AREA NAVIGATION COURSES

RNAV (GPS) approach procedures introduce their own tracking issues because they are flown using an onboard navigation database. They may be flown as coupled approaches or flown manually. In either case, navigation system coding is based on procedure design, including waypoint (WP) sequencing for an approach and missed approach. The procedure design will indicate whether the WP is a fly-over or fly-by, and will provide appropriate guidance for each. A fly-by (FB) waypoint requires the use of turn anticipation to avoid overshooting the next flight segment. A fly-over (FO) waypoint precludes any turn until the waypoint is overflown, and is followed by either an intercept maneuver of the next flight segment or direct flight to the next waypoint.

Approach waypoints, except for the missed approach waypoint (MAWP) and the missed approach holding waypoint (MAHWP), are normally fly-by waypoints. Notice that in the planview for figure 5-13 there are five fly-by waypoints, but only the circled waypoint symbols at RWY 13 and SMITS are fly-over waypoints. If flying manually to a selected RNAV waypoint, pilots should anticipate the turn at a fly-by waypoint to ensure a smooth transition and avoid overshooting the next flight segment. Alternatively, for a fly-over waypoint, no turn is accomplished until the aircraft passes the waypoint.

There are circumstances when a waypoint may be coded into the database as both a FB WP and a FO WP, depending on how the waypoints are sequenced during the approach procedure. For example, a waypoint that serves as an IAF may be coded as a FB WP for the approach and as a FO WP when it also serves as the MAHWP for the missed approach procedure.

ALTITUDES

Prescribed altitudes may be depicted in four different configurations: minimum, maximum, recommended, and mandatory. The U.S. Government distributes

Figure 5-13. Fly-over and Fly-by Waypoints.

approach charts produced by the National Geospatial- Intelligence Agency (NGA) and NACO. Altitudes are depicted on these charts in the profile view with underscore, overscore, or both to identify them as minimum, maximum, or mandatory, respectively.

• Minimum altitudes are depicted with the altitude value underscored. Aircraft are required to maintain altitude at or above the depicted value.
• Maximum altitudes are depicted with the altitude value overscored. Aircraft are required to maintain altitude at or below the depicted value.
• Mandatory altitudes are depicted with the altitude value both underscored and overscored. Aircraft are required to maintain altitude at the depicted value.
• Recommended altitudes are depicted without an underscore or overscore.

NOTE: The underscore and overscore used to identify mandatory altitudes and overscore to identify maximum altitudes are used almost exclusively by the NGA for military charts. Pilots are cautioned to adhere to altitudes as prescribed because, in certain instances, they may be used as the basis for vertical separation of aircraft by ATC. When a depicted altitude is specified in the ATC clearance, that altitude becomes mandatory as defined above.