11.19 Integrated Modular Avionics

• Integrated Modular Avionics (IMA) are real-time computer network airborne systems with computing modules supporting numerous applications.
• IMA architectures use a high-integrity, partitioned environment to host multiple avionics functions on a shared computing platform.

Federated Avionics Architecture

• The Boeing 767 and 757 were the first commercial aircraft to use federated digital architecture.
• The Airbus A320 was the first fly-by-wire transport aircraft.
• The A320 used ARINC 429 digital outputs from LRUs to supply digital flight computers with sensor, command, and feedback data.
• ARINC 429 data bus became a victim of its own success as the amount of digital information exchanged by LRUs grew beyond its capability.

Transition from Federated Avionics Architecture

• The Boeing 777 moved toward IMA architecture with the Airplane Information Management System (AIMS) cabinet.
• Several major functions previously implemented as independent LRUs were implemented within the AIMS processors.

IMA Concept

• The IMA concept replaces separate processors and LRUs with fewer, more centralised processing units.
• This reduces weight and maintenance in commercial airliners.
• Fewer avionics components drive higher reliability and require less maintenance.
• Loadable Software Aircraft Parts (LSAPs) system software is loaded onto servers and configured for the aircraft type.
• This approach saves wiring and reduces the number of LRUs.

Integrated Modular Avionic Functions

• Functions that can be integrated into the IMA modules include:
  • Bleed management
  • Air pressure control
  • Air ventilation and control
  • Avionics and cockpit ventilation control
  • Temperature control
  • Air traffic communication
  • Avionics communication router
  • Electrical load management
  • Circuit breaker monitoring
  • Electrical system Built-in Test Equipment (BITE)
  • Fuel management
  • Braking control
  • Steering control
  • Landing gear extension and retraction
  • Tyre pressure indication
  • Oleo pressure indication
  • Brake temperature monitoring

Advantages of Using Integrated Modular Avionics (IMA)

• Federated architecture has different subsystems existing on their own hardware, physically separated from one another.
• IMA systems have all subsystems on a common platform, sharing resources.
• IMA has gained popularity over other systems due to:
  • Reduced weight
  • Reduced size
  • Lower power consumption
  • Easier modification
  • Reduced recurring cost

