THE DEPTH OF FLASH OPTICAL LANDING SYSTEM.
NAVAL RESEARCH LAB WASHINGTON D C
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The Depth of Flash Optical Landing System is an optical landing aid which projects a positive glide-slope indication to the approaching pilot, enabling him to achieve highly accurate vertical control of his aircraft on the final landing approach. The signal gives accurate glide path information to a range limited only by the intensity of the light source and atmospheric conditions. Coding of the signal is by the color and depth of flash of a projected light source near the desired point of touchdown. Color coding provides high, low, and on-glide-slope information, while a gradually increasing flashing characteristic warns the pilot of increasing error from the prescribed glide path. On approaching the signal source, the pilot is guided onto the optimum path by correction of his altitude error in accordance with the signal received. Two unique design principles are featured in the Depth of Flash Optical Landing System. First, the backward projector principle causes the pilot to see only that color which is projected to his eye. The light projected to the area directly above the prescribed glide path is steady green, that below it is steady red, and the 0.2-degree-wide glide path is steady white. Second, the defocused shadow bar method introduces a flashing characteristic, gradually increasing as a function of angular error. As error increases beyond certain angular limits, the flashing characteristic is perceived in the red or green signal, first as a slight pulsation and then as a more and more noticeable flash. The Depth of Flash Optical Landing System is currently being evaluated under a Naval Air Systems Command program.
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