WEATHER RADAR SYSTEM - DESCRIPTION AND OPERATION

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1. General
The aircraft is equipped with an X-band weather radar system. This system complies with ARINC Characteristics 708. The weather radar enables detection and localization of the atmospheric disturbances in the area defined by the antenna scanning: plus or minus 90 deg. of aircraft centerline and up to 320 NM in front of the aircraft.
In addition the weather radar system enables:

detection of turbulence areas caused by the presence of precipitations
presentation of terrain mapping information by the combination of the orientation of the radar beam and of the receiver gain.

Five color displays are used to show precipitations and turbulences to the crew.
This system is associated to:

the Air Data/ Inertial Reference Units (ADIRU) for the attitude information
the Electronic Instrument System (EIS) for the generation of the distance scales and the display of the radar images.

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2. Component Location

Weather Radar - Component Location ** ON A/C NOT FOR ALL

Weather Radar - Control and Indicating ** ON A/C NOT FOR ALL

The installation of the system components on the aircraft is detailed below.

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FIN ! FUNCTIONAL DESIGNATION ! PANEL!ZONE!ACCESS ! ATA

! ! ! ! DOOR ! REF.

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1SQ1 XCVR - WEATHER RADAR, 1 109VU 121 811

3SQ CTL UNIT - WEATHER RADAR 11VU 210

7SQ DRIVE - WR ANTENNA 110 110AL

9SQ MTG TRAY - WR XCVR 109VU 121 811

11SQ ANTENNA - WEATHER RADAR 110 110AL

The waveguide assembly 301FM ensures the RF connection between :

the mounting tray installed in the avionics compartment and
the WR antenna drive installed at frame 1.

NOTE: For the layout of the components related to the weather radar system (FCU/EFIS control section and DMC), refer to 31-60.

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3. System Description

Weather Radar - Block Diagram ** ON A/C NOT FOR ALL

A. General
The weather radar system, which complies with ARINC Characteristics 708, consists of:

a transceiver 1SQ1
a single control unit 3SQ
a single antenna drive 7SQ
an antenna 11SQ
a single transceiver mounting tray.

B. General

NOTE: The weather radar image is shown on the Captain and First Officer Navigation Displays (ND). The NDs are connected to the three Display Management Computers (DMC) and to the Captain and First Officer EFIS control sections of the FCU.

NOTE: If the Enhanced GPWS is operative, the WR image is replaced by the terrain image, on the Captain and First Officer NDs, during a terrain alert or a crew action.
More explanations are given in 34-48.

NOTE: The ADIRUs give the attitude to the weather radar system (Refer to 34-14-00). These data ensure the radar antenna stabilization.

C. General Technical Characteristics
The weather radar system is mainly used to detect and localize various types of atmospheric disturbances in the area scanned by the antenna. The system shows the disturbance intensity through the use of colors which vary with the atmospheric precipitation rate (refer to the correspondence table below).
The disturbances are shown to the crew members on the NDs with different colors:

black, green, yellow, red to quantify the precipitation rates
magenta to represent the turbulence areas up to 50 NM.

NOTE: There is no detection of turbulence in clear sky.

The actual operating range of the system is 320 NM. The peak power emitted is approximately 100 W.
The antenna scans a 180 deg. sector in azimuth and has a tilt (pitch) coverage of plus or minus 15 deg. Stabilization limits are: plus or minus 40 deg. in the pitch and roll axes.
The antenna scans the 180 deg. sector in azimuth 15 times per minute.
The antenna which has a 28-inch diameter, radiates an RF beam. The beam width is 3.5 deg.
Additionally, the weather radar may be used as a navigation aid. In the mapping mode, it allows identification of major changes in the ground map: (e.g. a sea coast, an estuary, a lake, a mountain, an island, a big city, etc.).
Correspondence table

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! LEVEL DETECTED ! PRECIPITATION RATE ! COLOR OF ECHOES !

!------------------------!-------------------------!--------------------------!

! Z1 to Z2 10-20 dB ! less than 0.76 mm/h ! black !

! Z2 to Z3 20-30 dB ! from 0.76 to 3.81 mm/h ! green !

! Z3 to Z4 30-40 dB ! from 3.81 to 12.7 mm/h ! yellow !

! Z4 to Z5 40-50 dB ! from 12.7 to 50.8 mm/h ! red !

! ! ! !

!------------------------!-------------------------!--------------------------!

! Turbulence ! 50.8 mm/h and above ! magenta !

