Lecture 7b: Secondary Surveillance Radar (SSR) & Airborne Weather Radar (AWR)

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B) Secondary RADAR

• Secondary Radar is always known as Secondary Surveillance Radar (SSR).

• SSR is complement to the primary radar as it provide ATC with additional info about aircraft such as aircraft’s call sign, altitude, speed and destination.

• SSR requires an aircraft to be fitted with transmitter/receiver called as transponder.

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Secondary Surveillance Radar (SSR).

• SSR antenna mounted on top of Primary Radar

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How Secondary Radar Works?

• The ground secondary radar transmits 1030MHz signal.• The aircraft radar receives on 1030MHz and transmits back

0n 1090MHz.• The transponder reply is more powerful than the reflected

radar signal allowing for far greater range. (250nm).

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Advantages of Secondary Surveillance Radar SSR

• Requires much less transmitting power to provide coverage up to 200 to 250NM.

• Provides more information: aircraft’s identity (its code & call sign), indicates aircraft’s altitude, speed & destination.

• Can indicate if an aircraft has an emergency, has lost radio communications or is being hi-jacked.

• Reply signal is much stronger as it does not rely on returning reflected signals.

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Radar Display

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Secondary Radar DisplayWhat appear on secondary radar display?

• Aircraft Identity.

• Altitude

• Speed

• Direction

• Example

MH092 FL280

585• Meaning: Flight Malaysian 092 cruising at 28’000ft

with speed of 585knots

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2. AIRBORNE WEATHER RADAR (AWR)

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Introduction

• Airborne Weather Radar (AWR) is used to provide to provide the pilots about weather ahead.

• The installation include weather radar antenna located in the nose of the aircraft and weather radar display inside the cockpit.

• The radar information can be displayed in combination with the aircraft route on the EFIS Navigation Display (ND)

• Weather radar is used for severe weather avoidance

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The antenna is housed in a radome made of composite materials located in the nose of the aircraft.

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How Airborne Weather Radar Works

• A antenna which sweeps side to side transmits Super High Frequency (SHF) signals which is 9Ghz

• When hit the reflective objects (precipitation), the signals is reflected back to the antenna receiver.

• The returns (echo) are displayed to the pilot on the aircrafts radar screen.

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Precipitation

• Weather radar is function to detect, locate, and measure the amount of precipitation.

• Precipitation is within or falling from cloud.

• It includes rain, snow, ice & hail.

• Different precipitation has different reflective levels.

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Airborne Weather Radar Works

• The goal of weather radar is to display areas of heavy precipitation, which generally indicates areas of turbulence.

• Different types of precipitation have different reflective qualities.

• Reflectivity of precipitation is directly related to moisture content.

• Large water droplets show the strongest returns, while dry hail or snow will show light returns, or no returns at all.

• Weather radar detects raindrops, not clouds or fog.

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Airborne Weather Radar Works

• The precipitation painted (depicted) by airborne weather radar is not of primary concern, however it is representative of areas of severe weather.

• Areas of large raindrop size=high rainfall rate=intense storm=turbulence.

• The turbulence associated with convective clouds is often severe and always dangerous.

• Other dangerous factors associated with thunderstorms are: severe icing, hail, lightning, strong downdrafts.

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CAUTION: weather radar emits harmful radiation, it should not be operated when people are standing within 50 feet of radome or during refuelling.