Exploring the Corner Case Approach for a Pilot

Solar storm or poor signal quality can force a downgrade past minimums.

Max Trescott

Friday, August 28, 2026 at 08:00 AM ET

Verified

Edited By:

Travis Tingle

GA airplane approach point of view [Credit: FLYING Archive]

Key Takeaways:

LNAV/VNAV minimums are crucial for pilots to understand, especially when LPV signals are unavailable due to infrastructure limitations (e.g., internationally) or signal degradation (e.g., solar storms), leading to automatic approach downgrades.
Pilots must actively monitor GPS annunciators to confirm the authorized minimums, as LNAV/VNAV guidance involves flying within a fixed vertical window (+/- 75 feet) from the FAF to the MAP, indicated by a magenta pentagon between white lines, distinct from LPV's angular guidance.
While Baro-VNAV systems can fly LNAV/VNAV approaches, WAAS-capable GPS receivers offer greater flexibility and are not subject to the environmental and operational limitations (e.g., temperature, remote altimeter settings) that apply to Baro-VNAV.

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LNAV/VNAV minimums are a bit of a mystery to most U.S. pilots. That’s probably because they’re rarely encountered, except at the relatively few airports with RNAV (GPS) approaches that have LNAV/VNAV minimums but no LPV minimums.

However, as will be explained, I encountered them while flying an approach with LPV minimums when the satellite signal quality was insufficient to support LPV minimums.