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On A320 family aircraft: FAC,
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On A330/A340 family aircraft: FE part of FMGEC,
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On A340-500/600 aircraft: FE part of FMGEC,
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On A380 aircraft: PRIM.
The Severity Factor (SF) determines the severity of a wind shear.
SFLongitunal for longitudinal tail wind gradient
SF = SFLongitunal + SFVertical with
SFVertical for downward wind.
The Reactive Wind Shear triggers alerts when the estimated SF reaches a threshold. This threshold depends on the real aircraft energy. The lower the aircraft energy (or the higher the angle of attack), the lower the threshold for alerts.
The Reactive Wind Shear alerts are available in high lift configuration between 50 ft and 1300 ft RA.
6.1.5. WEATHER RADAR FUNCTIONS PER MANUFACTURER
The main manufacturers for weather radar on A320/A330/A340 aircraft are Honeywell and Rockwell Collins. They use two different philosophies for the weather detection: the Autotilt for Honeywell and the Multiscan for Rockwell Collins. The Autotilt and the Multiscan are commonly called the automatic mode for weather radars.
The following paragraphs describe functions that are specific to weather radar models, whereas the previous paragraphs were common to both models.
6.1.5.1. AUTOTILT (HONEYWELL)
6.1.5.1.1. Principle
The Autotilt function of the Honeywell weather radar automatically adjusts the tilt angle. The Autotilt function takes into account the aircraft altitude and the terrain information from EGPWS3 for the tilt angle adjustment.
For Autotilt purposes, the radar scan is divided into five sectors (refer to Figure 6-13). For each sector, the Autotilt function adjusts the tilt angle (beam 2 in Figure 6-19) according to the terrain altitude from the EGPWS, the aircraft altitude, and the selected range (i.e. geometric adjustment). When in MAP mode and the Autotilt is activated, the weather radar points the radar beam to the ground according to the aircraft altitude and the selected range.
Practically, the Autotilt function prevents errors encountered when the flight crew manually set the tilt angle. Refer to Figure 6-19.
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Beam 1 is too high. Weather and terrain are over-scanned.
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Beam 2 is the optimum beam determined by the Autotilt function.
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Beam 3 is too low. Weather and terrain are under-scanned.
Note: The Honeywell weather radar with the Autotilt function is based on ground returns. Therefore, the flight crew should pay attention for the interpretation of heavy rains or ground returns.
6.1.5.1.2. Autotilt Scan Pattern
. In weather mode
The Autotilt function operates both in short ranges (less than 80 NM) and in long ranges (more than 80 NM). Above 2 300 ft:
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If both flight crewmembers set NDs to ranges of the same magnitude (either short or long ranges), the weather radar updates both ND on clockwise and counterclockwise scans. With this scan pattern, the weather radar refreshes the weather display every 4 s.
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