How to Select the Right Databus Analyzer

[Avionics Magazine 09-24-2015] Avionics bus architectures on today’s aircraft continue to become varied and more complex, with modern airframes featuring MIL-STD-1553, ARINC 429, CAN, ARINC 664 (AFDX) as part of their overall systems arrangement. This continued bus evolution, variety and complexity makes the selection of an appropriate bus analyzer an essential part of developing and maintaining an aircraft from software development, to system integration, flight testing, maintenance and everywhere in between.

 

According to the recently published GE Intelligent Platforms white paper, “Selecting a Bus Analyzer 101,” there are two main types of bus analyzers available on the market today. One is the standalone box analyzer, which is highly specialized and typically designed to analyze and display data in one dedicated format, such as analyzing the one-direction flow of 32-bit messages from an ARINC 429 bus between a transmitter and receiver. The other type of analyzer is the PC-based analyzer, which uses a Graphical User Interface (GUI) usually hosted on a Windows operating system to present data in multiple forms including raw data, engineering units and graphical formats such as gauges or strip charts. The decision for one or the other is usually based on the type of function that the user is looking for, and at what stage in aircraft development or maintenance the analyzer will be used. 

 

Bill Tilman, a senior field application engineer for the GE Intelligent Platforms Avionics group, says that his company focuses mostly on developing bus analyzers hosted by Windows OS. The company also provides rugged avionics interface cards and intellectual property for embedded systems.

 

“When you talk about ARINC 429, MIL-STD-1553, ARINC 664 for the aerospace market, those are all different interfaces, very different electrically and protocol wise and they’re sequential in time and progress in the amount of data that flows over those wires, and you put them into the computer platform and put software around it with all different form factors,” said Tilman, noting that, over the years, GE and others have designed analyzers for Industry Standard Architecture (ISA), VME, PCI, and PCI Express bus standards. 

 

Based on industry demand and the types of bus architectures most frequently being featured on in-production aircraft, that’s how GE designs its bus analyzers, he said. 

 

The four primary functions of the more complex bus analyzers provided by GE and others include hardware component simulation, data display, data logging and analysis, and data bus traffic playback. By selecting the right bus analyzer, the end user can save time and reduce spending and program risk, such as being forced to perform more flight-testing than is necessary or delaying the introduction of a new device or system component to the market, says Tilman.

 

During the aircraft develop and systems integration phase, for current aircraft, the intended use of the analyzer is a major consideration because of the number of different buses, interfaces, systems and sensors that have to communicate with each other. This is especially true on today’s platforms, such as the Boeing 787, which features ARINC 429, 664 and Controller Area Network (CAN) bus types, as well as the new Airbus A350, which features ARINC 429, 664 and MIL-STD-1553. 

 

“When you’re starting to tie in different interfaces, you’ll want an analyzer capable of looking at multiple interfaces at the same time. You want to see analog values coming in and you want to see them digitized when they come out onto the serial digital interface. You want to see that those values are the same and then they cross that digitalization boundary into ARINC 664, or potentially into a different instrument; and you want to see that same piece of data in a given time, so you’re looking at the exact data or reformatted change of the data being put in the right place and within a certain time frame because time is often a critical element,” said Tilman. “With the integrated instruments, you have the data side by side, you can see the time tags along with that interface data, and you can look at that data flow all the way through the pipe from the sensor all the way to the final view on the cockpit potentially.”

 

Military end users of data bus analyzers are facing even more complexity than their commercial counter parts when it comes to selecting a bus analyzer. Defense applications are using more commercial platforms, requiring new integrations of commercial interfaces such as ARINC 429 and 664 with military interfaces such as MIL-STD-1553, 1760 and even Time Triggered Ethernet. While Time Triggered Ethernet is not an interface that GE currently supports in terms of databus analyzers, with programs such as the multi-mission S-97 Raider incorporating TTE, demand for analyzers that support that type of bus traffic will surely increase. Dave Adams, mission systems project lead at Sikorsky Aircraft, recently told Avionics Magazine about the benefits of including TTE on the S-97 Raider. 

 

“We are really looking at common sensors that support the flight controls, avionics pieces and not having dedicated sensors to each segment. We are really truly integrated with all these pieces, flight controls, and your displays, remote processing units are all tightly coupled together and all interfaced through this high bandwidth time triggered Ethernet backbone,” said Adams. 

 

Going forward, as Airbus, Boeing, Bombardier, Embraer and other airframe manufacturers continue to develop their next generation platforms, Tilman says selecting the right databus analyzer will continue to remain a constant need for those programs.

 

“It takes time to design these boxes, it takes time to architect and design these newer interfaces and newer sensors in these systems. It took a lot of years to develop ARINC 429, it took a lot of years and coordination between different companies and the military to develop the very detailed and complex requirements of the 1553 standard, and documents that fit behind it. It takes time to test those things out, prove that they work, put them in a system, qualify them and the concern that I see, certainly with the desire for that speed to market, it’s not a commercial commodity market, it’s very critical interfaces that have to be very well thought out and tested and there is that commercial market drive to make these things happen faster and I see steps being skipped. Speed is not the game here, it’s a critical system and when they are supporting these aircraft traversing our skies, you don’t want them falling on top of the trusting and unsuspecting public,” said Tilman.