Basic Definitions and System Terminology

• Aircraft Data Network (ADN) is any networked system used to transfer data between subscribers that meets reliability and safety standards.
  • Avionics Data Communication Network (Airbus) - ADCN
  • Common Data Network (Boeing) - CDN
• Avionics Full-Duplex Switched Ethernet (AFDX) is a type of ADN based on IEEE 802.3 Ethernet specification.
  • It utilizes commercial off-the-shelf hardware and a serial data transfer technology based on conventional Ethernet.
  • AFDX allows for transfer rates of either 10 or 100 Mbps over either a copper or fiber optic transmission medium.
  • AFDX had to be extended to ensure a deterministic behaviour and high reliability.
• ARINC 653 is a software specification for space and time partitioning in safety-critical avionics real-time operating systems.
  • It allows the hosting of multiple applications of different software levels on the same hardware in an IMA architecture.
• ARINC 664 defines the use of a deterministic Ethernet network as an avionic data bus.
• ARINC 664 Frame describes the data packet that is submitted across the network, inclusive of the protocol bit layers, as well as the payload.
• ARINC 664 Message is a data item that is packed into the payloads of one or more ARINC 664 frames.
  • If a message is larger than the max payload size for a frame, then the message data is split between multiple frames before transmittal, and then re-joined into a single message upon receipt of all frames for that message.
• Bandwidth Allocation Gap (BAG) is a mechanism for controlling the amount of information that an LRM/LRU can transmit.
• Commercial-Off-The-Shelf (COTS) is a Non-Developmental Item (NDI) of supply that is both commercial and sold in substantial quantities in the commercial marketplace that can be procured or utilized in the same precise form as available to the public.
• Cyclic Redundancy Check (CRC) is a technique to detect errors in data transmission or storage.
  • Redundant bits are added to the data to run a short check and detect data corruption.
• Deterministic Ethernet makes it possible to send a piece of information to a destination and receive a response in a repeatable time frame.
• End System is an active AFDX subscriber, connected to an AFDX network to communicate with other subscribers respecting AFDX rules.
• Ethernet is the family of computer networking technologies for Local Area Networks (LANs).
  • Ethernet divides a stream of data into shorter pieces called ‘frames’ that include source and destination addresses and error-checking data.
  • The Ethernet specification served as the basis for the Institute of Electrical and Electronics Engineers (IEEE 802.3) standard.
• Federated Architecture has major functions implemented in LRUs that interchange information over digital data buses.
• Hosted Application (HA) is a software application that utilizes the computingresources of the Common Core System (CCS).
  • It can consist of one or more software partitions.
• Hosted Function (HF) is a system that directly interfaces with the CCS at one or more of its communications and/or Input/Output (I/O) interfaces.
  • It's like that of a Federated System LRU.
• IMA Cabinet contains dedicated modules and provides power for all modules.
• Institute of Electrical and Electronics Engineers (IEEE) 802.3 is a group of IEEE standards that defines the physical layer and data link layer's Media Access Control (MAC) of wired Ethernet.
  • Physical connections are made between nodes and/or infrastructure devices by copper or fibre optic cable.
• Modules (hosting modules) are computers that host applications and functions.
  • Airbus uses the term Central or Core Processing Input/Output Module (CPIOM).
  • The Boeing equivalent is the General Processing Module (GPM).
• Partition is the virtual resource on the hosting module inside which an application runs.
• Remote Data Concentrators (RDC) connect end systems with the ARINC 664 network and other inputs and outputs.
• Switches route data between subscribers of the data network.
  • In an ARINC 664 data network, switches are modified to enable the VL routing system to ensure deterministic Ethernet functionality.
  • Switches are dual-channel to ensure system integrity.
• Virtual Link (VL) are the communication channels used to transfer user data from an end system to one or more end systems, across the switched AFDX network.
  • The VL uses a Bandwidth Allocation Gap (BAG), specifying a minimal gap between the sending of two consecutive frames for a VL.

General Integrated Modular Avionics (IMA)

• The IMA design concept connects all modules to an Aircraft Data Network (ADN) and routes information via AFDX switches.
• IMA replaces point-to-point cabling with a virtual backplane data communications network.
• The network connects software configurable LRUs that can adapt to changes in network functioning or operating modes.
• There is a potential path between any of the LRUs, with the software and network defining the active VLs in real-time.
• In the event of failures, the system can quickly reconfigure.

IMA Approach

• Boeing can save 907 kg of weight on the avionics suite of the Boeing 787 Dreamliner using the IMA approach.
• The IMA approach cuts in half the part numbers of processor units for Airbus’s A380 avionics suite.
• IMA also offers an open architecture allowing for the use of common software.

Manufacturer’s IMA Approaches

• The Boeing 787 and the Airbus A380's approach to IMA differ.
• Both aircraft have applications for specific LRUs that are on the aircraft and individual computers for certain systems.

The Boeing 787 IMA Avionics Suite

• On the Boeing 787 avionics suite, there is a central computing system called the “Common Core System (CCS)”, which eliminates more than 100 different LRUs.
• A twin cabinet is used with Core Processing Modules (CPMs) employed to host the functions.

The Airbus System

• Airbus applies the IMA concept with hosting computers capable of hosting different functions and integrated modular avionics connected by a network.
• The A380’s IMA approach uses eight processing modules, some tailored for specific applications, but all tied together by a common Avionics Full-Duplex Switched Ethernet (AFDX) communication network, in the form of an ARINC 664 standard network system.
• Seven of the computers are CPIOMs; the eighth is an Input/Output Module (IOM) which does not host any applications.

Conventional LRUs Are Replaced by Software Applications

• Conventional LRUs are replaced by software applications loaded onto the processing modules.

IMA General Layout

• Conventional LRU functions are done by avionics applications hosted in shared IMA modules.

General Layout Example: Airbus

• Airbus has preferred to develop what they call an “open IMA” – computing resources on which they can have different functions hosted.
• On the Airbus AFDX, there are seven hosting modules (CPIOMs) that host software applications each performing a different function.

