YD BARO ARM AP FD HDG NAV REV ALT APR A L T S EL DN UP Press to engage the approach function. APR The autopilot should maintain a greater  accuracy of track in the approach mode. NAV APR D E C R  I N C R HDG NAV APR REV ALT VS VS AP VSx100 NAV APR ALT D E C R  I N C R HDG NAV APR REV ALT VS VS AP VSx100 NAV APR ALT GS D E C R  I N C R HDG NAV APR REV ALT VS VS AP VSx100 NAV APR GS P When the glideslope has been captured, the autopilot automatically disengages the altitude function and  engages the glideslope function. The pilot must  adjust power and drag (flaps and landing gear) to  control airspeed. P When the aircraft comes within reception range of the glideslope, the autopilot automatically arms the  glideslope function. Use the approach and altitude functions to establish the aircraft on the localizer. X X X Figure 4-14. Flying a coupled nonprecision approach. Figure 4-15. Flying a coupled precision approach. Power Management Essential Skills functions of the autopilot are used in the same way to carry  out the lateral and vertical guidance and control of the aircraft.  This process is transparent to the pilot. Most “VNAV”  functions do not qualify as approach vertical functions and  many FMS/GPS units inhibit that function during approaches. Since most autopilots are not capable of manipulating power  settings, you must manage the throttle to control airspeed  throughout all phases of the approach. The power changes  needed during altitude changes must supply the necessary  thrust to overcome the drag. The pilot must coordinate the  powerplant settings with the commands given to the FD/ autopilot. Remember, the FD/autopilot can control the  aircraft’s pitch attitude only for altitude or airspeed, but not  both. The FD/autopilot attempts to perform as programmed  by you, the pilot. If the climbing vertical speed selection  is too great, the aircraft increases the pitch attitude until it  achieves that vertical speed, or the wing stalls. Selection of  an airspeed or descent rate that is too great for the power  selected can result in speeds beyond the airframe limitations.  Leveling off from a descent, without restoring a cruise power  setting results in a stall as the FD/autopilot attempts to hold  the altitude selected. 3. Use the FD/autopilot to couple to an RNAV approach. 4. Determine the power setting required to fly the  approaches. 5. Determine the power settings necessary for leveloff  during nonprecision approaches and go‑around  power settings for both precision and nonprecision  approaches. 1. Use the FD/autopilot to couple to a precision approach. 2. Use the FD/autopilot to couple to a nonprecision  approach. 4-13