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AFDX-Based Flight Test Computer Concept

With the introduction of the Airbus A380, the commercial aircraftindustry was in the process of defining new standards that incorpo-rate the latest digital information techniques, such as the AvionicsFull-Duplex Switched Ethernet (AFDX) on-board, real-time network.

The AFDX standard, a major innovation in aircraft technology first deployed on theAirbus A380 (see Figure 1), introduces telecom Ethernet-based technology as well as aswitch connection topology, rather than part-to-part links or buses.

Airbus and Creative Electronic Systems (CES) partnered to develop a general-purposebuilding block that allows the simulation, test, or connection of any AFDX-connectedequipment. The system is integrated into different packages, ranging from the small equip-ment tester or the complete aircraft integration test bench up to the full flight test computer.Appropriately, the system’s complete name is the AFDX General-Purpose Test Platform.

In the flight test applications, the system provides the interface between the AFDXavionic world and the commercial Ethernet switches through multiple AFDX inputs to atwin Ethernet output router. Redundancy and precise time control of the data transmis-sion are key elements of the specification.

Also of special interest is a very advanced source-synchronized datation system ableto guarantee a perfect time alignment of all data directly at the point of entry in the flighttest computer.

This article describes the different modular elements of the ground and flighttest computers, as well as the hardware and software tuning and performance anal-ysis tools that have been developed around these computers. All of these elementsare now in operation and have demonstrated the utility of the AFDX tools as real con-cepts that can be reused for other programs.

The rapid evolution of the computer and technological fields continuously creates oppor-tunities to develop new services in commercial aviation and to enable lower weight and costin aircraft design. The critical safety level, life duration requirements, and certification cycle

The AFDX standard brings telecom Ethernet-basedtechnology to the Airbus A380

Frederic Brajou and Philippe Ricco

This article first appeared in its original form at AUTOTESTCON 2004.

August 2005 IEEE Instrumentation & Measurement Magazine 551094-6969/05/$20.00©2005IEEE

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56 IEEE Instrumentation & Measurement Magazine August 2005

slow down this technological progress, meaning that it takesyears for a new technology to be introduced on a commercialaircraft. For example, the enhancement of processing capabili-ties and the now well-known network principles are just beingintroduced in the latest generation of aircraft, such as theAirbus A380, through the use of the new integrated modularavionics (IMA) and AFDX standards.

AFDXWith the impressive processor evolution, on-board aircraftcomputers can now be safely used for multiple applicationswith the same device. To guarantee the same security levelwhile conducting multiple activities, rather than using sepa-rate devices for each function, the IMA principle was intro-duced in the aviation world. With the same spirit, the datatransmission process for network technology is now matureenough to replace, in most cases, the old specialized avionicbuses. This is the goal, in particular, of the new ARINC 664standard, with the development of the AFDX avionic-specif-ic adaptation of the numeric network principles (ARINC664–Part 7). The use of these new technologies can improveservice capabilities, improve scalability and save weight byusing common resources (multifunction computers and wireconcentration), and save costs by using well-developed andimproved components.

Of course, the very high-level security requirement of air-craft development necessitates adaptations of the commer-cial components and principles to insure the completeindependence of functions and avoid service failure while atthe same time guaranteeing service. These principles weredeveloped in the ARINC 653 standard, which defines strongpartitioning rules with protections and independence verifi-cations and defines communication interfaces between thesepartitions [application executive (APEX)]. Also, the AFDX isnot just a standard Ethernet network; it includes switchingtechnology, deterministic properties, and a specific band-width allocation strategy, with strong separation betweendata flows. It also ensures a hardware redundancy, with spe-cific address management and a protocol stack. The ARINC653 rules found direct application in the AFDX specification.

CES Modular Test ElementsFor years, CES developed modular processing units and,with the Airbus flight test equipment team, built groundand flight test systems based on this modular technology(see Figure 2). CES was also selected by Airbus as a partnerin developing a specific, highly versatile AFDX test boardsuitable for all types of test benches. This board, built on theCES modular devices, provides a wide range of test applica-tions including: raw network traffic analysis, cables andhardware test benches, traffic generation, both 10- and 100-Mb/s link speeds, error injection, mono or multiple end-sys-tem emulation, various data management strategies,simulation, complete AFDX stack, all addressing modes,IEEE 802.3 compliance analysis, redundancy managementand separate flow capabilities, switch scheduling emulation,event generation, triggering, filtering, and detailed statistics.

