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United States Experience Using Forward Scattermeters for Runway Visual Range.
Final rept. Sep 96-Mar 97,
JOHN A VOLPE NATIONAL TRANSPORTATION SYSTEMS CENTER CAMBRIDGE MA
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The development of the forward scattermeter in the United States has spanned 25 years from the first design in 1969 to the 1994 commissioning of an airport runway visual range RVR system that uses a forward scattermeter rather than the conventional transmissometer to measure the atmospheric extinction coefficient. The forward scattermeter has many practical advantages over the transmissometer single mounting pole, greater dynamic range. etc.. However, before a forward scattermeter could be accepted for an RVR system, a number of criteria had to be satisfied 1 the calibration must be accurate and consistent from one unit to the next and for all important obstructions to vision 2 the windows of the sensors must not clog in blowing snow and 3 scatter measurements in a small volume of space must represent conditions over the runway as well as measurements made by a transmissometer which averages over a baseline 250 feet at U.S. airports. Many different scattermeter designs were tested extensively, both in the field and in climatic chambers, before all acceptance criteria could be satisfied. The report describes the evolution of scattermeter design and presents the test methodology and results for the new RVR system.
APPROVED FOR PUBLIC RELEASE