RADAR Altimeter operation is based on the measurement of time for an RF pulse to travel from the aircraft to the Earth's surface and back.

RADAR Altimeter operation is based on the measurement of time for an RF pulse to travel from the aircraft to the Earth's surface and back.

• A. The measurement of time required for an RF pulse to travel from the aircraft to the Earth's surface and return.
• B. The calculation of airspeed from pitot pressure differences.
• C. The determination of aircraft yaw from gyros.
• D. The measurement of wind speed from radar echoes.

Answer: (A)

Radar altimeters determine height by measuring the round‑trip time of a radio pulse to the ground and back. The transmitter sends a pulse toward the Earth's surface, the echo is received, and the system clocks how long the flight took. Since electromagnetic waves travel at the speed of light, the height above ground is half of the product of this round‑trip time and the speed of light. This direct time-of-flight approach is what yields the altitude reading. The other descriptions refer to different instruments or functions—airspeed from pitot pressure differences, yaw from gyros, and wind speed from radar echoes—which are not how a radar altimeter derives altitude.

Radar altimeters determine height by measuring the round‑trip time of a radio pulse to the ground and back. The transmitter sends a pulse toward the Earth's surface, the echo is received, and the system clocks how long the flight took. Since electromagnetic waves travel at the speed of light, the height above ground is half of the product of this round‑trip time and the speed of light. This direct time-of-flight approach is what yields the altitude reading. The other descriptions refer to different instruments or functions—airspeed from pitot pressure differences, yaw from gyros, and wind speed from radar echoes—which are not how a radar altimeter derives altitude.