The AFDX general-purpose test board is based on theCES PCI mezzanine card (PMC) form-factor multifunctionprocessor board, called the multifunction computing core(MFCC). This CES standard PMC is part of the completePowerPC-based board family, which includes the VME,CompactPCI, and PMC form-factor boards. The MFCC pro-vides an on-board PowerPC CPU and an application-freefield-programmable gate array (FPGA), with both front-endand PCI line control capabilities. A front-end electrical adap-tor module completes the MFCC CPU module, with a stan-dard connector to achieve the PMC format. For the AFDXtest board, an AFDX front-end adaptor (typically called the“nose;” see Figure 3) was developed with Airbus to providethe AFDX twin-Ethernet connector on the front-end, com-plete with various I/Os such as signal dating, external syn-chronization and triggers, and serial link.

The CES AFDX PMC also provides a 1-µs dating capabili-ty, with better than 1-ppm precision for all internal events,such as frame acquisition or trigger detection. The noseincludes a variable oscillator for local time reference sourceand a temperature sensor for base timing compensation. TheFPGA also includes a synchronization algorithm to drive itsinternal dating source and continuously adapt it to anexternal timing source (1-Hz signal for synchronization and

Fig. 1. The Airbus A380.

Fig. 2. CES modular function units.

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August 2005 IEEE Instrumentation & Measurement Magazine 57

a serial-coded date) from the front-end connector or by thebackplane PCI line.

Based on the same MFCC board, CES has developedanother front-end adaptor (with its associated FPGA pro-gramming) to create a global synchronization PMC. ThisPMC can receive external dating sources with various for-mats, including IRIG-B and 1-Hz top from a global position-ing system (GPS) station. This PMC distributes thesynchronization signals (1 Hz and serial date) through bothfront-end and back-end connectors.

CES has developed a complete family of functional unitsthat provides a large compatibility and homogeneous soft-ware communication layer, based on the same modulararchitecture, for a large family of avionic-oriented links(MIL-STD 1553, STANAG 3838, ARINC 429, and CANBUS).The MFCC (with its FPGA programmable logic), coupledwith the electrical front-end adaptor using the same logicalmodules (such as synchronization) and embedded softwarethat may include an OS-independent communication layer(the CES BP-Net technology), provides a very useful modu-lar construction. It constitutes a very easy bridging function-ality between the main standard avionic links for variousflight and ground applications.

The IENA SystemThe Instrumentation d'Essais des Nouveaux Avions (IENA)concept, translated as test instrumentation for new airplanes,is an Airbus in-flight data acquisition and analysis system.The latest generation designed for the Airbus A380 includesthe brand-new AFDX acquisition system based on the AFDXmultipurpose system.

CES has built a complete data acquisition system for theA380 “level 2” IENA equipment, based on the company’smodular processing units and chassis experience (see Figure4). This system is based on the VME 6U form-factor chassis,with functional units for data acquisition, frame formatting,concentration, and transmission to the next level of the IENAsystem. Each functional unit is based on a RIO3 VME 64X 6U(CES processor board) gateway, with up to six PMCs, usingPMC extension boards (PEBs). The IENA architectureincludes four clusters composed of RIO3s, MFCCs, and PEBs.In the case of the first A380 implementation, the PMCs usedin the data acquisition functional units are AFDX acquisitionboards (i.e., the AFDX multipurpose test PMCs) with a spe-cific IENA data formatting application on board. This is pos-sible due to the modularity of the CES building blocks alongwith the CES BP-Net communication layer within homoge-neous or heterogeneous software environments.

The IENA N2 system developed by CES also includes acontroller functional unit, along with an RIO3 board and adating PMC with a backplane distribution of the synchroniza-tion signals. All of the acquisition boards are synchronized tothe same time base (an IRIG-B and a 1-Hz separated sources),with 1-µs resolution and better than 1-ppm precision. Thisunit also transmits all of the acquired and formatted data ofthe chassis on two 100-Mb/s Ethernet links for redundancy.

The controller functional unit manages the entire IENAsystem. This RIO3 controls the system configuration andthe current state of each functional unit in the system,manages the hardware chassis controls (power supply,fans, etc.), and concentrates the IENA formatted data com-ing from the data acquisition units, including statisticsinformation. The IENA formatted frames are transmittedto the N4 storage and analysis levels by two parallel 100-Mb/s, full-speed redundant links.

