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Aviation Words — Green Light

By Ian Brown, Editor

May 2019 - How many of you have ever used a coloured light-controlled approach to a towered airport? Precious few I imagine, yet it continues to be a significant part of our medical evaluation for a pilot's license. How many of us ever experience a change in colour vision over our lifetimes, yet we're tested every time we have our medical exam. Use of red, amber, and green lights at a control tower probably dates to around the same time they were introduced for automotive traffic. I don't recall ever having my colour vision tested for an automotive permit yet we can drive perfectly safely because we know which position each light is in.

The first use of red, amber, and green for automotive traffic control was in 1920, though there were earlier attempts with red and green only or mechanical semaphores. Significantly, traffic control officers were still used to announce with a whistle when the lights were about to change. How many jobs were lost when someone thought of the yellow light? We'll never know.

To be given a "green light" has become common language these days. Of course, "three green lights" has a special meaning for pilots flying retractable gear aircraft, or two green lights if you're flying a taildragger: Undercarriage is down and locked.

So, back to the question, have you ever done a light-controlled approach to a towered airport? Does this happen so rarely that it's an anachronism? Couldn’t there be another way to arrive at an airport and signal an intention to land by visually checking for traffic and overflying? I guess it's a question of ATC needing to signal permission in all cases. Maybe in these days of technological marvels there is a way to do this without light signalling — like using a cellphone. Another solution might just be to use a white light and signal in Morse code. One exception where light-controlled approaches might be common is the rare deaf pilot with a valid medical.

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