Aircraft Electronics System (ACARS, ECAM, EFIS, EICAS, FMS) - PDF

Okay, here is the converted text from the images into a structured markdown format. # Aviation Australia ## Typical Electronic / Digital Aircraft Systems I (5.15) ### Learning Objectives 5.15.1 Describe the general arrangement of typical electronic/digital aircraft systems and associated Built-I...

Okay, here is the converted text from the images into a structured markdown format. # Aviation Australia ## Typical Electronic / Digital Aircraft Systems I (5.15) ### Learning Objectives 5.15.1 Describe the general arrangement of typical electronic/digital aircraft systems and associated Built-In Test Equipment (BITE) (Level 2). 5.15.1.1 Describe the general arrangement and BITE testing capabilities of the Aircraft Communications Addressing and Reporting System (ACARS) (Level 2). 5.15.1.2 Describe the general arrangement and BITE testing capabilities of the Electronic Centralised Aircraft Monitoring (ECAM) system (Level 2). 5.15.1.3 Describe the general arrangement and BITE testing capabilities of theElectronic Flight Instrument System (EFIS) (Level 2). 5.15.1.4 Describe the general arrangement and BITE testing capabilities of theEngine Indicating and Crew Alerting System (EICAS) (Level 2). 5.15.1.5 Describe the general arrangement and BITE testing capabilities of the Fly-By-Wire (FBW) control system (Level 2). 5.15.1.6 Describe the general arrangement and BITE testing capabilities of the Flight Management System (FMS) (Level 2). 5.15.1.7 Describe the general arrangement and BITE testing capabilities of the Global Positioning System (GPS) (Level 2). 5.15.1.8 Describe the general arrangement and BITE testing capabilities of theInertial Reference System (IRS) (Level 2). 5.15.1.9 Describe the general arrangement and BITE testing capabilities of the Traffic Alert and Collision Avoidance (TCAS) (Level 2). ## Integrated Test Equipment ### Aircraft Diagnostics Today's aircraft are so complex that design engineers must consider the ability to troubleshoot a system as equally important as the ability to repair or inspect that system. Troubleshooting a complex digital aircraft would be nearly impossible without self-diagnostic systems. Self-contained diagnostics used for electronic/avionics systems troubleshooting became known as BITE (Built-In Test Equipment). The second image is of an LRU (Line Replaceable Unit) housing BITE (Built-In Test Equipment). ## BITE Systems There are several versions of built-in test equipment which are in use today. Simple BITE systems typically incorporate a go/no-go red or green LED on the equipment black box or LRU. More complex systems use a multi-character display and monitor more than one LRU. Some BITE can also test the associated wiring. The current generation of self-diagnostics equipment incorporates the use of a centralized monitoring system which incorporate flight deck displays from which tests can be activated. Faults detected through several BITE systems are monitored in one location, include paper printouts of test results, and have a means to transmit data from the aircraft to the maintenance facility during flight. Here is the transcription of the images showing "MAINT BITE INDEX" and "FMCS BITE": ``` MAINT BITE INDEX 1/1 FMCS BITE 1/1 <FMCS <INFLT FAULT <DFCS <CDU TEST <A/T <SENSORS PERF FACTR> <IRS <DISCRETES IRS MONITR> <EFIS <FIXED OUTPUTS <INDEX FMC DOWNLOAD> <INDEX ``` ### BITE Information The advanced built-in troubleshooting system used by Boeing is known as CMCS (Central Maintenance Computer System). The advanced diagnostic system used by Airbus is called Centralized Fault Display System (CFDS). Each of these advanced systems incorporate enhanced BITE features that aid in troubleshooting. In general, the advanced systems are more easily accessible and understood than older systems. A commercial airliner may contain several BITE units used to monitor a variety of systems. Each BITE unit receives inputs from several individual components of the system being tested. A Boeing 757 or 767 aircraft, for example, utilizes built-in test equipment systems on approximately 50 LRUs located throughout the aircraft. Other individual systems also contain their own dedicated Built-In Test Equipment. These BITE systems are relatively simple and are contained within the LRU being monitored. This meant early BITE systems were accessed in the electronics equipment bay or similar area. ### BITE Philosophy Most aircraft systems are composed of several individual units called Line Replaceable