Textron Cessna 172R - Page 405

CESSNA
MODEL
172R
SECTION
9
-
SUPPLEMENTS
SUPPLEMENT
7
-
FAA
APPROVED
NOTE
An
exception
to
this
is
HDG
annunciation
which
will
flash for
5
seconds
along
with
steady
NAVARM, APRARM,
or
REVARM
annunciation
to
remind
the
pilot
to
set
the
HDG
bug
for
course
datum
use.
1.
Flashing
HDG
--
Indicates
a
failed
heading.
PRESS
HDG
button
to
terminate
flashing.
ROL
will
be
displayed.
2.
Flashing
NAV,
APR
or
REV
--
Indicates
a
flagged
navigation
source.
If
no
NAV
source
is
flagged,
a
failed
heading
mode
can
be the
cause.
PRESS
NAV,
APR
or
REV
button
to
terminate
flashing.
ROL
will
be
displayed.
NOTE
At
the
onset
of
mode
annunciator
flashing,
the
autopilot
has
already
reverted
to
a
default
mode
of
operation,
(i.e.,
ROL
mode).
An
immediate
attempt
to
reengage
the
lost mode
may
be made
if
the
offending
navigation
flag
has
cleared.
Effects of
instrument losses
upon
autopilot
operation:
1
.
Loss
of
the
artificial
horizon
--
no
effect
on
the
autopilot.
2.
Loss
of
the
turn
coordinator
--
autopilot
inoperative.
3.
Loss
of
the
Directional
Gyro
(DG)
--
The
directional
gyro
does
not
provide
any
system
valid
flag.
If
the
DG fails
to
function
properly
the
autopilot
heading
and
navigation
mode
will
not
function
correctly.
Under
these
conditions,
the
only
useable
lateral
mode is
ROL.
4.
Loss
of
Horizontal
Situation
Indicator
(HSI)
(if
installed)
--
If
the
HSI
fails
to
function
properly
the
autopilot
heading
and
navigation
mode
will
not
function
correctly.
Under
these
conditions,
the
only
usable
lateral
mode is
ROL.
S7-13
I
Revision
4
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