The weather radar system shows the flight crew weather conditions along the flight path. This lets them change the flight path to go around bad weather conditions. The flight crew also uses the weather radar system as a navigational aid.
The weather radar receiver/transmitter (RT) sends weather display data to the AIMS on a ARINC 453 data bus. AIMS then shows a four-color weather display on the NDs.
The on-side EFIS control panel selects weather returns to show on the ND and also controls the range for the weather display.
The weather radar button on the EFIS control panel selects weather returns to show on the on-side ND.
The flight crew selects the operation mode, receiver gain, and antenna tilt angle on the weather radar panel.
When the flight crew selects the weather mode on the weather radar panel:
• Heavy rainfall shows in red
• Moderate rainfall shows in yellow
• Light rainfall shows in green
• In the turbulence mode, turbulence from heavy rainfall shows in magenta
• Windshear conditions show with a special symbol to give a warning to the flight crew.
The map mode can show coastlines or large bodies of water. Weather returns show on the ND in
all EFIS modes but PLAN, full rose APPROACH, and full rose VOR.
The weather radar has a predictive windshear mode that can find conditions that cause a windshear. If it finds these conditions, it makes an aural warning and shows a special display on the ND. Because a windshear is most dangerous when the airplane is at low altitude, the
weather radar comes on automatically on the ground during takeoff and when the airplane goes
below 2200 feet during approach. Antenna attitude stabilization is done by the ADIRS for horizontal scan.
You put the mode selector switch of the weather radar control panel in the TEST position to do a system test. The CMCF of AIMS stores weather radar system faults.