Units (LRUs). A LRU can refer to a black box, a sensor, an actuator, a probe, or similar item. There is a picture included of a "Line Replaceable Unit (LRU)". Most LRUs are controlled by digital computers and for safety reasons these LRUs are permanently monitored so that testing and troubleshooting procedures can be performed. The example used below is an Airbus A330 On Board Maintenance System (OBMS). In each system, a particular section of a computer is dedicated to these functions. The section is referred as the BITE section. Where a system uses multiple computers, one computer may be dedicated to managing BITE. During normal operation BITE is continuously monitoring the internal LRU circuits, the LRU inputs and outputs, and the links between system LRUs. When a failure occurs, BITE can identify the possible failed LRU and determine if the failure is intermittent or permanent. Additionally, it can give a snapshot of the system environment at the time of the failure and save the details in a non-volatile memory for later analysis. Block diagram of BITE philosophy: ``` SYSTEM "X" SYSTEM "Z" SENSOR BITE NVM ACTUATOR MEMORISATION 0 ISOLATION DETECTION TESTS COMPUTER "A " COMPUTER "B" PROBE SYSTEM "Y" ``` ### BITE Function The BITE information stored in the system BITE memory is sent to a centralised maintenance device. Some BITE tests can be initiated via this centralised maintenance device with advantages including: * A single interface location (cockpit). * Easy fault identification. * Reduction of trouble shooting duration. * Simplification of technical documentation. * Standardisation of equipment. * BITE can be divided into 4 groups. ### Power Up Test The power up test is first a safety test to ensure compliance with safety objectives. The test duration is a function of the system which is currently not operational. It is executed only on the ground after any power cut the exceeds a nominal 200 milliseconds. If the aircraft is airborne, the power up test is limited to a few items to enable a quick return to the operation of the system. A power up test typically includes the following tasks: * Test of the microprocessor. * Test of the memories. * Test of the data lines and various input/output circuits. * A configuration test. ### Cyclic Tests Cyclic tests (also known as In Operation Tests) are carried out permanently without disturbing system operation. Tasks include: * A watchdog test (a watchdog is a device capable of restarting the microprocessor if the software fails). * A RAM test. * Data line (ARINC 429) message validity. ### System Test The purpose of this test is to offer the maintenance crew the ability to test the system for troubleshooting purposes. The test is performed after system restoration, following replacement of an LRU, to check the integrity of the system. It is like a power up test. ### Specific Tests For some systems, specific tests are available. The purpose of these tests is to generate stimuli to various command devices such as actuators or valves. They can have a major effect on the aircraft, e.g., movement of slats or flaps, engine dry cranking. Use of the LRU and BITE concepts greatly reduce aircraft maintenance down time. After the appropriate repairs have been made, the system should be run through a complete operational check. The BITE will once again monitor the system and verify correct operation if the system has been properly repaired. Flowchart displaying the BITE process: ``` POWER UP COMPUTER SOFTWARE PROCESS ↓ POWER UP TEST ↓ OPERATIONAL FUNCTION ↓ CYCLIC TESTS PERMANENT MONITORING ↓ ON GND (YES) MANUAL TEST REQUEST (NO) ↓ SPECIFIC TESTS SYSTEM TEST (YES) ``` ### Maintenance Control Display Unit (MCDU) The MCDU contains a screen for data display, a keyboard, function keys, mode keys, and line keys, used to send commands to the connected systems. The MCDU allows access to the following system components: * FM (Flight Management System) * ACMS (Aircraft Condition Monitoring System) * CMS (Central Maintenance System) * SAT (Satellite Communication System) * ATSU (Air Traffic Service Unit). There is an image included showing the "Multifunction Control Display Unit (MCDU)." ### MCDU Utilisation Using the MCDU to access a specific system to review its status or perform tests requires a series of keystrokes as given in the example below and shown on the graphics. When powered up the MCDU displays the STATUS PAGE. Select MCDU Menu to display the MCDU MENU page. The following text and diagrams explains how to access the MCDU Status