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Leaning Redux

It’s evidently time to revisit a topic I wrote about almost nine years ago–the importance of leaning the fuel mixture and when it is important.  A Plus One pilot recently elected not to fly because of unwarranted concern due to RPM drop during run-up.

All pilots learn that they should lean the fuel mixture for maximum power as they climb to cruise altitudes above 3,000 MSL.  Most pilots also learn to lean the mixture after engine start and during taxi to the run-up area, in order to avoid lead fouling of the spark plugs.  What some pilots may not realize (and the POH, at least for the 182RG, does not describe) is that the mixture often should be leaned somewhat for engine run-up to get the best indication of the magneto and spark plug conditions.

The POH is even a little misleading in this area, because the instruction is to apply RICH mixture when doing the run-up.  The POH does not even mention leaning the mixture for maximum power at high elevation airports.  Even the 427 MSL elevation at Montgomery Field warrants some leaning of the mixture during run-up.  For more discussion of how to lean for run-up, see the old article on this site at Leaning is Essential.