What is the primary purpose of the radar altimeter in flight displays?

What is the primary purpose of the radar altimeter in flight displays?

• A. To determine true altitude above mean sea level.
• B. To adjust airspeed reading.
• C. To provide radar altitude for display on HUD and HSI.
• D. To measure wind speed.

Answer: (C)

The radar altimeter is used to provide radar altitude for display on the HUD and HSI, giving you the real-time distance above the ground. It sends radio waves toward the terrain and measures how long they take to bounce back, converting that to height above ground rather than height above sea level. This is crucial during low-altitude operations and approaches, where knowing exact distance to the terrain helps maintain safe clearance and supports terrain/obstacle awareness shown on the flight displays. This is different from true altitude above mean sea level, which comes from the barometric altimeter and depends on air pressure. It isn’t involved in adjusting airspeed or measuring wind speed—the pitot-static system handles airspeed, and wind speed instruments serve other purposes.

The radar altimeter is used to provide radar altitude for display on the HUD and HSI, giving you the real-time distance above the ground. It sends radio waves toward the terrain and measures how long they take to bounce back, converting that to height above ground rather than height above sea level. This is crucial during low-altitude operations and approaches, where knowing exact distance to the terrain helps maintain safe clearance and supports terrain/obstacle awareness shown on the flight displays. This is different from true altitude above mean sea level, which comes from the barometric altimeter and depends on air pressure. It isn’t involved in adjusting airspeed or measuring wind speed—the pitot-static system handles airspeed, and wind speed instruments serve other purposes.