What is the indication for being on glidepath for a PAPI?

The indication for being on glidepath for a PAPI (Precision Approach Path Indicator) is represented by two white and two red lights. This arrangement signifies that the aircraft is in the correct vertical position for landing. The PAPI system uses a color-coding mechanism where red lights indicate that the aircraft is below the glidepath, while white lights indicate it is above. When the lights are balanced at two red and two white, it provides a visual confirmation that the aircraft is properly aligned with the glide slope for a safe approach. This standard visual approach guidance is essential for ensuring a successful landing without excessive altitude or approach angle deviations.