Finding Non-Precision

As we move forward in time with the proliferation of LPV approaches, the phaseout of non-precision approaches using ground-based navaids such as VOR, NDB, and LOC-only will result in fewer and fewer non-precision approaches. Furthermore, some WAAS navigators often provide an advisory glideslope to non-precision RNAV approaches: LNAV+V and LP+V. The +V refers to the advisory glideslope. An LP (localizer performance) approach is a non-precision RNAV approach that requires WAAS. Bottom line: there is almost always an electronic glideslope lurking in the shadows.

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Monday, July 01, 2019 at 12:00 AM ET

Verified

Key Takeaways:

The aviation landscape has largely shifted from traditional non-precision approaches to GPS-based "precision-like" (APV/LPV) approaches that provide vertical guidance, due to WAAS and the reduction of ground-based navaids.
This widespread availability of vertical guidance on most modern approaches creates a challenge for pilots needing to practice or demonstrate proficiency in true non-precision approaches, which are still required for instrument ratings and checks.
A practical solution for practicing non-precision approaches is to temporarily disable WAAS on the GPS navigator, which removes the electronic glideslope and converts APV/LPV approaches into LNAV approaches without vertical guidance, though pilots must be aware of potential ADS-B Out implications.

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With the advent of GPS approaches in the 1990’s and early 2000’s, we had many more opportunities to practice and fly non-precision approaches. Today in the U.S., with WAAS (wide area augmentation system), the reduction of VORs and the near elimination of NDBs, there are fewer and fewer available non-precision approaches. The result is more precision-like approaches which undoubtedly improves safety.

I say “precision-like” approaches because the only true precision approach available to us is the ILS with a ground-based glideslope transmitter. On the other hand, due to some technical differences that are immaterial to pilots, most RNAV (GPS) approaches with WAAS have an electronic glideslope and are referred to as APV (approaches with vertical guidance).