Describe types of approach indicators.

Description should include the following concepts:

The visual approach slope indicator (VASI) is a system of lights on the side of an airport runway threshold that provides visual descent guidance information during approach. These lights may be visible from up to 8 kilometers (5.0 mi) during the day and up to 32 kilometers (20 mi) or more at night.
Basic visual approach slope indicators consist of one set of lights set up 7 meters (23 feet) from the start of the runway. Each light is designed to appear white or red, depending on the angle from which it is viewed. When the pilot is approaching the lights at the proper angle, meaning the pilot is on the glide slope, the first set of lights appears white, and the second set appears red. When both sets appear white, the aircraft is too high, and when both appear red it is too low.
This used to be the most common type of visual approach slope indicator system; however, it is being phased out by precision approach path indicators (PAPI), which are closer together and therefore more efficient to site and maintain.

PLT147

Process/Skill Questions: