BACK EXEC XPND$^{Modify}$ Wpt Arwy Library KSQL SUNOL  21.7 ECA  55.0 027  21.7 DIST V195   33.3 BRG 060°   21.7 discontinuity BRG ---   --- FPL n m n m n m GPS ENR FLAGGED 119.000 121.600 114.10 116.00 1200 A  C  T A  C  T S  B  Y S  B  Y S  B  Y --.- vor BACK EXEC XPND Active KSQL 027 SUNOL  21.7 ECA  55.0 027  73.3 No Active Leg DIST ETE BRG 060°   21.7 V195   33.3 BRG 049°   18.3 FPL n m n m n m GPS ENR FLAGGED 119.000 121.600 114.10 116.00 1200 A  C  T A  C  T S  B  Y S  B  Y S  B  Y --.- vor route discontinuity appears when the  FMS cannot proceed from one waypoint  to the next. A route discontinuity can  simply be deleted. S B S B When a route discontinuity is deleted,  the FMS proceeds directly to the next  waypoint in the programmed route. Figure 3-15. A route discontinuity and deletion. was selected in the FMS. Every advanced cockpit offers  buttons or switches that allow you to choose which navigation  indications will be shown on which display or instrument. This situation becomes complicated in aircraft that contain  dual FMS/RNAV installations and redundant selectable  displays or instruments. The pilot must learn how to configure  each navigation instrument to show indications from each  possible navigation source. Figure 3-16  shows an example of a primary flight display  (PFD) navigation indicator that combines a course deviation  indicator (CDI) and a radio magnetic indicator (RMI), and  allows the pilot to display indications from one of two FMS  on either indicator. The annunciations showing which navigation sources are  displayed on which navigation instruments are often small, so  there is significant potential for displaying a navigation source  other than the one you intended to select. The consequences  of losing track of which navigation signals you are following  can be significant: you may think you are steering along one  course when in fact you are steering along a different one.  Be sure to verify these settings prior to departure, and again  each time you make changes to any navigation instrument.  Some installations compound this potential with automatic  source switching. The most common switching mode is a  GPS source to be automatically deselected when the VOR  is set to an ILS localizer frequency and a signal is present.  Typically, that is not a problem since the pilot intends to  switch to the ILS anyway. However, the error arises upon  missed approach, when the pilot selects another frequency  to follow a VOR missed approach routing. At that point,  some units revert back to the previous GPS or other RNAV  routing selected instead of the VOR frequency that the  pilot just picked. This can result in gross navigation errors  and loss of obstruction clearances. In some units, this is a  shop programmable or jumper selected option. Check your  unit’s features. Always check for correct navigation source  selection and cross‑check against the published procedure.  Be ready and able to fly and navigate manually. Common Error: Displaying the Wrong Navigation  Source 3-12