The AFDX standard brings telecom Ethernet-based technology to the Airbus A380
© IMAGESTATE
AFDX-Based Flight Test Computer Concept
Frederic Brajou and Philippe Ricco
ith the introduction of the Airbus A380, the commercial aircraft industry was in the process of defining new standards that incorporate the latest digital information techniques, such as the Avionics Full-Duplex Switched Ethernet (AFDX) on-board, real-time network. The AFDX standard, a major innovation in aircraft technology first deployed on the Airbus A380 (see Figure 1), introduces telecom Ethernet-based technology as well as a switch connection topology, rather than part-to-part links or buses. Airbus and Creative Electronic Systems (CES) partnered to develop a general-purpose building block that allows the simulation, test, or connection of any AFDX-connected equipment. The system is integrated into different packages, ranging from the small equipment 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 AFDX avionic world and the commercial Ethernet switches through multiple AFDX inputs to a twin Ethernet output router. Redundancy and precise time control of the data transmission are key elements of the specification. Also of special interest is a very advanced source-synchronized datation system able to guarantee a perfect time alignment of all data directly at the point of entry in the flight test computer. This article describes the different modular elements of the ground and flight test computers, as well as the hardware and software tuning and performance analysis tools that have been developed around these computers. All of these elements are now in operation and have demonstrated the utility of the AFDX tools as real concepts that can be reused for other programs. The rapid evolution of the computer and technological fields continuously creates opportunities to develop new services in commercial aviation and to enable lower weight and cost in aircraft design. The critical safety level, life duration requirements, and certification cycle
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This article first appeared in its original form at AUTOTESTCON 2004. August 2005
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slow down this technological progress, meaning that it takes years for a new technology to be introduced on a commercial aircraft. For example, the enhancement of processing capabilities and the now well-known network principles are just being introduced in the latest generation of aircraft, such as the Airbus A380, through the use of the new integrated modular avionics (IMA) and AFDX standards.
AFDX With the impressive processor evolution, on-board aircraft computers can now be safely used for multiple applications with the same device. To guarantee the same security level while conducting multiple activities, rather than using separate devices for each function, the IMA principle was introduced in the aviation world. With the same spirit, the data transmission process for network technology is now mature enough to replace, in most cases, the old specialized avionic buses. This is the goal, in particular, of the new ARINC 664 standard, with the development of the AFDX avionic-specific adaptation of the numeric network principles (ARINC 664–Part 7). The use of these new technologies can improve service capabilities, improve scalability and save weight by using common resources (multifunction computers and wire concentration), and save costs by using well-developed and improved components.
Fig. 1. The Airbus A380.
Fig. 2. CES modular function units.
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Of course, the very high-level security requirement of aircraft development necessitates adaptations of the commercial components and principles to insure the complete independence of functions and avoid service failure while at the same time guaranteeing service. These principles were developed in the ARINC 653 standard, which defines strong partitioning rules with protections and independence verifications and defines communication interfaces between these partitions [application executive (APEX)]. Also, the AFDX is not just a standard Ethernet network; it includes switching technology, deterministic properties, and a specific bandwidth allocation strategy, with strong separation between data flows. It also ensures a hardware redundancy, with specific address management and a protocol stack. The ARINC 653 rules found direct application in the AFDX specification.
CES Modular Test Elements For years, CES developed modular processing units and, with the Airbus flight test equipment team, built ground and flight test systems based on this modular technology (see Figure 2). CES was also selected by Airbus as a partner in developing a specific, highly versatile AFDX test board suitable for all types of test benches. This board, built on the CES modular devices, provides a wide range of test applications including: raw network traffic analysis, cables and hardware test benches, traffic generation, both 10- and 100Mb/s link speeds, error injection, mono or multiple end-system emulation, various data management strategies, simulation, complete AFDX stack, all addressing modes, IEEE 802.3 compliance analysis, redundancy management and separate flow capabilities, switch scheduling emulation, event generation, triggering, filtering, and detailed statistics. The AFDX general-purpose test board is based on the CES PCI mezzanine card (PMC) form-factor multifunction processor board, called the multifunction computing core (MFCC). This CES standard PMC is part of the complete PowerPC-based board family, which includes the VME, CompactPCI, and PMC form-factor boards. The MFCC provides an on-board PowerPC CPU and an application-free field-programmable gate array (FPGA), with both front-end and PCI line control capabilities. A front-end electrical adaptor module completes the MFCC CPU module, with a standard connector to achieve the PMC format. For the AFDX test board, an AFDX front-end adaptor (typically called the “nose;” see Figure 3) was developed with Airbus to provide the AFDX twin-Ethernet connector on the front-end, complete with various I/Os such as signal dating, external synchronization and triggers, and serial link. The CES AFDX PMC also provides a 1-µs dating capability, with better than 1-ppm precision for all internal events, such as frame acquisition or trigger detection. The nose includes a variable oscillator for local time reference source and a temperature sensor for base timing compensation. The FPGA also includes a synchronization algorithm to drive its internal dating source and continuously adapt it to an external timing source (1-Hz signal for synchronization and
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a serial-coded date) from the front-end connector or by the backplane PCI line. Based on the same MFCC board, CES has developed another front-end adaptor (with its associated FPGA programming) to create a global synchronization PMC. This PMC can receive external dating sources with various formats, including IRIG-B and 1-Hz top from a global positioning system (GPS) station. This PMC distributes the synchronization signals (1 Hz and serial date) through both front-end and back-end connectors. CES has developed a complete family of functional units that provides a large compatibility and homogeneous software communication layer, based on the same modular architecture, for a large family of avionic-oriented links (MIL-STD 1553, STANAG 3838, ARINC 429, and CANBUS). The MFCC (with its FPGA programmable logic), coupled with the electrical front-end adaptor using the same logical modules (such as synchronization) and embedded software that may include an OS-independent communication layer (the CES BP-Net technology), provides a very useful modular construction. It constitutes a very easy bridging functionality between the main standard avionic links for various flight and ground applications.
