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Tuesday, December 1, 2009

Product Focus: Databus

Highly reliable for flight-critical functions, 1553 military databus technology is getting a new look for civil aircraft applications

Barry Rosenberg

With digital flight control systems on aircraft like the under-development Airbus A350XWB becoming more prevalent, commercial manufacturers are beginning to follow the path laid by the military in using 1553 databus technology, adopting it for actuation of flight-control surfaces.

"1553 has been around for 30 years in the military, but use outside the military has been few and far between," said Mike Hegerty, principal marketing engineer for Data Device Corp. (DDC), acknowledging that a number of regional jets employ the technology. "Today, however, flight control systems are moving away from analog feedback loops to digital flight control, which is reliable, deterministic and can operate in lightning conditions even in composite aircraft."

Roy Nardin, data bus product line manager with National Hybrid, Inc. (NHI), Ronkonkoma, N.Y., said his company’s plastic ball grid array 1553 terminal is being designed into the rudder control system of the A350.

"It’s really the way to go," said Nardin. "What was 1553 originally designed for, what is it used for? It’s used for critical applications. Of course, it was first used in the military for weapons and for surface control — something that had to be highly reliable could not get corrupted by noise or any kind of interference on the bus.... Moving into the area of commercial aircraft seems to me a natural thing to do. And for safety, as commercial aircraft become more and more fly-by-wire, where everything is automatically controlled, it’s a natural. Anything that’s flight critical, I would expect to see 1553."

The biggest hurdle manufacturers of 1553 chips and circuit boards have had to deal with in getting their systems onboard commercial aircraft has been certification, specifically meeting DO-254, Design Assurance Guidance for Airborne Electronic Hardware, and DO-178, Software Considerations in Airborne Systems and Equipment Certification, both published by RTCA.

The fact, though, that the hardware has decades of service under its belt on the military side gave Airbus, for example, confidence that standards could be met.

"Chips with millions of flight hours talk to the reliability of these components," said Chris Stabile, DDC marketing communications manager. The use of proven 1553 technology made the certification process go faster, he added, something of particular importance to Airbus, which was trying to shave time off the two-year head start Boeing had with its 787 Dreamliner.

"How many Ethernet chips, for example, have flown at -50 degrees and in lightning conditions?" he asked rhetorically.

DDC, Bohemia, N.Y., considered going the route of ARINC 429, which is designed to limit electromagnetic interference but provides less protection against lightning, according to Hegerty.

In addition, technology based on the ARINC 429 standard adds weight. "The problem is that there are a lot of distributed elements (on a commercial aircraft) that need to communicate, and 429 is not a multi-drop bus, so a separate cable is needed for each element," he said. "1553 is a multi-drop bus, so it reduces weight."

Extended 1553

When the U.S. Air Force abandoned its efforts last year to develop aircraft databus technology that operated at 200 Mbps, it was thought that the Ottawa, Ontario-based company developing that technology would drop the effort. That’s not been the case for Edgewater Computer Systems, which continues to refine what it calls Extended 1553 (E1553), though at more down-to-Earth transmission speeds.

"Speaking only for Extended 1553, there are a couple important developments that have occurred," said Edgewater Vice President of Marketing Greg Fielding.

"Extended 1553 has been proven in a number of disparate platforms on a variety of dissimilar 1553 data buses to provide high throughput, deterministic capacity operating concurrently and in parallel with the legacy 1553 signaling. Extended 1553 has been proven to operate on the existing 1553 data bus without any changes to the 1553 data bus network and without changes or impact to the existing 1553 signaling solution."

The U.S. Department of Defense’s increased emphasis on intelligence, surveillance and reconnaissance (ISR) systems, for example, is driving the need for increased network capacity, and Fielding says E1553 provides an affordable solution for the rapid deployment of ISR systems that require higher bandwidth.

The need for greater bandwidth solutions is being met by advancements in higher performance data link solutions such as Enhanced Throughput from ViaSat and Flexible Access Secure Transfer (FAST) from BAE Systems. Both are approaches to increase the throughput of the Link 16 network by roughly one order of magnitude.

