BITE Systems in Aviation Maintenance

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Questions and Answers

What is the primary role of BITE in a multiple computer system?

Ensure the aircraft's fuel efficiency.

Monitor internal LRU circuits and system links. (correct)

Manage data storage effectively.

Facilitate pilot training simulations.

During which condition is the power up test executed?

After any power cut exceeding 200 milliseconds. (correct)

During regular flight operations.

Only when the aircraft is flying.

When performing scheduled maintenance checks.

Which of the following tasks is NOT typically included in a power up test?

Test of the microprocessor.

Test of the memories.

Watchdog test. (correct)

Configuration test.

What advantage does initiating BITE tests through a centralized maintenance device provide?

Simplification of technical documentation. Signup and view all the answers

What type of test is a watchdog test classified as?

Cyclic test. Signup and view all the answers

Which of the following statements about the BITE memory is accurate?

It stores information concerning system performance. Signup and view all the answers

What does the BITE system do when a failure occurs?

Identifies the possible failed LRU and its nature. Signup and view all the answers

What is a key characteristic of cyclic tests in BITE?

They run continuously without disrupting operations. Signup and view all the answers

What is the primary purpose of conducting a system test after system restoration?

To check the integrity of the system and troubleshoot issues Signup and view all the answers

What types of commands can the MCDU send to connected systems?

Commands for various components like valves and flaps Signup and view all the answers

Which of the following systems is NOT typically accessed through the MCDU?

Engine Maintenance System (EMS) Signup and view all the answers

What does the BITE concept help to reduce during aircraft maintenance?

Aircraft maintenance downtime Signup and view all the answers

When powered up, what is the first page displayed by the MCDU?

STATUS PAGE Signup and view all the answers

After repairs are made, what should be done to ensure correct operation of the aircraft systems?

Run a complete operational check of the system Signup and view all the answers

Which of the following is a function of the MCDU's keyboard?

To send commands to connected systems Signup and view all the answers

Specific tests in aircraft systems are primarily designed to generate stimuli for which of the following?

Actuating devices such as valves or actuators Signup and view all the answers

What does BITE stand for in the context of aircraft systems?

Built-In Test Equipment Signup and view all the answers

Which system is primarily focused on engine indicating and crew alerting?

Engine Indicating and Crew Alerting System (EICAS) Signup and view all the answers

Which system provides navigation and positioning capabilities for aircraft?

Global Positioning System (GPS) Signup and view all the answers

What is the significance of BITE in modern aircraft?

BITE simplifies the process of troubleshooting complex systems. Signup and view all the answers

Which of these systems is primarily used for managing flight operations?

Flight Management System (FMS) Signup and view all the answers

What functionality does the Traffic Alert and Collision Avoidance System (TCAS) provide?

Collision avoidance through traffic alerts Signup and view all the answers

Which of the following systems is NOT typically included in electronic/digital aircraft systems?

Mechanical Gyroscope Signup and view all the answers

What is a key feature of the Electronic Flight Instrument System (EFIS)?

Displays flight data digitally Signup and view all the answers

What is the primary function of Built-In Test Equipment (BITE) systems in aircraft?

To monitor and troubleshoot various aircraft systems. Signup and view all the answers

Which of the following statements about Line Replaceable Units (LRUs) is true?

LRUs are monitored continuously for safety and functionality. Signup and view all the answers

What distinguishes the Central Maintenance Computer System (CMCS) from older BITE systems?

CMCS includes enhanced functionality for troubleshooting. Signup and view all the answers

In the context of aircraft systems, what does a multi-character display typically indicate?

It monitors multiple LRUs simultaneously. Signup and view all the answers

What is a key benefit of the advanced BITE systems used by manufacturers like Boeing and Airbus?

They improve accessibility and understanding of troubleshooting procedures. Signup and view all the answers

How are faults detected in most advanced BITE systems documented?

