CHAPTER 3. Navigation

Wide area augmentation system (WAAS) of the standard GPS furnishes additional error correction information, allowing Category I precision approaches (similar to basic instrument landing system (ILS) minimums) to units equipped to receive and integrate the data. Most general aviation pilots learn to work with an FMS unit primarily using GPS signals, possibly with WAAS and LORAN-C options. Older RNAV units made use of VOR and DME information to compute positions within range of the navaids. Newer units contain databases that allow route programming with automatic sequencing through the selected navigation points. Therefore, flight management system (FMS) is the best descriptor of the current GPS units integrating VOR (and DME, optionally) to allow point-to-point navigation outside established flight routes. You will learn to use the FMS data entry controls to program a flight route, review the planned route, track and make modifications to the planned route while en route, plan and execute a descent, and fly an approach procedure that is based solely on RNAV signals. You should remember that FMS/RNAV units requiring external signals for navigation are usually restricted to line-of-sight reception (LORAN-C being somewhat of an exception). Therefore, navigation information in valleys and canyons that could block satellite signals may be severely restricted. Users in those areas should pay particular attention to the altitude or elevations of the satellites when depending on space-based signals and plan flight altitudes to ensure line-of-sight signal reception. Review the GPS unitís documentation sufficiently to determine if WAAS is installed and how WAAS corrections are indicated.

You will learn how the FMS can automatically perform many of the flight planning calculations that were traditionally performed by hand, and the importance of keeping flight planning skills fresh. You will also discover how the FMS can help you detect and correct errors made in the flight planning process, how the complexities of the FMS make some new kinds of errors possible, and techniques to help avoid them.

Last, you will see how advanced cockpit systems can be used to navigate using ground-based navigation facilities such as VOR and DME. Maintaining pilot skills using ground-based navigation facilities is a simple matter of occasionally using them as the primary means of navigation, and as a backup to verify position and progress when RNAV is used.

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