Overlay Approaches

Lets connect some dots. In 1969, NARCO (now defunct) introduced the CLC-60 VORTAC Offset Control Panel that allowed navigation to a phantom fix defined as a distance and direction (rho-theta) from an existing VORTAC. It was touted as the first RNAV system. In the 80s, Bendix/Kings KNS-80 Integrated Navigation System might be considered the first practical RNAV navigator (it had VOR, LOC, DME, RNAV, and GS). Like the CLC-60, it could electronically move a VORTAC and was IFR certified.

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Sunday, February 17, 2019 at 12:00 AM ET

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Key Takeaways:

Approach chart titles indicate required equipment for the Final Approach Segment (FAS), while "ADF Required" often pertains to transitions or missed approaches, with IFR GPS generally suitable for substitution.
Recent FAA guidance (AIM 2016) and subsequent regulatory AFM supplements (e.g., Garmin GTN 2018) now permit the use of a suitable RNAV system, such as an IFR-approved GPS, for navigation on the final approach segment of VOR or NDB approaches.
This allowance comes with critical conditions: the underlying conventional NAVAID (VOR or NDB) must be operational, its signal actively monitored for final approach course alignment, and the aircraft's conventional receiver must be functional.
While standalone RNAV (GPS) approaches are often preferred for their precision, this capability offers a practical alternative for conventional approaches, especially at airports lacking RNAV options or in international contexts, with the AFM supplement being the governing document.

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During an instrument proficiency check, or for that matter an instrument check ride, a common question is, “What does the title of an approach chart indicate? For Example: LOC/DME RWY 18 or VOR RWY 20.” And a follow-up question, “What does ‘ADF Required’ on an approach chart imply (not in the title)?”

Of course, we all know the answers to the questions. Right? The title of the approach indicates what equipment is required to fly the final approach segment (FAS).