What does VASI stand for?

The term VASI stands for Visual Approach Slope Indicator, which is a system used to provide visual information to pilots about their approach to an airport. The VASI helps pilots ensure that they are on the correct glide path during their descent towards the runway. It consists of lights that indicate whether the aircraft is above, below, or on the optimal approach slope.

This instrument is crucial for safe landings, especially under visual flight rules, as it aids in maintaining the appropriate descent angle. Knowing the correct slope can enhance the pilot's situational awareness and contribute to a safe and accurate approach to landing.

The other options relate to aviation concepts but do not accurately define VASI.