The controller functional unit manages the entire IENA system. This RIO3 controls the system configuration and the current state of each functional unit in the system, manages the hardware chassis controls (power supply, fans, etc.), and concentrates the IENA formatted data coming from the data acquisition units, including statistics information. The IENA formatted frames are transmitted to the N4 storage and analysis levels by two parallel 100Mb/s, full-speed redundant links. CES has developed two chassis versions: a ground version with commercial boards and a flight version using extended versions of the boards without any software modification (see Figure 5). The flight chassis is able to embed two complete IENA systems to provide two independent systems in one computer for acquisition of AFDX data, with up to 12 redundant or 24 nonredundant AFDX links. The flight chassis also includes a display board for healthy information presentation, available from the chassis itself. Thanks to the modularity of the CES functional units, a complete IENA chassis is composed of one display, one control unit, and two data acquisition units (one RIO3 gateway
The IENA System The 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 includes the brand-new AFDX acquisition system based on the AFDX multipurpose system. CES has built a complete data acquisition system for the A380 “level 2” IENA equipment, based on the company’s modular processing units and chassis experience (see Figure 4). 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 IENA system. Each functional unit is based on a RIO3 VME 64X 6U (CES processor board) gateway, with up to six PMCs, using PMC extension boards (PEBs). The IENA architecture includes four clusters composed of RIO3s, MFCCs, and PEBs. In the case of the first A380 implementation, the PMCs used in the data acquisition functional units are AFDX acquisition boards (i.e., the AFDX multipurpose test PMCs) with a specific IENA data formatting application on board. This is possible due to the modularity of the CES building blocks along with the CES BP-Net communication layer within homogeneous or heterogeneous software environments. The IENA N2 system developed by CES also includes a controller functional unit, along with an RIO3 board and a dating PMC with a backplane distribution of the synchronization signals. All of the acquisition boards are synchronized to the same time base (an IRIG-B and a 1-Hz separated sources), with 1-µs resolution and better than 1-ppm precision. This unit also transmits all of the acquired and formatted data of the chassis on two 100-Mb/s Ethernet links for redundancy. August 2005
Fig. 3. AFDX PMC: MFCC with “nose.”
Fig. 4. IENA chassis with monitoring applications.
Fig. 5. IENA ground and flight chassis.
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Fig. 6. ATR and ARINC 600 form factors.
Fig. 7. CAD-X.
and up to six acquisition PMCs). Also, with the same software object, the configuration can be changed easily. The IENA configuration can be reduced to a minimum configuration with just one control unit and one data acquisition unit (one gateway with one acquisition card). The same principles are applicable with various extensions and adaptations to other projects, sharing and reusing both hardware and software modules. CES is currently developing flight equipment with reduced form factors, 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 within the scope of CES developments and projects.
modules, ensure the same safety guaranty level as the previous generations of equipment. These modular concepts ease the development of testing tools for both ground and flight applications, with common parts and reusable concepts. These extremely versatile materials 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
Analysis Tools
2003), Toulouse, France, June 2003, pp. 106–112.
The IENA system also permanently provides various running information, such as acquisition statistics and synchronization status. This information can be displayed in real time with a status viewer graphic tool, directly from a serial link in the chassis. Alternatively, it can be recorded in the IENA formatted data frames. The same CES boards and software modules are used in the complete AFDX analysis tool CAD-X (see Figure 7). This analyzer uses the same AFDX test card in a gateway piloted by a graphic display interactive tool to manage the configuration, the AFDX activity, and the data. It can provide a wide range of functionalities, from raw frame analysis to full AFDX compliance tests, with full bandwidth acquisition and traffic generation, filtering, trigger input and outputs, statistics, periodic events, and error injection of all types (from raw protocol violation to high-level addressing errors or bandwidth allocation violation).
Conclusion Airbus has introduced a new generation of technologies for commercial aircraft. It is now possible to share powerful resources for the critical safety requirement certification rules of the aircraft. The modular construction and the redundancy, with the friability progress of the component 58
Frederic Brajou (
[email protected]) earned an M.Sc. degree in aeronautics and holds a postgraduate specialization in aircraft propulsion systems from ENSAE, France. As an engineer, he worked for the French MOD in a test and evaluation system center. He then worked in IT consultancy and services. Moving to England, he diversified his career in business development for companies in the United Kingdom and the United States, working in a pan-European role during the last decade. For the last few years, he has been working for Creative Electronic Systems (CES). His responsibilities encompass business development in the civil aerospace and defense markets. He is a member of the Royal Aeronautical Society (MRAeS) and also a professional affiliate to the Chartered Institute of Marketing (CIM) in England. Philippe Ricco studied in France and received a master of applied mathematics degree. He worked ten years for the French CEV (DGA Flight Test Center) on real-time computers for flight test simulators. He then worked for Airbus and Eurocopter. For the past seven years, he has been with the Swiss company Creative Electronic Systems (CES) working on its aeronautic systems development, including the AFDX products and DO-178B level A avionic applications.
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