page. ``` AIRCRAFT TYPE MCDU MENU ENG <FM1 (or FM2) ENGINE TYPE ACTIVE DATA BASE SELECT <ACMS 28 NOV-25 DEC AB49012001 MCDU <CMS SECOND DATA BASE MENU <SAT (REQ) +26 DEC - 22 JAN <ATSU (TIMEOUT) RETURN > CHG SELECT DESIRED SYSTEM CHG CODE () IDLE/PERF +0.0 +0.0 ``` The following text and diagrams explains how to acces the MCDU menu page ``` MCDU MENU MAINTENANCE MENU 1/2 <FLIGHT REPORT PRINT * <CMS (SEL) SELECT POST <FLIGHT REPORT PRINT * WAIT FOR SYSTEM RESPONSE PREVIOUS <AVIONIC STATUS <CMS <SYSTEM REPORT/TEST ↑⬆ ⬇︎⬇︎ <SERVICING REPORT UTC/DATE INIT SEND:-----> ``` The following text and images describe how to use the MCDU System Report/Test page. ``` SYSTEM REPORT/TEST 2/6 SYSTEM REPORT/TEST 1/6 ATA:23 COM(&33 LIGHTS) ATA:21 AIRCOND CABIN AVNCS-VENT CAB TEMP EMERG LIGHTS <AC CRG VENT SYSTEM REPORT/TEST CAB PRESS- ATA:24 ELEC AUTO PILOT EM (IND RDY AC SPD LIM EM2. GENERATION WINDSHEAR DET SYSTEM REPORT/TEST 3/6 SYSTEM REPORT/TEST 4/6 ATA:28 FUEL ATA:32 (L/G) (FUEL (STRERING ATA:29 HVD TIRE PRISS HYDRAULIC ATA 30 ICE&RAIN VIBRATION DETECTION> SYSTEM REPORT/TEST 5/6 SYSTEM REPORT/TEST 6/6 ATA:36 AIR BLEED ATA:52 DooRS Leak detection ATA: 70-080 ENG START/IGN PRESS/TEMP INDICATING CROSS FIRD REVERSERS ATA INTERFACE THRUST CTL FADEC <ENGINES ``` ### Simple BITE Circuit Many aircraft systems built in the 1980's or later incorporated some type of BITE circuitry. Independent systems, such as the radio altimeter, often contained BITE circuitry in the main LRU (Line Replaceable Unit) of the system. To run the radio altimeter BITE, provide power to the system. Following the instructions, press the TEST button and monitor the LEDs on the face of the LRU. Also monitor the appropriate display for the correct indications. Release the test button and verify the correct LED and display operation. The BITE circuitry performs simple tests on the transceiver, the antenna, and the radio altimeter display Here is the transcription of what the BITE test procedure is: ``` BITE TEST PROCEDURE 1. Test left RA T/R units BITE TEST Dendix Radio alitimeter BITE - A simple BITE test procedure A transport avionics RAO ALT 1 RIT ANT IND TEST RED SYSTEM FAIL LED GREEN SYSTEM GOOD LED RED ANTENNA FAIL LED RED INDICATOR FAIL LED TEST SWITCH a. Press and hold TEST switch on front panel of left RA receiver/transmitter (R/T) and check that: (1) All Monitor lights on left RA R/T front panel come on for three seconds and then go out for three seconds (2) Captain's EADI RA display and radio altitude Indicator (if present) indicate 40 +/- 2.0. feet (3) The red ANT LED comes on ONLY of the T/X or RX antenna is grounded. b. Release left RA R/T TEST switch. Check that green flight labeled R/T goes out and that captains EADI display indicates -6 +/- 2.0 feet: (1) A red R/T or LRU ST during test indicates a system fault present or 2 system faults have been detected in the last 4 flights. ``` Similar tests are extremely common on many LRUs found on aircraft. ## Self-Test BITE Some systems utilise a BITE feature which is initiated from a switch on the flight deck. One such system is the Ground Proximity Warning System (GPWS), which uses the test button on the panel to test the GPWS computer and interfacing system validity. The test feature is available in flight as well as on the ground. The test is initiated, after meeting certain conditions, by pressing and holding the test button. For a successful test the following sequence of events occurs: * The pilots BELOW G/S light will illuminate and remain illuminated for as long as the button is pressed and held. * The GLIDESLOPE aural will sound (once only), followed by the WHOOP – WHOOP – PULL UP aural, at reduced volume and repeating approximately 2 to 8 times, provided the TEST button remains pressed and held. * When the WHOOP – WHOOP – PULL UP aural is sounding, the pilots PULL UP light will be illuminated. * If the TEST button is released after the WHOOP – WHOOP – PULL UP has sounded once (at least) the aural will sound again at full volume. Here is a description of the diagram showing the GPWS self test system: "The diagram shows multiple components connected to the GPWS test, with the following labels: ADVISORY LIGHT (BELOW G/S), CAPTAIN'S INPH SPEAKER, FLASHER, CADC NO.1, VHF-NAV NO. 1, VHF-NAV NO. 3, CAPTAIN'S DEV SWITCH, LRRA NO. 1, GROUND PROXIMITY WARNING COMPUTER, GPWS, LANDING GEAR HANDLE POSITION SWITCH, 115V AC, ESS FLT INST, 22.5 FLAP POSITION SWITCH (S215), WARNING LIGHT (PULL UP), FIRST OFFICER'S INPH SPEAKER, PUSH TO TEST, PUSH TO INHIBIT GLIDE SLOPE". ### GPWS