close to it, as in  Figure 9-15 . The CDI deviates from side  to side as the aircraft passes over or nearly over the station  because of the volume of space above the station where the  zone of confusion exists. This zone of confusion is caused  by lack of adequate signal directly above the station due to  the radiation pattern of the station’s antenna, and because  the resultant of the opposing reference and variable signals  is small and constantly changing. The CDI in  Figure 9-15 indicates 180°, meaning that the  aircraft is on the 180° or the 360° radial of the station. The TO/ FROM indicator resolves the ambiguity. If the TO indicator is  showing, then it is 180° TO the station. The FROM indication  indicates the radial of the station the aircraft is presently on.  Movement of the CDI from center, if it occurs at a relatively  constant rate, indicates the aircraft is moving or drifting off  the 180°/360° line. If the movement is rapid or fluctuating,  this is an indication of impending station passage (the aircraft  is near the station). To determine the aircraft’s position  relative to the station, rotate the OBS until FROM appears  in the window, and then center the CDI needle. The index  indicates the VOR radial where the aircraft is located. The  inbound (to the station) course is the reciprocal of the radial. If the VOR is set to the reciprocal of the intended course, the  CDI reflects reverse sensing. To correct for needle deflection,  turn away from the needle. To avoid this reverse sensing  situation, set the VOR to agree with the intended course. A single NAVAID allows a pilot to determine the aircraft’s  position relative to a radial. Indications from a second  NAVAID are needed in order to narrow the aircraft’s position  down to an exact location on this radial. To track to the station, rotate the OBS until TO appears,  then center the CDI. Fly the course indicated by the index.  If the CDI moves off center to the left, follow the needle by  correcting course to the left, beginning with a 20° correction. When flying the course indicated on the index, a left deflection  of the needle indicates a crosswind component from the left.  If the amount of correction brings the needle back to center,  decrease the left course correction by half. If the CDI moves  left or right now, it should do so much more slowly, and smaller  heading corrections can be made for the next iteration. Keeping the CDI centered takes the aircraft to the station.  To track to the station, the OBS value at the index is not  changed. To home to the station, the CDI needle is periodically  centered, and the new course under the index is used for the  aircraft heading. Homing follows a circuitous route to the  station, just as with ADF homing. To track FROM the station on a VOR radial, you should  first orient the aircraft’s location with respect to the station  and the desired outbound track by centering the CDI needle  with a FROM indication. The track is intercepted by either  flying over the station or establishing an intercept heading.  The magnetic course of the desired radial is entered under the  index using the OBS and the intercept heading held until the  CDI centers. Then the procedure for tracking to the station  is used to fly outbound on the specified radial. If the desired course is not the one being flown, first orient  the aircraft’s position with respect to the VOR station and the  course to be flown, and then establish an intercept heading.  The following steps may be used to intercept a predetermined  course, either inbound or outbound. Steps 1–3 may be omitted  when turning directly to intercept the course without initially  turning to parallel the desired course. Course interception is illustrated in  Figure 9-16 . Typical pilot-induced errors include: Course Interception Tracking TO and FROM the Station VOR Operational Errors 1.  Determine the difference between the radial to be  intercepted and the radial on which the aircraft is  located (205° – 160° = 045°). 2.  Double the difference to determine the interception  angle, which will not be less than 20° nor greater  than 90° (45°  × 2 = 090°). 205° + 090° = 295° for  the intercept). 3.  Rotate the OBS to the desired radial or inbound course. 4.  Turn to the interception heading. 5.  Hold this heading constant until the CDI center, which  indicates the aircraft is on course. (With practice in  judging the varying rates of closure with the course  centerline, pilots learn to lead the turn to prevent  overshooting the course.) 6.  Turn to the MH corresponding to the selected course,  and follow tracking procedures inbound or outbound. 1.  Careless tuning and identification of station. 2.  Failure to check receiver for accuracy/sensitivity. 3.  Turning in the wrong direction during an orientation.  This error is common until visualizing position rather  than heading. 4.  Failure to check the ambiguity (TO/FROM) indicator,  particularly during course reversals, resulting in reverse  sensing and corrections in the wrong direction. 9-14