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4. Power Supply
Energization of the transceiver 1 is through 115VAC, 400 Hz normal bus:

115VAC BUS 1 1XP via sub-busbar 101XP-C and circuit breaker 5SQ1.

NOTE: Energization of the weather radar control unit and of the WR antenna drive is through the selected transceiver.
Consumption of each selected transceiver is 150 W maximum.

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5. Component Description

Weather Radar Architecture ** ON A/C NOT FOR ALL

A. Weather Radar Transceiver FIN: 1-SQ-1 FIN: 1-SQ-2

Weather Radar Transceiver - Component Description ** ON A/C NOT FOR ALL

The weather radar transceiver is a completely solid-state airborne unit.
It contains:

(1) A power amplifier
The 777.77 MHz drive signal is divided by the power amplifier into two and both signals are then amplified. Each signal is again divided and amplified and the four signals are then combined to produce two 777.77 MHz multiplier drive signals.

(2) A multiplier
The two 777.77 MHz drive signals are split and frequency-multiplied by three to produce four 2333.31 MHz signals. These signals are again multiplied by four to obtain four 9333.24 MHz signals which are then combined by power combiners to obtain the final transmitter output signal.

(3) A duplexer/monitor
The transmitter output is coupled through a duplexer/monitor to the wave guide antenna feed through a 4-port circulator. Incorporated in the duplexer operation are monitor circuits to monitor the output power level and to develop a frequency loop error signal for the correction of frequency chirp. The monitor circuit also accepts a test signal which causes a portion of the reference signal to be injected to the receiver for test and calibration. The 4-port circulator also couples the RF return from the wave guide antenna feed through a limiter to the receiver portion of the transceiver. The wave guide limiter protects the mixer diodes from all high power pulses while passing all low power inputs to the mixer.

(4) A mixer
The mixer circuit processes the detected RF return signal by mixing it with the first local oscillator signal and amplifying the resultant intermediate frequency signal. The first amplifier provides 25 dB amplification before the first intermediate frequency signal is applied to the second IF amplifier.

(5) A second IF amplifier
The second IF amplifier completes the receiver amplification of the RF return signal. The output from the first IF is converted to the 13.8888 MHz second IF signal by mixing it with the 152.776 MHz second local oscillator signal. The second IF signal is then buffered and applied to a synchronous detector. The third local oscillator signal is phase-split to obtain one signal in phase with the transmitter frequency and one signal phase shifted by 90°.

(6) An azimuth filter
The azimuth filter filters the range samples over multiple Pulse Repetition Frequency (PRF) samples and averages the returns for each range. Reflectivity data is extracted from the detected returns and filtered. A single presence detector establishes the minimum reflectivity level (Z. Level) to be displayed. Ground clutter processing circuits determine whether the returns are from precipitation or from ground clutter.

(7) A central processing unit
Control and internal functions, monitoring of system operation and formatting the processed data is accomplished by the central processing unit. It utilizes a microprocessor and a stored program to execute the following major routines that control the transceiver and system operations:

attitude routine, providing pitch and roll parameters for the stabilization routine.
stabilization routine, providing elevation position to the elevation maintenance routine.
scan maintenance routine, providing antenna scan drive.
elevation maintenance routine, providing antenna elevation drive.
control bus manager routine, determining correct control configuration.
problem control monitor routine, programming the internal data collection parameters of the transceiver.
data bus formatter routine, processing and assembling the control message of the serial data word sent to the EFIS.

(8) An input/output unit
All interface junctions from the microprocessor of the control processing unit and the remainder of the transceiver and other units within the system are provided by the input/output circuitry. Control word buses, digital and analog attitude buses and discrete buses are all connected to the multiplexer and shift register circuits of the input/output unit.

(9) A turbulence processor
The turbulence processor uses the doppler effect for the detection of air turbulences.
All detectable precipitation targets consist of water droplets of various sizes, moving in various directions at various velocities. Because of the doppler effect, the return signals appear as a spectrum of frequencies with varying amplitudes. The variance from the mean spectrum frequency would be an indication for turbulences associated with precipitation.
In order for the turbulence processor to determine turbulence, there must be some water droplet movement parallel to the axis of the antenna beam. The detection is not based on the absolute particle velocity but, on the contrary, it is based on the statistical variance in particle velocities. During normal precipitation modes, only the different amplitudes and ranges contained in a precipitation frequency spectrum are processed.
During turbulence modes, the doppler frequency of the returns and the spectrum width is measured and processed. If the spectrum width exceeds a threshold level of 5 m/s, the signals are identified as returns from precipitation areas with associated turbulence.

