DOC AIRBUS | AMM A320FRADIO ALTIMETER - DESCRIPTION AND OPERATION
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1. General
The function of the radio altimeter (RA) is to determine the height of the aircraft above the terrain.
One of the main characteristics of the system is that it locks onto the leading edge of the reflected wave. This permits to measure the distance between the aircraft and the nearest obstacle. The radio altimeter can therefore operate over non-flat ground surface.
The LRA-700 provides vertical distance to the terrain via the ARINC 429 bus outputs. The RA transmit a FM/CW (Frequency Modulated Continuous Wave) RF signal to the terrain, via the transmit antenna, and receives the reflection of that signal via the receive antenna. It independently computes an altitude by measuring and processing the characteristics of the transmitted and received RF signal.
The LRA-900 Provides vertical distance to the terrain via the ARINC 429 bus outputs. The RA transmit a FM/CW (Frequency Modulated Continuous Wave) RF signal to the terrain, via the transmit antenna, and receives the reflection of that signal via the receive antenna. It independently computes an altitude by measuring and processing the characteristics of the transmitted and received RF signal.
** ON A/C NOT FOR ALL The function of the radio altimeter (RA) is to determine the height of the aircraft above the terrain.
One of the main characteristics of the system is that it locks onto the leading edge of the reflected wave. This permits to measure the distance between the aircraft and the nearest obstacle. The radio altimeter can therefore operate over non-flat ground surface.
The LRA-700 provides vertical distance to the terrain via the ARINC 429 bus outputs. The RA transmit a FM/CW (Frequency Modulated Continuous Wave) RF signal to the terrain, via the transmit antenna, and receives the reflection of that signal via the receive antenna. It independently computes an altitude by measuring and processing the characteristics of the transmitted and received RF signal.
The LRA-900 Provides vertical distance to the terrain via the ARINC 429 bus outputs. The RA transmit a FM/CW (Frequency Modulated Continuous Wave) RF signal to the terrain, via the transmit antenna, and receives the reflection of that signal via the receive antenna. It independently computes an altitude by measuring and processing the characteristics of the transmitted and received RF signal.
2. Component Location
Radio Altimeter - Component Location ** ON A/C NOT FOR ALL
Radio Altimeter - Component Location ** ON A/C NOT FOR ALL
Radio Altimeter - Component Location ** ON A/C NOT FOR ALL
Radio Altimeter - Component Location ** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL Radio Altimeter - Component Location ** ON A/C NOT FOR ALL Radio Altimeter - Component Location ** ON A/C NOT FOR ALL Radio Altimeter - Component Location ** ON A/C NOT FOR ALL Radio Altimeter - Component Location ** ON A/C NOT FOR ALL | FIN | FUNCTIONAL DESIGNATION | PANEL | ZONE | ACCESS DOOR | ATA REF |
|---|---|---|---|---|---|
| ** ON A/C ALL | |||||
| 2SA1 | XCVR-RA, 1 | 152 | 34-42-33 | ||
| 2SA2 | XCVR-RA, 2 | 152 | 34-42-33 | ||
| 3SA1 | FAN-RA XCVR1 | 2005VU | 152 | 34-42-45 | |
| 3SA2 | FAN-RA XCVR2 | 2005VU | 152 | 34-42-45 | |
| 5SA1 | ANTENNA-RA RCPTN, 1 | 150 | 34-42-11 | ||
| 5SA2 | ANTENNA-RA RCPTN, 2 | 150 | 34-42-11 | ||
| 6SA1 | ANTENNA-RA XMSN, 1 | 150 | 34-42-11 | ||
| 6SA2 | ANTENNA-RA XMSN, 2 | 150 | 34-42-11 | ||
3. System Description
A. Principle
The principle of the radio altimeter is to :
The principle of the radio altimeter is to :
the height of the aircraft is calculated by determining the difference between the frequency of the reflected signal and the signal being transmitted at the instant the reflected signal is received. This difference frequency is directly proportional to the time required for the reflected signal to traverse the distance from the aircraft to the ground and back to the aircraft.The difference frequency is measured and converted to distance by a microprocessor in the altitude processor which also transmits the measured distance to user equipment over the ARINC 429 bus.
The reflected signal is fed from a dedicated receive antenna to the receiver where it is mixed with a portion of the transmitted signal now being radiated at the transmit antenna to develop a beat frequency (Fb).
The beat frequency is processed by the IF system and is sent to the altitude and monitor processors.
Two independent samples of transmitted RF are fed to two reference signal generators. Each generator produces an output (Fr) corresponding to the delay time that represents a 300-foot altitude. Fr1 is the reference signal for the altitude processor, Fr2 is the reference signal for the monitor processor.
The altitude processor samples the beat frequency input signal (Fb) and the reference frequency signal (Fr1) and converts each to digital form. The ratio of the measured frequency input signal (Fb) to the output of the 300-foot reference channel is calculated and multiplied by 300 to produce the total radio altitude. The total radio altitude is further modified by the AID and internal box delays to produce the actual aircraft altitude above terrain.
The principle of the radio altimeter is to :
- transmit a frequency modulated signal from the aircraft to the ground
- receive the ground reflected signal after a certain delay.
The principle of the radio altimeter is to :
- transmit a frequency modulated signal from the aircraft to the ground
- receive the ground reflected signal after a certain delay.
the height of the aircraft is calculated by determining the difference between the frequency of the reflected signal and the signal being transmitted at the instant the reflected signal is received. This difference frequency is directly proportional to the time required for the reflected signal to traverse the distance from the aircraft to the ground and back to the aircraft.The difference frequency is measured and converted to distance by a microprocessor in the altitude processor which also transmits the measured distance to user equipment over the ARINC 429 bus.
The reflected signal is fed from a dedicated receive antenna to the receiver where it is mixed with a portion of the transmitted signal now being radiated at the transmit antenna to develop a beat frequency (Fb).
The beat frequency is processed by the IF system and is sent to the altitude and monitor processors.
Two independent samples of transmitted RF are fed to two reference signal generators. Each generator produces an output (Fr) corresponding to the delay time that represents a 300-foot altitude. Fr1 is the reference signal for the altitude processor, Fr2 is the reference signal for the monitor processor.
The altitude processor samples the beat frequency input signal (Fb) and the reference frequency signal (Fr1) and converts each to digital form. The ratio of the measured frequency input signal (Fb) to the output of the 300-foot reference channel is calculated and multiplied by 300 to produce the total radio altitude. The total radio altitude is further modified by the AID and internal box delays to produce the actual aircraft altitude above terrain.
B. System Architecture
Radio Altimeter - Block Diagram ** ON A/C NOT FOR ALL
Radio Altimeter - Block Diagram ** ON A/C NOT FOR ALL
The radio altimeter comprises two independent systems. Each system consists of :
The radio height data is shown on the Primary Flight Display (PFD). In normal operation, system 1 provides information to the CAPT PFD and system 2 to the F/O PFD.
