PPRuNe Forums - View Single Post - Mag Checks - A cure for rough running.
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Old 6th Feb 2006, 01:02
  #12 (permalink)  
n5296s
 
Join Date: Jun 2003
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I'm pretty surprised by the people who don't lean on the ground. This seems to be standard practice in the US, iirc all of the student pilot textbooks recommend it. I can't imagine why anyone wouldn't do it. I can tell you that on my plane (TR182, Lycoming O540) running rich on the ground for any length of time guarantees fouling of the lower plugs.

If you do it properly there is no risk of taking off with the mixture too lean and damaging the engine. Just lean until the engine speeds up a bit, then richen by a twist. Applying full throttle or even enough for a fast taxi will stop the engine very quickly. (Of course if you have a GEM you can watch the actual temps anyway, and if you don't have a GEM, well why not? You are just asking to mismanage the engine one way or another).

If you DO get fouled plugs (rough running on a single mag) the remedy is simple - especially if you have a GEM. My procedure: run up to full take off power, lean and manage the mixture to keep TIT at around 1450 until the CHTs are up to normal level (about a minute). Of course without a GEM it's harder to be sure and it's prudent to limit to 65% power - then you can just lean until you get rough running and back off a bit, again without having to worry about damage - though watch the CHT if you have one.

John
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