B. Weather Radar Antenna

Weather Radar - Antenna ** ON A/C NOT FOR ALL

The weather radar antenna is controlled in azimuth and elevation by the transceiver. The antenna movements are ensured by 2 DC motors and the angular positions are recopied by LEDs and light sensitive transistors used to monitor the movement. The RF signal (transmitted or received) is conveyed by a wave guide between the antenna and the transceiver.
Energization of the antenna is 115VAC 400Hz through the selected transceiver.

C. Weather Radar Control Unit
The gain and tilt potentiometric data are digitized by an 8-bit analog-to-digital converter.
Moreover the different positions of the mode selector switch and the potentiometric data are formatted according to the ARINC 429 control word.

NOTE: Energization of the control unit is through the weather radar transceiver.

D. Weather Radar

(1) Wave Guide.
A wave guide assembly ensures the RF connection between the WR antenna drive and the WR transceiver mounting tray.
The wave guide assembly is made up of rigid and flexible parts which have a standard rectangular section (1 in. x 0.5 in.).

E. Data Word and Control Word Definition
This table contains all the output parameters in the digital form.
They are sorted as per the numerical order of their output label.
The following table gives :

EQ.SYS.LAB.SDI: (SDAC, FWC, DMC...) output label for which the parameter is available
PARAMETER DEFINITION: parameter name
WORD RANGE OPER RANGE RESOLUTION ACCURACY: measurement range. Maximum value transmitted. When the digital value changes, the change step is equal to the accuracy
UNIT: unit in which the digital value is transmitted
SIG BIT: indicates whether a sign bit is available
BITS: number of bits used by the parameter in the label
XMSN/INTV: output transmission interval. The refresh rate is given in milliseconds
CODE :
BNR: binary data word
BCD: binary coded decimal data word
ISO: data word coded in ISO5 code
DIS: discrete data word
HEX: hexadecimal coded
HYB: mixed code
ALPHA CODE: indicates the parameter mnemonic code
SOURCE ORIGIN: parameter source computer or system.

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| PARAMETER LIST PARAMETER CHARACTERISTICS (NUMERIC) |

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! 1.270.01 !CONTROL ! ! ! ! 19 !100 !DIS ! ! !

! !WORD 1 ! ! ! ! ! ! ! ! !

! 2.270.10 ! ! ! ! ! ! ! ! ! !

!--------------!----------!------------!----!----!----!----!----!-----!-------!

! 1.271.01 !CONTROL ! ! ! ! 7 !100 !DIS ! ! !

! !WORD 2 ! ! ! ! ! ! ! ! !

! 2.271.10 ! ! ! ! ! ! ! ! ! !

!--------------!----------!------------!----!----!----!----!----!-----!-------!

! 1.055.01 !WXR DATA ! ! ! !1549!7.82!DIS ! ! !

! 2.055.10 ! ! ! ! ! ! ! ! ! !

!--------------!----------!------------!----!----!----!----!----!-----!-------!

! 1.356.01 !Mainte- ! ! ! ! !100 !ISO5! ! !

! !nance ! ! ! ! ! ! ! ! !

! !message ! ! ! ! ! ! ! ! !

! !word ! ! ! ! ! ! ! ! !

! 2.356.10 ! ! ! ! ! ! ! ! ! !

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F. Data Word and Control Word Definition

(1) Control word
The control words comply with ARINC specification 429.

(a) The signal transmitted on the control bus line connecting the radar control unit to the transceiver complies with the format of control word 1 as defined by ARINC specification 708 (appendix 15.1) and compatible with ARINC specification 429.

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!CONTROL ! P !MATRIX !GAIN !TILT !MODE !STAB !IDNT !SCAN !SDI !CONTROL WORD 1 !

! WORD 1 ! ! ! ! ! ! ! ! ! ! LABEL (270-A8)!

!--------!---!-------!-----!-----!-----!-----!-----!-----!----!---------------!

!BIT No. ! 3 ! 3 3 ! 2-2 ! 2-1 !1 1 1! 1 ! 1 ! 1 ! 1 ! !

! ! 2 ! 1 0 ! 9-4 ! 3-7 !6 5 4! 3 ! 2 ! 1 ! 0 9! 8----------1 !

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(b) Among the signals transmitted on the bus line from the EFIS control section of the FCU, the radar transceiver uses the range data contained in control word 2 as defined in ARINC specification 708 (Appendix 15.1) and compatible with ARINC specification 429.

