Textron 172R180HP, Pilot Operating Handbook

Page: 234 / 396

SECTION 7
AIRPLANE & SYSTEMS DESCRIPTION
LOW VACUUM ANNUNCIATION
CESSNA
MODEL 172R {180 HP)
Each engine-driven vacuum pump is plumbed to a common
manifold, located forward of the firewall. From the tee, a single line
runs into the cabin to operate the various vacuum system
instruments. This tee contains check valves to prevent back flow
into a pump if it fails. Transducers are located just upstream of the
tee and measure vacuum output of each pump.
If output of the left pump falls below 3.0 in. Hg., the amber L VAC
message will flash on the annunciator panel for approximately 1 O
seconds before turning steady on. If output of the right pump falls
below 3.0 in. Hg., the amber VAC R message will flash on the
annunciator panel for approximately 10 seconds before turning
steady on. If output of both pumps falls below 3.0 in. Hg., the amber
L VAC R message will flash on the annunciator panel for
approximately 10 seconds before turning steady on.
ICLOCK / O.A.T. INDICATOR
An integrated clock / O.A.T. / voltmeter is installed in the upper
left side of the instrument panel as standard equipment. For a
ICOmplete description and operating instructions, refer to the
1supplements, Section 9.
STALL WARNING SYSTEM
The airplane is equipped with a pneumatic type stall warning
system consisting of an inlet in the leading edge of the left wing, an
lair-operated horn near the upper left corner of the windshield, and
associated plumbing. As the airplane approaches a stall, the low
pressure on the upper surface of the wings moves forward around
the leading edge of the wings. This low pressure creates a
differential pressure in the stall warning system which draws air
through the warning horn, resulting in an audible warning at 5 to 1 O
knots above stall in all flight conditions.
7-46
Oct 4/01