AFDX and IMA

IMA or integrated modular avionics is one of the four new avionics ATA for modern aircaft. IMA or integrated modular avionics is under the ATA 42, used by A380 and later aircraft.

AFDX is the data communication network utilized in the IMA system. Of course, there are other data network, such as ARINCS 429, 629 utilised in the IMA system, but AFDX was specifically designed to meet the IMA requirement. The AFDX is specified in the ARINC 664 part 7.

To assist in learning about AFDX, I include some links.

a. PDF powerpoint... at http://www.afdx.com/pdf/AFDX_Training_October_2010_Full.pdf

b. Youtube Video ///

Internet Understand OSI - Open System Interconnect

Understanding the basic computer networking is a must for a person to understand the AFDX in an aircraft. For that reason, I had embarked in a journey to learn about networking.

We know that the data sent through internet packages, each has the addresses of sender and receiver.

To enable the different computers understand the messages, in 1970's -  ISO formulate the standard OSI model - the open system interconnection.. The network is in 7 layers:
application, presentation, session, transport, network, data link, physical.

In order to remember, take the first letters of the words, and you will have... all  ... people seem to need data processing.

The Function of The Layers
application layer -deal direct with the user. When you have something to send, the application layer will say... "hai, I have something to send".

-  presentation layer will format the things that you want to send.

- session layer - syncronisation so the sending and receiving syn

- transport layer - manage the package, data when sent are broken into packages

- network - routing and addressing, like ip addressing.

- data link - data frame management, the actual packaging, putting into the proper envilope.

- physical layer is the actual hardware.

When you are receiving the information, the path is reversed. It start with the physical layer.

How Data is sent and received
As it move down, information is being added to the data. On the receiving side, the wrapper is unrapped layer by layer, until the pure data is read.

TCP IP Model
It is based on DARPA model with 4 layer of data.
They are...

Appication
Transport
Internet
Network Access

The 4 layers relate to the 7 layer OSI model. 

BASIC NETWORKING

The IMA (integrated modular avionics) on A380 and B787 uses AFDX (avionics full duplex) system for the communications between the different components. The AFDX is based on the off the shelf commercial ethernet technology used for LAN (local area network). As such, it is important for the students to have a working appreciation of networking, and for that reason, I include a youtube video on basic networking.

AFDX - Aircraft Avionics Full Duplex System

The AFDX stands for avionics full duplex, a communication system used by both Airbus and Boeing for the latest aircraft. It was developed by Airbus mainly for A380 jetliner and later used in its A400 and A350. Boeing use it for B787. It is also known as arinc 664 part 7.  It is replacing the arinc 429 and 629. The 429  offers point to point communication in its simplex data communication which is not suitable as the number of systems and LRUs had grown significantly. The 629 offers half duplex communication with full expansion potential, however it requires special interfaces and equipment, thus, it is costly.

Ethernet is the most common communication system used in the commercial computers it the LAN system, but it suffers the two main disadvantages. It works on data packages and there are instances of missing data. Secondly, it is limited ability in its to control and schedule the communication timing, thus it is NOT suitable for system that requires immediate action/ responses such as the flight control system.

The communication system of the avionics requires:
- guaranteed real time operation.
- support repetitive data such as the altitude and latitude.
- support file data such as used for database and video.

 The AFDX is designed based on the ethernet technology with the added features to:
- ensure real time communication
- enable sampling messages
- enable queuing and SAP messages.
The system group the packages into three different types of data such as sampling and queuing. Each package on each VL will have sequence number to ensure all data are received and no duplicate data are used twice.

To make it real time, the sources and destinations are predetermined, this easier as the aircraft systems are closed systems where the users are predetermined.This is done by using the concept of virtual virtual links where a transmitter may talk to multiple receivers, like the concept of ARINC 429.

DIAGRAM to be added

There 3 VL here...
T1 ==> R1
T1 ==>R2
T1 ==> R3

Virtual links can only have 1 source, and they are simplex.

Each VR is allotted the BAG ( bandwidth allocation gap)  such as 1st, 2nd, 3rd .... 128 millisec. It there are more than one receivers, the AFDX will keep the signal as buffer.

The jitter is the time different between the transmission and receiving.
The BAG determine the timing and the frequency of the link, but not the contents. The contents is designed as per ARINC 653.

