Flashy blinky.

May 29, 2008 8:55 AM

The Hancock building in Chicago has two different tower lighting systems. During the night the antenna structures have red lights to warn away aircraft. During the day the towers have strobes. Since I was a kid the towers always had red lights. Why did they make the change? It seems like two different systems would need twice as much maintenance.
posted by @homer to Grab Bag (3 answers total)

I read an article about aviation warning lights not too long ago. From what I recall, there are very strict guidelines as to the candle power of the beacon (either red or white light is acceptable; red is more commonly used in areas where aircraft regularly fly at night). The lights must be connected to an appropriate control device (photo cell, timer, etc.) so that the brightness is adjusted appropriately and automatically in relation to the sky illumination. In the event of a power outage or burned-out bulb, the local FAA office must be notified within 30 minutes, and repairs must be made promptly. The warning lights must be observed and logged daily, unless they are equipped with an automatic alarm system that detects any failure. Beacons erected after January 1996 are restricted in their light output at certain angles, and are allowed only 3% of peak intensity at 10 degrees below the horizon.
posted by Oriole Adams at 9:21 AM on May 29, 2008

spend two seconds googleing "strobe rule FAA" and you get the answers you're looking for.

article about wireless tower strobe lights

airliners.net discussion: What would be the reason for that white strobe?

the strobes aren't just about daylight hours, they are for low-visibility conditions. notice how the hancock and sears towers quite often are within the cloud base.
posted by krautland at 10:01 AM on May 29, 2008

From reading the articles I noticed that if the tower isn't painted then strobes must be used. Does the Hancock have an exemption for the use of red lights at night since the antenna towers are no longer painted?
posted by @homer at 12:21 PM on May 29, 2008