What are the rules on beacons, in the US and elsewhere? In the US they invariably alternate white/yellow and green (usually a pale green); is that the same everywhere? Which airports have to have them? It can be anywhere on the field?
As you see http://www.airliners.net/open.file/442352/M/ SFO's beacon used to be on top of the old tower, right below the new one. But when I flew in last week I didn't see it flashing, and I didn't see it anywhere else. Is it there?