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! CONTROL ! P ! MATRIX ! RANGE ! PROVI-! ANTI- ! PROVI-! RESER-! CONTROL WORD !

! WORD 2 ! ! ! ! SIONS !CLUTTER! SION ! VED ! 2 LABEL !

! ! ! ! ! ! ! ! SDI ! (271.A8) !

!---------!---!--------!-------!-------!-------!-------!-------!--------------!

! BIT ! 3 ! 3 3 ! 2---2 ! 2 1 ! 1 ! 1 ! 1 ! !

! No. ! 2 ! 1 0 ! 9---4 ! 3 3 ! 2 ! 1 ! 0 9 ! 8 -------- 1 !

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NOTE: Control word 1
SDI : reserved (Bits 9 and 10 frozen at 00)
SCAN : reserved (Bit 11 frozen at 0)
STAB : antenna stabilization (Bit 13 frozen at 1)
IDNT : clutter suppression (Bit 12 frozen at 0)

NOTE: Control word 2
The matrix (30-31) must be positioned as follows:

31 30

- 0 / 0 when the radar image is selected on the EFIS

control section of the FCU

- 1 / 1 when the radar image is not selected on the EFIS

control section of the FCU.

NOTE: The greatest interval between two word transmissions is 100 ms.

(2) Data word
The signal transmitted on the data bus line which connects the transceiver to the DMCs complies with data word format as defined by ARINC specification 708 (Appendix 15.2) and compatible with ARINC specification 453.

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! DATA ! SYNCHRO ! RANGE ! ! RANGE ! SPARE ! SCAN ! DATA !

! WORD ! WORD END ! BIN 511 ! ! BIN 0 ! ! ANGLE ! ACCEPT !

!---------!----------!----------!-----!---------!---------!---------!---------!

! ! ! 111 ! ! ! ! ! !

! Bit ! ! 655 ! ! ! ! ! !

! No. ! ! 099 ! --- ! 666 ! 6 ! 6-----5 ! 55 !

! ! ! 098 ! ! 765 ! 4 ! 3-----2 ! 10 !

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!--------------------DATA--------------------- !

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! SPARE! RANGE! GAIN! TILT! MODE! STAB! FAULTS!A B C D E! F! G! H! DATA! SYN- !

! ! ! ! ! ! ! ! ! ! ! ! WORD! CHRO !

! ! ! ! ! ! ! ! ! ! ! !LABEL! WORD !

! ! ! ! ! ! ! ! ! ! ! !(055)! STAR !

! ! ! ! ! ! ! ! ! ! ! ! ! TING !

!------!------!-----!-----!-----!-----!-------!---------!--!--!--!-----!------!

! 4 ! 4--4 ! 4--3! 3--3! 2--2! 2 ! 2--21 !1 1 1 1 1!11!1 !1 ! ! !

! 9 ! 8 3 ! 2--7! 6--0! 9--7! 6 ! 5--09 !8 7 6 5 4!32!1 !09! 8--1! !

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!--------------------------CONTROL-------------------------------!

A = Stab Sat
B = Sector
C = Idnt
D = Precip. Alert
E = Turb. Alert
F = Spare
G = Slave
H = Control Accept

NOTE: Data word message includes mainly rho and o data, which gives the position of the various echoes detected in range and azimuth.
RANGE BIN : definition of one point of radar echo in conjunction with color matrix.
DATA ACCEPT : data distribution matrix on indicators
STAB SAT : stabilization limit.
SECTOR : scan angle reduced to plus or minus 45 deg. (Not used).
IDNT : clutter suppression
PRECIP ALERT : bad weather warning (Not used).
TURB ALERT : turbulence warning
CONTROL ACCEPT : control data distribution matrix.

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6. Operation

A. Basic Principles
The weather radar system uses the principle of radio echoing. The weather radar transceiver generates microwave energy in the form of electromagnetic pulses. The energy is conveyed in space by a very high frequency wave (X band). When this wave intercepts an appropriate target, part of the energy is reflected back to the weather radar antenna then to the transceiver. The electronics circuits of the transceiver measure the elapsed time between the transmission of the wave and the reception of the echo to determine the target distance (it takes 12.36 microseconds for the electromagnetic wave to travel out and back for each nautical mile of target range).
The angular position of the target is detected by the angular position of the antenna in its scanning in azimuth. As the quantity of energy reflected to the antenna is proportional to the target density, the different levels of atmospheric disturbances are shown on the displays by different colors.
The detection of the turbulence areas is based on the Doppler effect applied to the movement of precipitation drops detected in clouds. Only movements parallel to the aircraft centerline are detected.