ViaSat’s Enhanced Throughput increases coded data throughput of the Link 16 waveform from a current maximum of 115.2 kbps to more than 800 kbps in Multifunctional Information Distribution System (MIDS) Low Volume Terminals. It is a stepping stone to the MIDS Joint Tactical Radio Systems (JTRS) now under development, which has been demonstrated to increase throughput of MIDS by a factor of four in flight testing on F/A-18E/F aircraft.

The BAE FAST waveform provides low-latency messaging, MANET (mobile ad hoc networking) and IP (Internet Protocol) connectivity. The addition of FAST to MIDS terminals provides Global Information Grid-enabling connectivity.

The throughput of these higher performance data link waveforms in some instances, though can exceed the capacity of legacy 1553 data bus interface solutions. Fielding said E1553 can help in this regard.

"Extended 1553 has been identified as a viable approach to affordably and rapidly support the consumption of this additional capacity within the platform," he said. "This approach will not only provide the additional capacity for the enhanced Link 16 waveforms, but will provide substantially more available capacity to support many other high-throughput applications such as multiple channels of streaming video.

"Funding within the DoD has been allocated to Link 16 enhancements, a portion of which is expected to support the tailoring of a low-risk, Extended 1553 form-factor solution consumable for integration by the MIDS data link vendors into the MIDS terminals," Fielding said.

One of the keys to acceptance for E1553, according to Fielding, is integration of the technology into a commonly accepted form factor.

Based on customer feedback and international military interests, Edgewater has designed E1553 into a single-width PCI Mezzanine Card (PMC) form factor. This solution will be targeted at a variety of line-replaceable units, including the integration into a mission computer and an advanced targeting pod (ATP) over the next 12 months. Again, the cost benefits of an Extended 1553 solution that enables the incremental upgrade of avionics to support increased bandwidth without having to add networks or rewire platforms remains an important and key consideration in the selection of Extended 1553.

Separate Network

The avionics databus technology that Edgewater has developed with E1553 allows wideband data to be carried over existing aircraft 1553 wiring and bus components without interruption or interference with other systems by maintaining the deterministic command-response nature of the legacy system. It is interoperable with Mil-Std-1553B terminals and cable assemblies, and results in the establishment of a separate network on the existing 1553 wiring infrastructure.

"When compared with legacy 1553, which is now over three decades old, Extended 1553 provides roughly two orders of magnitude of additional capacity and brings airborne data bus technology into the 21st century," said Fielding. "As important as capacity is, it is equally important to ensure the deterministic nature of the data throughput. Extended 1553 is designed to support a very low bit error rate to reduce the occurrences of retries, which, by their nature, are sporadic and lead to non-deterministic behaviors.

"This is one of the reasons that commercial networking solutions are less desirable for military applications," Fielding said.

"Commercial networking solutions are designed to support maximum throughput at the expense of errors that drive retries. These errors are typically due to unexpected changes in the conditions on the data bus due to interference from jammers, for example, a common occurrence in military platforms such as fighter jets and attack helicopters.

Extended 1553 has been designed from the outset to maintain very low error rates even in the presence of dynamic and degraded network conditions."

While it may have been unrealistic to expect that the technology could have resulted in a 200-fold increase in throughput at this moment in time, the basic architecture that creates a separate network continues to have merit in the eyes of Edgewater.

"There are a number of challenges associated with high bandwidth databus networking," said Fielding, "but fundamentally they all distill down to cost and time — the cost and time to integrate and certify a network that provides the necessary capacity, the cost and time to upgrade and certify the avionics and electronics to interface to the network, the cost and time to recertify the platform for weight and balance, the cost and time to rewrite and recertify the software that drives mission and flight-critical applications and ensures guaranteed determinism in the network.

"Extended 1553, by its nature as a network interface card solution, provides a separate, parallel high-speed network on the existing data bus which dramatically reduces both the cost and the time to integrate high-bandwidth data bus networking capability by eliminating the need to add cabling for new data networks, or to rewire the platform, or to upgrade all of the avionics residing on the new data bus, or by forcing changes to the existing 1553 data bus software solution," Fielding said.

