Dead Reckoning in IFR

Tuesday, February 23, 2021 at 11:33 AM ET

Verified

VORs are disappearing around larger airports, making even short VOR based short routes challenging. (Shaded VORs are on the MON hit list.)

Key Takeaways:

The FAA's move to a GPS-based Performance Based Navigation (PBN) system is leading to the decommissioning of VORs, making traditional VOR-only IFR navigation increasingly challenging.
Modern IFR en-route navigation requires certified equipment that meets specific Required Navigation Performance (RNP) criteria, which navigation solely by dead reckoning calculations does not satisfy.
While generally unsuitable for primary IFR en-route navigation, dead reckoning is authorized and necessary in limited, pre-vetted scenarios, including navigating MEA gaps, specific approach transitions, published visual flight paths, and some Obstacle Departure Procedures (ODPs).

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GPS in general aviation aircraft has become ubiquitous. So much so that the FAA’s move to a Performance Based Navigation (PBN) world based primarily on the Global Navigation Satellite System (GNSS) is well underway. We are already seeing the cancellation of “redundant” and “underutilized” VOR (and NDB) approaches. For en-route navigation, we have the Minimum Operational Network (MON) initiative, which plans to reduce reliance on VORs and the associated Victor airways in the Lower 48 while retaining just enough stations to act as a backup to a possible widespread GNSS outage. The goal is to shut down a little over a third of the VORs by 2025.

Now What?

Despite the prevalence of IFR GPS navigators, not all aircraft are so equipped. Or, even if they are GPS equipped, some pilots still prefer to fly in the familiar comfort of Victor Airways, whether they use VOR or GPS navigation. This raises questions about what to do as VORs and their associated airways disappear.