6. Radar

Question 1

How does the frequency of radar transmission affect detection capability and susceptibility to attenuation?

Answer 1

Detection capability of a high frequency microwave is excellent, but it’s attenuation is high.

The airport ASDE operates on SHF while the air route ARSR and approach radar ASR operate on UHF.

Question 2

Describe the capabilities of SSR Modes A, C, and S

Answer 2

The SSR mode A is capable of discriminating a squawk code selected on the aircraft transponder.

The mode C has a capability of automatic altitude reporting.

The mode S is capable of addressing a single specific aircraft with its unique mode S address.

Question 3

What do strong reflections of a radar beam cause?

Answer 3

Strong reflections of a radar beam causes appearance of a bright spot on the screen.

Question 4

What can cause radar shadows?

Answer 4

Large solid objects or intense rainfall can cause rain shadows.

Question 5

Side lobes

Answer 5

Side lines of parabolic antennas generate false images on radar displays

Question 6

Sweep line on radar display

Answer 6

The azimuth of the target is shown by the sweep line that is synchronised with the direction of the radar.

Question 7

Principle of RADAR

(Radio Detection and Ranging)

Answer 7

The distance is calculated from the elapsed time of the radar signal spent for the round trip between the antenna and the target)

Distance to Target = Cxt
2

Question 8

Principles of SSR and DME

Answer 8

The combined function of an interrogator and a transponder operates the secondary radar system.

The airborne unit of DME system works as an interrogator and the ground unit work as a transponder.

Question 9

Transponder &

TCAS

Answer 9

Transponder replies to the interrogation with the predetermined reply signal

Mode S transponders have a function of TCAS. Aircraft within a range of 40nm with mode S transponder reply to interrogations. The reply signal is processed to generate TA or RA depending on the closure rate of the approaching aircraft.

Question 10

Radar returns

Answer 10

The radar beam of airborne weather radar penetrates the ice crystal zones of thunderstorms (CB) without reflection. The zone of hail produces weak radar echoes. Radar reflections produce echoes in heavy rain zones below cloud base.

Question 11

Antenna Stabilization

Answer 11

IRS attitude signals stabilise radar antennas against attitude changes of the aircraft.