B. Control and Indicating
The various system controls are grouped on the weather radar control unit and EFIS control sections of the FCU.
Radar image control on the NDs is achieved through the scale selector switches located on Captain and First Officer EFIS control sections of the FCU.

C. Control and Indicating - Weather Radar Control Unit

Weather Radar Control Unit ** ON A/C NOT FOR ALL

D. Control and Indicating - Weather Radar Control Unit
The face of the radar control unit includes the following controls:
The face of the radar control unit includes the following controls:

(1) A MODE selector switch, item 2, which enables selection of WX, WX+T, TURB or MAP function.

(2) A TILT selector switch, item 3, for controlling antenna elevation.
Antenna position is read in degrees, opposite the notch on the switch:

Either from 0 to 15 degrees upwards (UP), or
From 0 to 15 degrees downwards (DN).

(3) A GAIN potentiometer, item 4, for manually adjusting transceiver gain.

(4) A GND CLTR SPRS switch, item 5, for the selection of ground clutter suppression.
This switch is a momentary ON toggle switch.

(5) A MODE selector switch, item 2, which enables selection of WX, WX+T, TURB or MAP function.

(6) A TILT selector switch, item 3, for controlling antenna elevation.
Antenna position is read in degrees, opposite the notch on the switch:

Either from 0 to 15 degrees upwards (UP), or
From 0 to 15 degrees downwards (DN).

(7) A GAIN potentiometer, item 4, for manually adjusting transceiver gain.

(8) A GND CLTR SPRS switch, item 5, for the selection of ground clutter suppression.

(9) A switch (item 1)
with two stable positions SYS ON/OFF which enables activation of the weather radar transceiver.

(10) INTEG LT/MAIN PNL & PED
The face of the control unit is provided with integral lighting. The INTEG LT/MAIN PNL & PED potentiometer enables lighting adjustment. The potentiometer is located on panel 111VU, at the left aft section of the center pedestal 11VU.

E. Control and Indicating - EFIS Control Section (on the FCU)

EFIS Control Sections - Lighting/Loud Speaker Control Panels ** ON A/C NOT FOR ALL

Only the controls related to the selection and use of the radar image on the NDs are described.

(1) A navigation display mode selector switch, item 1, made up of a rotary switch enabling the selection of ROSE or ARC function for display of a weather radar image on the CAPT and F/O NDs.

(2) A scale selector switch, item 2, common to EFIS, FMGS and radar systems, which enables the selection of 10, 20, 40, 80, 160 or 320 operation range in nautical miles (NM) for display of the weather radar image on the CAPT and F/O NDs.

NOTE: In the event of one FMGC fault, there is an automatic transfer of the weather radar image from one ND to the other one. Only one scale selector switch can then control the weather radar image display.

F. Control and Indicating - Lighting/Loud Speaker Control Panels

EFIS Control Sections - Lighting/Loud Speaker Control Panels ** ON A/C NOT FOR ALL

CAPT and F/O lighting/loud speaker control panels 301VU and 500VU which are connected to CAPT and F/O NDs, include ND concentric potentiometers for adjusting the brightness of the image displayed on the NDs. The outer knob of each potentiometer controls the brightness of the radar image only, item 3.

G. Utilization of Controls and Indicating

(1) Operation of radar areas

Weather Radar - Radar Precaution Areas ** ON A/C NOT FOR ALL

Special precautions to be taken.
On ground, on the weather radar control unit, before moving WX, TURB, WX+T or MAP control switch from OFF to 1 or 2 position (in dual configuration) and selecting a DISPLAY mode different than OFF, make sure that within an arc of +/- 135° on either side of the aircraft centerline, there is:

No one and no large metallic obstacle (such as a hangar) within a distance lower than 5 m from the antenna in movement
No fuel within a distance less than 1.5 m from the antenna in movement.

During maintenance phase, when system test is launched, no one and no obstacle should stand within the radome.

(2) Transceiver energization

NOTE: No pre-heating time is necessary for the weather radar transceiver.

AC busbar 101XP-C is supplied
XCVR1 circuit breaker is closed
on the radar control unit:
select WX, TURB, WX+T or MAP mode (when the aircraft is parked, TEST mode selected on the MCDU should preferably be selected as a safety precaution) and move SYS switch from OFF position to ON.
on either EFIS control section of the FCU, set the mode selector switch to ARC or ROSE to obtain image display on the corresponding ND and to activate the transceiver selected.

