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Old Vs. New ILS

Gemini Sparkle

Key Takeaways:

  • ILS approaches are increasingly incorporating Terminal Arrival Areas (TAAs), traditionally found in RNAV (GPS) procedures, replacing Minimum Sector Altitudes (MSAs).
  • Unlike MSAs, TAA altitudes are operationally usable for navigation, providing obstacle clearance and simplifying procedure entry with specific floor altitudes.
  • These new ILS/TAA approaches often require GPS for procedure entry and identifying fixes throughout the approach, indicating a shift towards Performance-Based Navigation.
  • The integration of TAAs with ILS approaches is a growing trend, partly driven by the decommissioning of VORs and the widespread use of IFR WAAS GPS in aircraft.
See a mistake? Contact us.

When I first saw the approach chart for the ILS Y or LOC Y RWY 3 at Raleigh Executive Jetport at Sanford-Lee County, South Carolina (KTTA), I thought I was seeing something unusual. I was. It’s an ILS approach with a Terminal Arrival Area (TAA). Yes, these are possible and we’re starting to see more, so let’s take a closer look. Let’s call this the “Y” approach. The “Y” also implies that there is a “Z” approach lurking nearby.

TAAs and MSAs

TAAs are typically associated with RNAV (GPS) approaches using the familiar “T” structure. Such designs frequently have initial approach fixes (IAF) at the end of the arms of the “T” and the center waypoint is usually an IAF and an intermediate fix (IF). However not all GPS “T” approaches have TAAs.

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