Cessna 172S Pilot Operating Handbook page 151

C ESSNA
MODEL 1 72S
3. Flashing GS -- I ndication of a flagged g lideslope.
rearm automatically if a valid GS signal is received. )
To continue tracking the localizer, observe the appropriate
m i n im u ms for a nonprecision approach .
i n rapid succession to terminate the flashing. Control the
pitch axis in the default VS mode.)
At the onset of mode annunciator flashing, the autopi lot has
already reverted to a default mode of operation, i.e. , ROL
and or VS mode. An immediate attempt to reengage to lost
mode m ay be made if the offending navigation , g lideslope
or compass flag has cleared .
The H DG annunciation will flash for 5 seconds upon
selection of NAV, APR, or REV modes to remind the pilot to
set the HDG bug for use as cou rse datum .
Effects of i nstrument losses upon autopilot operation :
1 . Loss of the artificial horizon -- no effect on the autopilot.
2. Loss of the turn coordinator -- autopilot i noperative.
3. Loss of the Directional Gyro (DG)-- The directional gyro does
not provide any system valid flag . If the DG fai ls to fu nction
properly the autopilot heading and navigation mode will not
fu nction correctly.
lateral mode is ROL.
4. Loss of Horizontal Situation I ndicator (HSI) (if i nstalled) -- If
the HSI fails to function properly the autopilot heading and
navigation mode will not function correctly. Under these con­
ditions, the only usable lateral mode is ROL.
5 . Loss of Blind Altitude Encoder -- Altitude Alerter and Altitude
Preselect function i noperative.
Origi nal Issue
S ECTI O N 9 - S U P PLEMENTS
S U P P L E M E NT 1 5 - FAA APPROVED
NOTE
NOTE
EXCEPTION
U nder these conditions, the only usable
(GS will
(Press AL T twice
S 1 5-1 9