Radio Altimeter - Block Diagram ** ON A/C NOT FOR ALL
Radio Altimeter - Block Diagram ** ON A/C NOT FOR ALL
Radio Altimeter - Block Diagram ** ON A/C NOT FOR ALL
The radio altimeter comprises two independent systems. Each system consists of :
The radio height data is shown on the Primary Flight Display (PFD). In normal operation, system 1 provides information to the CAPT PFD and system 2 to the F/O PFD.
Radio Altimeter - Block Diagram ** ON A/C NOT FOR ALL Radio Altimeter - Block Diagram ** ON A/C NOT FOR ALL - one transceiver 2SA1 (2SA2)
- one transmission antenna 6SA1 (6SA2)
- one reception antenna 5SA1 (5SA2)
- one fan 3SA1 (3SA2).
The radio height data is shown on the Primary Flight Display (PFD). In normal operation, system 1 provides information to the CAPT PFD and system 2 to the F/O PFD.
Radio Altimeter - Block Diagram ** ON A/C NOT FOR ALL Radio Altimeter - Block Diagram ** ON A/C NOT FOR ALL Radio Altimeter - Block Diagram ** ON A/C NOT FOR ALL - one transceiver 2SA1 (2SA2)
- one transmission antenna 6SA1 (6SA2)
- one reception antenna 5SA1 (5SA2)
- one fan 3SA1 (3SA2).
The radio height data is shown on the Primary Flight Display (PFD). In normal operation, system 1 provides information to the CAPT PFD and system 2 to the F/O PFD.
C. Utilization Technical Data
(1) Height data display (Item 3)
The aircraft height data with respect to the ground is shown in the sector 2 of the PFD. This indication is at the bottom of the attitude sphere, for height less than or equal to 2500 ft.
The dimension and color of the digits change in relation to the height (H) and decision height (DH) as follows :
With failure of both radio altimeters, a red RA warning message is shown in place of the radio height information (Item 4) in slats extented configuration only. The message flashes during 3 seconds then remains on.
When the aircraft is below 500 ft. height above the terrain : a red ribbon comes into view on the bottom of the altitude scale and moves up with this scale as the aircraft is in the descent phase (Item 2).
When the aircraft has touched down the ground : the top of this ribbon is at the middle of the altitude window.
With failure of both radio altimeters, the ribbon goes out of view.
Below 300 ft., the height is shown by the distance between the horizon line and the limit of the sector 2. The limit of the sector 2 moves up as the aircraft is in the descent phase.
The distance between these two lines is proportional to the ground height (sensitivity 5 ft./mm).
As it moves up, the limit line erases the graduations on the pitch scale.
With failure of both radio altimeters, this indication goes out of view.
The aircraft height data with respect to the ground is shown in the sector 2 of the PFD. This indication is at the bottom of the attitude sphere, for height less than or equal to 2500 ft.
The dimension and color of the digits change in relation to the height (H) and decision height (DH) as follows :
| H more than or equal to 400 ft. : 3 mm green digits |
| 400 ft. > H > DH + 100 ft. : 4 mm green digits |
| H < DH + 100 ft. : 4 mm amber digits. |
| The sensitivity of the digits is also a function of the height : |
| H > 50 ft. : 10 ft. increments |
| 50 ft > or = to H and H > or = to 5 ft : 5 ft. increments |
| H < 5 ft. : 1 ft. increments. |
With failure of both radio altimeters, a red RA warning message is shown in place of the radio height information (Item 4) in slats extented configuration only. The message flashes during 3 seconds then remains on.
When the aircraft is below 500 ft. height above the terrain : a red ribbon comes into view on the bottom of the altitude scale and moves up with this scale as the aircraft is in the descent phase (Item 2).
When the aircraft has touched down the ground : the top of this ribbon is at the middle of the altitude window.
With failure of both radio altimeters, the ribbon goes out of view.
Below 300 ft., the height is shown by the distance between the horizon line and the limit of the sector 2. The limit of the sector 2 moves up as the aircraft is in the descent phase.
The distance between these two lines is proportional to the ground height (sensitivity 5 ft./mm).
As it moves up, the limit line erases the graduations on the pitch scale.
With failure of both radio altimeters, this indication goes out of view.
(2) Decision height display (DH) (Item 1)
The pilot sets the DH on the MCDU. The DH data are shown on the R top corner of the PFD (3 mm high digits) as soon as the radio altimeter operates.
When the height is lower than the DH, a DH amber warning message comes into view at the bottom of the attitude sphere (Item 5).
The pilot sets the DH on the MCDU. The DH data are shown on the R top corner of the PFD (3 mm high digits) as soon as the radio altimeter operates.
When the height is lower than the DH, a DH amber warning message comes into view at the bottom of the attitude sphere (Item 5).
(3) Height data display (Item 3)
The aircraft height data with respect to the ground is shown in the sector 2 of the PFD. This indication is at the bottom of the attitude sphere, for height less than or equal to 2500 ft.
The dimension and color of the digits change in relation to the height (H) and decision height (DH) as follows :
With failure of both radio altimeters, a red RA warning message is shown in place of the radio height information (Item 4) in slats extended configuration only. The message flashes during 3 seconds then remains on.
When the aircraft is below 500 ft. height above the terrain : a red ribbon comes into view on the bottom of the altitude scale and moves up with this scale as the aircraft is in the descent phase (Item 2).
When the aircraft has touched down the ground : the top of this ribbon is at the middle of the altitude window.
With failure of both radio altimeters, the ribbon goes out of view.
Below 300 ft., the height is shown by the distance between the horizon line and the limit of the sector 2. The limit of the sector 2 moves up as the aircraft is in the descent phase.
The distance between these two lines is proportional to the ground height (sensitivity 5 ft./mm).
As it moves up, the limit line erases the graduations on the pitch scale.
With failure of both radio altimeters, this indication goes out of view.
The aircraft height data with respect to the ground is shown in the sector 2 of the PFD. This indication is at the bottom of the attitude sphere, for height less than or equal to 2500 ft.
The dimension and color of the digits change in relation to the height (H) and decision height (DH) as follows :
| H more than or equal to 400 ft. : 3 mm green digits |
| 400 ft. > H > DH + 100 ft. : 4 mm green digits |
| H < DH + 100 ft. : 4 mm amber digits. |
| The sensitivity of the digits is also a function of the height : |
| H > 50 ft. : 10 ft. increments |
| 50 ft > or = to H and H > or = to 5 ft : 5 ft. increments |
| H < 5 ft. : 1 ft. increments. |
With failure of both radio altimeters, a red RA warning message is shown in place of the radio height information (Item 4) in slats extended configuration only. The message flashes during 3 seconds then remains on.
