1200 FT
PWS WARNING PWS ALERTS ENABLED WHEN AUTO WHEN RADIO ALTIMETER SCALING BEGINS < 1200
400 FT 370 FT
PWS CAUTIONS INHIBITED RADIO ALTIMETER < 400 FT
50 FT PWS WARNINGS INHIBITED RADIO ALTIMETER < 50 FT
RUNWAY
GROUND
1.2 nm
APPROACH
Predictive Windshear System Operation
Figure 7
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5) The antenna scan pattern varies depending on the mode of operation. Above 1500 to 2300 feet, when the system is placed into a weather/windshear scan pattern, and no windshear is detected, the antenna scan pattern is as follow: a) Clockwise weather scan, with | 90 degrees of azimuth
coverage and processing for weather.
b) Counterclockwise windshear scan, with full | 90 degrees of azimuth cover, but with windshear processing limited to the | 45-degree sector.
6) When the system is in a weather/windshear scan pattern, and the system detects a windshear event, the antenna scan pattern is as follows: a) Clockwise weather scan, from | 90 degrees. b) Counterclockwise windshear scan, from +90 degrees
to -45 degrees, with windshear processing between | 45 degrees. c) The next clockwise scan is -45 degrees to +45 degrees, to validate windshear.
d) The next counterclockwise scan is from +45 to -90 degrees, to validate windshear. No processing occurs between -45 and -90 degrees.
e) Clockwise weather scan, -90 degrees to +90 degrees. The sequence is repeated as long as windshear event is detected.
7) If a windshear event is not validated, the system reverts to the weather/windshear scan pattern first described.
(f) PWS Flight Compartment Effects (Figure 9). 1) Windshear caution and warnings are displayed or annunciated on the navigation display (ND), primary flight display, captain's and first officer's warning speakers and the two master caution and warning lights. See Figure 9.
2) For both PWS cautions and warning alerts, a PWS ICON is shown on the WXR display. The size of the icon is proportional to the geographical size, but not in intensity, of the windshear event it represents.
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POSITION DIRECTION RADAR SCAN PAINT SWEEP ANGLE (DEGREES) TIME (SECONDS)
SWEEP 1 L-R BOTH WXR DATA UPDATED BOTH WXR PAINTED -90 TO +90 4
SWEEP 2 R-L BOTH WXR DATA UPDATED BOTH WXR PAINTED +90 TO -90 4
SWEEP 3 L-R BOTH WXR DATA UPDATED BOTH WXR PAINTED -90 TO +90 4
SWEEP 4 R-L BOTH WXR DATA UPDATED BOTH WXR PAINTED +90 TO -90 4
NORMAL WXR SCAN PATTERN
POSITION DIRECTION RADAR SCAN PAINT SWEEP ANGLE (DEGREES) TIME (SECONDS)
SWEEP 1 L-R BOTH WXR DATA UPDATED BOTH WXR WITH ICON PAINTED +90 TO -90 4
SWEEP 2 R-L UPDATED BOTH PWS DATA BOTH PWS ICONS PAINTED +90 TO -60 3
SWEEP 3 L-R BOTH WXR DATA UPDATED BOTH PWS ICONS PAINTED +60 TO -60 2
SWEEP 4 R-L BOTH PWS DATA UPDATED BOTH PWS ICONS PAINTED +60 TO -90 3
WXR AND PWS SCAN PATTERN - TAKEOFF
PWS SWEEP
COLLECTION = |45`
Antenna Scan During Weather and Windshear Operation Figure 8 (Sheet 1)
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