Self-Test BITE ## Aircraft Communications Addressing and Reporting System (ACARS) ### ACARS Introduction ACARS is a radio teletype mode developed in the early eighties as an addressable, digital data link for commercial and business aircraft by Aeronautical Radio, Inc. (commonly known as; "ARINC"). It was produced to reduce the flight crew's workload by using modern computer technology to exchange many routine reports and messages. Using an ACARS system, on board maintenance systems can transmit information to a ground station. This information can include aircraft system faults, and aircraft performance data, and helps operators reduce the number and length of aeroplane dispatch delays. On the ground, the fault data is logged along with flight and tail number and time. Maintenance personnel can make informed maintenance decisions, have a part prepared for fitment, or have a part transported to the destination for fitment. Maintenance personnel can also interrogate the aircraft's system - via the communications uplink - to ascertain the fault's status. The ground crew can assist in the diagnosis, schedule the repair, determine correct repair procedure, and then alert the destination station to assemble needed parts, tools and personnel required. As a result, everything is waiting the moment the aircraft touches down, thus providing a faster turnaround. The technicians, tooling and parts can be waiting, and work can begin as soon as the aircraft docks at the passenger terminal. A time-consuming maintenance task can be reduced to the time taken for a routine aircraft turn-around. Here again is that table showing "ACARS operation": | Taxi | Take-Off | Departure | En Route | Approach | Landing | Taxi | | :---------------------------- | :------------ | :-------------- | :------------------------------------------------------------------------------------------------------------------------------------------ | :------------------------------------------------------------------------------------------------------------------ | :-------- | :----------------- | | From Aircraft | From Aircraft | From Aircraft | From Aircraft | From Aircraft | | From Aircraft | | Link Test/Clock Update | Take-Off | Engine Data | Position Reports Weather Reports Delay Info/ETA Voice Requests Engine Information Maintenance Reports | Provisioning Gate Requests ETA Special Requests Engine Information Maintenance Reports | On Deck | Fuel Information | | Fuel/Crew Information | | | | | | Crew Information | | Delay Reports | | | | | | Fault Data from CMC| | Taxi Out | | | | | | | | To Aircraft | To Aircraft | To Aircraft | To Aircraft | To Aircraft | | | | PDC | | Flight Plan Update| ATC Oceanic Clearances Weather Reports Readabilty Ground Voice Request (SELCAL) | Gate Assignment Connecting Gates Passengers & Crew | | | | ATIS | | Weather Reports | ATIS | | | | | Weight & Balance | | | | | | | | Airport Analysis | | | | | | | | V-Speed | | | | | | | | Flight Plan | | | | | | | | Load FMC | | | | | | | ### ACARS Components The airborne components of ACARS are the Management Unit (MU), the Control Unit (CU) and a printer. The ACARS Management Unit (MU) is the unit that formats all the flight data that is sampled during the flight. The MU collects data from the Control Unit, aircraft sensors, and event sensors. The MU generates a GMT (Greenwich Mean Time) clock signal which is used in recording the time of the events. The MU controls the transmission of air to ground messages and receives digital messages through the VHF transceiver. This is a description of the diagram of an "ACARS system and components": "The diagram includes the following components: ACARS Control Unit, Various Aircraft & Avionic Systems, ACARS data, Data to MU, Data to CU, Aircraft data, ACARS Management Unit,Digital tuning, VHF transceiver, VHF antenna, Xmtr keying and printer." The flight crew interfaces with ACARS through the Control Unit (CU). The CU contains an alphanumeric keyboard for entering information or responding to a function inquiry. Here is the transcription of the Central Display Unit (CDU), which is the interface for ACARS. ``` CDU MENU 1. PRESS MENU KEY <FMC DSPL <CMC KEY EICAS CP MENU REQUESTS <ACARS REPORTS > <EFIS CP MENU RECEIVED MESSAGES > DATA <FLIGHT <LINK TEST <WEIGHT 215 <DEPARTURE COMM 2. PRESS CDU <ARRIVAL AC MAINTENANCE DATA CHIMEON KEY INIT REF RTE DEP ARR VNAV COMM FIX LEGS HOLD PROG EXEC NAD A B C D E PREV PAGE FGHI J KLMNO PQRST NEXT PAGE UV WXY Z/ CLR ``` The ACARS MU and related airborne subsystems are