When the aircraft is below 500 ft. height above the terrain : a red ribbon comes into view on the bottom of the altitude scale and moves up with this scale as the aircraft is in the descent phase (Item 2).
When the aircraft has touched down the ground : the top of this ribbon is at the middle of the altitude window.
With failure of both radio altimeters, the ribbon goes out of view.
Below 300 ft., the height is shown by the distance between the horizon line and the limit of the sector 2. The limit of the sector 2 moves up as the aircraft is in the descent phase.
The distance between these two lines is proportional to the ground height (sensitivity 5 ft./mm).
As it moves up, the limit line erases the graduations on the pitch scale.
With failure of both radio altimeters, this indication goes out of view.
(4) Decision height display (DH) (Item 1)
The pilot sets the DH on the MCDU. The DH data are shown on the R top corner of the PFD (3 mm high digits) as soon as the radio altimeter operates.
When the height is lower than the DH, a DH amber warning message comes into view at the bottom of the attitude sphere (Item 5).
The pilot sets the DH on the MCDU. The DH data are shown on the R top corner of the PFD (3 mm high digits) as soon as the radio altimeter operates.
When the height is lower than the DH, a DH amber warning message comes into view at the bottom of the attitude sphere (Item 5).
D. Warnings
The warnings related to the radio altimeter are :
The warnings related to the radio altimeter are :
- local warning on the instruments that use the radio altimeter data
- MASTER CAUT lights on the CAPT and F/O glareshield panels
- aural warning : single chime
- warning message shown on the upper ECAM display unit.
- local warning on the instruments that use the radio altimeter data
- MASTER CAUT lights on the CAPT and F/O glareshield panels
- aural warning : single chime
- warning message shown on the upper ECAM display unit.
4. Power Supply
Radio Altimeter - Block Diagram ** ON A/C NOT FOR ALL
Radio Altimeter - Block Diagram ** ON A/C NOT FOR ALL
Radio Altimeter - Block Diagram ** ON A/C NOT FOR ALL
Radio Altimeter - Block Diagram ** ON A/C NOT FOR ALL
Energization of each system is through 115VAC, 400 Hz normal buses :
** ON A/C NOT FOR ALL Radio Altimeter - Block Diagram ** ON A/C NOT FOR ALL Radio Altimeter - Block Diagram ** ON A/C NOT FOR ALL Radio Altimeter - Block Diagram ** ON A/C NOT FOR ALL Radio Altimeter - Block Diagram ** ON A/C NOT FOR ALL - 115VAC BUS1 101XP via circuit breaker 1SA1 for system 1
- 115VAC BUS2 202XP via circuit breaker 1SA2 for system 2.
5. Component Description
A. Transceiver FIN: 2-SA-1 FIN: 2-SA-2
(1) External description
The face of the transceiver is fitted with a handle, two attaching parts, a TEST pushbutton switch, a connector (TEST CONN) to connect test set for system test and four LEDs.
The name, color and function of the four LEDs are as follows:
The face of the transceiver is fitted with a handle, two attaching parts, a TEST pushbutton switch, a connector (TEST CONN) to connect test set for system test and four LEDs.
The name, color and function of the four LEDs are as follows:
- ANT FAIL (red) indicates a fault in the antenna circuit
- IND FAIL (red) indicates a fault in the indicating circuit
- LRU STATUS/PASS (green) indicates no fault during the self-test sequence
- LRU STATUS/FAIL (red) indicates that a fault is detected during the self-test sequence.
The back is equipped with one ARINC 600 electrical receptacle and a slot for the test connector.
(2) External description
The face of the receiver is fitted with a handle, two attaching parts, two momentary pushbutton switches and a front panel Liquid Crystal Display (LCD).
The LCD is used as a fault display and as an operator interface during certain modes. The front panel display also provides user interfaces for test and troubleshooting.
The front panel contains two momentary pushbutton switches for interfacing with the LCD pages.
The back is equipped with one ARINC 600 size one connector, which includes three plugs:
The face of the receiver is fitted with a handle, two attaching parts, two momentary pushbutton switches and a front panel Liquid Crystal Display (LCD).
The LCD is used as a fault display and as an operator interface during certain modes. The front panel display also provides user interfaces for test and troubleshooting.
The front panel contains two momentary pushbutton switches for interfacing with the LCD pages.
The back is equipped with one ARINC 600 size one connector, which includes three plugs:
- Top Plug (TP): connection with the reception antenna
- Middle Plug (MP): service interconnection and connection with the transmission antenna
- Bottom Plug (BP): connection with the power supply circuit.
(3) External description
The face of the transceiver is fitted with a handle, two attaching parts, a TEST pushbutton switch, a connector (TEST CONN) to connect test set for system test and three LEDs.
The name, color and function of the three LEDs are as follows:
The face of the transceiver is fitted with a handle, two attaching parts, a TEST pushbutton switch, a connector (TEST CONN) to connect test set for system test and three LEDs.
The name, color and function of the three LEDs are as follows:
- LRU STATUS: green indicates no fault detected during the self-test sequence and red indicates that a fault is detected during the self-test sequence
- XMIT ANT FAIL: red indicates a fault in the antenna circuit
- REC ANT FAIL: red indicates a fault in the antenna circuit.
The back is equipped with one ARINC 600 electrical receptacle and a slot for the test connector.
(a) Layout
The transceiver LRA-700 consists of a power supply, a modulator, an rf assembly and an instrumentation assembly (processor) along with the necessary interconnect functions.
The transceiver is a radio altimeter using a wideband frequency modulated continuous wave (FM/CW) technique to measure the distance between the aircraft and the terrain below.
The function of the modulator is to provide the transmitter with a 100 Hz triangular wave corrected for transmitter nonlinearities and also to maintain the transmitter deviation limits at 4250 MHz and 4350 MHz.
The modulator assembly also contains the high and low altitude if's, and two major closed loop circuits.
The first control loop controls the rate at which the transmitter output frequency changes.
The other major control loop defines and contains the transmitted frequency within the 4250 to 4350 MHz normal band of operation.
The rf assembly contains all of the 4300 MHz functions. It is comprised of the transmitter stripline, receiver stripline and discriminator assemblies.
The instrumentation assembly consists of the altitude processor, the monitor processor and the power supply.
The transceiver LRA-700 consists of a power supply, a modulator, an rf assembly and an instrumentation assembly (processor) along with the necessary interconnect functions.
The transceiver is a radio altimeter using a wideband frequency modulated continuous wave (FM/CW) technique to measure the distance between the aircraft and the terrain below.
The function of the modulator is to provide the transmitter with a 100 Hz triangular wave corrected for transmitter nonlinearities and also to maintain the transmitter deviation limits at 4250 MHz and 4350 MHz.
