OK. I honestly DON'T know what that light is for, but i do know that it usually triggers the radar detector in my car whenever i am within 2 miles of the airport!
As far as dangerman's claim of civilian aircraft not using precision approaches? THEY DO. We used to make jokes that when most US regional carriers were 'grounded' our pilots would be landing as if it was a sunny day.
SKILL+EXPERIENCE+BALLS. Note that half of this particular airline's crews had military training, therefore were not guessing. They would generally not TAKEOFF in this weather though!
To be accurate, it is a beacon, not a searchlight. But the reason is that it is still a reliable navigation aid even in the modern world of technology. If your radio shorts out, or the GPS satellites go offline, or the air traffic controllers go on a coffee break, the beacon is still there. Besides, there are a lot of smaller airports with no ATC services, and a lot of general aviation aircraft that do not have GPS, VORs or even radios. So to be able to find the airfield in unfamiliar or deteriorating weather conditions is invaluable. Also, in areas of high traffic and where a military airfield is only a few miles from a civilian field, they can help GA pilots make sure they are closing on the correct airfield and not mistakenly violate military airspace. Military airfields use the same beacon, but instead of alternating blue and white, they use a single blue light and dual peaked white lights spaced a few degrees apart, so from the air it appears as a single blue follo
wed shortly by two quick whites. An exapmple of this is in Arizona where Luke Air Force Base is only 5 miles or so from Glendale airport.
The beacon (green/white as previously corrected) operates anytime the weather is below 1000 foot ceiling or 3 miles visibility -- the legal definition of Visual Flight Rules (VFR)
Actually, the rotating beacon is supposed to be aviation green and white, not blue and white... Military airports flash one green and two white, while civilian airports flash one green and one white.
If you know what you're looking for, it makes it much easier to spot the airport when flying over a built-up area at night. The distinctive green/white beacon is easy to pick out from among steady burning street lights and business signs.
A little redundancy is a good thing. We still have quite a few operating light houses too
it's got two colours, green and white. they rotate and emit a code (short or long pulses) which identify which airfield it is.
Their purpose is for visual recognition of the airport at night. When you're several miles out they can be very helpful. A GPS will tell you exactly how far away an airport is however, you still need to have visual contact to know where to go. A trained eye can spot the white/green flashes and distinguish the airport from say a parking lot. They also identify the type of airport by their color sequence. I've got a feeling that this lighting system will be around indefinitely. It's simple and and tremendously helpful for general aviation pilots.
Many planes have no RNAV avionic equipment. There are planes without RNAV in airline operations. Radar coverage does not extend to all airports. The beacon is easy to spot from a good distance. It can be especially helpful when the airport is in the midst of many other lights.
so aircraft in case of an electronical gps alure can fingd the runway.
It is usually used to indicate when conditions are too bad to land, however as you said there are lots of nav aids to help land the AC when conditions are too bad. Its a hold over from the days without radio and in a lot of places they don't use it anymore. My local strip does but they are an uncontrolled airport.
BTW the ATC really doesn't help the AC land only the military use Precision Approaches because they have to land in all kinds of weather in the civilian side if the weather is too bad planes don't take off and land.
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