BY ORDER OF THE SECRETARY OF THE AIR FORCE AIR FORCE ...

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AFMAN 11-217V1 3 JANUARY 2005
that gathers aircraft position information from multiple onboard sensors and
navigation aids including VOR, DME, TACAN, Inertial Reference Systems (IRS)
and Inertial Navigation Systems (INS), Global Positioning System (GPS), and Air
Data Computers. From this sensor data the FMC computes and continually updates
the aircraft present position throughout the flight. Using this aircraft position
information, navigation functions such as course and distance to a waypoint, desired
track, groundspeed, and estimated time of arrival are computed and displayed on the
CDU and other aircraft instruments. Navigation information may also be provided in
the form of steering commands to autopilot and flight director systems. In addition,
fuel flow information may be used by the FMC to calculate and update fuel
consumption, specific range, and fuel overhead destination information.
5.4.1.2. Control Display Unit. The CDU serves as the aircrew’s interface to the FMC
and associated navigation sensors. The CDU normally consists of a display screen,
data entry pad, and function and line select keys. The CDU allows menu-driven
selection of various FMS modes, such as initialization, fuel planning, performance,
and navigation. The pilot may input flight plan route, vertical profile and speed
information, aircraft weight and fuel parameters, and certain waypoint data into the
FMC. Data from the navigation database may be displayed and reviewed by the pilot
on the CDU.
5.4.1.3. Navigation Database. An FMS normally contains an internal navigation
database with either regional or worldwide coverage. The database typically includes
information on navigation aids, airports, runways, waypoints, routes, airways,
intersections, departures and arrivals, and instrument approaches. Aircrews may also
store defined routes and waypoints in the database. Navigation databases require
periodic updates, normally on a 28-day cycle, to ensure data is current.