Through paper printouts and digital records during flights. Signup and view all the answers

What role does the BITE section play in aircraft computer systems?

It is dedicated to monitoring and troubleshooting functions. Signup and view all the answers

Which statement is true about the BITE systems in commercial airliners?

They are integrated into various systems monitoring numerous LRUs. Signup and view all the answers

Study Notes

Typical Electronic/Digital Aircraft Systems I (5.15)

Learning objectives include describing the general arrangement of typical electronic/digital aircraft systems and associated built-in test equipment (BITE), Aircraft Communications Addressing and Reporting System (ACARS), Electronic Centralised Aircraft Monitoring (ECAM) system, Electronic Flight Instrument System (EFIS), Engine Indicating and Crew Alerting System (EICAS), Fly-By-Wire (FBW) control system, Flight Management System (FMS), Global Positioning System (GPS), Inertial Reference System (IRS), and Traffic Alert and Collision Avoidance System (TCAS).
All learning objectives are at Level 2.

Integrated Test Equipment (BITE)

Aircraft are complex, so design engineers need to consider the ability to troubleshoot systems as important as repair and inspection. Self-contained diagnostics are used for electronic/avionics troubleshooting.
BITE is a built-in test equipment, used for troubleshooting electronic/avionics systems.
Various versions of BITE exist. Simple systems may use a go/no-go LED; more complex systems use a multi-character display. Some BITE can also test associated wiring.
Modern self-diagnostics integrate centralized monitoring systems, which have flight deck displays for activating tests. Results are often printed, and data can be transmitted to ground maintenance.
Boeing uses Central Maintenance Computer System (CMCS). Airbus uses Centralized Fault Display System (CFDS).
Commercial aircraft can have numerous BITE units monitoring various systems, each receiving inputs from individual components.
Newer systems are more user-friendly and accessible compared to older ones.

BITE Systems

There are numerous versions of BITE, from simple to complex ones.
Simple systems use a go/no-go LED.
Complex systems are used for more LRU's.
Modern systems use a centralized monitoring system with flight deck displays for test activation.
Fault detection involves monitoring, including paper printouts of test results and transmission of data to maintenance facilities during flight.

BITE Philosophy

Most aircraft systems are made up of Line Replaceable Units (LRUs), such as black boxes, sensors, actuators, probes, or similar items.
Digital computers manage and monitor most LRUs.
This monitoring is for safety reasons, so that testing and troubleshooting procedures can be done.
BITE continually monitors circuits, inputs, outputs and connections among LRUs.
When a failure happens, BITE identifies its type (intermittent or permanent) and documents the system status during failure, which is stored in non-volatile memory.

BITE Function

BITE information is sent to a centralised maintenance device.
The device offers single-interface locations like cockpits, easy fault identification, shorter troubleshooting periods, more simplified technical documentation, and standardized equipment.

Power Up Test

A safety test conducted when the aircraft is on the ground, after a power cut for more than 200 milliseconds.
Tasks include microprocessor, memory, data lines, and circuit testing.
Airborne, the power up test is limited, enabling quick system restarts.

Cyclic Tests

Testing is done without disrupting system operation.
Includes watchdog tests (for software failure), RAM tests, and message validity (ARINC 429) tests.

Specific Tests

For some systems, specific tests are available, stimulating various command devices (actuators or valves), like slats or flaps movement, or dry cranking of the engine.
The tests help generate necessary stimuli for troubleshooting and verification of proper operation after repair.
An important benefit is that using both BITE and LRU concepts can reduce aircraft maintenance downtime.

Maintenance Control Display Unit (MCDU)

The MCDU is a device with a screen, keyboard, and function keys that allows access to aircraft systems like the FMS (Flight Management System), ACMS (Aircraft Condition Monitoring System), CMS (Central Maintenance System), SAT (Satellite Communication System), and ATSU (Air Traffic Service Unit).
The MCDU uses a series of keystrokes to access required system information.
Upon powering on, the unit displays a status page where users can select the MCDU Menu to display more options.

