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off phases of flight. If a windshear hazard is detected, the radar issues
either an Advisory, a Caution, or a Warning (♦page 4-50) to the flight
crew through visual and aural indications. If the radar has automatically
enabled and a display mode has not been selected (the display is
OFF), the aural alerts and cockpit annunciators will still be operational.
In this case the crew will be notified of a Caution or Warning. Advisory
detection will not be present as this is a display-only alert.
Windshear icons are displayed in either the Weather (WX) or Weather
Plus Turbulence (WX+T) display modes. If the radar is on, but in MAP
or TEST mode and the system detects a windshear hazard event, the
system display will automatically change to the WX+T mode to display
weather and windshear icons. The selected range does not change
automatically.
During the windshear scan (below 2,300 feet AGL), the antenna tilt
position is automatically controlled to optimize system windshear
detection performance.
COLLINS’ WINDSHEAR PHILOSOPHY
Collins’ windshear coverage is designed to provide an alert to potentially
hazardous microburst in the landing and take off environment.
Collins’ windshear philosophy attempts to provide the best balance
between desired windshear alert coverage and unnecessary windshear
detections.
The Collins’ windshear coverage philosophy can best be understood by
examining the Albany ILS approach (figure 6-34). Note the following:
1. The approach has a three degree glide slope (i.e., a normal ILS
approach).
2. The approach is a normal straight in approach from the initial
approach fix (IAF).
3. The aircraft intercepts the ILS glide slope at 2,215 feet AGL.
4. The initial approach fix (IAF) is 7 NM from touchdown.
5. Windshear indications are made available to the flight crew when
the aircraft passes through 1,200 feet AGL. On a standard ILS
approach, such as this one, this occurs 4.3 NM from touchdown.
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COLLINS HOW RADAR WORKS
MultiScan™ Radar Windshear
Figure 6-34 ILS Rwy 1 Approach, Albany NY
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HOW RADAR WORKS COLLINS
Windshear MultiScan™ Radar
Figure 6-35 provides a more detailed look at the coverage area at the
moment the aircraft passes through 1,200 feet and windshear alerts are
activated in the cockpit. The windshear detection region is to scale.
Note that the windshear detection region fully encompasses the runway
touchdown zone.
When windshear alerts are activated in the cockpit (passing 1,200
feet AGL) the runway touchdown zone is fully encompassed by the
windshear detection region.
Figure 6-35 Windshear Coverage From IAF, ILS Rwy 1 Approach
Figure 6-36 demonstrates windshear coverage in a crosswind situation.
The wind is from the east. The windshear detection region continues to
fully encompass the runway touchdown zone. Note that a windshear
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6-38 18 Sep 03
COLLINS HOW RADAR WORKS
MultiScan™ Radar Windshear
is located just to the left of the aircraft approach path. This windshear
would not affect the aircraft flight path because it is downwind of the
aircraft flight path and will continue to move further from the flight
path as the aircraft approaches the runway. Therefore, it is not in the
windshear coverage region.
In a crosswind scenario, Collins’ windshear radar continues to provide
coverage of the touchdown zone. Windshears that do not affect the
aircraft flight path are not displayed.
Figure 6-36 Windshear Coverage in Crosswind on Approach
ALERT LEVEL ACTIVATION REGIONS
The following figures illustrated the regions of flight where the different
windshear alerts are activated. Airbus and Boeing aircraft differ as to
when the different alerts are displayed in the cockpit. Alerts, however,
are automatically enabled and disabled and happen in the background
during the different flight transitions.
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18 Sep 03 6-39
HOW RADAR WORKS COLLINS
Windshear MultiScan™ Radar
AIRBUS
Airbus alert activation regions for takeoff: Warnings, Cautions and
Advisories are enabled from the beginning of the takeoff roll (0 knots)
until the aircraft passes 1,200 feet. All alerts are disabled from the time
the aircraft passes 100 knots until it reaches 50 feet.
Figure 6-37 Airbus Windshear Alert Activation Region for Takeoff
Airbus alert activation regions for landing: Warning, Cautions and
Advisories are enabled from the time the aircraft descends through
1,200 feet until it passes through 50 feet. From 50 feet until touchdown,
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Collins Weather Radar operator’s guide(42)
