6.1.5.5. GAIN PLUS (ROCKWELL COLLINS)
The GAIN PLUS includes a set of functions available in the automatic Multiscan mode:
-Conventional increase and decrease of receiver sensitivity,
-Variable temperature based gain,
-Path Attenuation Compensation (PAC) alert,
-Over-flight protection,
-Oceanic weather reflectivity compensation.
6.1.5.5.1. Conventional Increase and Decrease of Receiver Sensitivity
This function manages the color variation for display when the gain is manually set. The MAX setting approximately represents an increase of one and half color level (+16 dB). The MIN setting approximately represents a decrease of one and half color level (-14 dB).
The CAL setting is the default setting that provides a color code as depicted in
6.1.1.4 – Gain.
6.1.5.5.2. Variable Temperature Based Gain
The reflectivity of water changes according to its state (i.e. liquid or ice). Refer to
6.1.1.1 – Reflectivity of Water Molecules. Therefore, the reflectivity changes
according to the temperature.
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When the temperature is above 0°C, the gain is constant.
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When the temperature is below 0°C, the Variable Temperature Based Gain function increases the gain to compensate the reflectivity diminution.
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When the temperature is below –40°C (water exclusively in ice crystal form), the Variable Temperature Based Gain function increases the gain by approximately one color level.
6.1.5.5.3. Path Attenuation Compensation (PAC) alert
When the radar beam is attenuated (radar shadow, refer to 6.1.1.6.2 – Attenuation), the Path Attenuation Compensation (PAC) alert provides a visual cue on ND: a yellow arc on the outermost range ring.
The PAC alert is available when the gain is set to CAL and the attenuation is within 80 NM.
6.1.5.5.4. Over-Flight Protection
The Over-Flight Protection tracks thunderstorms in the aircraft flight path, and until the aircraft passes the thunderstorms. The Over-Flight Protection improves the weather awareness, and may prevent inadvertent penetration of thunderstorm tops.
With conventional weather radars, the wet part of a thunderstorm (that is the most visible on radar display) may get below the radar beam when the aircraft approaches the thunderstorm. Consequently, the thunderstorm may disappear from the display when the aircraft is getting closer to it.
Thanks to the pair of Multiscan radar beams, the Over-Flight Protection scans down to 6000 ft below the aircraft to keep the reflective part visible (step 2, Figure 6-26).
When the thunderstorm is within 15 NM from the aircraft, the Over-Flight Protection compares the image of the thunderstorm stored in the database with the image of the last scan. The Over-Flight Protection displays the image with the strongest returns. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：getting to grips with surveillance(100)
