Which statement best describes the PAPI lighting arrangement?

• A. A row of lights similar to VASI that indicates glide slope.
• B. A row of lights for taxiway guidance only.
• C. An array of four green lights used for takeoff minimums.
• D. A row of lights in which a correct glideslope is indicated by two white lights and two red lights.

Answer: (D)

PAPI uses a single row of four lights to give you a visual glide slope. When you’re on the correct path, two lights will appear white and two will appear red. If you see more white lights, you’re above the glide path; more red lights means you’re below it. This specific arrangement distinguishes PAPI from other lighting systems like VASI, which is a different visual cue, or ground/takeoff lighting, which serves other purposes. So, the description of a row of lights where two are white and two are red for the proper glide slope is why this option is correct.