A slightly high glide slope indication from a precision approach indicator is

• A. Three white lights and one red light
• B. Four white lights
• C. Two white lights and two red lights
• D. All red lights

Answer: (A)

Visual glide slope indicators use a row of four lights to show your position relative to the glide path. Each light can appear white or red, and the pattern changes as you are above, on, or below the path. When you’re on the glide slope, the common pattern is two white and two red. If you’re slightly high, more lights appear white, and in this specific case you’d see three white lights with one red. That three-white/one-red signal tells you you’re just above the glide path, so you should descend a little to bring the indicators back to two white and two red.

If you saw four white lights, you’d be higher still and need a larger descent to reintersect the slope. If all red, you’d be well below the path and would need to climb. If you saw two white and two red, you’re on the correct glide slope.