The modulator assembly also contains the high and low altitude if's, and two major closed loop circuits.
The first control loop controls the rate at which the transmitter output frequency changes.
The other major control loop defines and contains the transmitted frequency within the 4250 to 4350 MHz normal band of operation.
The rf assembly contains all of the 4300 MHz functions. It is comprised of the transmitter stripline, receiver stripline and discriminator assemblies.
The instrumentation assembly consists of the altitude processor, the monitor processor and the power supply.
(b) Processing
The beat and reference frequencies from the if circuit board are converted to a binary number in the counter array and the microprocessor calculates the radio altitude based on the counter array data.
The altitude information is converted to ARINC 429 ternary data by being formatted and sent by the UART through the driver circuits to the FMGCs and PFDs once every 30 or 40 milliseconds depending on aircraft altitude.
The beat and reference frequencies from the if circuit board are converted to a binary number in the counter array and the microprocessor calculates the radio altitude based on the counter array data.
The altitude information is converted to ARINC 429 ternary data by being formatted and sent by the UART through the driver circuits to the FMGCs and PFDs once every 30 or 40 milliseconds depending on aircraft altitude.
(c) Monitoring
The monitor processor counts and computes altitude, in the same manner as the altitude processor. Instead of transmitting ternary data, however, the monitor processor receives it and compares it with its own previously computed altitude. Any altitude disparity (outside of a fixed error window determined by software) generates a failure indication.
An incorrect word or altitude also causes the monitor processor to inhibit transmission of this data to the autopilot if the optional AFS interrupt mode is selected.
This is accomplished by disabling the AFS power supply during periods of incorrect data transmission and thereby shutting down the ALT bus No.1 ARINC 429 transmitter.
The monitor processor counts and computes altitude, in the same manner as the altitude processor. Instead of transmitting ternary data, however, the monitor processor receives it and compares it with its own previously computed altitude. Any altitude disparity (outside of a fixed error window determined by software) generates a failure indication.
An incorrect word or altitude also causes the monitor processor to inhibit transmission of this data to the autopilot if the optional AFS interrupt mode is selected.
This is accomplished by disabling the AFS power supply during periods of incorrect data transmission and thereby shutting down the ALT bus No.1 ARINC 429 transmitter.
(5) Internal description
The transceiver includes the following boards:
The transceiver includes the following boards:
- an RF module
- a main processor module
- a monitor processor module
- a power supply module
- a rear interconnect module
- a display data module
- a memory card module.
(a) RF module
The RF module, controlled by the main processor, transmits and receives the altimeter signal. BITE circuitry is included to both test and continuously monitor the RF module functions.
The process of generating a transmission begins with the Voltage Controlled Oscillator (VCO) output which is split between the transmitter and receiver Local Oscillator (LO).
The received signal is mixed with the VCO signal, producing a difference frequency signal that is amplified and fed to an Analog-to-Digital (A/D) converter on the main processor module.
The RF module, controlled by the main processor, transmits and receives the altimeter signal. BITE circuitry is included to both test and continuously monitor the RF module functions.
The process of generating a transmission begins with the Voltage Controlled Oscillator (VCO) output which is split between the transmitter and receiver Local Oscillator (LO).
The received signal is mixed with the VCO signal, producing a difference frequency signal that is amplified and fed to an Analog-to-Digital (A/D) converter on the main processor module.
(b) Main processor module
The main processor module controls the radio altimeter operation, performs signal processing of the difference frequency and test signals, and controls the aircraft interfaces and the data displayed on the front panel.
The main processor module is divided into three major sections: the Digital Signal Processor (DSP) section, the 486 CPU microprocessor section, and the Input/Output (I/O) section.
The main processor module controls the radio altimeter operation, performs signal processing of the difference frequency and test signals, and controls the aircraft interfaces and the data displayed on the front panel.
The main processor module is divided into three major sections: the Digital Signal Processor (DSP) section, the 486 CPU microprocessor section, and the Input/Output (I/O) section.
1 DSP section
The DSP section is used to process the analog outputs from the RF module and to generate some of the control signals to the RF module for transmit modulation, automatic gain control, and test signals.
The DSP processes the difference frequency and calibration frequency into altitude information.
Data is exchanged with the CPU section through a dual-port Random Access Memory (RAM), providing maximum throughput of both processors.
The DSP section is used to process the analog outputs from the RF module and to generate some of the control signals to the RF module for transmit modulation, automatic gain control, and test signals.
The DSP processes the difference frequency and calibration frequency into altitude information.
Data is exchanged with the CPU section through a dual-port Random Access Memory (RAM), providing maximum throughput of both processors.
2 486 CPU microprocessor section
The CPU section does frame-to-frame processing of the altitude data from the DSP section providing the resulting altitude to the I/O section.
The microprocessor in the CPU section controls all major functions of the radio altimeter. Programmable logic devices serve as the microprocessor controller and provide the interfaces to the memory devices (boot routine, program, fault, and data), the data recorder/data loader flash card, and the front panel display driver.
The CPU section does frame-to-frame processing of the altitude data from the DSP section providing the resulting altitude to the I/O section.
The microprocessor in the CPU section controls all major functions of the radio altimeter. Programmable logic devices serve as the microprocessor controller and provide the interfaces to the memory devices (boot routine, program, fault, and data), the data recorder/data loader flash card, and the front panel display driver.
3 I/O section
The I/O section provides the two ARINC 429 altitude outputs as well as ARINC 429 interfaces with other aircraft systems including the Centralized Fault Display Interface Unit (CFDIU).
All discrete inputs external to the radio altimeter are processed by the I/O section. The I/O section also generates the external discrete outputs which are buffered to prevent damage to the processor circuitry.
The I/O section provides the two ARINC 429 altitude outputs as well as ARINC 429 interfaces with other aircraft systems including the Centralized Fault Display Interface Unit (CFDIU).
All discrete inputs external to the radio altimeter are processed by the I/O section. The I/O section also generates the external discrete outputs which are buffered to prevent damage to the processor circuitry.
(c) Monitor processor module
The monitor processor module provides a second signal processing path using a Digital Signal Processor (DSP). The DSP processes the received signal and calibration signal supplied in digital form from the main processor A/D converter. Also present are a clock, an ARINC 429 receiver/selector and static memory.
The monitor processor module provides a second signal processing path using a Digital Signal Processor (DSP). The DSP processes the received signal and calibration signal supplied in digital form from the main processor A/D converter. Also present are a clock, an ARINC 429 receiver/selector and static memory.
(d) Power supply module
The power supply module is a self-contained, high-efficiency, switching power supply that converts the 115VAC, 400 Hz A/C power into the required +5VDC, +12VDC, -12VDC, and +24VDC operating voltages. A power-down interrupt provides advanced notice of a power loss allowing the processors to temporarily retain their status.
