"Perry J. Mick" wrote:

Jerry Hey wrote:

Air cooled engines have generous clearances in order to survive temp
fluctuations.  Still, they get too hot on hot days and too cold on
long power off decents.   The only thing I have seen pilots do is
either open the cowl flaps all the way or close them all the way.
Not much real temp. controlling.   I would still like to  hear from
the guys who have no thermostats.   Is there a problem with
over-cooling on cold days?   It seems unavoidable to me.    Jerry

I initially flew, probably the first 80 hours with no thermostat.  When
I started my takeoff the engine wasn't warmed up yet, so I was concerned
I was stressing the engine.  During descents it would also run very cool.

So I installed a thermostat and I like the way it works.  I have a little
heater core that is always on from the heater port, that acts like a
thermostat bypass.  So my engine still runs cool on descents, and
even in cruise, but not nearly as cool as before.

So if you close cowl flaps while descending to get your engine a
little warmer, I don't see where the big advantage is in reduced drag,
since you would rather be draggy when you are descending, unless
your engine quit and you want to maximize your glide, but then you
don't care about cooling.

During climb and probably in cruise [???] you are going to have to have
the cowl flaps open, thus draggy when you don't want it.

--
Perry Mick
Duckt N7XR
http://www.ductedfan.com

The cowl flaps should be closed in cruise Perry. Mine are in the 182.

Only during climb do I need the flaps open. During climb a lot of
HP is needed to merely lift the weight of the airplane.
In that phase aerodynamic drag is a much smaller percentage of
the total load on the engine therefore the flaps being open or closed
have little effect on the climb rate.

Paul Lamar

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