Domains

• The three functional domains of the Airbus IMA model are:
  • Flight control domain – includes flight control systems.
  • Cockpit domain – includes communications and warning systems.
  • Cabin domain – includes air conditioning and pneumatic functions.

Functional Areas

• On the Airbus AFDX system, “Functional Areas” connect into these domains.
• The functional areas are:
  • Energy – The energy domain includes electrical systems.
  • Power – The power domain includes the engine functionality.
  • Utilities – The utilities domain includes fuel functions and landing gear functions.
• There are 30 LRMs, and 22 software functions hosted in the CPIOMs.
• Each CPIOM integrates new hardware and software technology and hosts independent applications in the same computing and memory resource.
• The CPIOM also supplies an input/output interface service to some of the conventional avionics; this capability has been increased thanks to additional IOMs.
• CPIOMs and IOMs are LRMs.
• These LRMs communicate through the AFDX known by Airbus as ‘ADCN’.
• The Functional Domains of Open IMA System Communicate with the ADCN.

General Layout Example: Boeing

• The CCR system consists of General Processor Modules (GPMs), Power Conditioning Modules (PCM), Fibre Optic Translators (FOX), ARINC 664 Cabinet Switches (ACS) housed in two cabinets, ARINC 664 Remote Switches (ARS), and Remote Data Concentrators (RDC).
• The GPMs host the functions and applications for numerous systems employed on the Boeing 787.
• GPMs are loaded with operational, configuration, and airline modifiable information software.
• Software is partitioned within each hosting module (GPMs) and identified by a Software Location ID (SLID) for each part number.

Virtual LRU

• The CCS architecture presents a “Virtual LRU” concept to replace the systems packaged as physical LRUs in a federated architecture system.
• Four separate system LRUs are no longer required using IMA infrastructure as hosted functions and applications are data-loaded and separated by the ARINC 653 hosting platforms.
• The virtual system consists of the same logical groupings of components as contained by a physical system.
• To provide all the virtual systems that are required to be part of the CCS, several GPMs are necessary, all housed in a single unit – the Common Computing Resource (CCR) cabinet.

Hosted Applications and Functions on Hosting Modules (GPMs)

• Hosted applications and functions on hosting modules (GPMs) are connected via the CDN to the system sensors and effectors.
• Each cabinet (left and right) is powered separately and has two PCMs to provide the system power required.
• On the CCS, data from the GPMs are switched by both the ARINC 664 Cabinet Switches (ACS), and by the Remote Switches (ARS).
• Data is switched firstly by cabinet switches onto the fibre optic translators, which is where electrical ARINC 664 copper data is converted to ARINC 664 optical data, for transmission to the remote switches.
• Optical data from the fibre optic translators fed to the ARINC 664 Remote Switches (ARS) is converted back to copper ARINC 664 within the remote switches and is then supplied to the Remote Data Concentrators (RDCs).
• RDCs convert the ARINC 664 copper data into Controller Area Network (CAN) bus, ARINC 429, analogue, discrete, or ground as required by the aircraft system LRUs.
• Data is both transmitted and received to/from the aircraft system LRUs by the RDC, however, data validation is a function of the ARINC 664 switches, both ACS and ARS.

Avionics Full Duplex Switched Ethernet (AFDX)

• The most important characteristics of an ADN are Quality of Service (QoS), bandwidth, weight, and cost.
• New generation aircraft are designed with more sophisticated functions, leading to more complex avionics systems that need to process more data.
• It is desirable to utilise already existing commercial technologies adapted to the requirements of ADNs.

Previous ADNs

• Prior to the Airbus 380 Aircraft, the three main ADNs were ARINC 429, MIL-STD-1553, and ARINC 629 with a maximum bandwidth of 100 kbps, 1 Mbps, and 2 Mbps, respectively.
• For the new-generation A380, none of these ADNs would fulfil the aircraft's requirements.
• Consequently, the AFDX was conceived by Airbus and was first implemented on the A380.