NOTE: The radar transceiver is de-energized:

by placing the mode selector switches on both EFIS control sections in any position other than ROSE or ARC
or by placing the SYS switch on the radar control unit in OFF position, with the mode selector switches on the EFIS control sections in ARC or ROSE position.

(3) Weather radar control unit utilization

Weather Radar Control Unit ** ON A/C NOT FOR ALL

(4) Weather radar control unit utilization - Mode selection (item 2)
The modes are selected by placing the notch provided in mode selector switch in front of the engraving of the function selected.

WX
This mode corresponds to normal operation in weather detection.
The radar images are displayed on the NDs in four colors (black, green, yellow, red); their intensity corresponds to the strength of the return signal.
TURB
This mode corresponds to operation in turbulence detection. Turbulence detection is limited to the first 50 NM regardless of the weather radar range selected and displayed.
Turbulence areas are displayed on the NDs in magenta.
WX+T
This mode corresponds to operation in weather and turbulence detections.
All turbulent/non turbulent areas beyond 50 NM are displayed in the conventional black, green, yellow and red as in weather (WX) mode.
MAP
This mode is only used for display of the ground map. A combination of transceiver gain, antenna position (TILT) and a range selection enables the display of a larger area.
If the image is too bright, due to too great a reflection intensity, it can be dimmed by the GAIN potentiometer, item 4.

(5) Weather radar control unit utilization - System selection and start up
The SYS ON/OFF switch, item 1, enables:

the activation of the transceiver
the suppression of the radar image on the NDs when these NDs are in ARC or ROSE mode.

(6) Weather radar control unit utilization - Gain control
The GAIN potentiometer, item 4, is used to adjust the sensitivity of the receiver in WX, WX+T, TURB and MAP modes.
The CAL gain position provides minimum gain setting and corresponds to the normal gain for operation. In this case, the radar system is aligned to give an accurate representation of rain levels corresponding to the real weather situation.
The manual use of the GAIN potentiometer mainly allows to see as many precipitations as possible and in particular to view very light rain.
In MAX position, the receiver sensitivity, the transmitter pulse width and the antenna beam width are increased. MAX gain is used for the same reasons as manual use and also to better display the leading edges of cells and to view patterns and characteristics of these cells.
Therefore the GAIN potentiometer must be in the CAL position to determine the actual calibrated precipitation rate before taking an avoidance decision.

(7) Weather radar control unit utilization - TILT control
The TILT selector switch, item 3, enables variation of the antenna elevation angle in 1/4 deg. steps on a non-linear scale graduated in degrees, within a range of +15 deg. (UP) to -15 deg. (DOWN) in relation to a horizontal plane defined by the stabilization system. The tolerence between the values selected by means of the TILT selector switch in the antenna actual angle is + or -0.5 deg.
This antenna elevation angle is displayed in cyan in the R lower corner of the ND and progresses in steps of 0.25 degrees.
Should the antenna position be different from the TILT selector switch position, an amber ANT (antenna) flag replaces the TILT indication in the R lower corner of the ND.

(8) Weather radar control unit utilization - GCS system
Activation of the ground clutter suppression switch, item 5, in the WX mode reduces the intensity of the ground clutter.

(9) Utilization of EFIS control sections and lighting/loud speaker control panels

EFIS Control Sections - Lighting/Loud Speaker Control Panels ** ON A/C NOT FOR ALL

(a) Mode selector switch, item 1
It enables image display on the corresponding ND whenever ARC or ROSE mode is selected and the transceiver is supplied. In that case, the radar image is displayed in the background of the navigation image.

(b) Scale selector switch, item 2
This selector switch enables display of the range selected for an optimum use of the radar image on the corresponding ND. For each of the following ranges: 10, 20, 40, 80,160 and 320 four concentric range arcs are displayed respectively spaced 2.5, 5, 10, 20, 40 and 80 NM, when the mode selector switch is in ARC mode. Only two range arcs are displayed in ROSE mode.

(c) Radar image brightness control, item 3
The ND potentiometer enables adjustment of brightness and contrast of radar echoes in relation to the navigation image, which is superimposed.
However, the adjustment range does not allow total extinction of the image. Potentiometer OFF position corresponds to minimum brightness. BRT position corresponds to maximum brightness.

