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COMMUNICATIONS PROTOCOLS IN AERONAUTICS

by George Novacek

Start ý Data Bus Systems ý Timing is the Secret ý ARINC 429 ý CSDB and ASCB ý MIL-STD-1553B ý ARINC 629 and Beyond ý ARINC 429 Implementation ý Data Format ý Wrap Up ý Sources and PDF

ARINC 629 AND BEYOND

ARINC 629 protocol is relatively new and not widely used, but it must be included for completeness. It was developed by Boeing Commercial Airplane Group (BCAG) as the Digital Autonomous Terminal Access Communication (DATAC) protocol and recognized as an air transport standard by ARINC in specification 629. [2]

It is a bidirectional, distributed control bus capable of supporting up to 120 users at a transmission rate of 2 Mbps. Touted as the future aeronautical communications standard in the early ý90s, it found its way into the huge Boeing 777 and Airbus 330/340 airplanes, which were both being developed at that time. Since then, it appears to have been limited to the largest commercial aircraft only and Boeing in particular. It started as a Boeing proprietary communications protocol and, despite its performance and ARINC specifications, seems to have failed to gain industry-wide acceptance. I can only offer my own speculation for why this happened, but probably the most important driver at the time of introduction was the prohibitive cost of the hardware, which overshadowed even the expensive MIL-STD-1553B RT set. The other reason is probably the unprecedented growth in commercial computer technology and, with it, the developments of commercial networks, not to mention the spiraling data throughput requirements.

About a year ago, Boeing (together with Rockwell Collins) announced a new, Ethernet-based protocol called Avionics Systems Network (ANS). It was installed on the then ready-to-be-certified Boeing 767-400ER (extended range) derivative. The ANS boasts 10-Mbps data throughput, which is just enough to satisfy the quickly expanding data exchange on increasingly electric airplanes. It is said that 100 Mbps is just around the corner.

There are several other protocols, such as those developed by the Society for Automotive Engineers, SAE AS4074 Linear Token Passing Bus (LTPB), and High Speed Ring Bus (HSRB) for military applications, but they are presently too far off the mainstream to make a substantial effect on the wider industry.

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