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1st Edition, 1st Revision
6-40 18 Sep 03
COLLINS HOW RADAR WORKS
MultiScan™ Radar Windshear
Figure 6-38 Airbus Windshear Alert Activation Region for Landing
1st Edition, 1st Revision
18 Sep 03 6-41
HOW RADAR WORKS COLLINS
Windshear MultiScan™ Radar
BOEING
Boeing alert activation regions for takeoff: Warnings and Cautions are
enabled from the beginning of the take off roll (0 knots) until the aircraft
reaches 80 knots. From 80 knots until the aircraft passes 400 feet, only
Warnings are enabled. From 400 feet through 1,200 feet, Warnings and
Cautions are enabled. All alerts are disabled from the time the aircraft
passes 100 knots until it reaches 50 feet. Boeing aircraft do not display
Advisories (♦page 4-48).
Figure 6-39 Boeing Windshear Alert Activation Region for Takeoff
Boeing alert activation regions for landing: Warnings and Cautions are
enabled from the time the aircraft passes 1,200 feet until 400 feet.
From 400 feet until 50 feet, only Warnings are enabled. From 50 feet
until touchdown (0 feet), all alerts are disabled. Boeing aircraft do not
display Advisories (♦page 4-48).
1st Edition, 1st Revision
6-42 18 Sep 03
COLLINS HOW RADAR WORKS
MultiScan™ Radar Windshear
Figure 6-40 Boeing Windshear Alert Activation Region for Landing
MVD™ WINDSHEAR RECORDING
MVD™ is a data recording system inside the WXR-2100 R/T that
automatically stores windshear Magnitude, Velocity, and Deviation
information. These three key pieces of windshear information allow
detailed engineering analysis of windshear events. The radar is able to
store up to three events of twelve sweeps each. If further analysis of a
windshear event is required the information can be down loaded with
a lap top computer.
1st Edition, 1st Revision
18 Sep 03 6-43
HOW RADAR WORKS COLLINS
Alien Radar MultiScan™ Radar
ALIEN RADAR
The WXR-2100 radar incorporates a sophisticated alien radar rejection
algorithm that is designed to prevent interference from other airborne
weather radars. However, high power military radars and military
radar-jamming systems will “burn through” and cause display artifacts.
Figure 6-43 shows a typical interference pattern caused by a high
powered military radar.
Figure 6-41 Interference Pattern From Military Radar-Jamming
System on Radar Display
RADIATION HAZARDS
To provide a practical safety factor, the American National Standards
Institute has specified a maximum level of 10 mw/cm2 for personnel
exposure of 6 minutes or longer to radar antenna electromagnetic
radiation. The exposure time is limited to the amount of time within the
antenna pattern during each sweep.
In 1980, Collins engineering personnel measured the radiation
emissions of an actual weather radar system on the flight line. A
General Microwave radiation hazard meter (Model 481B) was used to
measure the emitted radiation. It was placed 1.5 feet in front of the
radar’s flat-plate antenna during normal operation with the radome
1st Edition, 1st Revision
6-44 18 Sep 03
COLLINS HOW RADAR WORKS
MultiScan™ Radar Radiation Hazards
removed. System range was set to 320 NM to provide the maximum
pulse width. Under these conditions, the maximum power density meter
reading was 0.3 mw/cm2.
In a similar fashion, the United States Air Force’s Armstrong Laboratory
measured the power density of the military version of the windshear
radar and found the highest power density level to be 0.13 mw/cm2.
The Collins WXR-2100 radar system falls well below the 10 mw/cm2
standard. However, it should be noted that there is some disagreement
that the 10 mw/cm2 standard is low enough. Microwave ovens represent
a more public safety concern and their leakage standard has been set
at 4 mw/cm2. The WXR-2100 power density is half or less than that
of the microwave oven standard.
N NOTE
Some sources suggest that any radiation exposure can be harmful,
especially long term. Each airline must make their own decision on
this, as exposure to radiation is occasionally cited by an employee
as a cause of some physical injury.
N NOTE
For specific requirements and limitations, refer to FAA Advisory
Circular 20–68B, “Recommended Radiation Safety Precautions for
Ground Operation of Airborne Weather Radar.”
1st Edition, 1st Revision
18 Sep 03 6-45
HOW RADAR WORKS COLLINS
MultiScan™ Radar
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1st Edition, 1st Revision
6-46 18 Sep 03
COLLINS OPERATOR’S GUIDE
　
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