WINDSHEAR VISUAL AND AURAL MESSAGES
Note: Although the windshear mode is intended to be transparent unless an alert is generated, the crew may notice that the radar update rate is delayed when both radar and windshear modes are active. This delay of up to 12 seconds is caused by the sharing of antenna and processing between the weather and windshear modes in an alternate scan technique.
Alternate Scan
When the radar is operated in a weather mode and the conditions for windshear mode operation are satisfied, the radar switches to the alternate scan function. In an alternate scan operation, the radar uses one sweep for radar mode, the next sweep for windshear mode. On the radar sweep, gain and tilt are controlled by the settings in the flight deck. On the windshear sweep gain and tilt is automatically set by the R/T units programming for optimum windshear detection.
Maximum Permissible Exposure Level (MPEL)
In order to avoid the envelope in which the radiation level may exceed the
U.S. Government standard of 10 milliwatt per square centimeter, all personnel should remain beyond the distance indicated in the illustration below. The distance to the MPEL boundary is determined by calculating the near field/far field intersection per FAA Advisory Circular 20-68B.
Continental
Rev. 12/01/00 #29 Flight Manual
WINDSHEAR ALERT / WARNING AREAS WINDSHEAR ALERT RANGES AND ALTITUDES
Continental
Rev. 12/01/00 #29 Flight Manual
System Annunciator Lights
Red and amber WINDSHEAR annunciator lights are installed on the forward instrument panel in front of each pilot. The red lights illuminate in conjunction with a warning level alert and the aural warning of “WINDSHEAR AHEAD, WINDSHEAR AHEAD” on takeoff, or “GO AROUND WINDSHEAR AHEAD” on approach. The amber lights illuminate in conjunction with a caution level alert and a two tones aural warning.
An amber WINDSHEAR INOP annunciator is installed on the annunciator panel. This light illuminates any time the windshear systems detects a fault which renders the system inoperative. The windshear annunciator circuit breaker is located on the right radio DC bus, E-4.
Windshear Icon
The windshear icon consists of red and black bands with straight sides formed by the radials from the aircraft which bound the event. The arcs closest and furthest from the aircraft depict the minimum and maximum range of the event.
Yellow radial lines appear at the edges beyond the event and extend to the edge of the display to provide directional information for the event.
Procedures
The following procedural chart applies to the predictive windshear system. Continental policy is to avoid all windshear and other hazardous weather.
Note: Windshear alerts are inhibited on the ground above 100 KIAS to 50 feet AGL.
Phase of Operation Warning Alert Caution Alert Advisory Alert System Failure
Before Takeoff Advise ATC of the location of the Warning Alert. Delay takeoff until the warning is no longer present. Advise ATC of the location of the Caution Alert. At the Captain’s discretion, delay the takeoff, or takeoff and maneuver to avoid the hazard. Advise ATC of the location of the windshear hazard. After takeoff, maneuver to avoid the windshear hazard area. Select the alternate radar system if available. If no alternate system is available, use standard windshear avoidance procedures.
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