AFDX Standard

• AFDX is a next-generation ADN.
• It is based upon IEEE 802.3 Ethernet and utilises Commercial-Off-The-Shelf (COTS) hardware.
• Each LRU has an AFDX end system, which has both transmit and receive ports connecting it to the switch.
• The path from one LRU to the others is known as a Virtual Link (VL).

Deterministic Aspect

• The deterministic aspect of AFDX is implemented by the architecture of a given aircraft LAN configuration.
• The controlled traffic that flows through the VLs, plus the bounded transit times through end systems and switches allows a determination of maximum latency between a sender and receiver.

System Integrity

• The integrity of each packet sent across the VL is checked using a Cyclic Redundancy Check (CRC), in which data validity checking is performed at each stage of transmission.
• These stages including the cabinet switches, remote switches, and AFDX switches.
• Each network has one or more AFDX switches.
• All messages are transmitted to both networks.
• Each receiving end system implements a policy of accepting the first valid copy of any message.
• By implementing this policy in the end system, the application software is relieved of any responsibility for dealing with the redundancy in the network.

AFDX/A664 Standard

• The AFDX standard was originally defined by Airbus in the AFDX Detailed Functional Specification (DFS) standard.
• The same standard also exists as an ARINC standard which is called ARINC 664.
• Boeing has based the AND backbone of their 787 aircraft on the ARINC 664 standard, however with some minor extensions - called “Interoperability Specification” for the 787-end system.
• AFDX allows for transfer rates of either 10 or 100 Mbps over either a copper or fibre optic transmission medium.
• AFDX had to be extended to ensure a deterministic behaviour and high reliability to comply with the stringent requirements of ADNs.

AFDX Traffic Control

• AFDX ensures deterministic behaviour through traffic control.
• Traffic control is achieved by guaranteeing the bandwidth of each logical communication channel, a VL.

Twin Channels

• To improve reliability, the AFDX standard requires each AFDX channel to be a dual redundant channel, with two channels transmitting the same data stream at the same time.
• At any one-time AFDX only forwards one data stream to the upper layers, and automatically excludes an erroneous data stream from being forwarded.
• AFDX ensures a Bit Error Ratio (BER) as low as 10-12 while providing bandwidth up to 100 Mbps.

AFDX End Systems

• Aircraft system data is sent simultaneously from one ADN subscriber to another on networks A and B through AFDX switches.

The Virtual Link (VL)

• The central feature of an AFDX network is the use of its Virtual Links (VL).
• VLs are simplex connections that begin from one end system to one or more destination end systems via the AFDX network,.
• Each AFDX end system is able to support multiple VLs.
• Bi-directional communications must require the specification of a complementary VL.
• Data is routed through the network via AFDX switches according to the VL identifier.
• The VL ID ensures that transmitted frames are switched and routed to their correct destination address.
• To avoid inter-link interference, each link is given two parameters:
  • Bandwidth Allocation Gap (BAG) - BAG is the maximum rate data that can be sent.
  • Lmax - represents the maximum frame size that can be transmitted on the VL (64 – 1518 bytes).

Virtual Link - Characteristics

• Consider the VL like a unidirectional pipe through the ADN:
  • It carries the AFDX frame
  • It has one specific identification
  • It is sent by one transmitter only
  • It is received by one or more subscribers in receive mode
• Each AFDX switch has a switching function that receives the VL coming from one emitter and routes it to the appropriate output port(s) based on its configuration table.
• The sender sends data via a VL simultaneously to both AFDX switches (one per network).
• Each AFDX switch routes it to the following AFDX switch until it reaches the receiver.

Each VL:

• Is unidirectional
• Has a unique sender and one or more receivers
• Always follows a ‘frozen’ route on the network
• Has a maximum fixed bandwidth = size/BAG

Network Components

• Traditional avionic systems are based on federated architecture where different subsystems exist on their own hardware.
• The two main types of Integrated Modular Avionic (IMA) systems are:
  • The Boeing Common Core System (CCS) IMA system
  • The Airbus Avionics Full-Duplex Switched Ethernet (AFDX) IMA system where the Airbus Core System of IMA is introduced

The Core Network System

• These computer systems are the hosting and processing modules forming the core of the Integrated Modular system.
• Airbus uses the expression Core Processing Input/Output Modules (CPIOM) and Boeing uses the expression General Processing Module (GPM).

