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The weather radar (WXR) system supplies these visual


Weather conditions

Windshear events

Land contours.



WXR operates on the same principle as an echo. The WXR system transmits radio frequency (RF) pulses in a 180 degree area forward of the airplane. Objects reflect the pulses back to the receiver. The receiver processes the return signal to show weather, terrain, and windshear events.


The WXR returns show in four different colors on the navigation displays (ND). Colors of the indications give the crew information about the intensity of the returns.


Abbreviations and Acronyms

ac - alternating current

ADF - automatic direction finder

ADIRS - air data inertial reference system

ADIRU - air data inertial reference unit

alt - altitude

ant - antenna

app - approach

ARINC - Aeronautical Radio, Inc.

arpt - airport

AZ - azimuth

baro - barometric

BITE - built-in test equipment

BL - buttock line

CAL - calibrate

capt - captain

CDU - control display unit

con - control

CP - control panel

CPU - central processing unit

dc - direct current

DEU - display electronics unit

DH - decision height

dn - down

EFIS - electronic flight instrument system

EGPWS - enhanced ground proximity warning system

EL - elevation

elex - electric

F/O - first officer

FMC - flight management computer

FMCS - flight management computing system

FPV - flight path vector

fwd - forward

gnd - ground

GS - ground speed

hPa - hectopascals

in - inch

intlk - interlock

IRS - inertial reference system

kg - kilograms

L - left

lb - pounds

mag - magnetic

max - maximum

MDA - minimum descent altitude

MHz - megahertz

MINS - minimums

MTRS - meters

nav - navigation

NCD - no computed data

ND - navigation display

NM - nautical miles

OK - good or pass

PFD - primary flight display

pos - position

PRF - pulse repetition frequency

PWS - predictive windshear

R - right

rad - radio

RF - radio frequency

R/T - receiver/transmitter

sta - station

stab - stabilization

stb - stabilization

std - standard

TAS - true air speed

TCAS - traffic alert and collision avoidance

trk - track

TRU - true

V - volts

VOR - very high frequency omnidirectional range

wpt - waypoint

WX - weather

WX/TURB - weather/turbulence

WX+TURB - weather+turbulence

WXR - weather radar

Z - zulu (universal coordinated time)




These components supply weather radar (WXR) system control:

Left and right EFIS control panels

Weather radar control panel.


System Inputs

These components supply signals to the WXR transceiver for predictive windshear:

Air data inertial reference system sends air data for the PWS function

Radio altimeters send altitude to enable or disable PWS during takeoff and approach

Autothrottle switch packs enable PWS during takeoff

Landing gear lever switch sends a landing gear down discrete to enable PWS during approach

An air/ground relay sends an air/ground discrete for flight leg counting.


System Outputs

The weather radar transceiver sends these signals out for

predictive windshear:

PWS video to the WXR/TERR relays

PWS warnings or cautions to the GPWS to prioritize any callouts

Audio inhibit to TCAS when there is a PWS warning

Audio to the REU for PWS.



WXR data shows on the navigation displays (NDs). The weather data from the WXR receiver/transmitter (R/T) goes to the weather radar/terrain (WXR/TERR) relays.

The ground proximity warning computer (GPWC) controls and switches the relays. If TERR is selected on the EFIS control panel or there is a Terrain Awareness/Terrain Clearance Floor warning from the GPWC, then the EGPWS terrain data shows on the navigation display (ND). If TERR is not selected and there are no EGPWS warnings, WXR data shows on the ND.


The WXR antenna sends the RF pulses and receives the RF returns. The R/T gets air data inertial reference unit (ADIRU) pitch and roll data for antenna stabilization.

Receiver/Transmitter (R/T)

The primary component of the WXR system is the weather radar R/T. The WXR R/T does these functions:

Transmits RF pulses

Processes the RF returns

Detects windshear events and sends warnings and cautions to the flight crew

Supplies the WXR display data.


Date: 2016-01-14; view: 2424

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