Fiber optic AFDX for flight control systems

Abstract

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Fiber optic systems are often cited as a way to gain EMI immunity, reduce weight, and increase bandwidth. Avionics Full-Duplex Switched Ethernet (AFDX), specified in ARINC 664 Aircraft Data Network, Part 7, is a fiber optic avionics bus specification used on the Airbus A380, Boeing 787, and others. It was designed as an upgrade to the standard Ethernet protocol which added guaranteed determinism with bounded jitter and latency. This was done to allow hard real time, critical systems to communicate using standard IEEE 802.3 Ethernet protocol. It uses dual redundancy and full duplex links to minimize jitter and latency and eliminate packet collisions. Although AFDX was designed with hard real time systems in mind, it has not yet been used in a safety critical flight control system. Airbus has expressed interest in extending its use of AFDX from mission critical to flight critical systems[1]. The use of AFDX for flight control systems could provide a number of benefits over legacy systems such as MIL STD 1553 and ARINC 429 (A429). Other fiber optic busses do exist, including MIL STD 1773, ARINC 629, ARINC 636 and Fiber Channel, but these are not currently used for flight controls and comparisons to these busses is beyond the scope of this study.