1. Chapter 19
Weather Detection

2. Weather Radar
Weather radar helps pilots avoid dangerous weather by creating a picture on the radar screen of storms and where they are most intense.
Weather radar works by transmitting a pulse and that pulse hits rain droplets and reflects back.
New weather radar displays are color which can also express intensity of the storm and rain moving horizontally which indicates turbulence.
In the new “glass cockpits” weather radar is displayed on a multifunction display along with, for example a compass card.

5. Weather Radar Block Diagram
The antenna sends and receives the pulse generated by the unit.
The Elevation Motor raises and lowers the antenna, the Azimuth Motor makes the antenna sweep side to side.
Inertial Reference keeps the antenna stabilized
The duplexer allows for both transmission and reception through one antenna.
The symbol generator converts weather data into the display.

6. Weather Radar Antenna

7. Weather Radar Antenna

8. WX Radar Radome

9. WX Radar Radome

10. Radar Display Textbook page 137 Here is a weather radar display.
The colors indicate the intensity of the storm.
Black less than .4” of rain per hour.
Green ” of rain per hour
Yellow ” of rain per hour
Red .5-2” of rain per hour
Magenta over 2” of rain per hour
Textbook page 137

11. Weather Radar Control Panel
Here is a weather radar control panel.
There is only one weather radar system in the aircraft but the control panel has 2 sets of controls: the Captain’s depicted in white and the First Officers depicted in blue.
Gain Control increases the power output.
Tilt causes the Elevation Motor to move the antenna up or down.
WX/T is turbulence mode.
WX is weather radar mode.
MAP adds ground mapping to the display, allowing the pilot to see lakes and coastlines.
IDNT suppresses “ground clutter”. “Ground clutter” is the strong echoes bounced off the earth which gives a false reading.
This control panel has 2 sets of controls: the Captain’s depicted in white and the First Officers depicted in blue.

12. Weather Radar on Multifunction Display
Textbook page 137
Here is an example of a weather radar display on a Multifunction Display.
This is showing the weather overlay and the compass card, TCAS for traffic threats, lightening strikes and terrain hazards.

13. Multifunction Display Block Diagram
The multifunction display
takes many inputs:
GPS
FMC
TCAS GPWS
Weather Radar
Textbook page 138

19. Ground Mapping with WX Radar

21. DATALINK
Datalink sends images and text via satellite from the National Weather Service.
Nextrad, is a system of high-power ground radar stations that sweeps the sky for five minutes, mapping precipitation horizontally and sampling 14 different elevations up to 140 miles away.
The horizontal sweep give a conventional weather radar view while the elevation sampling provides a storm profile.

23. Lightening Detection/Storm Scopes
Here is a display of lightening strikes.
The lightening detector is tuned to 50KHz, the frequency where lightening energy is concentrated.

24. Windshear

25. Windshear System Block Diagram

26. AWOS Automated Weather Observing System ASOS Automated Surface Observing System

29. Weather Radar Block Diagram

30. Weather Radar Block Diagram

31. Review Q&A Chapter 19 Weather Detection
19.1 What is the greatest threat of a thunderstorm to an aircraft?
Answer: Turbulence
19.2 On a weather radar display, what color indicates maximum hazard to aircraft?
Answer: Magenta
19.3 Weather radar detects storms by transmitting ____ of radio energy and measuring their echoes from water droplets.
Answer: Pulses
19.4 Detecting turbulence in a storm is done by measuring echoes from the ____movement of water droplets.
Answer: Horizontal.
19.5 What is the normal use of the tilt control?
Answer: Ground Mapping.
19.6 What raises and lowers the radar antenna in a vertical direction for tilt control?
Answer: Elevation Motor
19.7 What causes the radar antenna to scan left and right (horizontal motion)?
Answer: Azimuth Motor
19.8 How is the radar antenna stabilized as the airplane maneuvers through pitch and roll?
Answer: Inertial Reference.
19.9 What is a typical frequency for an airborne weather radar?
Answer: 9,333.8MHz
Lightening detection systems are usually tuned to a frequency of ____.
Answer: 50KHz
What is the most recent method for delivering weather images to the cockpit?
Answer: Datalink.
What is the purpose of a radome?
Answer: To provide an aerodynamic cover for the antenna.
Radomes must reduce radar power by no more than ____.
Answer: 10%.
Wind shear is a sudden change in wind ___ and is most dangerous near the ____.
Answer: Direction, Ground
A dangerous form of windshear, which occurs over a small area, is known as a ____.
Answer: Microburst
1916 Windshear detection systems warn the pilot and also provide____.
Answer: Guidance