System Operation
3-15
GNS-XLS Flight Management System
Rev. 8
Apr/00
Oceanic/Remote operation using GPS as the sole navigation source,
an FDE prediction to determine sufficient GPS availability must be
performed prior to departure. Refer to the Special Procedures sec-
tion for instructions on performing the FDE prediction procedure.
BEFORE TAXI (IRS EQUIPPED)
The Inertial Reference System (IRS) should be aligned and placed in
the Navigation Mode using the IRS manufacturer’s operating instruc-
tions.
1. MSG Key - DEPRESS for IRS Sensor Messages.
SENSOR MESSAGES Page will show IRS-ALIGN during align-
ment sequence. When the IRS is in normal Navigation Mode no
IRS messages will be displayed.
2. IRS Status - VERIFY NAV. Observe that no IRS messages
appear on the SENSOR MESSAGES Page.
RUNWAY LINE-UP (IRS EQUIPPED)
Provided an accurate alignment position was entered and the IRS was
placed in the Navigation Mode prior to taxi, no further action is required.
IRS, VLF (RPU), GPS AND/OR VPU EQUIPPED
On the ground the system will navigate deriving composite position
and groundspeed from the GPS or IRS, provided the IRS was
aligned and placed into the Navigation Mode prior to taxi. All other
sensors (VLF and VPU) will enter the Primary Navigation Mode auto-
matically at 50 kts (IRS) groundspeed or weight-off-wheels, provided
they have sufficient stations to begin navigation. Momentarily
depressing HOLD Key, then ENTER, and ENTER again will also put
the sensors in the primary NAV mode if sufficient stations are avail-
able.
VLF (RPU) AND/OR VPU EQUIPPED ONLY
This procedure is used to manually place the system into the Primary
Navigation Mode at the designated departure position i.e. the end of
the departure runway. The VLF is a position keeping sensor that can
navigate with as few as two suitable stations. The VPU is a position
finding sensor that can navigate once airborne or within line of sight
of suitable navaids.
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