Flight management computer (FMC) navigation database capacity

Navigation database (NDB) capacity (memory size) has always been an issue in aircraft Flight Management Computers (FMC). And, that issue is a concern for Performance-based Navigation (PBN) Implementation as so many new next generation (NextGen) procedures are being developed and many FMCs no longer have the capacity for additions to their NDBs. For the near-term, the problem will just keep getting worse for aircraft with FMCs limited by capacity due to the growth in the number of coded procedures and waypoints to store and limitations in the storage size. Anecdotal evidence finds navigation database suppliers estimating that worldwide procedure production will increase database size approximately 3% to 8% annually for the forseable future.¹ In many cases, the airlines must already strictly tailor the available sets of procedures in their databases according to geographic areas to meet current FMC memory capacity constraints. Fortunately, the trend for the mid-term and far-term is that the projected growth rate will not be such an issue given the actual and “potential” additional memory expansion of new FMCs.However, a related concern is a means to move away from the binary packing of data into a general standard that works with all FMCs. Database development groups are proposing using a version of Extensible Markup Language (XML) which will take up significantly more storage. FMC vendors and airlines have expressed concern over this proposal because of memory storage requirements. This proposal is still in its infancy and has yet to be proposed as a formal standard. This paper provides background on FMC database capacity and factors that influence memory requirements. It addresses airline's tailoring of navigation databases and the status of memory in current FMCs operating within the United States National Airspace System (NAS). It also introduces the methods the airlines use to reduce the size of their NDBs despite the tide of procedures being developed worldwide.