Winds aloft page
SECTION
1
NAV KEY
Winds Aloft &
VNAV Functions
Vertical navigation page
The GNC 250XL’s
winds aloft function
is used to calculate the true direction and
speed of any winds, and indicates whether you are flying with a head wind or tail
wind, and the wind speed.
To calculate winds aloft:
1. Press
N
and rotate
O
until NAV Menu 1 is displayed.
2. Press
C
twice and rotate
O
until ‘Winds?’ is highlighted. Press
E
.
3. Use
K
and
O
to enter your present heading in the ‘hdg:’ field. If your installation
includes a fuel/air data computer, this will be displayed automatically. Press
E
.
4. Use
K
and
O
to enter your true airspeed (TAS) in the ‘tas:’ field. If you have previously
calculated it using the density altitude/true air speed function, it will be displayed as the
default. Press
E
. The wind direction and speed and head/tail wind will be displayed.
The
VNAV function
calculates vertical speed requirements to reach a desired altitude before
or after a specified distance from a waypoint. This is helpful when you’d like to descend to a cer-
tain altitude near an airport or climb to an altitude before reaching a route or direct-to waypoint.
To calculate vertical navigation parameters:
1. Press
N
and rotate
O
until NAV Menu 1 is displayed.
2. Press
C
twice and rotate
O
until ‘Vnav Plan?’ is highlighted. Press
E
.
3. Use
K
and
O
to enter the initial (from) altitude. Your current GPS altitude will be dis-
played as the default. Press
E
.
4. Use
K
and
O
to enter the desired final (to) altitude. Press
E
.
5. Use
K
and
O
to enter the distance from the waypoint. Press
E
.
6. Use
K
to select ‘before’ or ‘after’ the waypoint. Press
E
.
7. Use
K
and
O
to select the waypoint identifier (it must be a waypoint in the active route
or a direct-to waypoint). Press
E
.
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250xl manual 2 7/17/98 1:27 PM Page 26
