Textron 172R180HP, Pilot Operating Handbook

Page: 208 / 396

SECTION 7
AIRPLANE & SYSTEMS DESCRIPTION
CESSNA
MODEL 172R (180 HP)
I
Markings for the oil temperature indicator indicate a normal op­
erating range of 100 to 245 ° F (green arc), and a maximum tem­
perature of 245
°
F (red line).
Oil pressure signals are generated from an oil pressure
line/transducer combination. An oil pressure line is routed from the
upper front of the engine case to the rear engine baffle. At the
baffle, the oil pressure line is connected to a transducer. This
transducer produces an electrical signal which translates into a
pressure reading at the instrument panel gauge.
Oil temperature signals are generated from a resistance-type
probe located in the accessory case. As oil temperature changes,
the probe resistance changes. This resistance is translated into oil
temperature readings on the cockpit indicator.
In addition, a separate low oil pressure indication is provided
through the panel annunciator. This annunciator is wired to a
pressure switch located on the rear of the engine accessory case.
When oil pressure is below 20 PSI, the switch grounds and
completes the annunciator circuit, illuminating the red OIL PRESS
light. When pressure exceeds 20 PSI, the ground is removed and
the OIL PRESS light extinguishes.
The engine driven mechanical tachometer is located on the
instrument panel to the right of the pilot's control wheel. The
instrument is calibrated in increments of 100 RPM and indicates
both engine and propeller speed. An hour meter in the lower section
of the dial records elapsed engine time in hours and tenths.
Instrument markings include the normal operating range (multiple
width green arc) of 2100 to 2700 RPM, and a maximum (red line) of
2700 RPM. The multiple width green arc has steps at 2500, 2600,
and 2700 RPM which indicate the maximum recommended power
settings for altitudes of sea level, 5,000, and 10,000 feet,
respectively.
7-20 Oct 4/01