|CHAPTER 3. Navigation
Common Error: Noncompliance With Initial Missed Approach Instructions
The immense capability of the FMS/GPS may tempt you to follow its directions rather than fly a missed approach procedure exactly as published on the instrument approach procedure chart. Always fly procedures as published, especially with respect to the initial climb and turn instructions. GPS as a line-of-sight navigation aid can display courses and distances to a ground-based navaid even though the navaid is on the other side of a mountain range and itself cannot be received, because GPS signals are spaced based.
Ground-Based Radio Navigation
Configuring FMS To Receive Ground-Based Radio Navigation Signals
Most advanced avionics systems include receivers for conventional radio navigation signals from VOR, localizer, and glideslope transmitters. To display these signals on the navigation display indicator(s), you need two fundamental skills.
Tuning and Identifying Radio Navigation Facilities
The first fundamental skill in ground-based radio navigation is tuning and identifying a ground-based radio navigation facility. Figure 3-59 illustrates how a VOR station can be tuned using two different systems.
Some systems automatically attempt to identify ground-based radio navigation facilities that are selected by the pilot. Note the identifier that appears beside the selected frequency in the upper left corner of the PFD in Figure 3-59 (116.00 = ECA).
Displaying Radio Navigation Signals on the Navigation Indicator
The second fundamental skill is displaying indications from a ground-based radio navigation facility on the navigation display indicator in the aircraft. In addition to setting the navigation indicator to display indications from different navigation sources, you must also know where to look to double-check which indications are currently being displayed. It is crucial to remain constantly aware of the navigation source for each indicator. Many systems use color coding to make a visual distinction between different RNAV navigation sources (GPS, INS, etc.) and ground-based radio navigation sources.
Awareness: Using All Available Navigation Resources
Looking at the two systems shown in Figure 3-59, you can see that two VOR frequencies appear in the active windows at all times, regardless of whether VOR or GPS is being used as the primary navigation source. To maximize situational awareness and make best use of this resource, it is a good practice to keep them tuned to VOR stations along your route of flight. If you have two navigation indicators, you can have one indicator set to show GPS course indications, with the other to show VOR indications. Used in this way, VOR and GPS can serve as backups for each another.
Flying a Precision Approach Using Ground-based Navigation Facilities
Flying a precision approach requires tuning the required frequencies, configuring the navigation indicator to display localizer course indications, and flying the approach. For aircraft equipped with multiple navigation radios, the localizer frequency can go into one receiver, while a second navigational facility used as a cross-radial can be set in the other receiver. As you come within range of the localizer and glideslope, the course deviation and glideslope indicators will show position with respect to the localizer and glideslope.
Flying a Nonprecision Approach Using Ground- Based Navigation Facilities
Nonprecision approaches such as VOR, localizer, and LDA approaches are flown using the same procedures used to fly a precision approach. If the aircraft is equipped with an autopilot, be sure to develop a thorough understanding of how the autopilot works with the FMS. While these systems automate some tasks, others (e.g., flying the procedure turn course reversal) maybe left to the pilot.
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