WEATHER RADAR
GENERAL
The Primus 660 is the standard radar installed
in the Learjet 45. It is an X-band radar system
designed for weather detection and analysis.
The radar can also be used for ground mapping.
The unit incorporates the receiver, transmit-
ter and antenna (RTA) into a single unit, lo-
cated in the nose of the airplane. The only
remaining radar component is the cockpit con-
trol panel which is mounted on the center
pedestal. The antenna is a 12" flat-plate that
is stabilized from the #1 AHRS. Weather pat-
terns can be displayed on both PFDs, on the
ARC or MAP format, and on the MFD MAP
format.
The radar should only be operated with cau-
tion while on the ground. When operating on
the ground, position the nose of the airplane
so that the antenna scan sector is free of large
metallic objects such as hangars or other air-
planes for a distance of at least 100 feet. Avoid
radar transmission during refueling of the air-
plane or any refueling operations within 100
feet. Do not operate the radar when personnel
are within 9 feet of the antenna.
DESCRIPTION AND
OPERATION
Weather is selected for display on the PFDs
by selecting the ARC or MAP display on the
PFD and depressing the WX button on the
display controller. Weather is selected for
display on the MFD MAP by depressing the
WX bezel button on the MFD main menu
(Figure 16-51).
When the radar is being displayed on the PFDs,
the radar primary mode of operation is an-
nunciated at the left end of the mid-range ring
(Figure 16-32). On the MFD, the radar mode
is annunciated approximately halfway down
on the left side of the display.
Radar Mode Control
A switch is provided on the radar control panel
for selecting the different radar modes:
OFF –
This position removes electrical power
from the system.
SBY (Standby) –
When standby is selected,
the RTA is powered up but it does not radiate
any RF energy nor does the antenna scan. The
system performs a warm up for approximately
45 seconds when SBY is selected.
The radar has a forced standby feature (FSBY).
This permits the WOW (weight-on-wheels)
switch to force the radar into standby auto-
matically whenever the airplane is on the
ground. FSBY can be overridden by depress-
ing both range buttons on the radar control
panel simultaneously. On some versions of
the radar, the operator must depress the STAB
switch 4 times within 4 seconds to override
forced standby.
WX (Weather radar) –
Selects the weather
radar main operating mode. The receiver and
transmitter become active at the selected range
and tilt, and the antenna sweeps 120° in front
of the airplane. Although the RTA is operat-
ing when WX is selected to ON, the crew still
needs to select WX for display on the DUs.
Storm intensity levels are displayed in the four
standard radar colors. Areas of heaviest rain-
fall appear in magenta, next heaviest is red,
rainfall of medium intensity in yellow, and
areas of weak rainfall appear in green. See
Table 16-7 for a description of the intensity
levels.
If WX is selected for display prior to the ex-
piration of the initial RTA warm up period
(approximately 45 seconds) the “WAIT” an-
nunciation is displayed on the PFDs/MFD.
Upon completion of the warm up period, the
system will automatically switch to WX mode.
GMAP (Ground map) –
In the ground map-
ping mode, the system internal parameters are
set to enhance returns from ground targets
L E A R J E T 4 5
P I L O T T R A I N I N G M A N U A L
16-93
FOR TRAINING PURPOSES ONLY
FlightSafety
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