Cessna 172P - Page 288

12A
R,NAV
(TYPE
ANS-351C)
PILOT'S
OPEA,ATING
HANDBOOK
SUPPLEMENT
5.
Ground speed, time-to-waypoint,
and dístance-to-waypoint
func-
tions require
stabilization
time
after initial
function selection has
been
made.
Allowing 10
minutes
for
etabilization
when
operating
in the ENR
mode will
provide
a display
that is
90
percent
of the
final calculated
value; 12
minutes
after initial
selection,
a display
that is
95
percent
of
the
final
calculated
value
wiì.I be
provided.
Stabilization
time
can be
greatly
reduced
if
the APPR mode
is
selected
j
ust
prior
to, or imnrediately
after, the time that
any
one of
the subject functions
is
selected. The
APPR, mode
switches
in
a
speed-up circuit that reduces
the
time for
g0
peroent
of final value
display to 4 minutes,
and the time
for 95
percent
of
final value
display to 5 minutes.
After
stabilization
is achieved, the
ENR/APPR
control may be switched
back
to ENR
for
normal
enroute operation,
6.
Course changes in excess
of 45 degrees
will result
in temporary
display changes
for
ground
speed,
time-to-waypoint,
or distance-
to-waypoint.
Initially,
ground
speed
wiII decrease
and both time-
to-waypoint and distance-to-waypoint
will increase
after
the
course cha,nge is made. After
the
new course has
been established
for
several
minutes,
all functions
will
again stabilize
and display
final calculated
values, Course
changes exceeding
120 degrees
require
stabilization time
greater
than 12 minutes in ENF,
mode or
5 minutes in APPF,
mode.
7.
For accurate CDI sensitivity,
aÞproa,ch
mode is restricted
to 50
nautical miles or less from
the waypoint
in use. Enroute mode is
restricted to distances no
greater
than 200 nautical miles from
the
waypoint in use.
8. VOR,/DME facilities must
be co-located.
9. The display
of time-to-station/waypoint
on
the DME
display,
when
in
RNAV mode, is only valid if
aircraft track is
"TO"
the
waypoint.
GROUND
CHECK
PROCEDURES:
Before each flight
in
which RNAV is to be used
for
primary guidance,
the following
procedures
should
be used, when
possible,
to verify
RNAV system
performance.
Taxi the aircraft
to
position
free
and clear of metal structures and
within
good
reception distance
of a local VOR/DME facility.
10
30
May 1980