What indicates being on glidepath for a VASI?

Being on glidepath for a Visual Approach Slope Indicator (VASI) is indicated by having a red far bar over a white near bar. This configuration means that the aircraft is descending correctly along the glide slope and is on the proper approach path to the runway.

A VASI system typically consists of multiple light units that change color depending on the aircraft's altitude in relation to the ideal glide slope. When an aircraft is on glidepath, the light configuration will show the red far bar (indicating that the aircraft is slightly high) above the white near bar.

This visual cue is crucial for pilots, as it guides them to maintain the correct approach angle required for a safe landing. Different configurations, such as all white lights or two red lights, correspond to different scenarios that indicate deviations from the glidepath. Thus, understanding these signals is vital for flying safely during landing approaches.