"Further, an environment such as that found in a fighter jet or an attack helicopter requires that the data bus network is robust and immune to electromagnetic interference and, itself, does not generate or radiate electromagnetic interference into the surrounding avionics suite. Extended 1553 has passed the necessary EMC compliance testing to ensure it falls within the necessary parameters for deployment in military platforms."

Over the next 12 to 18 months, Edgewater expects to see E1553 being part of a number of integration activities for mission computers, data links, ATPs and other avionics and electronics in both fixed-wing and rotary-wing platforms.

Without naming names, Fielding said some of these integration activities will be for demonstration, some for System Development and Demonstration phases and others for rapid deployment into the battlefield.

"We will continue to reduce the form factor, drive down the power, and increase the density and number of interfaces per square unit of area as we expand the family of products based on Extended 1553 technology," he said.

Avionics Magazine’s Product Focus is a monthly feature that examines some of the latest trends in different market segments of the avionics industry. It does not represent a comprehensive survey of all companies and products in these markets.

Companies

Actel Corp. www.actel.com
Aero Express www.aeroexpress.com
Aeroflex www.aeroflex.com
AIM GmbH and AIM-USA www.aim-online.com
Airflair www.airflair.co.uk
Alta Data Technologies www.altadt.com
Avionica, Inc. www.avionica.com
Ballard Technology www.ballardtech.com
Beta Transformer Technology Corp. www.bttc-beta.com
Curtiss-Wright Controls www.cwcontrols.com
DAC International, Inc. www.dacint.com
Data Bus Products www.databusproducts.com
Data Device Corp. www.ddc-web.com
Edgewater Computer Systems www.edgewater.ca
Emteq www.emteq.com
Excalibur Systems www.mil-1553.com
GE Fanuc Intelligent Platforms www.gefanucembedded.com
Holt Integrated Circuits www.holtic.com
Hytronics Corp. www.hytronicscorp.com
ITCN www.itcninc.com
Kontron www.kontron.com
MAX Technologies www.maxt.com
Milestek www.milestek1553.com
National Hybrid Inc. www.nationalhybrid.com
North Atlantic Industries www.naii.com
North Hills Signal Processing www.northhills-sp.com
Phoenix Logistics www.phxlogistics.com
Raycom Electronics Inc. www.raycomelectronics.com
RTX Systems, Inc. www.rtxsystems.com
Sanmina-SCI Technology www.sanmina-sci.com
Sital Technology www.sitaltech.com
Tech S.A.T GmbH www.techsat.com
Teledyne Controls www.teledynecontrols.com
Tepro of Florida www.Tepro-Vamistor.com
Trompeter www.trompeter.com
Ultra Electronics BCF www.bcfdesigns.co.uk
Western Avionics Ltd. www.western-av.com
YED USA www.yed.com

Databus Manufacturers, Providers Report New Products, Ongoing Innovation

  • Test and simulation products manufacturer AIM GmbH, Freiburg, Germany, said it introduced the first AFDX/ARINC 664 Test & Simulation card to support users transition from the field-proven 10/100 Mbit/sec AFDX/ARINC 664 implementation to new, high-rate 1 Gbit/s AFDX/ARINC 664 Ethernet variant with software compatibility to existing 10/100 Mbit/s products. "With the introduction of the latest Gigabit AFDX/ARINC 664/Ethernet product, AIM entered the domain of the high-speed data transmission protocols at the 1 Gbit/s boundary and beyond, which requires different (hardware) architectures and data processing methods," the company said. "The support of redundancy and multiple channels of corresponding test and simulation interfaces multiply the data rates, which must be handled accordingly."

  • Ballard Technology, of Everett, Wash., introduced the fifth generation family of PCI Express (PCIe) and PCI interface cards for Mil-Std-1553 and ARINC 429/717. The interface cards have programmable data buffers and 32MB of built-in memory. All models provide capability to transmit, receive and monitor messages while supporting maximum data throughput on all avionics databuses, the company said.

