ARINC 424A — A next generation navigation database specification

ARINC 424 ldquonavigation system databaserdquo has been the industry standard for exchanging navigation data between data suppliers and avionics vendors for more than 30 years. The format defined is fixed length text files with 132 characters per line. For use in flight management computers (FMC), these files are converted into loadable binary images by ground packaging software unique to the individual FMC vendor. A consequence of this approach is that many airlines with mixed fleets and different avionics vendors have to deal with dozens of navigation database packages which have to be delivered and loaded to the right aircraft each 28 days according to AIRAC schedule. Even though the raw data used to create the packages is identical, this creates significant logistic effort and cost. This issue has been addressed recently by the ARINC NDBX proposal. NDBX is based on an UML model for Aeronautical Navigation Data containing element and attribute specifications and the associated documentation. Navigation data are initially prepared in XML format and later converted into Binary-XML (BXML) for smaller file sizes and easier parsing. The main concern surrounding NDBX was that it would have created a second navigation data exchange standard, with all the efforts needed to maintain two parallel lines of documentation and development for the same data. In order to combine the advantages of the newer concepts developed as part of NDBX with existing ARINC 424 data specifications, processes and technologies, the ARINC AEEC has made a decision to merge the 424 and the NDBX standards. This effort is currently in progress under the working title ARINC 424A ldquonavigation database standardsrdquo. ARINC 424A will be based on a common UML model for all navigation data related specifications, documentation, and requirements. This model will be used to generate an ASCII representation (the former ARINC 424 text), and a XML / BXML representation (the former NDBX) of that data. The n- ew ARINC 424A document will mirror 424 Supplement 19, with enhancements related to the new XML and BXML representations.