Runway Visibility Value (RVV) is determined by which instrument?

• A. Transmissometer
• B. Radar
• C. Barometer
• D. Anemometer

Answer: (A)

RVV is a measurement of how far you can see along the runway, and it’s determined by a transmissometer. This instrument sends a beam of light along a fixed path to a receiver near the runway. The amount of light that reaches the receiver is attenuated by fog, mist, or other aerosols. By comparing the transmitted light to what is received over that known path, the system calculates the extinction along the line of sight and converts it into a runway visibility value. This direct optical measurement along the runway path is why the transmissometer is the instrument used for RVV.

Radar, barometers, and anemometers measure different things—precipitation echoes, atmospheric pressure, and wind speed, respectively—and they don’t provide the direct path-specific visibility along the runway that the transmissometer does.