Evaluation of a Red Silicone Coated Visual Approach Slope Indicator (VASI) Lens

The subject effort was to test and evaluate the results of a new method of producing the red/white color-coded signal used in a Visual Approach Slope Indicator (VASI) system. The present system utilizes a split lens assembly to produce the color
coding, which consists of a clear lens segment and a red lens segment, the clear being somewhat smaller than the red, to construct one single VASI lens assembly. A new method of providing the signal was developed by coating the upper part of a circular clear lens with a heat-resistant red-silicone-pigment paint, leaving the lower part clear to transmit the white signal. Laboratory and field tests conducted on the coated lens resulted in no appreciable deterioration of the red signal; therefore, it was determined that this method of providing the signal was comparable to the split lens assembly. The results of the tests indicate that this method of producing the signal would be suitable for present and future VASI systems.

Author: Raymond E. Johnston