Key Reprints from the Lycoming Flyer, in discussing leaning of
non-turbocharged direct-drive engines, says "For 5000 feet density altitude
and above, or high ambient temperatures, roughness or reduction of power may
occur at full rich mixture. The mixture may be adjusted to obtain smooth
engine operation."

Bob Gardner

"Jose" wrote in message
. ..
There was a discussion in my club about leaning the engine (of our
cherokees) below 5000 feet in cruise. This was prompted by the
observation in the manual that the engine should be leaned above 5000 feet
at all times in cruise, and below 5000 feet at the pilot's discrescion.
So, how should the pilot discrede? The old timers seemed to agree that:

1: at low power (say 65% or less) you can't hurt the engine by leaning to
peak EGT, but...

2: at high power (above that, including the 75% many like to fly at to go
fast) one should only lean if it's cold enough, and that the best thing to
do is run full rich if you're in doubt.

This runs counter to my understanding and practice. I lean (50 degrees
ROP) in cruise at all altitudes, including the ones where I can pick the
leaves off the trees, and I run 70-75% power. Running full rich is just
dumping a third of the fuel out the tailpipe.

Any opinions on Usenet about this?

Jose
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