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| ARINC 629 | |
|---|---|
| Name | ARINC 629 |
| Type | Avionics databus |
| Developer | ARINC |
| Introduced | 1980s |
| Usage | Commercial aircraft avionics |
| Successor | ARINC 664 (AFDX) |
ARINC 629 is a multiterminal avionics data bus standard used in commercial aircraft for low- to medium-speed communication among line replaceable units. It defines a deterministic, self-clocking, multiple-access protocol enabling components such as flight control computers, navigation systems, and display units to exchange messages without a central controller. The standard was developed to replace point-to-point wiring schemes and earlier databus protocols to support increasingly complex avionics suites.
ARINC 629 was developed by Aeronautical Radio, Incorporated to serve airlines and manufacturers like Boeing, Airbus, and McDonnell Douglas. It supports up to 128 terminals per data bus and was designed with avionics suppliers including Honeywell Aerospace, Rockwell Collins, Thales Group, GE Aviation, and Smiths Group in mind. The technology addresses challenges faced during programs such as Boeing 767, Airbus A320, and Boeing 747-400 modernization efforts, providing a shared medium alternative to standards used on platforms like Lockheed L-1011 and McDonnell Douglas MD-11. ARINC 629 complements other avionics initiatives associated with organizations such as RTCA, Inc., EUROCAE, and SAE International.
The physical layer for ARINC 629 typically uses twisted-pair wiring and transceivers produced by vendors like Microsemi and Intel, with signaling characteristics tuned for the avionics environment. The bus operates at a nominal data rate defined by the specification and employs a self-clocking, self-synchronizing waveform to simplify terminal design. Message formats include label fields, source/destination identifiers, and parity/error-checking mechanisms similar in spirit to error control methods considered by NASA for early spacecraft telemetry. The standard prescribes electrical characteristics to meet environmental and electromagnetic compatibility requirements laid out by authorities such as Federal Aviation Administration and European Union Aviation Safety Agency.
ARINC 629 implements a collision avoidance and arbitration scheme permitting any terminal to transmit when the line is idle, using deterministic timing to prevent bus contention. Terminals perform carrier sensing and transmit with built-in priority handling inspired by earlier multiple access techniques used in networks associated with Xerox PARC research and standards debates involving IEEE 802 committees. The bus uses bit-level timing to encode data and relies on distributed control so that devices like inertial reference units, flight management systems, and engine indication and crew alerting systems coordinate without a master controller. Error detection and recovery procedures echo practices from avionics certification projects such as Boeing 777 avionics integration.
Aircraft programs employing ARINC 629 integrated it with systems from suppliers including Garmin, Eaton Corporation, UTC Aerospace Systems, and Boeing Avionics divisions. Typical installations link flight control computers, flight management computers, weather radar processors, and cockpit display units to provide shared situational data across cockpits exemplified by suites found on Airbus A330, Boeing 757, and retrofit programs for McDonnell Douglas DC-10 platforms. Maintenance practices draw on techniques from Rolls-Royce engine health monitoring and line-replaceable unit logistics used by carriers such as American Airlines, Delta Air Lines, and Lufthansa.
ARINC 629 differs from the point-to-point ARINC 429 standard by supporting multiple terminals and distributed arbitration, whereas ARINC 429 uses unidirectional, point-to-point labeling suitable for devices like pitot-static indicators and altimeters produced by manufacturers such as United Technologies. Competing and subsequent technologies include MIL-STD-1553, with its redundant dual-redundant bus controller architecture used on military platforms like the F/A-18 Hornet; and the deterministic switched Ethernet variant ARINC 664 (AFDX) used on modern airliners such as the Airbus A380 and Boeing 787. Differences involve topology, throughput, determinism, and implementation complexity relevant to integrators like Thales Alenia Space and avionics integrators at Bombardier Aerospace.
Certification of ARINC 629 installations follows safety assessment frameworks from RTCA DO-178C for software and RTCA DO-254 for airborne electronic hardware when applicable. System-level safety analyses reference guidelines from ICAO and safety cases reviewed by authorities like the FAA and EASA. Redundancy strategies, fault isolation, and failure modes are evaluated similarly to practices used in certification projects for systems on aircraft such as the Boeing 737 MAX and Airbus A350. Suppliers must address electromagnetic interference and lightning protection per standards promulgated by SAE International and harmonized with military practices like those in MIL-STD-461 when applicable.
Development of ARINC 629 began as avionics demands grew in the late 1970s and 1980s, paralleling avionics integration programs at Boeing and Airbus and corporate research at firms including Hughes Aircraft Company and Texas Instruments. The spec evolved through ARINC committees involving airlines such as British Airways and United Airlines, and aerospace contractors including Northrop Grumman and Lockheed Martin. Over time, ARINC 629 gave way to higher-capacity and switched-network solutions like ARINC 664 (AFDX), driven by projects including Boeing 787 and Airbus A380 that demanded greater bandwidth and integrated modular avionics conceived in concepts popularized by NASA studies and industry white papers from Control Data Corporation era research.
Category:Avionics