The RADALT is a flight instrument that provides

• A. Absolute height or vertical distance above terrain.
• B. Altitude above mean sea level.
• C. Vertical speed.
• D. Distance to terrain.

Answer: (A)

The main idea is that a radar altimeter tells you how high you are above the ground directly beneath you. It sends a radio pulse downward, measures the time it takes to return, and converts that into vertical distance above terrain (ground level). This is different from altitude above mean sea level, which is measured by a barometric altimeter and references sea level, not the ground below. It’s also not a measure of vertical speed, which is the rate of climb or descent, nor is it a measure of distance to terrain in general—the radar altimeter focuses on height above the terrain right below the aircraft. This height-above-ground information is crucial for safe low-altitude operations and landings, especially over varied terrain.