An Analysis of Runway Visual Range

The results of a controlled observational program have been 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.

A mobile laboratory was positioned on an airfield runway during low visibility conditions. Observers were stationed on top of the vehicle to make RVR observations. The high intensity runway edge lights, and other visual range targets, were observed under various weather conditions, target light intensities, and illumination conditions. Simultaneous measurements were made of atmospheric transmittance.

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.

A complete review is presented of the evolution of runway visual range from conception to the current system.

RD-66-100
Author: Matthew Lefkowitz, Ernest E. Schlatter