Wx Radar

Question 1

What is a Wx radar entirely dependent of?

Answer 1

Reflections from WD. The ˚ of reflectivity depends on WD size, composition and quantity.

Question 2

What freq does a Wx radar operate on?

Answer 2

9Ghz

Wavelength 3cm
Decimetric

Question 3

How is a Wx radar gyro stabilised on modern A/C?

Answer 3

In pitch using the A/C’s attitude reference system.

So the A/C’s tilt is irrespective of the pitch of the A/C under normal operating envelope.

Question 4

Old types of Wx radar use 2 types of radiation patterns:

Answer 4

• A pencil (cone shaped) for Wx detection

* A cosecant squared (spoiled) beam for ground mapping (range 60-80nm)

Question 5

What type of beam do modern A/C use?

Answer 5

Pencil beam

Width 3-5˚

Question 6

What is the tilt angle of a Wx radar using a gryo stabilised system?

Answer 6

Tilt angle is the angle between the centre of the beam to the horizontal.

Question 7

What do the colours black, green and amber represent on MAP mode of a Wx radar system?

Answer 7

Black - water

Green - Land

Amber - high ground or large settlements and cities.

Question 8

What does gain control do on a Wx radar system?

Answer 8

In radar terms, gain is sensitivity.

Too much gain and entire screen may rep. Huge areas of amber and red. Too low may cause too much green return.

Gain control switch should normally be placed in a calibrated or auto position to give an ave presentation of radar returns.

Question 9

In tilt control of a Wx radar, what is the difference between stabilised and unstabilised radar?

Answer 9

Stabilised: the value on the tilt switch refers to the tilt angle in relation to the horizon.

Unstabilised: the value on the tilt control switch refers to the tilt angle in relation to the longitudinal axis of the A/C

Question 10

What is radar shadowing?

Answer 10

When there is a large area of WD ahead and relatively close to the A/C, radar pulses are reflected and/or returns are attenuated. This thus gives false representation of the actual Wx i.e the severe weather is ‘hidden’.

Question 11

How does Wx radar detect turbulence and windshear detection?

Answer 11

It does so indirectly by analysing movement of the WD.

This option is usually deliberately selected, and more commonly used during T/O and LDG as A/C more sensitive to these conditions at that time.

Question 12

The Wx radar’s control panel has a function switch WX+T mode, what does this do?

Answer 12

WX+T mode shows all the Wx ahead of the A/C, plus any turbulent air masses.