The power supply module is a self-contained, high-efficiency, switching power supply that converts the 115VAC, 400 Hz A/C power into the required +5VDC, +12VDC, -12VDC, and +24VDC operating voltages. A power-down interrupt provides advanced notice of a power loss allowing the processors to temporarily retain their status.
(e) Rear interconnect module
To prevent High Intensity Radiated Fields (HIRF) from entering via rear connector cables, an HIRF compartment is formed in the rear of the RA. The signal and power cables are filtered by using discrete and distributed filter elements and limiting devices on the rear interconnect module located inside this HIRF compartment. The filtered lines are then fed to the appropriate points in the RA.
To prevent High Intensity Radiated Fields (HIRF) from entering via rear connector cables, an HIRF compartment is formed in the rear of the RA. The signal and power cables are filtered by using discrete and distributed filter elements and limiting devices on the rear interconnect module located inside this HIRF compartment. The filtered lines are then fed to the appropriate points in the RA.
(f) Display date module
The display data module is mounted behind the front panel and provides an interface to an operator via a low-power Liquid Crystal Display (LCD) which is visible from the front of the RA. In addition to the LCD, the module contains LED "Light Box" backlighting, temperature compensation circuitry, and a PC board containing an associated LDC driver, two pushbutton switches, and a 9-pin D connector.
The display data module is mounted behind the front panel and provides an interface to an operator via a low-power Liquid Crystal Display (LCD) which is visible from the front of the RA. In addition to the LCD, the module contains LED "Light Box" backlighting, temperature compensation circuitry, and a PC board containing an associated LDC driver, two pushbutton switches, and a 9-pin D connector.
(g) Memory card module
The memory card interface is used to load data into the CPU or record data from the CPU. The memory card module supports either flash cards or RAM cards via the front panel Personal Computing Memory Card Interface Adapter (PCMCIA) slot.
The flash card or RAM card is inserted through the front panel. In one mode, data stored on the flash card memory manual is used to update program or data memory in the RA. In another mode, the flash card functions as a data recorder.
The memory card interface is used to load data into the CPU or record data from the CPU. The memory card module supports either flash cards or RAM cards via the front panel Personal Computing Memory Card Interface Adapter (PCMCIA) slot.
The flash card or RAM card is inserted through the front panel. In one mode, data stored on the flash card memory manual is used to update program or data memory in the RA. In another mode, the flash card functions as a data recorder.
(a) Layout
The transceiver LRA-900 consists of an interconnect assembly, an RF assembly, a modulator/IF assembly, an instrumentation assembly (processor) and a power supply assembly.
The transceiver is a radio altimeter using a wideband frequency modulated continuous wave (FM/CW) technique to measure the distance between the aircraft and the terrain below.
The transceiver LRA-900 consists of an interconnect assembly, an RF assembly, a modulator/IF assembly, an instrumentation assembly (processor) and a power supply assembly.
The transceiver is a radio altimeter using a wideband frequency modulated continuous wave (FM/CW) technique to measure the distance between the aircraft and the terrain below.
(b) Modulator assembly
The function of the modulator is to provide the transmitter with a 100 Hz triangular wave corrected for transmitter non linearities and also to maintain the transmitter deviation limits at 4250 MHz and 4350 MHz.
The modulator assembly also contains the high and low altitude IF's, and two major circuits.
The first is a closed loop circuit which controls the rate at which the transmitter's output frequency changes.
The other major circuit controls the transmitter bandwidth within the 4250 to 4350 MHz normal band of operation.
The function of the modulator is to provide the transmitter with a 100 Hz triangular wave corrected for transmitter non linearities and also to maintain the transmitter deviation limits at 4250 MHz and 4350 MHz.
The modulator assembly also contains the high and low altitude IF's, and two major circuits.
The first is a closed loop circuit which controls the rate at which the transmitter's output frequency changes.
The other major circuit controls the transmitter bandwidth within the 4250 to 4350 MHz normal band of operation.
(c) Instrumentation assembly
The instrumentation assembly consists of the altitude processor, the monitor processor, a system monitor and AFCS bus driver power switch.
The instrumentation assembly consists of the altitude processor, the monitor processor, a system monitor and AFCS bus driver power switch.
1 Altitude processor
The beat and reference frequencies from the IF circuit board are converted to a binary number in the counter array and the microprocessor calculates the radio altitude based on the counter array data.
The altitude information is converted to ARINC 429 ternary data by being formatted and sent by the UART through the driver circuits to the FMGCs and PFDs once every 35 or 40 milliseconds depending on aircraft altitude.
The beat and reference frequencies from the IF circuit board are converted to a binary number in the counter array and the microprocessor calculates the radio altitude based on the counter array data.
The altitude information is converted to ARINC 429 ternary data by being formatted and sent by the UART through the driver circuits to the FMGCs and PFDs once every 35 or 40 milliseconds depending on aircraft altitude.
2 Monitor processor
The monitor processor counts and computes altitude, in the same manner as the altitude processor. Instead of transmitting ternary data, however, the monitor processor receives it and compares it with its own previously computed altitude. Any altitude disparity (outside of a fixed error window determined by software) generates a failure indication.
An incorrect word or altitude also causes the monitor processor to inhibit transmission of this data to the autopilot if the optional AFCS interrupt mode is selected.
This is accomplished by disabling the AFCS power supply during periods of incorrect data transmission and thereby shutting down the ALT bus No.1 ARINC 429 transmitter.
The monitor processor counts and computes altitude, in the same manner as the altitude processor. Instead of transmitting ternary data, however, the monitor processor receives it and compares it with its own previously computed altitude. Any altitude disparity (outside of a fixed error window determined by software) generates a failure indication.
An incorrect word or altitude also causes the monitor processor to inhibit transmission of this data to the autopilot if the optional AFCS interrupt mode is selected.
This is accomplished by disabling the AFCS power supply during periods of incorrect data transmission and thereby shutting down the ALT bus No.1 ARINC 429 transmitter.
(d) RF assembly
The RF assembly contains all of the 4300 MHz functions. It is comprised of the transmitter and receiver microstrip circuitry.
The RF assembly contains all of the 4300 MHz functions. It is comprised of the transmitter and receiver microstrip circuitry.
