Charting Two for One

The note is correct as written-and an IFR GPS alone is fine. Now follow me down a logical rabbit hole to understand why, as well as see how GPS and digital tech in general are changing how we fly IFR.

jwanwest

Friday, March 03, 2017 at 12:00 AM ET

Verified

Key Takeaways:

The "GPS and DME required" note on co-charted approaches like ILS Z or LOC Z Rwy 23 is correct because the chart represents two distinct approaches: GPS is required for the missed approach procedure of both the ILS Z and LOC Z, while DME (or GPS in lieu of DME) is additionally needed for specific points on the localizer-only (LOC Z) approach.
This "two-for-one" charting practice, a legacy of paper chart efficiency, combines different procedures with varying equipment requirements onto a single document, which can complicate the interpretation of notes for pilots.
The FAA plans to address this confusion with new briefing strip areas that will explicitly state equipment requirements for specific approach components, and modern GPS databases are improving by offering separate localizer approach options that include unique waypoints.

See a mistake? Contact us.

Someone asked me about a note on the ILS Z or LOC Z Rwy 23 at Walterboro, SC (KRBW). The note says: “GPS and DME required.” (Emphasis added.) How can that be? GPS can be used in lieu of DME, but it can’t be a typo because it would just say “DME required.”

The note is correct as written—and an IFR GPS alone is fine. Now follow me down a logical rabbit hole to understand why, as well as see how GPS and digital tech in general are changing how we fly IFR.