Cessna 172P - Page 287

PILOT'S
OPEN,ATING HANDBOOK
SUPPLEMENT
12A
RNAV
(TYPE
ANS-351C)
AREA NAVIGATION
OPERATION NOTES
1.
Proper
RNAV operation
requires vatid VOR and DME inputs
to
the
RNAV system. In certain &re&s,
the
ground
station antenna
patterns
and transmitter
powerma,y
bo inadequate to
provide
valid
signals to the
RNAV.
F
or
this reason, intermittent RNAV signal
loss
may be
experienced
enroute. Prolonged loss of RNAV signal
shall requiro the
pilot
to
revert
to other
navigational
procedures.
2.
As the flight
progresses,
sequence tJrrough
waypoints in order,
always keep
within
ra,nge of
VORTAC
being
used by maintaining
propor
altitudo and distance from the facility.
If usable range
is
exceeded,
the OFF
flag
will eppeer on
the
CDI.
Normally, switch-
ing waypoints
should
be
done
long before flag appearancos
to
ensure the
aocurate
distance,
ground
speed, time-to-waypoint
and
minimum croestrack
deviation
that will result if closest
and
strongest signal is
used.
3.
Selection of
the
Nav
1,
Hold, or
Nav 2
positions
on tho DME
Nav
mode soleotor switch electrically eliminates
the ANS-351C from
the RNAV system, making the computor
non-receptive to all
inooming data.
When
operating in these conventional VOF,/DME
modes, the ANS-3õlC
RADIAL
display will spell
out
"Vor" or
"Loc"
to
prevent
being misled
into believing
that an F,NAV
waypoint is
being flown. Rotating
the waypoint selector
knob
allows
preview
and set up
of
waypoints even
though operating
in
the
qonventional
DME modes. Attempting
to
activate
a waypoint
in the conventional DME
modes
by
pressing
the
USE
pushbutton
will
yield
no
results
and the
WPT number display
will remain
blinking, indicating
a
preview
waypoint.
Pressing the
F,TN
button
will
restore
the
"Vor"
or
"Loc"
annuncia,tion on
the RADIAL
display and the
previously preset
waypoints will
remain
in
memory.
NOTE
The
ILS mode
selection takes
precedence
over
all other
mode
selection
and is automatic whenever an
ILS fre-
quency
is selocted
on
the
No.
2 navigation
receiver.
4.
If
at anytime
an ILS
frequenoy is
selected on the
No. 2 set, with
the
ANS-85lC
operating
in the
RNAV
mode,
operation will be
restored
on the
same
wa,ypoint
when
a
VOR
frequency
is
again
selected.
This feature
allows
channeling
through ILS frequencies
without
changing
the
selected
waypoiñt
numbãr.
I
30 May 1980