04 Airborne Weather Radar

Question 1

The two main tasks of an airborne weather radar (AWR) system?

Answer 1

The two main tasks of an airborne weather radar (AWR) system are for the detection of adverse weather and for ground navigation.

Question 2

Requirement for weather radar?

Answer 2

5,700kg and more then 9 seats

Question 3

Frequency of AWR?

Answer 3

Modern AWR systems use wavelengths of approx. 3 cm transmitting pulses, which reflect best off wet hailstones.

X-Band - 9.345Ghz - SHF

Question 4

Range of AWR?

Answer 4

160nm - 320nm.

However normally used at about 80nm

• 90 degrees L and R.
• 15 degrees up and down.

Question 5

AWR Stabalisation?

Answer 5

Modern AWR systems are stabilised in pitch and roll using the aircraft’s attitude reference system.

Question 6

AWR Beam shape?

Answer 6

The AWR system utilises a 3–5° cone shaped (pencil) beam for weather detection.

Question 7

Beam shape for ground mapping?

Answer 7

Skyworx- Fan shaped beam, effective maximum range of 50Nm to 60NM

ATPLQ - A narrow conical beam is used for weather detection that is approximately 5º in beam width, called a pencil beam.

Question 8

The AWR control panel has the following controls?

Answer 8

• off/on switch;
• function switch with WX, WX+Turbulance(T) and MAP modes;
• gain-control setting (auto/manual);
• tilt/auto tilt switch.

Question 9

Gain control?

Answer 9

Sensitivity, the higher the gain, the more sensitve the radar.

Question 10

The colours used on the AWR display, in order of increasing intensity of precipitation, are:

Answer 10

• Green. - Light returns 0.7-4mm/hr
• Amber. - medium returns 4-12mm/hr
• Red. - strong returns >12mm/hr
• Magenta. - turbulance due to rainfall intensity.

Question 11

AWR on the ground?

Answer 11

AWR should be used with extreme caution on the ground, with the beam tilted up.

Question 12

Ground mapping

Good and bad returns for ground mapping function?

Answer 12

Good returns - Mountains, cities and skyscrapers
Bad returns - calm seas, fine sand, flat terrain

Question 13

Ground mapping

Hill shadowing?

Answer 13

Gives a false impression of radar shadowing areas as being water. Corrected by flying higher to reduce shadowing.

Question 14

AWR Range?

Answer 14

An AWR display uses azimuth and range marker lines to indicate bearing and range to targets.

Question 15

Pilot use of the AWR?

Answer 15

The tilt and gain functions can be used, together with the azimuth and range lines, to determine flight paths around thunderstorms, as well as the altitudes of weather systems and elevations of ground features.

Question 16

AWR shadowing?

Answer 16

The AWR system may not be able to detect anything behind heavy rain, owing to the total beam energy being reflected by the rain.

Question 17

Errors using AWR?

Answer 17

With the tilt set too high, AWR may not detect the upper sections of thunderstorms, which may be composed of dry, frozen particles.

Question 18

AWR Turbulance?

Answer 18

AWR may be used to detect turbulence and windshear indirectly by analysing the movement of water droplets.

The most turbulent areas of thunderstorms are also those areas that contain the most water and ice. Note that the areas in which the concentration of droplets decreases rapidly (which are marked on the radar screen by a sharp fall in signal intensity) are normally areas in which the most severe turbulence can be encountered.

Question 19

How can tilt be used to estimate cloud tops?

Answer 19

Cloud Top(ft) = Range(nm) x tan(Tilt-(beamwidth/2)) x 6080

T

Question 20

Tilt angle?

Answer 20

Angle from AC horizontal to the centre of the beam.

Question 21

Multi-scan Radars?

Answer 21

Scans ahead of the aircraft at various levels to form a 3D representation.

Question 22

GCS?

Answer 22

Ground clutter suppression, used to reduce the effect of ground returns which could be confused with weather.

Radar sidelobes bouncing off the ground are recieved as ground returns at short ranges. GCS removes there from the picture.

Question 23

On the ground weather radar test?

Answer 23

Tests can be conducted on the ground.

Hazard range for Wx radars is usually about 5m.

Question 24

Radar reflectivity?

Answer 24

• Wet Hail
• Rain
• Wet Snow
• Drizzle
• Dry Hail
• Dry Snow

Water is 5 times more reflective then Ice.

Question 25

Tilt at different stages of flight?

Answer 25

• T/O and climb: 4 up, reducing as climb angle reduces
• Cruise: 2 down to avoid ice crystal
• Descent: Initially down but then 4 to avoid groudn clutter on approach.

Question 26

Blind Alley or Box Canyon?

Answer 26

Important to look at range.

Question 27

Doppler Turbuance Detection?

Answer 27

Detects Horizontal movement of water particles.

Shown as a cone and read bars on ND.

Range of 40nm.

Question 28

Squall, Turbulance, Finger, Scalloping, Hook

Answer 28

Question 29

Autotilt?

Answer 29

Changes the tilt of the AWR according to altitude of AC.