lennuvälja maandumisraja kõrval paiknev pilootidele mõeldud visuaalne abivahend maandumise lihtsustamiseks, a visual glide slope indicator (VGSI) consisting of four light units normally situated on the left side of the runway (on both sides of the runway, in the case of the military) in the form of a wing bar and indicating that the aircraft is on slope if the two units nearest the runway show red and the two units furthest from the runway show white, too high if all units show white, and too low if all units show red