LNAV

LNAV stands for lateral navigation. In aviation, LNAV refers to the horizontal navigation guidance provided by GNSS-based navigation systems and flight management systems. It defines a route in the horizontal plane—typically a sequence of waypoints or predefined paths along airways—without prescribing vertical guidance.

In the context of instrument approaches, LNAV is categorized as a non-precision approach because it provides only lateral guidance. Aircraft following an LNAV path may descend to a minimum descent altitude (MDA) rather than a decision altitude (DA), and vertical guidance is not mandated. More advanced GPS-based approaches—LNAV/VNAV and LPV—offer vertical guidance and can provide lower minimums, with LPV approaches delivering performance similar to precision approaches in the vertical dimension.

LNAV is also a mode in aircraft navigation systems and autopilots. When selected, LNAV allows the airplane to follow the published route using lateral guidance, while altitude and vertical profile are managed by separate VNAV logic or the pilot’s control. In RNAV and PBN operations, LNAV forms the lateral component of a navigation specification.

Performance and limitations: LNAV relies on GNSS signals and provides lateral guidance within the performance specification of the chosen navigation setup. It is susceptible to GNSS outages, signal interference, or database errors, and operations must account for potential degradations in accuracy or minimums during such events.

History: LNAV emerged with the development of GPS-based RNAV in the 1990s and became widely used as part of performance-based navigation (PBN) requirements in civil aviation.