comanche fouled plugs

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Saucey12
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Joined: 01 Nov 2020, 10:42

comanche fouled plugs

Post by Saucey12 »

Hey guys I'd just like some guidance and council for those of you who fly the comanche often and are very familiar with it. I like to think that I fly this thing by the book and overall everything is well except for the fouled plugs. I understand that you should lean the aircraft on the ground and during taxi, which I already do. I typically fly 100 miles here or there on short flights to different GA airports. About every other flight the maintenance hanger says the airplane is in excellent shape with the exception of some fouled plugs. What could be causing this if I am leaning on the ground as I should? I typically pull the mixture back to 50%. Is this a correct habit or am I missing something? Or could it be something I am doing airborne to cause this?
I appreciate any help I could get, Thanks..

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Nick - A2A
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Re: comanche fouled plugs

Post by Nick - A2A »

Hello Saucey12,

The main culprit for plug fouling will be idling for too long at idle or very low RPM. If you'd like to avoid the plug fouling issue completely however, your best bet is to simply install the fine wire plugs in the maintenance hangar.

Thanks,
Nick
A2A Simulations Inc.

SubtleOrc
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Joined: 23 Jul 2023, 03:43

Re: comanche fouled plugs

Post by SubtleOrc »

Can I please jump on this and ask for best practice with idling on the ground ...

I have read the manual and it says "Warm-up the engine at 800 to 1200 RPM for not more than 2 minutes
in warm weather, or 4 minutes in cold weather. If electrical power is
needed from the generator, the engine can be warmed up at 1200 RPM
at which point the generator cuts in."

I'm a bit confused at what I should do in terms of setting the GPS up etc. I start the engine, then start fritzing about entering flight plans etc so it may take me up to 5 mins to do that. Should I be doing it at around 1000 RPM with the mixture leaned right out? Or should I be doing this on batteries? The start procedure has engine starts before avionics get turned on so I guess I should be starting the engine.

I'm so paranoid about fouling the plugs that I tend to sit the engine idling at fairly high speeds and my taxi is a bit fast I think ;)

After we do the run up checks at 2000 RPM do we idle back to around 800-1000 rpm to finish the taxi out to the runway? Also do we do the run ups with the mixture leaned or fully rich? If leaned then when do we enrichen it?

Thank you for indulging what might seem like silly questions.

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Scott - A2A
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Re: comanche fouled plugs

Post by Scott - A2A »

Forget about leaning on the ground, it won't prevent plug fouling at least it never did on my Comanche. RPM is what prevents plug fouling, so if you use massive plugs, keep your RPM at 1000 or above. If you use fine wires, then idle speed doesn't really matter all that much. They won't foul as long as you clean them every annual.

Also, don't idle for long periods regardless of the engine temperature. It's not necessary to wait for the oil temperature to rise. As long as your cylinder head temps are all at 160 or above, you are good to takeoff. This is all straight from Lycoming engineers.

Scott
A2A Simulations Inc.

Saucey12
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Posts: 44
Joined: 01 Nov 2020, 10:42

Re: comanche fouled plugs

Post by Saucey12 »

Scott - A2A wrote: 26 Jul 2023, 19:33 Forget about leaning on the ground, it won't prevent plug fouling at least it never did on my Comanche. RPM is what prevents plug fouling, so if you use massive plugs, keep your RPM at 1000 or above. If you use fine wires, then idle speed doesn't really matter all that much. They won't foul as long as you clean them every annual.

Also, don't idle for long periods regardless of the engine temperature. It's not necessary to wait for the oil temperature to rise. As long as your cylinder head temps are all at 160 or above, you are good to takeoff. This is all straight from Lycoming engineers.

Scott
Great! Thanks scott!

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