MCDU Utilisation

The display presents a status or allows specific tests.
Keystrokes access specific systems and display status and run tests.
Multiple pages are accessible through various keystrokes as referenced in the study guide.

ACARS System

ACARS uses a digital data link to reduce flight crew workload and exchange many routine reports and messages.
Ground stations receive fault data and aircraft performance data.
Maintenance staff can create repair plans or order parts.

ACARS Components

ACARS has airborne components (Management Unit (MU), Control Unit (CU), and printer).
The MU formats data from the flight, aircraft sensors, and event sensors.
The MU sets a GMT (Greenwich Mean Time) clock and manages communication across the data bus and the VHF transceiver.
The CU is where crews enter and receive data through an alphanumeric keyboard.

ACARS Management Unit (MU)

Monitoring of ACARS and its components is done by its internal BITE circuit.
An ACARS test can be initiated from the MU test switch.
During a test, four LED lights will flash (green for OK, red for failure).

Data Bus Fundamentals

Digital microprocessor electronics allow replacing mechanical instruments with electronics.
Interconnecting components via a digital data bus is used, transferring data from sensors (or other sources) to display devices.

Airbus' Electronic Centralised Aircraft Monitoring (ECAM)

Airbus aircraft use ECAM.
ECAM displays system status and warnings/cautions/failures on two displays, enabling flight crew identification and access of failure indicators.
Maintenance staff can also use ECAM to view system status, diagrams, and recorded failure indications.
ECAM displays often take the spot on the panel where older aircraft had analog engine instruments.
The modern model can be configured to be in place of EFIS displays.

ECAM Displays

ECAM displays system statuses and warnings/cautions/failures and generates information, like various warnings, cautions, and ancillary messages.
They also show primary system information, secondary system information, and ancillary warning messages.

Electronic Flight Instrument System (EFIS)

EFIS systems provide flight crew with operational information.
The system consists of four CRT displays, three symbol generators, and interface and control panels.
Each pilot has two displays, with backup systems in case the primary is unavailable.

Primary Flight Display (PFD)

The PFD combines EADI and EHSI data onto one CRT.
The PFD displays attitude, flight controls, and some primary air data (like altitude, airspeed, vertical speed) for primary operation.
A PFD integrates various system data to provide a comprehensive overview.

An MFD (or ND) can be used for navigation, lateral navigation, compass, radar, TCAS, flight management data (with map summary), and diagnostics.
The MFD (or ND) serves as a backup in case the primary flight displays fail.
The MFD (or ND) uses the same data bus inputs as the PFD.
It also receives information from other systems (like weather radar), the central maintenance computer, and the flight management computer.

Boeing's Engine Indicating and Crew Alerting System (EICAS)

EICAS systems provide electronic displays of information about an aircraft's engine and systems.
EICAS uses CRT or LCD displays.
The information on the display is automatically updated if a system fails.
The flight crew can visually and audibly access system status.
The EICAS system communicates with systems like ACARS, alerting ground staff about issues.

EICAS Upper Display

Shows primary engine data, alert messages, and system settings.
Displays critical status information needed for pilots to safely operate the aircraft.

EICAS Lower Display

Displays additional system data.
Shows auxiliary data, while the upper one displays primary information; the blank screen on the lower screen is for reasons like reducing interference and maintaining safe flight operations.

EICAS System Operation

An EICAS computer operates at a time, with another in standby to take over if necessary.
A single computer is automatically selected while another remains in standby for redundancy.

EICAS Control Panel

The panel is used to control and select EICAS functions and display modes.
System testers can be started from the panel.
Test results are displayed on the panel, and printed results are available on-board.
Maintenance data is only available on the ground.

