Range View Aux OFF Bearing OFF Nav VLOC1 Baro Set 29.92" VSI Bug 0 FPM Alt Bug 5000 FT Hdg Bug 270° Hdg Sync Range View ECA BRG 058° 38.8 NM 00:24:15 15 24 33 6 3 N 30 W 21 S 12 E -20 -10 060 ° 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  20 D E C R I N C R HDG NAV APR REV ALT VS VS AP VSx100 NAV CO The CDI is coupled to the VOR receiver, so the NAV function  steers the aircraft along the desired track to the selected radial. Figure 4-7. Using the navigation mode to follow a VOR radial. Maintain Altitude Fly Heading autopilots make an abrupt bank if engaged when there is a big  change to be made in heading or track. The heading function  is illustrated in  Figure 4-8. Depending on the FMS, the highly automated flight that  results when the navigation mode is used to follow a  published route from the database uses a different skill set  from using the navigation mode to track discreetly tuned VOR  radials. Learning how to select preprogrammed routes from  the database of airways can be challenging. Programming  or tuning discreet VORs en route in turbulent conditions  presents different challenges. Either skill set can result in a  greater sharing of duties between pilot and technology and  an increase in safety. You should note that, when using the heading mode, the FD/ autopilot ignores the pilot‑programmed route in the FMS or  any VOR radials you set. When in heading mode, the FD/ autopilot will fly the selected heading until fuel starvation. The autopilot’s altitude mode maintains an assigned  barometric altitude. When the altitude mode is engaged, the  autopilot seeks to maintain the same barometric pressure  (altitude) that the aircraft was flying at the time that the  altitude mode was engaged.  Figure 4-9  shows how to engage  the altitude mode for one manufacturer’s autopilot. The heading mode is used to steer the aircraft automatically  along a pilot selected heading. Using the FD/autopilot to fly  a heading is a simple matter of selecting the assigned heading  and then engaging the heading function or, more commonly,  accomplished by first engaging the heading mode and gently  turning the heading selection knob to the new heading. Gently  turning the knob with the mode already engaged allows you  to make a smooth change from level to turning flight. Many  In addition to determining and carrying out the pitch  commands necessary to maintain the flight’s assigned  altitude, most autopilots are also able to trim the aircraft.  4-7