monitored by a BITE circuit within the MU. The BITE circuit continuously monitors the health of ACARS components and reports all failures to the central maintenance computer system. The MU test switch, located on the face of the MU, can also be used to initiate an ACARS test. During the test, all four lights should illuminate for three seconds (to test lamp operation), all lamps should extinguish for the next three seconds. After six seconds, the appropriate lamp should illuminate; green means 'OK', red means failed system. Here is a block diagram of the ACARS management unit: "The diagram shows the main components of the ACARS Management Unit, MU and CU test switch, GREEN and RED leds, identification Plate". ## Data Bus Fundamentals The use of digitally based microprocessor electronics allows several mechanical instruments to be replaced with modern electronic flight instruments displaying the information on one or more Multi-Function Display (MFDs) or Digital Display Indicators (DDIs). The signals sent to the various systems components are linked through a digital data bus, and the information is transmitted to the symbol generators digitally, either directly from the sensors (ARINC 429 and 629), or by the Bus Controller (MIL-STD 1553). Here is a description of the "Multifunction displays and digital data bus system" diagram. "The diagram depicts a digital databus system where information flows between the simple analogue systems navigation computer and the air data computer to different elements of the digital databus system such as ADC & DAC, HSI DISPLAY, Flight Management Computers, AutoFlight computer, Thrust management computer, Central Maintenance Computer and EFIS control Panel" ## Airbus' Electronic Centralised Aircraft Monitoring (ECAM) ### ECAM Introduction The ECAM system used by the A320, and the subsequent range of Airbus aircraft, displays information from all major systems on two display units. The display provides flight crew with an indication of system status, and any warnings, cautions or failures. Maintenance staff can also access the ECAM system to view systems status, synoptic diagrams, and to identify failure indications recorded in the flight warning computers memory. The ECAM displays are in the centre of the instrument panel, corresponding to where the analogue engine instruments were located in older model Airbus aircraft. In the latest model aircraft with data bus technology, the ECAM display is not restricted to centre CRT's, it can be displayed in front of captain or first officer in place of EFIS displays, if so selected. There is a picture of the ECAM displays and the ECAM control panel, it describes the major elements. ### ECAM Displays ECAM operates in normal and abnormal circumstances by displaying colour coded warnings, caution and advisory messages and systems status. The upper-most screen is used to display primary engine information, basic system information, and all the warning, caution and ancillary messages that are generated by the aircraft's Central Maintenance Computers and the ECAM Flight Warning Computers. In the diagram below, the display on the right shows primary engine information, basic system information, all warning, caution and ancillary messages. The display on the left shows secondary engine information, aircraft status and system detail. ### ECAM System Operation The main component in the ECAM system is the Flight Warning Computer (FWC). The FWC receives the inputs from the aircraft systems. Inputs from analogue based systems or sensors are routed through the Signal Analogue to Digital Converter before being sent to the FWC's. Both FWC's receive the same information as each other and both continually monitor the other for errors or malfunctions. The following list describes the ECAM schematic system operation. The output from the FWC's is then sent to the ECAM symbol generators, which transform the signal for input into the ECAM displays. Under normal operations, the FWC provide output to only one of the symbol generators at a time. In latest model Airbuses, symbology generators are incorporated within display units - they are not separate avionics boxes. Here is a description of that 'ECAM schematic - system operation' diagram: "The diagram shows different components of the ECAM system, The Left and e Right system displays, symbol generator unit, ECAM Control Panel, Signal data analogue computer, flight warning computer, inputs and warning light display panel" ## Electronic Flight Instrument System (EFIS) ### EFIS