CES has developed two chassis versions: a ground ver-sion with commercial boards and a flight version usingextended versions of the boards without any software modi-fication (see Figure 5). The flight chassis is able to embed twocomplete IENA systems to provide two independent sys-tems in one computer for acquisition of AFDX data, with upto 12 redundant or 24 nonredundant AFDX links. The flightchassis also includes a display board for healthy informationpresentation, available from the chassis itself.

Thanks to the modularity of the CES functional units, acomplete IENA chassis is composed of one display, onecontrol unit, and two data acquisition units (one RIO3 gateway

Fig. 4. IENA chassis with monitoring applications.

Fig. 3. AFDX PMC: MFCC with “nose.”

Fig. 5. IENA ground and flight chassis.

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58 IEEE Instrumentation & Measurement Magazine August 2005

and up to six acquisition PMCs). Also, with the same softwareobject, the configuration can be changed easily. The IENA con-figuration can be reduced to a minimum configuration withjust one control unit and one data acquisition unit (one gate-way with one acquisition card).

The same principles are applicable with various exten-sions and adaptations to other projects, sharing and re-using both hardware and software modules. CES iscurrently developing flight equipment with reduced formfactors, in particular ATR and ARINC 600 (see Figure 6).The software adaptation for certifiability under DO 178B(up to level A, applying ARINC 653 rules) is currently with-in the scope of CES developments and projects.

Analysis ToolsThe IENA system also permanently provides various run-ning information, such as acquisition statistics and synchro-nization status. This information can be displayed in realtime with a status viewer graphic tool, directly from a seriallink in the chassis. Alternatively, it can be recorded in theIENA formatted data frames.

The same CES boards and software modules are used inthe complete AFDX analysis tool CAD-X (see Figure 7). Thisanalyzer uses the same AFDX test card in a gateway pilotedby a graphic display interactive tool to manage the configu-ration, the AFDX activity, and the data. It can provide awide range of functionalities, from raw frame analysis to fullAFDX compliance tests, with full bandwidth acquisition andtraffic generation, filtering, trigger input and outputs, statis-tics, periodic events, and error injection of all types (fromraw protocol violation to high-level addressing errors orbandwidth allocation violation).

ConclusionAirbus has introduced a new generation of technologies forcommercial aircraft. It is now possible to share powerfulresources for the critical safety requirement certificationrules of the aircraft. The modular construction and theredundancy, with the friability progress of the component

modules, ensure the same safety guaranty level as the previ-ous generations of equipment.

These modular concepts ease the development of testingtools for both ground and flight applications, with commonparts and reusable concepts. These extremely versatile mate-rials are available for a very broad range of applications.

References[1] P. Ricco, M. Weymann, F.-H. Worm, “Joint account,” Aerosp. Test.

Int., pp. 40–43, Oct. 2003.

[2] P. Ricco, M. Weymann, F.-H. Worm, “Merging military aircraft

and commercial aircraft flight test architecture and

technologies,” in Proc. European Test and Telemetry Conf. (ETTC

2003), Toulouse, France, June 2003, pp. 106–112.

Frederic Brajou (frb@ces.ch) earned an M.Sc. degree in aero-nautics and holds a postgraduate specialization in aircraftpropulsion systems from ENSAE, France. As an engineer, heworked for the French MOD in a test and evaluation systemcenter. He then worked in IT consultancy and services.Moving to England, he diversified his career in businessdevelopment for companies in the United Kingdom and theUnited States, working in a pan-European role during thelast decade. For the last few years, he has been working forCreative Electronic Systems (CES). His responsibilitiesencompass business development in the civil aerospace anddefense markets. He is a member of the Royal AeronauticalSociety (MRAeS) and also a professional affiliate to theChartered Institute of Marketing (CIM) in England.

Philippe Ricco studied in France and received a master ofapplied mathematics degree. He worked ten years for theFrench CEV (DGA Flight Test Center) on real-time comput-ers for flight test simulators. He then worked for Airbus andEurocopter. For the past seven years, he has been with theSwiss company Creative Electronic Systems (CES) workingon its aeronautic systems development, including the AFDXproducts and DO-178B level A avionic applications.

Fig. 7. CAD-X.Fig. 6. ATR and ARINC 600 form factors.

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