Cessna 150 Cruising

: I take off full throttle and then throttle back
: to 2600.
Remember that throttle placement provides limited indication of
power setting at differing altitudes. I have a friend with a Cherokee 140
who says he always cruises at 2400 RPM. I asked what altitude, and he
said *any* altitude. That's a bunch of crap, since at 8000', 2400 RPM is
about 55% power, and the plane's wallowing through the sky.

:The CHT will be around 380 F, below
: the 400 F mark my mechanic advised me not to
: exceed.
This is true. 400 degrees is considered the beginning of the
"bad" area. I put CHT probes in my O-360 lycoming last fall, and was
worried when I routinely saw 400-425. I did a whole bunch of testing,
calibrating, etc to discover that it was because I was using the
spark-plug type probes. The factory-recommended probes are the bayonet
ones, and they read around 50 degrees cooler than the spark plug type. I
actually put 5 CHT probes on my 4 cylinder... one of them is a bayonet one
and does indeed read about 50 cooler than the spark plug ones. Even on a
climbout when I see 425, it's still actually 375 or less.

I don't think the O-200 in your C-150 has bayonet holes. I also
don't know Continental's recommendation on placement and temps. If it is
a spark plug type, however, it's less of a concern.


: With 2600 RPM, I get about 95 knots indicated.
: (My C150 has no wheelpants. Word is, you'll see
: 5 to 10 knots more with wheelpants.)
Slower airspeed give less cooling too.


: Typical cruising altitudes for me are 3500, 4500
: and 5500.
Ah yes... flatlander. At these altitudes, running 2600 RPM is
pretty reasonable "cruise" setting. Probably 75%@3500 and 65%@5500.

:Went to 10500 once, overflying SFO
: class Bravo (full throttle of course), but the CHT
: was slightly over 400 F and this is not the best
: thing to do. I don't think I'll do that again.

A C-150 at 10500? Cool... I know I pretty much *need* full
throttle at those altitudes to keep flying. It's only 20" of MP... the
same as about 2400 RPM @ 5000'.

-Cory

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