Purpose The purpose of the EFIS display system is to provide the flight crew with the information required to operate the aircraft. This is a description of the "Captains Display System" and the "First Officer Display systems". The Diagram shows multiple electronic display units which provide a backup in case any element would happen to fail. ### Electronic Flight Instrument System (EFIS) components An EFIS system consists of four interchangeable Cathode Ray Tubes displays, two for each pilot, three symbol generators, two control panels, and two source select panels. The third (centre) symbol generator is incorporated so that its drive signals can be switched to either the Captain or First Officer's display unit in the event of their primary symbol generator failing. The Symbol Generators provide the analogue, discrete and digital interfaces between an aircraft's navigation and sensor systems, and the display units and the control panel. They produce the signals to drive the deflection plates in the display to produce the required symbology, provide power control and system monitoring. The display controller provides the pilot with switches and buttons to select the information sources he/she wishes to have displayed relevant to the phase of flight. The EFIS display is not restricted to the CRT's directly in front of the Pilot; it can be displayed on whichever display is selected. ### Primary Flight Display (PFD) A PFD combines the information provided by an EADI and an EHSI onto one CRT. The PFD displays attitude, lateral navigation/compass, flight control and primary air data (altitude/airspeed/vertical speed) functions. The PFD receives data bus inputs from analogue-digital converters interfacing non-digital equipment to the data bus, other avionics systems, Traffic Alert Collision Avoidance System (TCAS), Inertial Reference Units and Air Data system. Here is Primary Flight Display (PFD) on an aircraft, ### Multifunction or Navigation Display (MFD or ND) The MFD or Navigation Display (ND) displays lateral navigation/compass, radar, TCAS, flight management (map/summary) and diagnostic information. The MFD also provides a reversion backup for the PFD or the EICAS if that display fails. The MFD receives the same data bus inputs that are applied to the PFD. It also receives input buses from weather radar, EICAS control panel, Central Maintenance Computer and Flight Management Computer. There is a graphic showing a "Multifunction or Navigation Display (MFD or ND)". ## Boeing's Engine Indicating and Crew Alerting System (EICAS) ### EICAS Introduction Just as Airbus use modern display systems for the representation of aircraft system indication, modern Boeing jets also display electronically aircraft system information on Cathode Ray Tubes (CRT) or Liquid Crystal Displays (LCD). EICAS was first introduced in Boeing 757 and 767 aircraft. Engine and system operating data is displayed on centrally located CRT's, eliminating the need for traditional analogue engine instrumentation. Primary engine data is always on display, but in the event of any failure the flight crew's attention is drawn to them by an automatic display of messages in appropriate colours to indicate the significance of the problem. The displays also provide indications of systems status and operating values as selected by the crew through the control panel of the system. In conjunction with the Central Maintenance Computers (CMC), the EICAS system monitors all of the aircraft's systems to ensure no system failures occur. The system will also record all faults generated by the aircraft's systems for later investigation by the flight crew or ground engineering staff. Through the use of an ACARS system, the EICAS system is able to transmit information to a ground station. This information can include aircraft system faults and aircraft performance data. The following are components to a Boeing 757 EICAS The diagram shows the various displays with pilots selection panel, a simple diagram. ### EICAS Upper Display The upper Indicator Display Unit (IDU) normally shows primary engine indications, crew alert messages, flaps and landing gear status, fuel quantity and environmental control system information. ### EICAS Lower Display The lower EICAS display normally shows the auxiliary EICAS formats. The available auxiliary EICAS formats are secondary engine, status page, synoptics and maintenance pages. During normal flight, the lower EICAS display will be blank, with information only being displayed when the pilots select the