Airbus Core System Example

• In the Airbus configuration, there are seven types of CPIOM: A to G.
• Each CPIOM hosts the following avionics applications:
  • CPIOM-A Pneumatic and optional air conditioning applications
  • CPIOM-B Air conditioning applications
  • CPIOM-C Cockpit and flight controls applications
  • CPIOM-D Data link applications
  • CPIOM-E Energy applications
  • CPIOM-F Fuel applications
  • CPIOM-G Landing gear applications

Hosting Module Components (Airbus)

• A hosting module (CPIOM) consists of various components:
  • Hardware boards
  • CPIOM core software
  • CPIOM configuration table software
  • ATA application software
• The CPIOMs are considered core to the modular system, but there are some variations.
• The computers have different part numbers, but the memory and power supply cards are common to all the computers.
• Of the power supply cards, it is only the input/output card that is different, depending on what type of system the computer interfaces with.

System Integration

• CPIOM-A computers host the pneumatic and optional air conditioning applications, including Engine Bleed Air System (EBAS), Overheat Detection System (OHDS), Pneumatic Air Distribution System (PADS), and Supplemental Cooling System (SCS).
• CPIOM-B computers host the air conditioning applications, including Air Generation System (AGS), Avionics Ventilation System (AVS), Cabin Pressure Control System (CPCS), Temperature Control System (TCS), and Ventilation Control System (VCS).
• CPIOM-C computers host the cockpit and flight controls applications, including Flight Control Unit (FCU) backup, Weight and Balance Backup Computation (WBBC), Flight Control Data Concentrator (FCDC), and Flight Warning System (FWS).
• CPIOM-D computers host the data link applications, including Air Traffic Control (ATC) system and Avionics Communication Router (ACR).
• CPIOM-E computers host the energy applications, including Circuit Breaker Monitoring System (CBMS), Electrical Load Management System (ELMS), and Electrical System Bite (ESB).
• CPIOM-F computers host the fuel applications, including fuel Specific Gravity (SG) measurement, fuel measurement (FMMS), fuel management, fuel system Built In Test Equipment (BITE), fuel Centre of Gravity (CG) measurement, fuel integrity, and fuel monitor.
• CPIOM-G computers host the landing gear applications, covering Braking control system, Steering control system, Landing Gear Extension and Retraction System (LGERS), Steering control system BITE, LGERS High (HI), landing gear monitoring system, Braking control system BITE, LGERS BITE, and landing gear monitoring system BITE.
• Applications include Airbus AFDX System, as loaded onto one of the CPIOMs.
• The AVS interfaces with, and controls, the many components of the aircraft ventilation and cabin pressurisation systems.

Boeing Core System

• The Boeing CCS is a hardware/software platform that provides computing, communications, and I/O services for implementing real-time embedded systems, known as Hosted Functions (HFs).
• Multiple systems are applied and overlaid on the partitioned platform resources to form a highly integrated system.
• The CCS can simultaneously support critical and non-critical applications, with both high and low integrity levels.
• The CCS uses two CCR cabinets to host software and the Common Data Network (CDN) to transport the data required for the systems to run.
• Hosting Functions (HFs) are allocated to the CCS resources.
• Hosting Functions (HFs) are allocated to the CCS resources to form functional architecture specific to each system to meet the availability, operational, and safety requirements for each function.
• Multiple HFs share the CCS resources within a virtual system environment enforced by partitioning mechanisms.
• Resource allocations are pre-determined and communicated to the CCS components through loadable configuration files.
• Hosted software applications on the GPMs perform fault reporting, processing, and calculations for many aircraft functions.
• The HAs in the left cabinet are presented in red, and the HAs hosted in the right cabinet are presented in blue.

