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This report briefly describes the evolution of the FAA/NBS Runway Visual Range RVR transmissometer system into a breadboard Airport Visibility Measuring System (ARVIS) which has been laboratory tested and which will undergo field tests at the National Aviation Facilities Experimental Center (NAFEC) in Atlantic City, NJ during 1975. Appendix I of this report documents in detail the development of a Signal Data Converter Unit (SDCU) as a replacement for the SDCU used in the FAA/NBS RVR system. Appendix II describes an analog computer for calculating RVR., Prepared in cooperation with Charles Stark Draper Lab., Inc., Cambridge, MA. See also Rept. no. TSC-FAA-72-1, AD-744 873.

The runway visual range (RVR) for a Type L-850 bidirectional centerline runway light has been calculated for the red and white output ports at three different current settings for both day and night illuminance thresholds. The calculations are based on certain parameters measured in our laboratory on a sample light. The resulting RVRs are compared to the standard RVRs based on the High Intensity Runway light (HIRL). An analysis is also included on the error introduced by ignoring the spectral transmittance of the atmosphere. (Author)

Values of Runway Visual Range (RVR) were developed for various atmospheric transmittances utilizing Allard's Law and Koschmieder's Law. Commonly employed constant's of pilot's contrast threshold and visual illuminance threshold are utilized in the appropriate RVR equations. Computations are based on a 250 foot baseline transmissometer with light target intensities of 10,000, 2,000 and 400 candela, values which are presently used in the United States. Information is presented in tabular form showing transmittances corresponding to runway visual range readings from 600 feet to 7000 feet in 50 foot increments. Each table includes data for each of the three light target intensities. A total of eight tables is provided. The computer program which was utilized to develop each set of data is included with each table.

A test program was conducted to evaluate multi-transmissometer systems. These consisted primarily of instruments at touchdown, midpoint, and roll-out locations on a runway at five airfields distributed across the U. S. continent in differing climatic regimes. The airfields were located at Atlantic City, N. J., New York, N. Y., Chicago, Ill., Denver, Colo., and Los Angeles, Calif. The data acquisition program is discussed as is the analyses of data. Primary objective of the program was to determine if a need exists for three transmissometer systems per runway under a variety of weather categories. (Author)

A test program was developed and implemented to evaluate multi-transmissometer systems. These consist primarily of instruments at touchdown, mid-point, and rollout locations at five airfields distributed across the continent in differing climatic regimes. The airfields are located at Atlantic City, N. J., New York City, N. Y., Chicago, Ill., Denver, Colo., and Los Angeles, Calif. The data acquisition technique and program are described. Further data processing is scheduled. Partial analysis of available data indicates that no single transmissometer will always be most representative of lowest visibility conditions at any airport and even with three systems along the runway unreported variations in RVR will still occur. Analysis of 55-, 45-, and 15-second sampling intervals for RVR computation shows little difference between 55- and 45-second sampling. The number and magnitude of differences increase when RVR from a 15-second sampling is compared to RVR from a 55-second sampling especially during rapid changes in transmittance. (Author)

The results of a controlled observational program were used to validate the credibility of the current runway visual range system, and to provide a basis whereby future visual range systems and lighting methods can be compared. It was found that the current runway visual range system concept is generally credible although certain areas were noted to be considered for modification. Runway visual range for day is conservative in that most static observers could see farther than the current system predicts. The static observer's visual range of runway lights by day does not conform to Allard's Law when the visual illuminance threshold value is fixed. Night runway visual range, as predicted by the current system, approximates the average visual range of the static observations and generally conforms to Allard's Law. The fact was established that runway visual range represents a probability of sighting light targets, and as such should be recognized by the user as not being an exact absolute value. A benchmark system is proposed whereby other visual range systems and lighting techniques can be compared.