lower screen for required secondary information. The reason for the blank screen is that the display is placed in the centre pedestal and to reduce interference from screen glow during flight operations. ### EICAS System Operation Only one computer operates at a time, the other is for redundancy and remains in standby ready to take over automatically if the primary computer fails, or it can be switched over manually (selection available on display select control panel). The EICAS system does not incorporate separate symbology generators; this function is performed by the EICAS computers. EICAS provides an improved level of maintenance data for the ground crew without causing any extra workload for the flight crew. This is achieved by designing a system that will automatically record subsystem parameters when malfunctions are detected. Flight crew can also initiate manual data recording at the push of a button, which eliminates the need for manual handwritten recordings of system and performance data for later provision to maintenance engineers to facilitate rectification. These features increase the accuracy of maintenance data recordings and improve the communication between the aircrew and maintenance crews. When a warning message is received, the level is accessed by the EICAS system, based on pre- programmed criteria, and sent to the relevant areas for aural and visual display. There is a dedicated Maintenance Control Panel in the EICAS system for use by engineers for the purpose of displaying maintenance data stored in the computer's memory. System failures which have occurred in flight will be automatically recorded in computer memory and can be retrieved for display by engineers after the aircraft has landed. Here is a discription of the EICAS schematic for system operation, "The diagram displays the various components to its engine system" ### EICAS Control Panel The EICAS control panel provides control of EICAS functions and to select display modes. ### EICAS Maintenance Control Panel System failures which have occurred in flight will be automatically recorded in computer memory, and can be retrieved for display by engineers after the aircraft has landed. The maintenance displays (which appear on the lower display) are unavailable in flight. ### EICAS BITE Tests The EICAS BITE test is used to perform testing of the EICAS computers, upper and lower display units, the master caution and warning displays, and various EICAS interfaces. The BITE test is initiated by pressing the test switch on the MCP. The aircraft must be on the ground, and the parking brake set, for the test to begin. Each EICAS computer is tested individually. At the beginning of each test the EICAS message "LEICAS TEST" and "TEST IN PROGRESS" will appear on the upper display. The message "R EICAS TEST" will be presented during the test of the right computer. ## Fly-By-Wire Flight Control System ### Fly-By-Wire General Arrangement A fly-by-wire flight control system uses digital computers which have complete control over all the flight control surfaces. When a pilot wants to change the aircraft's attitude, they move the side-stick, or rudder pedals and electrical signals from the connected transducers are processed by the computers. The signal is then transmitted to the electrically operated actuators, which deflect the control surfaces to achieve the desired attitude change. There is no mechanical connection between the pilot's controls and the control surfaces. The image is of a fly-by-Wire side stick. The function of the system is being managed by CPU's. The surfaces selected to perform the manoeuvre are dictated by the software program. During aircraft design and test flying of prototypes, phases of flight are tested within the flight envelope and the software program to manage the flight control system is designed for efficiency and flight safety. For example selecting a spoiler or aileron to achieve a roll will depend on the rate of roll requested by the pilot (degree of stick deflection), airspeed, Angle of attack and outside air temperature to name but a few. The amount of deflection will also vary greatly with the same stick input depending on the phase of flight. With a CPU managing the flight control surfaces all factors affecting control of flight can be considered before the electrical signal is transmitted to the control surface actuator to deflect the surface the desired amount. It is the flight control computer software which selects the most efficient method to achieve the attitude