position information for navigation fixes so it may perform  the required geodetic calculations to determine the  appropriate tracks, headings, and distances to be flown.  [Figure 6-3]  Modern FMS are capable of a large number of functions  including basic en route navigation, complex departure  and arrival navigation, fuel planning, and precise vertical  navigation. Unlike stand-alone navigation systems, most  FMS use several navigation inputs. Typically, they formulate  the aircraft’s current position using a combination of  conventional distance measuring equipment (DME) signals,  inertial navigation systems (INS), GPS receivers, or other  RNAV devices. Like stand-alone navigation avionics, they  rely heavily on airborne navigation databases to provide  the information needed to perform their numerous  functions.  Beginning in the 1970s, the requirement for airborne  navigation databases became more critical. In 1973,  Airborne Navigation Database Standardization  6-3  Figure 6-3. FMS display.  I RNG  PULL SCAN  PUSH ON  BRT  PROC  CRSR  MSG  OBS  ALT  NRST  CLR  ENT D  MENU  DTK  TK  . nm  LEG  VOR NDB INT USR ACT NAV FPL SET AUX APT1 A  B  C  D  E  F  G  H  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z  SPC  BKSP  PFD  MFD  NAV  COM  PFD  MENU  FPL  PROC  CLR  ENT SEL  DFLT MAP  SOFTKEY SELECT  EMERG  PUSH CRSR/PUSH 1-2  FMS/  NAV-COM  PUSH  PAN  RANGE  + − 1  2  3  4  5  6  7  8  9  − 0  +  The display allows you to view information stored in the FMS.  Controls such as  buttons and knobs  allow you to make  entries into the FMS.  Figure 6-2. GPS with a flight route on display. 