Wxr system - system select and system on/off System Select

The receiver transmitter (R/T) gets 115v ac from XFR bus 2. The keep alive power supply makes unregulated and regulated 28v dc. The unregulated 28v dc power goes to the power relay in the R/T and also provides the interlock (INTRLK) signal through the WXR control panel to switch S1. S1 is held closed.

System On

To make the WXR system operate, push the WXR switch on one of the EFIS control panels.

When you push the WXR switch, the on-side display electronics unit (DEU) supplies a ground through the WXR control panel. The ground then goes through switch S1 of the R/T. This ground lets the unregulated 28v dc power from the power supply energize the relay to close switches S2 and S3. The keep-alive power supply sends regulated 28v dc power through switch S2 to energize the WXR CP power supply. The 115v ac goes through switch S3 to energize these things:

• R/T low voltage power supply

• WXR antenna drive

• WXR cooling fan.

Certain conditions cause the predictive windshear (PWS) function to turn the WXR system on automatically. When this happens, the ground signal comes from the PWS card in the R/T instead of the DEUs.

System Off

To make the WXR system go OFF, push the WXR switch on the EFIS control panel to OFF. This removes the ON discrete from the DEU. If more than one WXR switch is on, push all of the switches to OFF.

Display Modes

The navigation display (ND) shows WXR system data in these modes:

• Expanded approach

• Expanded VOR

• Center MAP

• Expanded MAP.

WXR System Display Data

The ND shows these displays:

• WXR data

• WXR system messages

• WXR alert messages.

WXR Displays

The WXR data on the ND shows the weather or the terrain in front of the airplane. Colors show the strength of the RF return signals from the weather or the terrain. These are the four colors for the WXR displays:

• Green - light weather

• Yellow - medium weather

• Red - heavy weather

• Magenta - turbulence.

The WXR system calculates and shows turbulence only to 40 NM.

WXR System Messages

This weather radar data shows on three lines in the bottom left of the navigation display:

• Mode

• Antenna tilt

• Gain.

Line 1 shows mode. Mode shows this data:

• WXR

• MAP

• WX+T

• TEST.

Line 2 shows the antenna tilt value set on the WXR panel.

Antenna tilt shows 0.0 to + 15 or - 15 degrees.

Line 3 shows gain. Gain shows this data:

• VAR - R/T has gain set by gain switch

• Blank - normal operation (gain switch in AUTO).

All WXR system messages show cyan. There is no annunciation for the standby mode.

Wxr system - pws operation General Description

If the PWS detects a windshear threat, it makes an alert. The alert may be a warning or a caution. The alert the crew receives depends upon these conditions:

• Position of the windshear relative to airplane heading

• Distance to the windshear

• Airplane flight phase - takeoff or approach.

Pws Warning Area

During takeoff, PWS gives a warning if it detects a windshear threat in this area:

• Less than 0.25 NM on either side of the airplane projected magnetic heading

• More than 0.5 NM but less than 3 nm ahead of the airplane.

During approach, PWS gives a warning if it detects a windshear threat in this area:

• Less than 0.25 NM on either side of the airplane projected magnetic heading

• More than 0.5 NM but less than 1.5 nm ahead of the airplane.

PWS inhibits new windshear warnings during takeoff and approach if both of these conditions exist:

• Airspeed more than 100 knots

• Less than 50 feet radio altitude.