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 note "GPS and DME required" on an "ILS Z or LOC Z" chart is correct because it refers to two distinct approaches (ILS Z and LOC Z) co-charted for efficiency, each with specific equipment needs.
GPS is required for the combined missed approach procedure of both the ILS Z and LOC Z, while DME (or GPS as a substitute) is separately required for identifying the FAF/MAP on the LOC Z approach.
Charting practices are evolving; the FAA plans clearer requirement briefings, and GPS databases are improving to include specific waypoints for localizer approaches previously only available in the ILS database.

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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.