What does a Radar Altimeter do?

• A. Uses radio echoes to determine altitude above ground level
• B. Indicates altitude above sea level using atmospheric pressure
• C. Calculates true heading from magnetic north
• D. Measures aircraft airspeed

Answer: (A)

Radar altimeter measures height above the surface by sending downward radio waves and timing their return. By transmitting a pulse and detecting how long it takes to bounce off the ground, and using the speed of light, it calculates the distance to the terrain directly below. This gives a precise altitude above ground level, which is crucial for low-altitude flight, terrain avoidance, and precise landings. It’s different from altitude above sea level, which comes from atmospheric pressure readings (barometric altitude) and can vary with weather. The other options don’t fit because a radar altimeter isn’t used to determine heading (that’s a compass/heading indicator) or measure airspeed (that’s done by the pitot-static system).