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1st Edition, 1st Revision
4-40 18 Sep 03
COLLINS MULTISCAN OPERATION
MultiScan™ Radar MultiScan Automatic Operation
Figure 4-42 Pitfalls of Over-Scanning Thunderstorms
OverFlight protection is designed to prevent thunderstorms that are in
the aircraft flight path from falling below the radar beam and off the
radar display during high altitude cruise. At extended ranges the upper
radar beam scans the wet, reflective portion of a thunderstorm in the
same manner that conventional radars scan weather today. As the
aircraft approaches the storm and the cell begins to fall below the upper
radar beam, MultiScan utilizes 6,000 feet of bottom beam information
to keep the reflective part of the storm in view. Within approximately
15 NM of the aircraft MultiScan compares the stored digital image
of the thunderstorm with the latest sweep information and displays
whichever return is greater. If a cell that is a threat to the aircraft begins
to fall below the radar beam MultiScan displays the stored digital image
(figure 3-6) of the storm, thus ensuring that any threat thunderstorm
will remain on the display until it moves behind the aircraft. OverFlight
protection is operational above 22,000 feet MSL.
Figures 4-43 through 4-46 illustrate OverFlight functionality. Compare
the MultiScan weather returns with the manual returns in figure 4-42 for
a clearer understanding of OverFlight benefits.
1st Edition, 1st Revision
18 Sep 03 4-41
MULTISCAN OPERATION COLLINS
MultiScan Automatic Operation MultiScan™ Radar
Figure 4-43 Wet Top of Thunderstorm in Upper Beam
Figure 4-44 Wet Top of Thunderstorm in Lower Beam
Figure 4-45 Wet Top of Thunderstorm in Memory
1st Edition, 1st Revision
4-42 18 Sep 03
COLLINS MULTISCAN OPERATION
MultiScan™ Radar MultiScan Automatic Operation
Figure 4-46 OverFlight Protection to 22,000 Feet
OCEANIC WEATHER REFLECTIVITY COMPENSATION™
During automatic operation the MultiScan radar uses aircraft navigation
inputs to identify oceanic regions and adjusts gain and tilt to account
for the decreased reflectivity of oceanic thunderstorms (♦page 5-16).
Thunderstorm thresholds are adjusted to more accurately represent the
true thunderstorm threat to the aircraft.
GAIN CONTROLS
Airbus: Move the GAIN knob to the CAL detent (figure 4-47) to select
calibrated gain. Sensitivity is increased by rotating the knob clockwise
from the CAL position. Sensitivity is decreased by rotating the knob
counter clockwise from the CAL position (♦page 6-8).
There is no EFIS indication for CAL gain because CAL gain is the
standard gain setting. The EFIS will display MAN or MAN GAIN,
depending on the aircraft display configuration, when gain is either
increased or decreased from the CAL position (♦page 4-4).
1st Edition, 1st Revision
18 Sep 03 4-43
MULTISCAN OPERATION COLLINS
MultiScan Automatic Operation MultiScan™ Radar
Figure 4-47 Airbus GAIN Control
Boeing: Move the black triangle (▼) on the GAIN knob to the 12
o’clock position to select CAL gain. Sensitivity is increased by rotating
clockwise from the CAL position. It is decreased by rotating counter
clockwise from the CAL position (♦page 6-8).
There is no EFIS indication for CAL gain because CAL gain is the
standard gain setting. The EFIS will display VAR when gain is set
above or below the CAL gain position (♦page 4-7).
Figure 4-48 Boeing GAIN Control
1st Edition, 1st Revision
4-44 18 Sep 03
COLLINS MULTISCAN OPERATION
MultiScan™ Radar MultiScan Automatic Operation
N NOTE
During oceanic flight, increasing gain above CAL may allow sea
and island clutter to be displayed.
WINDSHEAR
WINDSHEAR DETECTION
Below 2,300 feet the weather scan switches from a 180° scan to a 120°
scan, which indicates the windshear detection system is activated.
Windshear alerts are displayed in the cockpit at 1,200 feet and below
(figure 4-49).
N NOTE
The 120° weather scan below 2,300 feet provides rapid weather
and windshear updates, and allows weather and windshear to be
displayed simultaneously during the entire windshear event.
Windshear detection is always activated when the aircraft is below
2,300 feet and the proper qualifier logic has been met (i.e., in the
takeoff and landing environment (♦page 6-35) even when the radar is
turned off. The only exception occurs for Airbus aircraft when the PWS
OFF/AUTO switch is selected to OFF (♦page 4-52). N NOTE
Windshear detection is activated during both manual and automatic
radar operation.
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Collins Weather Radar operator’s guide(18)