change requested by the pilot. Another added benefit is that the flight control surfaces can be easily controlled by the autopilot, to navigate a pre-programmed course and track, to fly an approach down an Instrument Landing System localiser and glideslope, and functions such as altitude hold, attitude hold, and heading hold. The Airbus fly-by-wire system offers significant tangible benefits in terms of greater safety through unconstrained control input freedom within the flight envelope, and protection against exceeding operating limits, stalling, over speeding or overstressing the aircraft outside the flight envelope. To these can be added windshear protection, reduced pilot workload, lower costs and improved aircraft performance. It makes a major contribution to reducing maintenance costs by eliminating much of the complex mechanical system of cables, pulleys and associated gear which need post-maintenance rigging work and checks. To achieve redundancy and improve safety it is normal for an active control system to comprise several different computers, each having a specific function. No single computer will be permitted to exercise control without its commands being monitored by at least one other computer. In addition each computer will use a different microprocessor type, different suppliers, have physical segregation of data buses, and separation of computer installations. Each computer will use a different power supply and hydraulic system. ## Flight Management System (FMS) ### FMS General Arrangement The FMS interfaces with many areas of the aircraft to aid in its primary functions. These include such areas as the fuel quantity system, flight control system, air ground data link systems, radio navigation systems, the Inertial Reference System, the Thrust Management System, and the aircraft EICAS/ECAM and EFIS systems. Here is a discription of the diagram which depicts the "Flight Managment System (FMS)": "The diagram shows the thrust manangement computer, fuel qualtity and fuel flow, air and gnd datalink systems, radio navigation systems, the intertial reference system, and the aircraft EICAS/ECAM and EFIS Systems. The image consists of multiple components centralized around the Flight management Computere(FMC) system" The FMS is used by the flight crew to reduce the crew workload when planning, undertaking, monitoring and executing a flight plan. The FMC is, in effect, the master computer, which integrates the functions of the inertial navigation unit, flight control computers, thrust management computers, air data computers, navigation sensors and EICAS computers. The FMS has the capability of automatically controlling the aircraft from just after take-off, through to roll out on the runway after landing, at the destination. Not all flights use a flight management system to its fullest capacity, but the autopilot and flight director will be used for some portion of each flight. ### FMC Operation One two or three FMC units are fitted to an aircraft, with each FMC allocated to a crew position. All FMC's receive the same input data from the aircraft systems. A Control Display Unit (CDU) is used for data entry into the FMC. Data entered into a CDU is sent to all the FMC's fitted, and each FMC will action the data independently. The output from an FMC is only sent to its CDU. This provides system redundancy should one FMC fail, as the other has all the current aircraft data to control the operation of the aircraft. Here isa description of the "FMC schematic:" "The FMC schematic includes an interface connection for the left and right components. It receives the same input data from the aircraft systems" ### Control Display Unit (CDU) The CDU provide control of the FMC and allows access to FMC fault data. System tests are started from the CDU, and test results are displayed on the CDU screen. Printing of the CDU display can be carried out using the on-board printer. The maintenance pages of the CDU show maintenance related data that is accessible on the ground only. ### FMS BITE The FMS continually monitors itself using BITE software programmed into the FMC. BITE is automatically initiated at every power-up of the FMC. BITE can also be initiated through the central maintenance computer system, or using the test switch on the front of the FMC. During this 15 second test, the EICAS, PFD, and ND each present specific test messages. During the test, the master caution and warning lights and aural tones sound for a short period. On the FMC, the red 'fail' lamp illuminates while