C RING MSG FPL PROC NRST OBS GPS COM  C V PWR VOL/ SQ PUSH VOL/ ID PUSH VLOC 114. 10 116.00 COM 121.300 135. 400 NAV CRS 009 SUNOL DTK DIS BRG TRK GS ETE  6.9nm m m  85 kt m 04:52 5.0 5.0 OBS 0 9 18 27 3 33 24 21 15 12 30 6 TO N A V To switch to the nonsequencing mode, press . OBS displays above the button to indicate that the nonsequencing mode is in use. OB Once in the non- sequencing mode,  use the OBS knob  to dial the inbound  course of 009°. OBS Figure 3-38. Setting a different course to the active waypoint. 2. Nonsequencing mode stops the waypoint sequencing  feature of the FMS/RNAV unit. If engaged in  nonsequencing mode, the FMS/RNAV program does  not automatically sequence to the next waypoint in  the flight plan when the aircraft arrives at the active  waypoint. Awareness: Remembering To Make Needed Mode  Changes Intercepting and Tracking a Course to a Different  Waypoint Common Error: Forgetting To Re-Engage  Sequencing Mode After Course Intercept the course has been intercepted. The result is that the FMS  will not sequence to the next waypoint in the flight route  upon reaching the active waypoint. The best indicator of this  event is the “To/From” navigation display showing “From.”  Normally all FMS fly “To” the waypoint, unless that unit  does holding patterns. Flying “From” a waypoint can only  be done in the “OBS”/“Hold”/“Suspend” mode. Every FMS/RNAV offers a way to switch to the nonsequencing  mode. There is typically a button marked OBS (or Hold), and  an OBS or course selection knob to select an inbound course  to the active waypoint. Figure 3‑38 illustrates the procedure  for one particular FMS. Once you switch to nonsequencing mode and select the  inbound course of 009°, the navigation indicator reflects  aircraft position with respect to the 009° course. The  navigation indicator in  Figure 3-38 shows that you are  west of course. The assigned heading of 080° provides an  acceptable intercept angle. As you fly the 080° heading, the  needle centers as you reach the 009° course. Once the 009°  course is reached and the needle has centered, you can turn  to track the 009° course inbound to SUNOL. The use of the sequencing and nonsequencing modes  illustrates another aspect of maintaining good mode  awareness—remembering to make required mode changes  at future times during the flight. Remembering to do tasks  planned for the future is a particularly error‑prone process  for human beings. Aviation’s first line of defense against  such errors is the checklist. Creating your own checklist or  callout procedures for maneuvers such as course intercepts  is a good way to minimize this error. For example, a simple  callout procedure for the course intercept maneuver might  commence when the aircraft nears the point of interception.  “Course is alive. Course is captured. Changing back to  sequencing mode.” It is important to remember that the nonsequencing  mode suspends the FMS/RNAV’s waypoint sequencing  function. If you reach SUNOL and the unit is still set in the  nonsequencing mode, it will not sequence on to the next  waypoint. Generally, once established on a direct course to  waypoint or navaid, switching back to sequencing (releasing  the Hold or Suspend function) mode allows the FMS/RNAV  to continue to the programmed point and thence onward  according to the programmed routing. Setting the computer  back to the sequencing mode is usually accomplished by  pressing the OBS (Hold or Suspend) button again. Figure 3-39  illustrates a slightly more complicated request  often made by air traffic control. While en route to SUNOL,  ATC instructs you to fly a heading of 060° to intercept and  track the 049 course to TRACY. This situation requires two  separate tasks: changing not only the inbound course, but  also the active waypoint. The first step is to change the active waypoint using the  direct‑to function, as illustrated in  Figure 3-40.  Remember,  though, that if you use the direct‑to function to make TRACY  the active waypoint, the FMS calculates a desired track that  takes you from the present position to TRACY intersection. By far the most common error made with the nonsequencing  mode is forgetting to re‑engage the sequencing mode once  3-26