EICAS BITE Tests

BITE tests the EICAS computers, upper and lower displays, caution/warning displays, and interface elements.
Aircraft must be on the ground.
Parking brake must be set to proceed.
Individual computers are tested separately using commands that are input on the control panel.
A message appears on the display to indicate the start of the test.

Fly-By-Wire Flight Control System

Systems use digital computers to fully control flight surfaces.
Aircraft attitude change is determined by pilot stick/pedal commands.
Electrical signals are sent to actuators to move flight surfaces, which alters the attitude.
Flight control systems have no mechanical connections between pilot input and surface movements.
Software dictates which surfaces move for each maneuver.

Flight Management System (FMS)

The FMS is an aircraft system that integrates many areas, including fuel quantity systems, flight controls, air traffic communications, radio navigation, the Inertial Reference System, thrust management systems, and EICAS/ECAM and EFIS.
The Flight Management Computer (FMC) is central to the FMS.
It is used to assist pilots in planning, controlling, and monitoring their flight plan.
The FMC integrates many functions like inertial navigation, flight control computers, air data computers, navigational sensors, and EICAS computers.

FMS Operation

Various FMC units (one per crew position) receive input data.
Control Display Unit (CDU) is used for entering data.
Each unit processes this input data independently.
The output from one FMC unit is directed only to its associated CDU.

FMS BITE

The FMC is continually monitored using BITE software.
BITE is initiated at every FMC power-up.
Also, through the central maintenance computer, or a dedicated test switch on the FMC.
During this test, the system checks various parameters using messages.
Warning and caution lights will indicate if the test is underway or if a fault is detected with the specific FMC.

Global Positioning System (GPS)

GPS uses satellites for precise navigation, used by planes, ships, cars, and even hikers.
GPS satellites orbit Earth and enable GPS operation worldwide.
Airborne GPS components: combination of control panel and receiver, a remote receiver communicating via a digital bus to an FMS, or a dedicated multifunction panel connected to other computers.

Receiver BITE Test

BITE checks the receiver's operations and interface with the antenna.
The test duration is approximately 36 seconds.
LED indicators present the status of the test.

Inertial Reference System (IRS)

IRS provides crucial navigational data like attitude and velocity.
The system uses components like laser gyroscopes and accelerometers to sense angular rates and accelerations.
The data is independent of other systems except for occasional GPS updates.
The IRS provides computations for attitude and velocity.

IRS Components

IRS typically includes an Inertial Reference Unit.
A Mode Selection Unit.
One Display Unit for each flight crew.

IRS Standby Power Supply

IRS requires an uninterruptible power supply.
The system has a power supply that transfers from 28 VDC to 115 VAC when a power failure occurs on the primary system.
An IRS always has access to the main aircraft battery.

IRS BITE

IRS performs a BITE test upon initial power-on.
The test verifies system health and power supply switching.
If the test is successful, the IRS is ready for operation and will have an initial alignment process.

Traffic Alert and Collision Avoidance System (TCAS)

TCAS helps pilots avoid collisions in the air due to warnings about other aircraft.
The TCAS constantly monitors aircraft movements within a defined area.
It provides alerts when collisions are possible which is typically done through two levels. Traffic Advisory (TA), which gives the distance and bearing information, and Resolution Advisory (RA), providing visual and audio instructions for ascending or descending to mitigate potential collisions.
Equipment in a TCAS system includes a computer, display screen, and antenna.

TCAS BITE

Continuous and automatic monitoring for system and interface faults during operation.
Signals are sent to monitor signal processor, receiver, and transmitter circuits in a test.
Fault information, if detected, is saved in the system memory.
The related data is transferred to other related units.

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Description

This quiz explores the Built-In Test Equipment (BITE) systems used in multiple computer systems, particularly in aviation. It covers various tests such as power-up tests, watchdog tests, and cyclic tests, and delves into the roles and advantages of BITE in aircraft maintenance. Test your knowledge on how these systems ensure reliability during operation and maintenance.