(7) Digital outputs
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 :
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.
| ------------------------------------------------------------------------------- |
| | PARAMETER LIST PARAMETER CHARACTERISTICS (NUMERIC) | |
| ------------------------------------------------------------------------------- |
| |EQ.SYS.LAB.SDI|PARAMETER | WORD RANGE |UNIT|SIG |BITS|XMSN|CODE|ALPHA|SOURCE | |
| | |DEFINITION| OPER RANGE | |BIT | |INTV| |CODE |ORIGIN | |
| | |(*=REMARK)| RESOLUTION | | | | | | |BUS No.| |
| | |(X=NOTE) | ACCURACY | | | | | | |ATA REF| |
| | | | | | | | | | |CONV | |
| ------------------------------------------------------------------------------- |
| ! 164 !RADIO ! 8192 ! FT ! 29 ! 16 ! 80 !BNR !RALT ! ! |
| ! !HEIGHT ! 0.125 ! ! ! ! ! ! ! ! |
| ! ! ! ! ! ! ! ! ! ! ! |
| ------------------------------------------------------------------------------- |
(8) Digital outputs
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 :
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.
| ------------------------------------------------------------------------------- |
| | PARAMETER LIST PARAMETER CHARACTERISTICS (NUMERIC) | |
| ------------------------------------------------------------------------------- |
| |EQ.SYS.LAB.SDI|PARAMETER | WORD RANGE |UNIT|SIG |BITS|XMSN|CODE|ALPHA|SOURCE | |
| | |DEFINITION| OPER RANGE | |BIT | |INTV| |CODE |ORIGIN | |
| | |(*=REMARK)| RESOLUTION | | | | | | |BUS No.| |
| | |(X=NOTE) | ACCURACY | | | | | | |ATA REF| |
| | | | | | | | | | |CONV | |
| ------------------------------------------------------------------------------- |
| ! 164 !RADIO ! 8192 ! FT ! 29 ! 16 ! 35 !BNR !RALT ! ! |
| ! !HEIGHT ! 0.125 ! ! ! ! or ! ! ! ! |
| ! ! ! ! ! ! ! 40 ! ! ! ! |
| ------------------------------------------------------------------------------- |
B. Antennas
The transmission and reception antennas are identical. The small - thickness antenna is installed on the skin of the aircraft.
Each antenna is supplied through a coaxial connector linked to the transceiver. The operating range of the antenna according to the attitude of the aircraft is limited to + or - 30° for roll and pitch.
The transmission and reception antennas are identical. The small - thickness antenna is installed on the skin of the aircraft.
Each antenna is supplied through a coaxial connector linked to the transceiver. The operating range of the antenna according to the attitude of the aircraft is limited to + or - 30° for roll and pitch.
C. Fans
The six-blade fan is integral with a removable base plate attached under the transceiver mount. It is contained in a square aluminum alloy case. It is supplied with 115VAC through a connector and associated wiring connecting it to the transceiver. Interference is suppressed by a capacitor mounted on the fan case.
The six-blade fan is integral with a removable base plate attached under the transceiver mount. It is contained in a square aluminum alloy case. It is supplied with 115VAC through a connector and associated wiring connecting it to the transceiver. Interference is suppressed by a capacitor mounted on the fan case.
6. Operation
A. Control
In normal operation, system 1 automatically provides the height data for the CAPT PFD and system 2 for the F/O PFD.
With failure of one system, the valid system is automatically switched to both CAPT and F/O PFDs.
With failure of the two systems, the digits go out of view from the PFD : in place of the digits, a red RA warning message flashes during three seconds then remains on.
For information : the pilot sets the DH on the MCDU. The Flight Warning Computer (FWC) generates the DH warning message.
With loss of DH information, the DH data are not shown.
In normal operation, system 1 automatically provides the height data for the CAPT PFD and system 2 for the F/O PFD.
With failure of one system, the valid system is automatically switched to both CAPT and F/O PFDs.
With failure of the two systems, the digits go out of view from the PFD : in place of the digits, a red RA warning message flashes during three seconds then remains on.
For information : the pilot sets the DH on the MCDU. The Flight Warning Computer (FWC) generates the DH warning message.
With loss of DH information, the DH data are not shown.
B. Reconfiguration Switching
In normal utilization, the radio altimeter data are shown on the CAPT PFD and F/O PFD through the Display Management Computers 1 and 2 (DMC).
With failure of the radio altimeter transceiver 1, the DMC 1 and 2 automatically switch over to the transceiver 2.
With failure of the DMC 1 (2), it is possible to switch over to the DMC 3 with the EIS DMC selector switch.
This selector switch is located on panel 8VU on the center pedestal.
In this case the DMC 3 totally replaces the DMC 1 (2) through the stage of the output switching relay of the failed DMC.
With failure of the PFD, there is an automatic transfer of the PFD image onto the Navigation Display (ND).
When you set the PFD potentiometer to OFF on panel 301VU (500VU), this causes :
In normal utilization, the radio altimeter data are shown on the CAPT PFD and F/O PFD through the Display Management Computers 1 and 2 (DMC).
With failure of the radio altimeter transceiver 1, the DMC 1 and 2 automatically switch over to the transceiver 2.
With failure of the DMC 1 (2), it is possible to switch over to the DMC 3 with the EIS DMC selector switch.
This selector switch is located on panel 8VU on the center pedestal.
In this case the DMC 3 totally replaces the DMC 1 (2) through the stage of the output switching relay of the failed DMC.
With failure of the PFD, there is an automatic transfer of the PFD image onto the Navigation Display (ND).
When you set the PFD potentiometer to OFF on panel 301VU (500VU), this causes :
- deactivation of the PFD
- transfer of the PFD image onto the ND.
7. Test
Radio Altimeter - Maintenance Test Procedure ** ON A/C NOT FOR ALL
Radio Altimeter - Maintenance Test Procedure ** ON A/C NOT FOR ALL
Radio Altimeter - Maintenance Test Procedure ** ON A/C NOT FOR ALL
Radio Altimeter - Maintenance Test Procedure ** ON A/C NOT FOR ALL Radio Altimeter - Maintenance Test Procedure ** ON A/C NOT FOR ALL Radio Altimeter - Maintenance Test Procedure ** ON A/C NOT FOR ALL A. Access to Radio Altimeter Sub-menu Functions
It is possible to select the maintenance functions of the radio altimeter transceiver 1(2) by pressing the line key adjacent to the SYSTEM REPORT/TEST indication on the CFDS menu, and then selecting the relevant RA on the NAV menu.
After these actions the RA 1(2) provides its own menu page and the sub-menu functions can then be chosen by the operator.
Pre SB LRA-700-34-G
CURRENT STATUS:
The RA CURRENT STATUS function can be activated by pressing the line key adjacent to the corresponding indication on the LRA 1(2) maintenance sub-menu. The current status gives the status of the RA before entering menu mode. It print CURRENT STATUS OK when no fault is detected or print the failure when fault is detected.
Post SB LRA-700-34-G
It is possible to select the maintenance functions of the radio altimeter transceiver 1(2) by pressing the line key adjacent to the SYSTEM REPORT/TEST indication on the CFDS menu, and then selecting the relevant RA on the NAV menu.
After these actions the RA 1(2) provides its own menu page and the sub-menu functions can then be chosen by the operator.
After these actions the RA 1(2) provides its own menu page and the sub-menu functions can then be chosen by the operator.
