(2) Windshear mode (if the predictive windshear function is activated) The WR/PWS, by a doppler mode, determines the wind field ahead of the aircraft. By a mathematical treatment, the system determines the hazard factor (so-called "F factor") related to the danger of a windshear event. An hazard factor exceeding a value of 0.13 and within 5NM ahead of the aircraft is considered as the presence of a dangerous event and a corresponding windshear alert is generated. The display of windshear hazard consits of an icon of red and black bands superimposed on the radar returns. As these events are dangerous during takeoff and landing maneuvers, the PWS mode is automatically activated below 2300 ft radio altimeter and at least one of the qualifier-A and one qualifier-B inputs have to be valid. Windshear detection operates automatically with the above-mentioned reasons, even if the radar function selector switch is set to OFF, but windshear switch has to be set to AUTO. The windshear mode is transparent to the pilot until a windshear event is detected. When a windshear event is detected, the system generates the appropriate annunciations (visual and aural) to the flight crew. The WR/PWS generates a graphic symbol (icon) to the displays indicating where the windshear was detected. The windshear function detection can operate either with weather radar modes activated or independently without these modes. This is accomplished by sharing the antenna scanning:
-
in clockwise weather scan or windshear scan
-
in counterclockwise windshear scan. In windshear mode, the TILT and GAIN are controlled automatically on the WR/PWS for the scanning. However, the TILT displayed on the NDs is in accordance with this selected on the radar control panel. When the weather radar transceiver fails, the amber message PRED W/S is displayed on the NDs associated with the amber messages:
-NAV: PRED W/S DET FAULT on the upper ECAM DU,
-PRED W/S DET in the INOP SYS item of the STATUS page on the SD.
NOTE : The system has to reject echoes due to ground clutter or
____
moving surface.
NOTE : The pilot has to deselect windshear mode (AUTO/OFF switch to
____
OFF) for the following reasons:
-
when the aircraft is at a gate area or in maintenance hangars to avoid radiating danger for persons
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when nuisance aural alerts are generated.
NOTE : There is no danger of radiation to persons on the ground if
____ the ATC switch on the ATC/TCAS control unit is set to OFF or
R 1EFF : 001-049, 101-105, 151-199, 1 34-41-00Page 43 1 1 Config-3 May 01/05 1 1 1CES 1 STBY after landing, even if the windshear switch on the weather radar control unit is still at AUTO.
NOTE : In order to ensure optimum performance for the predictive
____ windshear function, the radome must be at least equal to class B category 1.
(3) Logic of scanning mode (Ref. Fig. 009) The antenna scan pattern varies depending on the mode of operation.
(a)
Weather radar scan pattern In weather radar mode, the antenna scans a 180 deg. in azimuth and has tilt (pitch) coverage of plus or minus 15 deg. Stabilization limits are plus or minus 25 deg. in the pitch axis and plus or minus 40 deg. in the roll axis. An antenna scanning is performed in 4 seconds, this causes the transmission of 760 data words at each antenna scanning. The weather radar system features a 4-second constant refresh rate of the WX image whatever the ranges selected on the CAPT and F/O EFIS control sections of the FCU.
(b)
Weather and windshear scan pattern, no detected windshear event When the system is placed into alternate weather/windshear scan pattern and no windshear event is detected, the antenna scan pattern is as follows:
-clockwise weather scan with plus or minus 90 deg. of azimuth coverage and processing for weather
-counterclockwise windshear scan with full plus or minus 90 deg. of azimuth coverage, but with windshear processing limited to the plus or minus 45 deg. sector. However, the WR/PWS have to update the refresh rate of the WX image to 12 seconds due to sharing of processing between windshear and radar.
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