    The LE1553-5 (PCIe) and LP1553-5 (PCI) models offer 1 to 4 dual redundant Mil-Std-1553 channels plus 16 avionics level input/output discretes and IRIG time synchronization/generation. Single and multi-function models are offered. Each Mil-Std-1553 channel is independently configurable as a Bus Controller (BC), Remote Terminal(s) (RT), and/or Bus Monitor (BM). The LE429-5 (PCIe) and LP429-5 (PCI) offer 4 to 32 ARINC 429 channels, and up to 4 ARINC 717 channels plus 16 avionics level input/output discretes and IRIG time synchronization/generation.

  • Excalibur Systems, of Elmont, N.Y., announced in May that it had added Remote Terminal (RT) Mode to Exalt, its database monitor and analyzer software tool. Each module may be configured to simulate up to 32 RTs, with the user selecting which RTs are active. Options to inject communication errors or status word errors into the message responses are available, the company said. Exalt analyzes and displays real-time data, from multiple types of buses. It works in conjunction with Excalibur’s family of Multi-Protocol 4000 cards.

  • In August, GE and Fanuc Ltd. of Japan dissolved their GE Fanuc Automation Corp. joint venture. GE retains the software, services, embedded systems and control systems businesses globally, which will be known as GE Intelligent Platforms. In October, GE Intelligent Platforms, based in Charlottesville, Va., received a $1 million order from Northrop Grumman for QPMC-1553 PMCs and CEI-830 ARINC boards to upgrade its Integrated Avionics System on UH-1Y, AH-1Z helicopters.

  • Holt Integrated Circuits, of Mission Viejo, Calif., released HI-6120 and HI-6121, the smallest Mil-Std-1553 remote terminal systems in the industry, according to the company. The devices provide a single-chip, 3.3V remove terminal system, including dual transceivers. The HI-6120 uses a 16-bit parallel host bus interface in a 100-pin plastic quad flat pack (PQFP) package. The HI-6121 uses a four-wire Serial Peripheral host Interface and comes in a 52-pin PQFP or 64-pin quad flat no lead (QFN).

    Both devices handle all aspects of the Mil-Std-1553 protocol including message encoding, decoding, error detection, illegal command detection and data buffering.

  • National Hybrid Inc., Ronkonkoma, N.Y., this year introduced Bus+ and Terminal + products. Bus +, developed for FPGA developers, integrates transformer and transceiver in a single package. "So now, there’s no need to put an external transceiver on the board," said Roy Nardin, NHI data bus product line manager. "Now, basically what you have is a 1553 terminal that has integrated transceivers, integrated protocol, integrated 64K words of RAM and two integrated transformers. In one very small, compact package, you have basically the whole ball of wax." Terminal + is a complete, integrated 1553 terminal on a chip.

  • Sital Technology, based in Kfar-Saba, Israel, in October released a Mil-Std-1553 IP Core with the addition of PCI interface. The core can connect directly to a PCI bus, relieving the user from adding a PCI bridge or designing an interface to the local bus, according to the company. The core has a 33/66MHz PCI back-end interface, and is suitable for any Mil-Std-1553 BC, RT, MT implementation.

  • Development of the SAE AS6802 Time-Triggered Ethernet (TTEthernet) standard, approved by SAE in April and planned for release in 2011, will establish Ethernet as a high-bandwidth network protocol for time, mission and safety-critical systems, reports TTTech Computertechnik AG, of Vienna, Austria. "The biggest challenge is that available high-bandwidth technologies target a broad set of different applications, the majority in non-critical, less deterministic or best-effort communication domains. Critical embedded systems are too small to drive the development of high-bandwidth communication technologies," the company said. "Second, the support for scalable design of highly dependable system design in all its dimensions (availability, integrity, safety, maintainability, confidentiality, reliability) is tough to get right using existing high-bandwidth technology. Both challenges are solved by SAE AS6802.

    Initial supporters of the SAE AS6802 standardization project, according to SAE, are Lockheed Martin, Bombardier, Embraer, General Dynamics, Sikorsky Aircraft, Honeywell, BAE Systems, Ultra Electronics, GE Intelligent Platforms, TTA-Group and TTTech Computertechnik. The first production program to use SAE AS6802-compliant COTS components will be the NASA Orion crew exploration vehicle.

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