It is possible to select the maintenance functions of the radio altimeter transceiver 1(2) by pressing the line key adjacent to the SYSTEM REPORT/TEST indication on the CFDS menu, and then selecting the relevant RA on the NAV menu.
After these actions the RA 1(2) provides its own menu page and the sub-menu functions can then be chosen by the operator.
NOTE: The test can be performed on the ground only. It is inhibited (the EIU1 (EIU2) sends a ground discrete to the RA1 (RA2)) as soon as N2 rating (high pressure compressor rotational speed) is greater than minimum idle rating.
Pre SB LRA-700-34-G
CURRENT STATUS:
The RA CURRENT STATUS function can be activated by pressing the line key adjacent to the corresponding indication on the LRA 1(2) maintenance sub-menu. The current status gives the status of the RA before entering menu mode. It print CURRENT STATUS OK when no fault is detected or print the failure when fault is detected.
Post SB LRA-700-34-G
It is possible to select the maintenance functions of the radio altimeter transceiver 1(2) by pressing the line key adjacent to the SYSTEM REPORT/TEST indication on the CFDS menu, and then selecting the relevant RA on the NAV menu.
After these actions the RA 1(2) provides its own menu page and the sub-menu functions can then be chosen by the operator.
NOTE: The test can be performed on the ground only. It is inhibited (the EIU1 (EIU2) sends a ground discrete to the RA1 (RA2)) as soon as N2 rating (high pressure compressor rotational speed) is greater than minimum idle rating.
It is possible to select the maintenance functions of the radio altimeter transceiver 1(2) by pressing the line key adjacent to the SYSTEM REPORT/TEST indication on the CFDS menu, and then selecting the relevant RA on the NAV menu. After these actions the RA 1(2) provides its own menu page and the sub-menu functions can then be chosen by the operator.
NOTE: The test can be performed on the ground only. It is inhibited (the EIU1 (EIU2) sends a ground discrete to the RA1 (RA2)) as soon as N2 rating (high pressure compressor rotational speed) is greater than minimum idle rating.
B. Activation of the Test Function
(1) SYSTEM TEST
The RA SYSTEM TEST function can be activated by pressing the line key adjacent to the corresponding indication on the LRA 1(2) maintenance sub-menu.
The following sequence occurs :
The RA SYSTEM TEST function can be activated by pressing the line key adjacent to the corresponding indication on the LRA 1(2) maintenance sub-menu.
The following sequence occurs :
- on the PFD :
* the bottom sector line moves down from the horizon line.
* the radio altimeter is 40 ft. - on the MCDU, at the end of the test, the TEST OK message comes into view.
NOTE: During the test :
- You can hear auto call-out announcements 40, 41 or 42
- You must open the RA1 circuit breaker to hear auto call-out announcements during the RA2 SYSTEM TEST.
END OF SB LRA-700-34-G
(2) Self-Test
The self-test can be activated by pushing the TEST pushbutton switch as designed on the front panel LCD, if the test inhibit discrete is not active.
A "TEST IN PROGRESS" message is displayed approximately one second after the TEST pushbutton is pressed.
At the end of the self-test, either a TEST COMPLETE, NO FAILURES message screen or a TEST COMPLETE, FAILURES message screen is displayed. The TEST COMPLETE, NO FAILURES screen contains two pushbutton selections (MAINT and RETURN). The TEST COMPLETE, FAILURES screen also contains two pushbutton selections (MAINT and WHY?).
For both screens, pressing the left (MAINT) pushbutton initiates the extented maintenance pages of the system for troubleshooting. The right (RETURN) pushbutton associated with the TEST COMPLETE, NO FAILURES screen returns the system to its normal mode screen. The right (WHY?) pushbutton associated with the TEST COMPLETE, FAILURES screen places the system in the display-failures mode where individual system failures (fault memory codes) are displayed, one per page.
The self-test can be activated by pushing the TEST pushbutton switch as designed on the front panel LCD, if the test inhibit discrete is not active.
A "TEST IN PROGRESS" message is displayed approximately one second after the TEST pushbutton is pressed.
At the end of the self-test, either a TEST COMPLETE, NO FAILURES message screen or a TEST COMPLETE, FAILURES message screen is displayed. The TEST COMPLETE, NO FAILURES screen contains two pushbutton selections (MAINT and RETURN). The TEST COMPLETE, FAILURES screen also contains two pushbutton selections (MAINT and WHY?).
For both screens, pressing the left (MAINT) pushbutton initiates the extented maintenance pages of the system for troubleshooting. The right (RETURN) pushbutton associated with the TEST COMPLETE, NO FAILURES screen returns the system to its normal mode screen. The right (WHY?) pushbutton associated with the TEST COMPLETE, FAILURES screen places the system in the display-failures mode where individual system failures (fault memory codes) are displayed, one per page.
(3) RAMP TEST
The RAMP TEST function can be activated from the MCDU by pressing the line key adjacent to the SYSTEM REPORT/TEST indication on the CFDS menu then selecting the RA1 (RA2) on the NAV menu and then selecting the RAMP TEST page.
The RA then begins simulating a ramp starting from 500 ft. down to 0 ft. (with a slope of 10 ft/s from 500 ft. to 50 ft. and approximately 3 ft/s from 50 ft. to 0 ft.).
The RAMP TEST function can be activated from the MCDU by pressing the line key adjacent to the SYSTEM REPORT/TEST indication on the CFDS menu then selecting the RA1 (RA2) on the NAV menu and then selecting the RAMP TEST page.
The RA then begins simulating a ramp starting from 500 ft. down to 0 ft. (with a slope of 10 ft/s from 500 ft. to 50 ft. and approximately 3 ft/s from 50 ft. to 0 ft.).
(4) SYSTEM TEST
The RA SYSTEM TEST function can be activated by pressing the line key adjacent to the corresponding indication on the RA 1(2) maintenance sub-menu.
The following sequence occurs :
The RA SYSTEM TEST function can be activated by pressing the line key adjacent to the corresponding indication on the RA 1(2) maintenance sub-menu.
The following sequence occurs :
- on the PFD :
* the bottom sector line moves down from the horizon line.
* the radio altimeter is 40 ft. - on the MCDU, at the end of the test, the TEST OK message comes into view.
NOTE: During the test :
- You can hear auto call-out announcements 40, 41 or 42
- You must open the RA1 circuit breaker to hear auto call-out announcements during the RA2 SYSTEM TEST.
NOTE: If the system test or the ramp test cannot be initiated on ground from the MCDU (which means that a fault affects either the LGCIU, the EIU or the RA) a TEST page comes into view on the MCDU.
(5) SYSTEM TEST
The RA SYSTEM TEST function can be activated by pressing the line key adjacent to the corresponding indication on the RA 1(2) maintenance sub-menu.