NOTE: A photoelectric cell associated with each ND also adjusts image brightness as a function of ambient light variations.

(10) Utilization of the data displayed on the NDs

Weather Radar - Data Displayed on the NDs ** ON A/C NOT FOR ALL

An example of the radar image display on the NDs is shown in the following figure. Images a) and b) correspond respectively to ARC and ROSE ND modes for which radar image display is possible.
Various messages informing the crew of the tilt angle selected and gain selected on the radar control unit and of the faults which affect radar system operation are displayed in the R lower corner of each ND whenever a radar image is selected.

NOTE: Tilt information and gain selection are displayed on the ND when no flag is generated, or when the TEST mode is not selected.

The various faults which may affect the radar image are listed in descending order of importance.
If several faults occur, only the most important one is displayed (parts c and d).
Two types of faults are likely to affect the radar system:

(a) Faults which result in a loss of radar image
The corresponding messages are displayed in red

WR indicates a radar transceiver fault
T-R
WR indicates a radar antenna fault
ANT
WR indicates a radar control unit fault
CTL
WR indicates a range error
RNG

(b) Faults which do not affect the radar image
The corresponding messages are displayed in amber

WR indicates loss of transceiver calibration
WEAK
WR indicates an attitude fault from the ADIRU
ATT
WR indicates a loss of radar antenna stabilization
STAB
WR indicates that radar TEST mode is selected
TEST

NOTE: In case of ventilation failure or when the BLOWER and EXTRACT pushbutton switches are both released, the colored backgrounds of the weather radar image disappear.

** ON A/C NOT FOR ALL

7. Test

A. Maintenance Test

Weather Radar - Test Pattern on the ND ** ON A/C NOT FOR ALL

The TEST mode becomes active when it is selected through the CFDS via MCDU 1 or 2.
It enables an operational check of the main circuits which constitute the system.
The transmission/reception channel is tested for less than one second, then a special test pattern is displayed on the NDs as long as TEST mode is active.
Moreover the elevation and azimuth control circuits of the antenna drive are excited during the test period. The complete test period lasts 15 seconds approximately.
When the TEST mode is activated:

Weather Radar - Antenna Test Sequence ** ON A/C NOT FOR ALL

The antenna carries out an elevation scanning sequence from up to down positions (+ 15 deg., - 15 deg.) then an azimuth scanning sequence from right to left, then stabilizes at 0°, perpendicular to the aircraft centerline.
It should be noted that:

the special test pattern, with TEST indication displayed in the R lower corner of the NDs, can only be displayed if no fault is detected
the antenna no longer responds to the stabilization signals from the ADIRU when the TEST mode is active. At the first ground supply, the antenna test sequence is performed independently of the TEST mode selection and SYS switch. The test image is not displayed on the ND. This antenna test sequence is the same as the Bite test sequence.

B. Maintenance Indicators on Transceiver and Antenna Drive

(1) Transceiver

Weather Radar Transceiver - Component Description ** ON A/C NOT FOR ALL

The weather radar transceiver is installed on its mounting tray in the forward avionics compartment. On the transceiver face are:

a test receptacle making internal electrical signals available.
an hour meter totalizing the number of transceiver operating hours.
an overheat indicator connected to an internal sensor which indicates when transceiver temperature is above the recommended operating threshold.
a reset pushbutton switch which ensures switching of the indicator when transceiver overheating has been detected.

(2) Antenna drive

Weather Radar - Antenna ** ON A/C NOT FOR ALL

One SCAN switch and one ELEVATION switch are installed under a removable cover on the part of antenna pedestal which connects to both axis drivers of antenna flat plate.

NOTE: When the cover is installed, the switches are automatically placed in ON position.

C. BITE Function

(1) General
The purpose of the Built-In-Test Equipment (BITE) is to ease the line maintenance of the aircraft and thus to detect anomalies and faults of the various items of equipment associated to each system.
The BITE of the weather radar transceiver installed on the aircraft is an extension of the BITE already incorporated in the basic transceiver and of which one part of the detected faults is already shown on the transceiver face.
For this purpose, a maintenance processor has been added to fulfil the functions of interface and control with the CFDS.
The weather radar system is completely monitored and the various detected faults are reported and stored in two zones associated with the flight and ground phases.
The BITE of the weather radar transceiver dialogues with the CFDS to present the detected faults and to activate the test sequences of the transceiver, in normal mode and in menu mode respectively.
In normal mode, the fault memory is organized to store 64 flight legs.
A fault code is stored only once per flight leg. If an intermittent fault occurs, only 4 events max. are stored.
In menu mode on the ground, only the faults of 3 LRUs and 72 fault codes can be detected and stored.

