Range View Aux OFF Bearing OFF Nav GPS1 Baro Set 29.92" VSI Bug 0 FPM Alt Bug 5000 FT Hdg Bug 270° Hdg Sync Range View SUNOL BRG 060° 6.8 NM 00:04:15 -20 -10 270 ° C RING MSG FPL PROC CDI OBS GPS COM  C V PWR VOL/ SQ PUSH VOL/ ID PUSH VLOC 114. 00 116. 00 COM 119.000 120. 600 NAV SUNOL DTK DIS BRG TRK GS ETE 6.80 059 060 nm m m  96 060 kt m 1.0 1.0 KSQL 04:15  D E C R I N C R HDG NAV APR REV ALT VS VS AP VSx100 NAV The CDI is coupled to the area navigation computer, so the autopilot streets the aircraft along the desired track to the active waypoint showing on the navigation computer. C CO O OM M 11 GPS N Hd B UNOL SU 20 The autopilot NAV function steers the aircraft to keep the CDI needle centered. Figure 4-6. Using the navigation function to follow the programmed flight route. Following a VOR Radial GPS Steering (GPSS) Function When combined, use of the FMS and the FD/autopilot’s  navigation function result in an automated form of flight that  was formerly limited to very complex and expensive aircraft.  This same level of avionics can now be found in single‑engine  training airplanes. While it is easy to be complacent and let  down your guard, you must continuously monitor and stay  aware of automated systems status and function and the  track of the aircraft in relation to the flight plan and air traffic  control (ATC) clearance. The FD/autopilot’s navigation function can also be used to  directly track VOR radials. The navigation display must be  configured to show indications from one of the aircraft’s VOR  receivers. Once you have tuned and identified a VOR station  and selected the desired radial, you can select the navigation  mode to track the selected radial.  Figure 4-7  demonstrates  how to use the navigation mode to follow a VOR radial. When the navigation mode is used to follow a route defined  by VOR radials, you must still tune and identify each new  VOR facility manually and select the appropriate radials  along the way. The autopilot’s navigation function cannot  automatically manipulate the VOR receiver. However, some  highly automated FMS units tune and identify VORs along a  defined route, such as Victor or Jet routes. You should check  the FMS documentation and installed options. Many autopilots offer a global positioning system steering  (GPSS) function. GPSS does all of the same actions as  the navigation function, but achieves a higher degree of  precision by accepting inputs directly from the GPS receiver.  Consequently, the GPSS function follows the desired track to  the active waypoint more aggressively, permitting only small  excursions from the desired course. On some installations,  pressing the autopilot NAV button twice engages the GPSS  function. 4-6