Cessna 172S Nav III User Manual

SECTION 7
AIRPLANE AND SYSTEMS DESCRIPTION
CESSNA
MODEL 172S NAV
III
VACUUM SYSTEM AND INSTRUMENTS
The vacuum system (refer to Figure 7-9) provides the vacuum
necessary to operate the standby attitude indicator. The system
consists of one engine-driven vacuum pump, a vacuum regulator,
the standby attitude indicator, a vacuum system air filter, and a
vacuum transducer. The
GEA-71 Engine and Airframe unit receives
the signal from the vacuum transducer and shows vacuum
on the
IEIS ENGINE page. If vacuum available through the pump drops
below 3.5 in.hg.,
LOW VACUUM will appear in amber on the PFD.
ATTITUDE INDICATOR
The standby attitude indicator is a vacuum-powered gyroscopic
instrument, found
on the center instrument panel below the MFD.
The Attitude Indicator includes a low-vacuum warning "flag"
("GYRO")
that comes into view when the vacuum is below the level
necessary for
reliable gyroscope operation.
VACUUM INDICATOR
IThe vacuum indicator is incorporated on the EIS ENGINE page,
found along the left side of the
PFD during engine start or the left
edge of the
MFD during normal operation. During reversionary
operation, the
EIS bar appears along the left side of the operational
display.
LOW VACUUM ANNUNCIATION
A low vacuum condition is annunciated along the upper right side of
the
PFD by a amber "LOW VACUUM" text box.
7-60 U.S.
172SPHAUS-03

Cessna 172S Nav III Specifications

General

Brand	Cessna
Model	172S Nav III
Category	Aircrafts
Language	English