Avoiding Shock Cooling in Quick Descent

James M. Knox wrote:
: Not a lot. The article is not restricted to planes with GAMIjectors, but
: it *is* relevant to engines that can operate with acceptable smoothness
: LOP. That rules out most every carb'd engine (although sometimes you get
: lucky), and most every big-bore TCM engine. Smaller engines and Lycoming
: engines are a "sometimes can and sometimes can't" proposition.

: Try it at 65% power and see what happens, especially if you have all-cyl.
: monitoring. [I did once have an O-320 engine that would run absolutely
: smooth all the way to idle-cutoff. Just a fluke.]


I pretty much run my Lycoming O-360 as lean as I can get it with
at most just a slight hint of roughness. This typically amounts to
slightly lean of peak for a couple cylinders, and at peak for others.
Since Lycoming calls that "economy mode" and is acceptable for 75% power
cruise or less, I cruise at 65% max power for a margin. Watching CHT
on the hottest (#3), the spark plug probe stays at 400 or less, which is
actually more like 340 or less (on a bayonet probe). I figure that's
probably as aggressive as you can get with a normal carb'd engine. The
big thing I came away with from all the reading is if you lean
agressively, you need to know what power you're running at. Basically,
you can do anything you want with the red knob at 65% or below, provided
the CHT's are acceptable.

FWIW
-Cory

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