The Sensitivity Time Control (STC) compensates the beam attenuation within 80 NM. The STC increases the radar sensitivity over time while the aircraft is getting closer to a precipitation.
Conventional radar Radar with Sensitivity Time Control
6.1.1.6.4. Weather, Ground and Sea returns
. Weather/Ground Returns
The weather radar links radar returns to a color according to their intensity. As ground returns are of high intensity, colors are then useless to distinguish weather returns from ground ones. The shape of displayed patterns and the use of tilt help in determining the nature of returns (weather or ground):
- Ground returns: sharp or broken shape, significant color variation when the tilt setting changes
- Weather returns: large and diffuse shape, light color variation when the tilt setting changes.
. Sea Returns
Returns of large bodies of water (e.g. sea, lake) are different according to the state of the water surface and the direction of waves. Radar returns are weak from calm waters but are strong if the radar pulses hit the downwind side of waves on a choppy water.
6.1.1.7. INTERFERING RADIO TRANSMITTERS
Radio transmitters that operate a frequency close to the weather radar one (i.e. 9333 MHz) can interfere and produce unusual displays. Those transmitters may be military radar, radar-jamming equipment, or satellite ground earth station.
The Rockwell Collins WXR 2100 weather radar includes a filter that partly attenuates these interferences.
Figure 6-11 shows a display when the radar does not filter the interferences from radio transmitters.
6.1.1.8. RADIATION HAZARDS
Refer to FAA AC 20-68B “Recommended Radiation Safety Precautions for Ground Operation of Airborne Weather Radar”.
As a reminder, the following table gives the fuselage cross sections of AIRBUS aircraft. It gives an idea about the radiation hazard clearance.
Aircraft Fuselage
diameter
A300/A310 5.64 m
A320 Family 3.85 m
A330/A340 5.64 m
A380* 7.14 m
* for A380 aircraft, it is the fuselage width.
6.1.2. WEATHER, TURBULENCE AND WIND SHEAR DETECTION
6.1.2.1. COVERAGE
The weather and turbulence detections (Honeywell and Rockwell Collins weather radars) cover an area as defined in. Figure 6-13.
For Honeywell radar only, the horizontal plane is divided into five sectors (dashed on Figure 6-13) for Autotilt purposes. Refer to 6.1.5.1 – Autotilt
Note: For any radars, the tilt angle refers to the horizon and not to the longitudinal centerline.
The wind shear detection covers a sector of 60° from the centerline on either side of the aircraft. Wind shear events are displayed within a sector of:
- 30° for Rockwell Collins radars,
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