Common Computing System (CCS) Architecture

• The CCS is an IMA solution to provide common computing, communication, and interfacing capabilities to support multiple aircraft system functions.
• The CCS consists of the following three major components:
  • Common Computing Resources (CCR) cabinets
  • Remote Data Concentrators (RDCs)
  • Common Data Network (CDN)
• The CCRs contain the General Processor Modules (GPM) which support the system's functional computer processing needs.
• RDCs support the system analogue, discrete and serial digital interfaces, for both sensors (Inputs) and effectors (Outputs).
• The 21 RDCs are the interface between the network switches, ARINC 664 Remote Switches (ARS) or ARINC 664 Cabinet Switches (ACS) in most aircraft systems.
• Some systems have a direct ARINC 664 interface with the network switches and do not use RDCs.
• The RDCs can:
  • Change the aircraft system data from analogue, ARINC 429, or CAN bus data to ARINC 664 format.
  • Send the ARINC 664 data to the ARINC Remote Switches (ARS) or ARINC 664 Cabinet Switches (ACS).
  • Receive the ARINC 664 data from the ARS or ACS.
  • Change the ARINC 664 data to analogue, ARINC 429, or CAN bus data for aircraft systems.
• The advantages in using of Remote Data Concentrators (RDCs) is:
  • Reduction in wiring
  • Reduction in the number of devices that connect to the CDN
  • A reduction in the spare parts inventory
• Each RDC has two channels, channel A and channel B.
• The RDCs are the interface between the Common Data Network (CDN) and aircraft systems that do not use ARINC 664 data communication.
• The capacity of the RDC is:
  • Analog/discrete interfaces (120)
  • ARINC 429 transmit channels (6)
  • ARINC 429 receive channels (10)
  • CAN bus channels (10)

Common Data Network (CDN)

• This is the data highway between all components of the CCS and follows the ARINC 664 protocol for communication between the system elements.
• The CDN 10 switches, six remotes, four cabinets, and 21 RDCs are distributed throughout locations within the aircraft to facilitate separation and minimise wiring to subsystems, sensors, and effectors.

Fibre Optic Translator (FOX) Modules

• There are two Fibre Optic Translator (FOX) modules in the CCR cabinet.
• The FOX is part of the CDN.
• To operate the ARINC 664 bus at higher speeds, the FOX alters the electrical signals to light signals.
• An open system environment is provided within the CCS to enable independent suppliers to design and implement their systems on the CCS.
• The CCS is an asynchronous system, ensuring that each component's operation schedule is independent of the other components.

Boeing CCS Components

• The Boeing CCS contains the following system components:
  • 16 General Processor Modules (GPMs)
  • 21 Remote Data Concentrators (RDCs)
  • 4 ARINC 664 Cabinet Switches (ACSs)
  • 6 ARINC 664 Remote Switches (ARSs)
• GPMs are Fail Passive.
• The CCS employs the CDN, which is the ARINC 664 Part 7 protocol network, as its communication backbone.
• Data partitioning within the CDN is enforced using Virtual Links (VLs).
• Hosted Function (HF) is defined as a system that directly interfaces with the CCS at one or more of the following CCS communications and/or I/O interfaces.
• An HA is defined as a software application that employs the computing resources of the platform and can consist of one or more partitions.
• The ARINC 653 interface provides an environment for the Hosted Application (HA) software.

Common Computing Resource (CCR) Cabinet

• The CCR is a high-integrity computing platform that provides HAs in a robust partitioned operating environment.
• The CCR system provides:
  • The ability to communicate over a CDN
  • The ability to process data
  • RAM and non-volatile file storage/retrieval
• The CCR has a modular architecture that is composed of:
  • A Cabinet
  • GPMs
  • ARINC 664 Switch Modules (ACSs)
  • Power Conditioning Modules (PCMs)
  • FOXs
  • Capacity for third-party (ASM) supplies
• The GPM provides the computing resources for the HAs that reside in the CCR.
• The ARINC 664 Cabinet Switch (ACS) provides independent 100Base-TX signal routing to ten of the modules in the CCR cabinet for signals from the FOX module.
• The Power Conditioning Module (PCM) converts aircraft power to filtered and regulated power for the modules in the CCR cabinet.
• The FOX (Fibre Optic translator) provides a bi-directional CDN signal conversion from electrical (copper) signals to optical signals and vice-versa, to and from the ACSs.

Common Data Network (CDN) Input

• The CCR cabinet external connectors provide CDN connections between the modules inside the cabinet and external LRUs connected to the CDN.

