Warning: do not open the nose radome if the wind is more than 15 knots. If you open the radome in a wind, the radome can move quickly. This can cause injury to persons or damage to equipment.

 

 

 

WXR SYSTEM - EFIS CONTROL PANEL - OPERATION

EFIS Control Panel

These are the functions of the EFIS control panel (CP) for WXR control:

· Supplies the on and off control of the WXR R/T

· Enables the navigation displays (ND) to show WXR data

· Supplies the selection of different ND modes

· Supplies the selection of different ranges for WXR data to show on the NDs.

 

WXR Map Switch

These are the things that occur when you push the WXR map switch:

· The WXR R/T starts to operate

· The WXR data shows on the on-side ND.

To stop the operation of the WXR R/T, the WXR map switches on both EFIS control panels must be off.

Mode Selector

Use the mode selector switch to select an ND mode. A WXR display can show in these ND modes:

· Expanded APP (approach) mode

· Expanded VOR mode

· Expanded MAP mode

· Centered MAP mode.

 

Range Selector

The EFIS control panel range selector has eight positions. The range selections are 5, 10, 20, 40, 80, 160, 320, and 640 nautical miles (NM). With the 640 NM range selection, the 640 NM range shows on the ND. But the WXR R/T only shows weather displays out to a maximum range of 320 NM.

The weather/turbulence mode shows turbulence data up to a maximum range of 40 nautical miles (NM). If a range more than 40 NM is set on the EFIS control panel, the NDs show weather data only.

 

 

 

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.

 

PWS Caution Area

PWS gives a caution if it detects a windshear threat in this area:

· Within 25 degrees on either side of the airplane projected magnetic heading

· More than 0.5 nm but less than 3 nm ahead of the airplane

· Not in the PWS warning area.

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

· Airspeed more than 80 knots

· Less than 400 feet radio altitude

All PWS alerts are inhibited above 1200 feet radio altitude.