Short definition: LNAV, or lateral navigation, is an aircraft guidance mode that follows the programmed horizontal flight path in the flight management system.
Detailed explanation: LNAV controls the aircraft laterally, meaning it manages turns and track over the ground to follow the route entered into the FMC or FMS. This can include airways, direct-to legs, standard instrument departures, arrivals and approaches where the aircraft is authorised and properly set up to use them. LNAV does not control climb, descent or speed by itself, as those are handled by other modes or pilot inputs. In practice, pilots use LNAV to reduce manual heading changes and improve route accuracy, but it only works correctly if the route is entered, sequenced and activated properly. Pilots still need to monitor the aircraft’s position, confirm mode engagement and ensure the navigation source and route data are correct.
Key considerations:
- A practical limitation is that LNAV depends on correct route programming and valid navigation data.
- A common mistake is assuming LNAV is active or tracking the intended leg without checking the flight mode annunciations.
- A real-world impact is that correct LNAV use improves lateral accuracy and reduces cockpit workload during route tracking.
Further Reading: LNAV – Wikipedia
