page 45 - American Bonanza Society

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This spark plug readout will either
scan all six cylinders sequentially or
will indicate whichever cylinder is
the hottest. I have always advertised
that the difference between those
two points on the cylinder where
temperature may be measured will
have the spark plug temperature
30°F to 40°F hotter than the threaded
boss temperature. That turns out
to be generally true during takeoff,
climb, and ROP cruise. However, that
relationship changes when operating
LOP. The spread between those points
may be as high as 30° but also may
be only 10°. This G1 display opens up
several windows of engine information
but somewhat closes the airplane
windows for the now busy pilot to
look out of. In other words, there is
a lot more time spent looking at the
engine instrumentation than in the
past, at least above the 6000 feet or so
altitude when real LOP is begun. One
advantage of the changing colors of
the CHT columns is that only a quick
glance is required to tell if everything
is okay or if we’ve gotta do something
about ole number 4.
One note about the installation of
the G1 that is important, or at least
important in my installation: Because
the G1 is a 2-1/4 inch instrument and
there is a lot of displayed information
on the rather small instrument face, the
digital readouts are small. My engine
instrument panel is at the far right of
the airplane directly in front of the
passenger’s seat. I mounted my G1,
as all of the other engine instruments
are mounted, at a 45° angle and also
angled up so I am looking straight into
the G1 face with no parallax. Since this
display is referred to often while flying,
such mounting affords the quickest
read time possible.
On a recent breakfast trip from
Reno/Stead, Nevada, to Petaluma,
California I took some readings in
level cruise flight. I think all of the
instrument readouts are accurate to
within a very small percentage:
8500 MSL
OAT +38°F
Aircraft weight 2800 lbs
The EGT was ranging from
10 to 80° F LOP
21.5 MP / 2150 RPM—
148 MPH indicated airspeed
at 8.6 GPH
Bayonet CHTs
380/ 375 / 361 / 382 / 326 / 298
EGTs 1445/1494/1448/1481/1466/1470
Oil pressure 46 PSI/Oil temp 175°F.
I failed to take the exact numbers
of the LOP during the readings but
I recall that range being there. The
engine has 1900 hours SMOH and 1100
on the first-run Continental cylinders.
Not bad for such an old beast.
As stated above, there is a very fine
line in the movement of the mixture
control to keep the engine running
smoothly and still staying on the lean
side of peak. Without the vernier
mixture control I doubt that satisfactory
operation could be achieved. Maybe,
but I doubt it. When the PS-5C, or
at least my PS-5C, is adjusted to the
correct point LOP, it is very close to
beginning to shut the engine down. It
will run rough if just another miliwinkle
of movement toward lean is made. I do
have an automatic warning system
that a too-lean-of-peak area has been
entered. That would be my beautiful
wife Carmen giving me the “whadda
you doin’” look.
24 AMERICAN BONANZA SOCIETY MAY 2013