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Aviation History
1988
1988 - 0368.PDF
Keeping the complex simple As the Airbus A320 prepares for certification and commercial service, Gilbert Sedbon describes how Sfena seeks to ensure optimum integration of the complete flight, from control of the surfaces to flight trajectory management. mtm wwwnmm iwfl I3RHR1QC1 i nnniiiiiiiiiniTiniiiniiii SFENA^ \U- 220 M C5397AAAM 4PteI Clockwise from top left A frequency stabilised helium neon laser, EPROMs on a plug-in memory board, the Airbus A320 cockpit showing the computer-driven displays, a complete plug-in board, and the computerised fuel transfer system Introducing a new item of equipment into an aircraft cockpit inevitably brings some operational and mainte nance problems in its wake. From the outset, and despite the complexity of the problem, Sfena decided that its part of the Airbus A320 fly-by-wire system should be simple to operate and easy to maintain. A plug-in memory module is one of many ways Sfena sought to achieve this goal. Like the diskettes in micro computers, this module stores modifiable software for a given function, and can be replaced or altered without removing the entire onboard computer. Each function is contained in a single module. This can be replaced without opening the computer, and enormously simplifies future development of the system, says Sfena. The components used are the most powerful commercially available; Intel 80286 and 80287 16-bit microprocessors; electronically programmable memories for the functional circuits and electronically erasable memories for the control and maintenance circuits. The general use of low-power semiconductor technology and the incorporation of semi-custom devices allows a considerable reduction in size. Sfena hardware embodying this approach is used at all levels in the A320, for the fly-by-wire controls—three spoiler/elevator computers and two flight augmentation computers—and for the flight management and guidance system. The fly-by-wire processing system performs 2.5-3 million operations a second, Sfena notes. The flight management and guidance computer, produced in association with Sperry, BGT of Germany, and Inisel of Spain, with Sfena as prime contractor, is the interface between the crew and the A320 flight management and autopilot functions. Computer functions range from trajectory management during the cruise to Category III automatic landing. The computer contains six processors oper ating as three pairs, of parallel processors, and has 2.5 megabytes of memory. The associated flight control unit, mounted on the instrument panel coaming, enables the A320 crew to display heading, speed, and altitude reference data. Two multifunction control display units with CRT screens and alphanumeric keyboards are mounted on the central pedestal to allow the pilots to commu nicate with the flight management computers. Another important A320 system for I! FLIGHT INTERNATIONAL, 13 February 1988
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