Runway Visual Range (RVR) Systems

The AWI Runway Visual Range (RVR) system combines a Model 8364-E Dual Technology Visibility Sensor with a Model M488104 Ambient Light Sensor (ALS) to generate RVR parameters based on high accuracy extinction coefficient and ambient light data.Visibility SensorThe FSVS measures the amount of light scattered by atmospheric particles of fog, dust, or precipitation. The sensor provides a highly accurate measurement of extinction coefficient from 0.15 to 600 miles-1. Extinction coefficients of RVR interest are 2.6 to 600 miles-1. Unlike other visibility sensors, the Model 8364 uses a unique dual sensor monitoring technique that measures direct and scattered optical energy. Because the visibility sensor does not depend upon absolute measurements, measurements are independent of the effects of the environment, thereby maximizing accuracy, reducing recurring calibration, and minimizing maintenance requirements.NOTE: The ICAO (International Civil Aviation Organization) has determined that Forward Scatter Visibility Sensors can be used for international RVR applications instead of Transmissometers. Read ICAO's RVR acceptance and independent test results.FSVS Features Provide Reliable RVR Calculations The FSVS consists of four sensor heads: two infrared emitters and two solid-state photodetectors. The detectors measure the light transmitted directly through the sample volume between the sensors, as well as the light scattered by particles in the sample volume. Scattered light is measured at a preset detection angle that provides the most linear intensity for particles of fog, dust, rain, and snow.The measuring process of the sensor cancels several variables during calculation and ensures that the visibility measurement is not affected by contaminants on the lenses, or by temperature effects on the emitters and electronics. An optical filter allows the detectors to respond to only a narrow band of light to ensure that the input measurement and the output signal are unaffected by background light or light sources in the detectors' field of vision.The four-head configuration of the FSVS allows the sensor to continue operating with only three sensor heads if one of the heads should fail. Built-in test (BIT) functions report the sensor head failure so that appropriate maintenance can be scheduled. The BIT functions also monitor power supply voltages, heater status, and indications of abnormal operation.The FSVS's internal microprocessor functions as a control unit, directing the operation of the sensor as well as performing the required calculations. The data collected is an average value, with averaging intervals of 1, 3, 5, or 10 minutes. The control unit also performs the BIT functions, which are run as a regular part of sensor operation.Using the QMet Handheld Maintenance Terminal or a laptop computer with terminal emulation software, the operator can select the output interval, and specify the output format (extinction, coefficient, or visibility in miles or kilometers).The FSVS has been specifically designed for reliable operation in harsh environments. Heaters keep the lenses free of rain, snow, and ice buildup. The operating temperature range is -55