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If flight crewmembers set NDs to ranges of different magnitude (short and long ranges), the weather radar alternately scans for short and long ranges. With this scan pattern, the weather radar refreshes the weather display every 8 s.
3 Only Honeywell EGPWS is able to provide the terrain altitude to Honeywell Autotilt function. The Autotilt function is not compatible with ACSS T2CAS.
. In PWS Mode The Autotilt function does not modify the PWS mode. Below 2 300 ft, the weather radar alternately scans for weather and wind shear (the first sweep for weather, the second sweep for wind shear). In PWS mode, the radar scans are
limited to short ranges. With this scan pattern, the weather radar refreshes the weather display every 12 s.
6.1.5.2. MULTISCAN (ROCKWELL COLLINS)
6.1.5.2.1. Principle
The Multiscan function develops an ideal radar beam that would detect significant weather right below the aircraft up to 320 NM, taking into account the curvature of the Earth.
Figure 6-21: Ideal beam and Multiscan To that end, the Multiscan function uses two radar beams: the upper beam to scan medium ranges, the lower beam to scan short and long ranges. The Multiscan function automatically adjusts the tilt and gain settings. The information from both beam is stored in a database and is cleared of ground returns thanks to the Ground Clutter Suppression (GCS) function (refer to 6.1.5.3 – Ground Clutter Suppression – GCS (Rockwell Collins)). According to the range selected on
ND, the relevant information is extracted from the database for display.
6.1.5.2.2. Multiscan Scan Pattern
. In weather mode
The weather radar alternatively scans for the upper beam (e.g. clockwise) and the lower beam
(e.g. counterclockwise). With this scan pattern, the weather radar refreshes the weather display every 8 s.
. In PWS mode
The weather radar alternatively scans for weather and wind shears, and for the upper beam and for the lower beam.
illustrates the alternation of weather radar scans. With this scan pattern, the weather radar refreshes the weather display every 11.2 s.
6.1.5.3. GROUND CLUTTER SUPPRESSION – GCS (ROCKWELL COLLINS)
The Ground Clutter Suppression function automatically removes ground returns for display. The GCS function is:
- Available in WX and WX+T modes
- Not active in MAP mode (ground returns are called for display) and manual operations.
In automatic Multiscan mode, the flight crew may manually and temporarily deactivate the GCS function at its discretion.
In manual mode, the GCS function is deactivated.
6.1.5.4. LONG RANGE COLOR ENHANCEMENT (ROCKWELL COLLINS)
The Long Range Color Enhancement by Rockwell Collins compensates the beam attenuation beyond 80 NM. It emulates a red core bordered with yellow and green for a precipitation that would have appeared fully in green without the color enhancement. When the aircraft gets closer to the precipitation, the display gets more accurate.
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