The following sequence occurs :
The RA SYSTEM TEST function can be activated by pressing the line key adjacent to the corresponding indication on the RA 1(2) maintenance sub-menu.
The following sequence occurs :
- on the PFD :
* the bottom sector line moves down from the horizon line.
* the radio altimeter is 40 ft. - on the MCDU, at the end of the test, the TEST OK message comes into view.
NOTE: During the test :
- You can hear auto call-out announcements 40, 41 or 42
- You must open the RA1 circuit breaker to hear auto call-out announcements during the RA2 SYSTEM TEST.
(6) RAMP TEST
The RAMP TEST function can be activated from the MCDU by pressing the line key adjacent to the SYSTEM REPORT/TEST indication on the CFDS menu then selecting the RA1 (RA2) on the NAV menu and then selecting the RAMP TEST page.
The RA then begins simulating a ramp starting from 500 ft. down to 0 ft. (with a slope of 11 ft/s from 500 ft. to 50 ft. and approximately 3 ft/s from 50 ft. to 0 ft.).
The RAMP TEST function can be activated from the MCDU by pressing the line key adjacent to the SYSTEM REPORT/TEST indication on the CFDS menu then selecting the RA1 (RA2) on the NAV menu and then selecting the RAMP TEST page.
The RA then begins simulating a ramp starting from 500 ft. down to 0 ft. (with a slope of 11 ft/s from 500 ft. to 50 ft. and approximately 3 ft/s from 50 ft. to 0 ft.).
C. Power-up Tests Initialization and Cockpit Repercussions
(1) Conditions of power-up tests initialization
- How long the computer must be de-energized: 2 s.
- A/C configuration:
- whatever the A/C configuration on ground
(2) Progress of power-up tests
- Duration: 3 s.
- 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):
- MASTER CAUT light on
(3) Results of power-up tests
(cockpit repercussions, if any, in case of tests pass/tests failed).
(cockpit repercussions, if any, in case of tests pass/tests failed).
- Tests pass:
- MASTER CAUT light off - Tests failed:
- MASTER CAUT light on
- ECAM warning
NAV RA 1 or 2 FAULT
- ECAM STATUS
RA 1 or 2 INOP
D. CFDIU Interface
(1) BITE description
The BITE facilitates maintenance on in-service aircraft. It detects and identifies a failure related to the RA system. The BITE of the radio altimeter is connected to the CFDIU (Ref. AMM D/O 31-32-00-00).
The BITE:
The BITE facilitates maintenance on in-service aircraft. It detects and identifies a failure related to the RA system. The BITE of the radio altimeter is connected to the CFDIU (Ref. AMM D/O 31-32-00-00).
The BITE:
- transmits permanently RA system status and its identification message to the CFDIU
- memorizes the failures which occurred during the last 63 flight legs
- monitors data inputs from the various peripherals
- transmits to the CFDIU the result of the tests performed and selt-tests
- can communicate with the CFDIU through the menus.
The BITE can operate in two modes: - the normal mode
- the menu mode.
(a) Normal mode
During the normal mode the BITE monitors cyclically the status of the RA system. It transmits its information to the CFDIU during the concerned flight.
In case of fault detection the BITE stores the information in the fault memories.
These items of information are transmitted to the CFDIU by an ARINC 429 message with label 356.
During the normal mode the BITE monitors cyclically the status of the RA system. It transmits its information to the CFDIU during the concerned flight.
In case of fault detection the BITE stores the information in the fault memories.
These items of information are transmitted to the CFDIU by an ARINC 429 message with label 356.
(b) Menu mode
The menu mode can only be activated on the ground.
This mode enables communication between the CFDIU and the RA BITE by means of the MCDU.
All the information displayed on the MCDU during the BITE Test configuration can be printed by the printer (Ref. AMM D/O 31-35-00-00).
The RA menu mode is composed of:
The menu mode can only be activated on the ground.
This mode enables communication between the CFDIU and the RA BITE by means of the MCDU.
All the information displayed on the MCDU during the BITE Test configuration can be printed by the printer (Ref. AMM D/O 31-35-00-00).
The RA menu mode is composed of:
- LAST LEG REPORT
- PREVIOUS LEGS REPORT
- LRU IDENTIFICATION
- GND SCANNING
- TROUBLE SHOOTING DATA
- CLASS 3 FAULTS
- GROUND REPORT.
- SYSTEM TEST.
- RAMP TEST.
(2) List of components
All the components are listed in the Para. 2. Component Location.
All the components are listed in the Para. 2. Component Location.
(3) BITE description
The BITE facilitates maintenance on in-service aircraft. It detects and identifies a failure related to the RA system. The BITE of the radio altimeter is connected to the CFDIU (Ref. AMM D/O 31-32-00-00).
The BITE:
The BITE facilitates maintenance on in-service aircraft. It detects and identifies a failure related to the RA system. The BITE of the radio altimeter is connected to the CFDIU (Ref. AMM D/O 31-32-00-00).
The BITE:
- Transmits permanently RA system status and its identification message to the CFDIU
- Memorizes the failures which occurred during the last 63 flight legs
- Monitors data inputs from the various peripherals
- Transmits to the CFDIU the result of the tests performed and self-tests
- Can communicate with the CFDIU through the menus.
The BITE can operate in two modes: - The normal mode
- The menu mode.
(a) Normal mode
During the normal mode the BITE monitors cyclically the status of the RA system. It transmits its information to the CFDIU during the concerned flight.
In case of fault detection the BITE stores the information in the fault memories.
These items of information are transmitted to the CFDIU by an ARINC 429 message with label 356.
During the normal mode the BITE monitors cyclically the status of the RA system. It transmits its information to the CFDIU during the concerned flight.
In case of fault detection the BITE stores the information in the fault memories.
These items of information are transmitted to the CFDIU by an ARINC 429 message with label 356.
(b) Menu mode
The menu mode can only be activated on the ground.
This mode enables communication between the CFDIU and the RA BITE by means of the MCDU.
All the information displayed on the MCDU during the BITE Test configuration can be printed by the printer (Ref. AMM D/O 31-35-00-00).
The RA menu mode is composed of:
The menu mode can only be activated on the ground.
This mode enables communication between the CFDIU and the RA BITE by means of the MCDU.
All the information displayed on the MCDU during the BITE Test configuration can be printed by the printer (Ref. AMM D/O 31-35-00-00).
The RA menu mode is composed of:
- LAST LEG REPORT
- PREVIOUS LEGS REPORT
- LRU IDENTIFICATION
- TROUBLE SHOOTING DATA
- GND SCANNING
- CLASS 3 FAULTS
- GROUND REPORT
- SYSTEM TEST
- RAMP TEST
- SPECIFIC DATA
(4) List of components
All the components are listed in the Para. 2. Component Location.
All the components are listed in the Para. 2. Component Location.