carburated engines will lean at all RPM's and apparently some won't.
I think most Old Wives tales have a grain of truth, like pulling through an engine before starting it. I wouldn't want to start an old radial that had been sitting for a while without pulling it through two complete revolutions because on those things you can get hydro-lock with oil in the bottom cylinders and can do some serious damage with the starter, but on flat motors I don't think it does any good.

John,

You are correct, but the point is that to accomplish what you're suggesting, you have to pull the mixture control waaaaayyyyyy out, where just a tiny bit more and the engine quits. And, when pulled out this far, if you advance the throttle to move, the engine will stumble or die. In other words, its not a particularly practical means to use, and furthermore most pilots who use this "technique" don't pull the mixture anywhere near far enough out to do any good.

So, the point remains that FUNCTIONALLY, it is not really practical to lean the mixture on a Marvel carb equipped engine and have it do anything positive reference lead fouling. The good news, as someone noted, is that if you actually DO get to this point in leaning, advance the throttle and the engine will stumble, so it's hard to hurt yourself on takeoff because you failed to go to rich mixture.

I see people pulling the mixture out 1/2 inch, or 3/4 inch, or whatever, which, as I noted has no practical effect on the mixture during idle operations.

As you point out, you CAN get it to lean during idle operations, but.....it's not really that practical, and you REALLY have to yard the mixture out, nearly to the stop. Again, call Lycoming and ask their advice on this. I have, and spoken with two of their tech reps, and what I've cited is their information.

a64, you're right, some Stromberg equipped Continentals could not be shut off with mixture. I remember on my J-3 there was that admonition in the manual, though my airplane had long since had a C-90 installed, which would shut down with mixture, since it was equipped with a Marvel carb.

And, yes--you're also correct on pulling props through. Lycoming specifically recommends against this practice on horizontally opposed engines, since it wipes the oil film off many of the moving parts of the engine prior to start, and in fact does no good. On a radial, as you noted, you pull the engine through prior to start to detect hydraulic lock, which is a far worse deal than wiping some oil off the moving parts.
MTV