NOTE: The manual test of the system can be activated only on the ground and in menu mode.

REMARK : The BITE operation and the operational utilization of the

MCDU linked to the CFDS is dealt with in the CFDS (Ref. 31-32).

(2) Functional description
Operation of the BITE system is through the two MCDUs installed on the center pedestal.

(a) Operation in normal mode
Upon energization, the weather radar transceiver permanently transmits the maintenance data. Two types of data are transmitted on the label 356 : NO FAULT or DETECTED FAILURE ; in addition the equipment identification ID (008) is transmitted on the label 377.
The normal mode is transmitted in flight as well as on the ground, except when the menu mode is selected on the ground.

The NO FAULT data is transmitted on the label 356 every 100 ms approx. if no fault is detected.

The faults detected during the flight phase are transmitted on the label 356 every 250 ms approx. ; each fault word contains the ATA reference plus the text of the fault.

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! LRU ! ATA !

!-------------------------------------!------------------!

! TRANSCEIVER ! 34-41-33 !

! CONTROL UNIT ! 34-41-12 !

! ANTENNA ! 34-41-11 !

! NO DATA FROM ADIRU ! 34-14-00 !

! NO DATA FROM EFIS 1 PANEL ! 22-81-12 !

! NO DATA FROM EFIS 2 PANEL ! 22-81-12 !

! NO DATA FROM CFDIU ! 31-32-34 !

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NOTE: In a single radar installation, the system self-test is activated when you switch the SYS switch from OFF position to ON on the weather radar control unit.

(b) Operation in menu mode

Maintenance Test Procedure ** ON A/C NOT FOR ALL

Weather Radar - Maintenance Test Procedure ** ON A/C NOT FOR ALL

Reminder : the menu mode can be used on the ground only.
The weather radar is so designed that it ignores any request for the menu mode during the flight phases.
The control words of the CFDS are received with the label 227 and the menu words are sent with the label 356.
In the case of a dual installation, the menu mode can be activated either on the operating equipment or on the standby equipment.
The different selections provided by the menu mode are: (Menu No. 1)

LAST LEG REPORT (Menus No. 2 and 3)
This menu page is transmitted with the ATA chapter reference, text, date and GMT relative to the detected faults.
PREVIOUS LEGS REPORT (Menu No. 5)
This menu page is transmitted with the ATA chapter reference, text, date, GMT and the flight leg count relative to the faults detected before the last flight.
LRU IDENTIFICATION (Menu No. 6)
Only the P/N of the weather radar transceiver is transmitted.
TEST (Menus No. 7, 8 and 9)
Selection of the TEST page and activation of this mode cause the system self-test, the transmission and the presentation of the TEST result on the MCDU.

NOTE: As soon as the TEST function is selected on the Menu page, the SYSTEM OFF. CHANGE CONTROL PANEL SYSTEM SWITCH TO ON. AFTER TEST SWITCH SYSTEM TO OFF information is shown on the MCDU until test is completed.
The TEST can be achieved on the operating equipment as well as on the standby equipment.

The test is stopped

By action on the RETURN key on the MCDU

After 3 mn display if no action is made on the displayed page.

D. Power-up Tests Initialization and Cockpit Repercussions

(1) Conditions of power-up tests initialization

How long the computer must be de-energized: 1 s.
A/C configuration:
- whatever the A/C configuration on ground.

(2) Progress of power-up tests

Duration: 15 s minimum and 30 s maximum
Cockpit repercussions directly linked to power-up test accomplishment (some other repercussions may occur depending on the A/C configuration but these can be disregarded):
- none

NOTE: The antenna moves up and down ( + 10 deg., - 10 deg.)
then turns in azimuth from left to right.

(3) Results of power-up tests
(cockpit repercussions, if any, in case of tests pass/tests failed).

Tests pass:
- ND:
weather radar display available
Tests failed:
* ND right bottom part:
WR TR in red in case of WR transceiver fault
WR ANT in red in case WR antenna fault
WR CTL ind red in case of control unit fault
WR RNG in red in case of range fault
In case of multiple faults only the fault with the highest priority is displayed
ILS 1 (2) and LOC and GLIDE scales in red.

NOTE: The radar display is not available when the PLAN mode is selected on the EFIS control section of the FCU.

[Rev.10 from 2021] 2026.04.02 06:23:20 UTC