Redundancy - It is a concept designed for safety of the system. The data is transmitted in 2 different network.The first valid frame received will be used and the second data will be ignored.

Resources:
http://youtu.be/LxTVxz5ogag

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Additional Information.

1. ARINC 664 consists of 8 parts. They are...
a. systems concept and overview
b. ethernet physical and data links layers.
c. internet based protocol and services.
d. address structure and numbers.
e. network domain and interconnect
f. network management
g. AFDX
h. Operation with non-IP protocols and services

Platform Services for IMA 2G

With the development of 2G for IMA, the existing 1G infrastructure is modified to meet the needs of the system. This short presentation by SCARLETT provide the overview of the transition.




The above video is a presentation made by SCARLETT -  a company involved in the development of the IMA (Intergrated Modular Avionics), with the quoted partners, Airbus, Sysgo, Skysoft and Thales.


 Advantages of IMA2G - The images extracted from the above video.

IMA A380 Glossary

Reading through the documents from Airbus can be difficult if you do not know the short forms and abbreviations used. My personal experience require me to pause and search for the meaning of the abbreviations, as such I and collecting the data and put it in this blog.

ADCN - Analogue/Digital Converter
ADDA - Analogue/ Digital Digital Analogue
AFDX - Aircraft Full Duplex
AIMS - Aircraft Information and Management System
API - Application programming interface
ARINC 664 is the standard for deterministic ethernet network used in avionics databus for A380 and B787.
COTS - Commercial Off the Shelf.
CPIOM - Core Processor and Input/ Output Module
GWM - Gate Way Module
IMA - integrated modular avionics
Incremental qualification - each system manufacturer has to integrate his own functions without concern with the others. ( Refer aslo partitioning)
LRU - Line Replaceable Unit
PDM - Product Data Management
PSM - power supply unit
RDC - Remote Data Concentrator
VL - Vertical Link

I  an putting the relevant reference that I manage to pick into this blog to assist those sitting for EASA category B1.1 examination.

IMA Integrated Modular Avionics for Licensed Personnel

With the changes in the Easa Part 66 and 147, the three new technology modules are added. They are ATA 42, 45 and 46. In preparing for the modules, I am doing secondary research through the internet and later, to be enrolled in a course. One possible training provider is the Club 66.

1. OBJECTIVE
The purpose of the project is to prepare myself for the module ATA 42 - Integrated modular avionics

2. LITERATURE REVIEW.
a. Definition
Quoted (Philippa)..Integrated Modular Avionics (IMA) is a blanket term used to describe a distributed real-time computer network aboard an aircraft. This network should consist of a number of computing modules capable of supporting numerous applications of differing safety criticality levels.

Wiki (http://en.wikipedia.org/wiki/Integrated_modular_avionics ) defined it as ...Integrated modular avionics (IMA) represent real-time computer network airborne systems. This network consists of a number of computing modules capable of supporting numerous applications of differing criticality levels.

b. Historical Perspective
In the early 1980s, the avionics started to replace the mechanical functions in the commercial aircraft.  (Henning Butz 20xx). In early 1990s, the classical concept of "1 function = 1 computer" can no longer be maintained, due to the increasing number of demands for the computers. Then the designers came out with concept of multiple software with different criticality level operated within a single processor. It did solve the weight and number of computers, but it had lead to the "transparent fault propagation", which affect the reliability and the maintenance cost.

In 1995, Honeywell introduced the concept of "IMA" on B777, featuring...
- modularized cabinet packaging with
- "time triggered back plane data communication" and
- "application progam interface" API
- strong "SW/SW" partitioning
- HW/SW segregation
- precise fault monitoring
The IMA had proven to meet the reliability and the required performance.
  
The development on A380, focused on the open system.
The followings are the features.
- maintain the segregation features and the API services
- the proprietary cabinets and backplane solution were replaced.
- Introduced CPIOM (core processor-input output module) usinf ARINC 600 standard box.
- Aircraft Full Duplex (AFDX) of 100Mbit connecting the CPIOM.




REFERENCES
- Philippa at http://www-users.cs.york.ac.uk/~philippa/IMA.html on 26 Dec 2012
- Wiki at http://en.wikipedia.org/wiki/Integrated_modular_avionics on 26 Dec 2012