Cessna 172R Pilot Operating Handbook page 288

SECTION 9 - SUPPLEMENTS
CESSNA
SUPPLEMENT 5 - FAA APPROVED
MODEL 172R
NAV/GPS SWITCH - Toggles from Nav 1 to GPS and vice
versa to control the type of navigation data to be displayed on
the CDI (Course Deviation Indicator). The
No. 1 CD! Omni
Bearing Selector (OBS) provides analog course input to the
KLN 89B
in OBS
mode when the
NAV/GPS
switch/annunciator is in GPS.
When the NAV/GPS switch
annunciation is in NAV, GPS course selection in OBS mode is
digital through the use of the controls and display at the KLN
89B.
NOTE
Manual CDI course centering in OBS mode using the
control
knob can
be difficult,
especially at
long
distances. Centering the Course Deviation Indicator
(CD° needle can best be accomplished by pressing the
Direct-To button and then manually setting the
No. 1
CD! course to the course value prescribed in the KLN
89B displayed message.
NOTE
The Directional Gyro heading (HDG) bug must also be
set to provide proper course datum to the autopilot
if
coupled to the KLN 89B in LEG or OBS.
(When the
optional HSI is installed, the HSI course pointer provides
course datum to the autopilot.)
NAVIGATION SOURCE (NAV) ANNUNCIATOR
- The NAV
annunciator will illuminate steady to inform the pilot that NAV
1 information is being displayed on the NAV 1 CD!.
NAVIGATION SOURCE (GPS) ANNUNCIATOR
- The GPS
annunciator will illuminate steady to inform the pilot that GPS
information is being displayed on the NAV 1 CDI.
Figure 1. GPS Annunciator/Switch (Sheet 3 of 3)
S5-8
Dec 2/96
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