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upper beam detects intermediate range weather while the lower beam
detects short and long range weather by automatically adjusting the
beams’ tilt and gain settings (figure 3-7). The information is then stored
in a temporary database. When the captain or first officer selects a
range, the computer extracts the appropriate portions of the desired
information, merges the data, then eliminates the ground clutter. The
result is an optimized weather display for whichever range scale the
flight crew selects.
Figure 3-6 The MultiScan Process
Figure 3-7 MultiScan Upper and Lower Scan
1st Edition, 1st Revision
3-6 18 Sep 03
COLLINS THEORY OF OPERATION
MultiScan™ Radar Update Rates
UPDATE RATES
The total time required to complete one cycle of the MultiScan process
in all modes except windshear is 8 seconds. When in windshear mode,
the total cycle time for both MultiScan and windshear is 11.2 seconds.
Thus, there is no significant change to observed weather during one
cycle of the MultiScan process. What does change is the relationship
of the aircraft to the weather. To compensate for this, MultiScan
translates (figure 3-8) and rotates (figure 3-9) the stored digital image
to compensate for aircraft movement.
The result is that the Collins MultiScan updates all radar displays every
four seconds in all modes except windshear, in which case the displays
update every 5.5 seconds. One interesting element of this process is
that the antenna scan is no longer tied to the display sweep. This frees
the antenna to perform multiple functions without interrupting the pilot’s
weather presentation.
Figure 3-8 MultiScan Updates Image For Aircraft Movement
1st Edition, 1st Revision
18 Sep 03 3-7
THEORY OF OPERATION COLLINS
Automatic Gain MultiScan™ Radar
Figure 3-9 MultiScan Updates Image After Heading Change
AUTOMATIC GAIN
During automatic operation, MultiScan uses variable gain that is based
on atmospheric temperature profiles to compensate for variations
in geographic location, time of day, and altitude in order to optimize
weather returns in all phases of flight (♦page 4-38). Gain is thus
adjusted to suit the environment in which the aircraft is flying and
provide the optimum weather picture in the prevailing conditions.
THE END RESULT
Because MultiScan can examine the weather in front of the aircraft
using multiple tilt settings and because the radar is able to look down
into the ground clutter to pick out significant weather, MultiScan is able
to display all the weather from 0 – 320 NM that will affect the aircraft
on a single, essentially clutter-free display (figure 3-10). And the whole
1st Edition, 1st Revision
3-8 18 Sep 03
COLLINS THEORY OF OPERATION
MultiScan™ Radar The End Result
process is entirely automatic, freeing the flight crew to concentrate on
weather avoidance rather than weather detection and interpretation.
MultiScan is able to look down into ground clutter to detect the reflective
portion of thunderstorms. Figure 3-10 shows the radar picture with
the ground clutter suppression turned off. Weather is masked by the
ground clutter.
Figure 3-10 MultiScan Display With GCS Off
1st Edition, 1st Revision
18 Sep 03 3-9
THEORY OF OPERATION COLLINS
The End Result MultiScan™ Radar
Figure 3-11 demonstrates when Ground Clutter Suppression (GCS) is
activated. All significant weather (in this case from right in front of the
aircraft out to 160 NM) is visible on a single, essentially clutter-free
display. Significantly, the radar no longer needs to compromise between
a tilt that will eliminate ground clutter and a tilt that will give the best
weather returns.
Figure 3-11 MultiScan Display With GCS On
N NOTE
In the figure above, when Ground Clutter Suppression (GCS) is
activated, all significant weather (in this case, right in front of the
aircraft out to 160 NM) shows on a single, essentially clutter-free
display.
1st Edition, 1st Revision
3-10 18 Sep 03
COLLINS MULTISCAN OPERATION
MultiScan™ Radar Table of Contents
TABLE OF CONTENTS
Title Page
MultiScan Control Panels ................................................................. 4-1
Airbus Control Panel ..................................................................... 4-1
Boeing Control Panels .................................................................. 4-2
Display Annunciations ...................................................................... 4-4
Airbus Display Annunciations ....................................................... 4-4
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Collins Weather Radar operator’s guide(10)
