@Marns: MaxSez: Here's a bonus addition to your great post. Well Done!
PAPI (Precision Approach Path Indicators) primarily assists by providing visual glide slope guidance in non-precision approaches environment. These systems have an effective visual range of at least 3 miles during the day and up to 20 miles at night. The row of light units is normally installed on the left side of the runway and the glide path indications are as two red and two white (2 red 2 red dots) when on proper glide path angle of approach. Light combinations indicate when slightly high (3 white 3 white dots), significantly high (4 white 4 white dots), slightly low (3 red 3 red dots) and significantly low (4 red 4 red dots). Red over Red yr Dead! (Wiki & me)