Discrete Input/Output

• The CCR Cabinet contains seven open/ground discrete inputs/outputs, providing the cabinet and the fitted modules, with encrypted cabinet location data.

Airbus Input/Output (I/O) Modules

• An Input/Output Module is used on some functions whenever an LRU needs to dialogue with other network subscribers via the network.
• The I/O Modules convert the aircraft system data sent and received by LRUs directly connected to them from non-AFDX into AFDX format and vice versa.
• This data takes one of the following formats:
  • Canbus
  • A429
  • Discrete
  • Analogue

The Mirror I/O Module Principle (Airbus)

• There are eight IOMs connected to their ADCN.
• The IOM 1/3/5/7 are all mirror IOMs of IOM 2/4/6/8 and vice versa.
• An LRU exchanges messages with the ADCN subscribers must use both mirror IOMs.
• If one IOM is lost, the communication between a LRU and an ADCN subscriber is not lost thanks to the mirror IOM.
• An I/O Module is composed of various components.
• I/O Module Software does not host avionics applications.
• All I/O Modules are fully interchangeable.

Data Transmission on the Network

• Aircraft system data are sent simultaneously from a network subscriber to other network subscribers on both redundant sub-network A and B.
• This is done through AFDX switches according to predefined paths called VLs.
• An AFDX switch is composed of various components:
  • Hardware Boards
  • Field Loadable Module Software
• Normal AFDX Switch Operation, the VL is transmitted onto both redundant sub-networks A and B, however the following failures may occur:
  • Single AFDX Switch Loss
  • Multiple AFDX Switches Loss (Same sub-network)
  • Multiple AFDX Switches Loss (Both sub-networks)
  • All AFDX Switches Loss
  • Single AFDX Switch or Cable Loss
  • Multiple AFDX Cables Loss

Boeing Remote Data Concentrator (RDC)

• The RDC is Boeing's version of Airbus’ CRDC to convert any non-ARINC 664 signals into ARINC 664 and vice-versa.
• In the CCS, the RDC acts as a remote interface unit providing input/output signal consolidation across the CDN.
• The RDC provides a high-speed interface reducing the amount of aircraft wiring and reducing aircraft weight, cost, and recurring maintenance costs.
• RDCs are physically located throughout the aircraft to provide local interface points for the various aircraft systems.
• Each RDC provides several interfaces of different types and is selected so that the multiple systems using them can be routed through a single RDC whilst still maintaining functional separation.
• The RDC provides a digital gateway, analogue inputs and outputs, discrete inputs and outputs, and frequency inputs.
• As such, it provides analogue-to-digital or digital-to-analogue conversion services along with network formatting, range checking, scaling, offset, linearisation, threshold, and filter services that are specific for each signal.
• The RDC can interface a variety of analogue devices that require excitation.
• The RDC provides a digital-to-digital gateway between ARINC 429 and/or CAN and ARINC 664 protocol.
• The RDC provides remote input/output of both digital and analogue data over the CDN for the Hosted Systems.
• The RDC has no knowledge of the aircraft functions performed by the Hosted Functions, but simply provides the functionality to interface different types of aircraft signal with the CDN.

Fuel Measurement and Management System (FMMS) on the A380

• The Airbus A380 features an IMA suite, comprising of a number of Central Processor Input/Output Modules (CPIOM) units.
• These are interconnected by an AFDX-switched ethernet digital data bus to operate and communicate between the numerous aircraft systems, that include the FMMS.
• The Hosting Modules are arranged in pairs to form computing lanes - one CPIOM is Command (COM) channel and the other Monitor (MON) channel.
• Each of the two fuel system computing lanes perform all the system functions using one of the two lanes as the primary lane controlling the system, while the other lane operates as a standby lane.
• Each lane interfaces with the two Fuel Data Concentrators (FDC1 and FDC2) for fuel quantity, which interface with the in-tank equipment.
• Each pair of fuel system CPIOMs within the IMA suite execute FMMS software with the COM and MON functions partitioned.
• The fuel system supplier is responsible for the functionality of the embedded software in the CPIOMs.