One day on my drive home, I saw three towers. One of them had a bunch of blinking white lights, another one had red lights that kind of faded in and out, and the third one, well, it wasn't doing anything. I'm lucky to have a radio engineer for a dad, so Dad: why do some towers blink?
Joe: Well, blinking I would call like the way you described it, "flashing", "white light", or "strobe". All these lights are to aid pilots and air traffic. helicopters, fighter planes, regular jets. So that's the purpose of it.
Jeff: Well that one tower that I saw had red lights that faded in and out, but I even think there's a freestanding tower just north of here that has red and white on top.
Joe: Well red lighting is a thing. It's in the regulations, it specifies red lighting or white lighting, and one of the things like the red lights can be a bulb like this inside of a red housing, could be LED.
Giant Bulbs
Jeff: Where'd you find this bulb? This was not in my studio.
Joe: This bulb is a spare bulb for a tower site. And most of us use the same bulb, same socket, 620 watts. It's a very standard broadcast bulb for a broadcast tower. And a lot of the beacons, they're pretty tall and they'll have one right-side up, and one upside-down. So they'll have two bulbs in the socket. That way, when one bulb burns out, you realize you have a bulb out, but you're still legal with the second bulb.
Jeff: At my house, I don't have any of this kind of bulb anymore [incandescent]. I have, you know, this is a little bit different size, these are LED. Is that similar on towers?
Joe: Yeah. So it is the same. Like an LED assembly for a tower could be kind of flat, and it has, you know, it's set to just do what it needs to do. So in like white light, that's, typically it used to be always strobes. And at KMOX, you remember we had the whole assembly there. and you see the glass bulb, with xenon gas inside.
So those were the old way for that, but the newer ones are all white LED, and they can be little pancake-looking things compared to what the things are now. They can direct that LED light really to help airplanes and have less trouble for people who live in homes or apartment buildings nearby.
Jeff: So if they have a tower like the one that's just north of here that's in a residential area, you're not just flashing everybody constantly.
Joe: Yes, yes.
Red light, white light?
Jeff: You know, thinking about that tower, though, why do different towers have different lighting and different colors and things? And I even remember, like, on the tower that's right by here, there's actually teeny tiny little lights that are, like, on the sides, on the legs of the tower.
Joe: Yeah, well, tower lighting is in the responsibility of FAA, and they have a detailed plan. The options depend on the heights of the tower, where they are at. The location is obviously important. And sometimes red is a good solution, sometimes white, and sometimes both, red and white solution. And an example is the tower that you're talking about.
Jeff: So why would you want both? It seems like that's twice the complexity.
Joe: You would have strobe in the day and red at night. And people in their homes at night, a pulsing red light is a lot easier than a big flashing white light.
Jeff: So sometimes if people are complaining about it, you might go to that solution.
Joe: You can propose the red at night and the dual lighting works. And then you literally see these two packs and one will be red and one will be white. That's what I've seen mostly, although I heard that they make one now. It's all in one.
Jeff: [sarcastically] You could have RGB lights—could you do Home Assistant for your tower lighting?
Joe: You'd have RGB, but that would not be allowed by the FAA.
Jeff: We'll actually talk about that a little bit too later, because there are some regulations for how you actually monitor these things.
Joe: Yes, there are.
No lights at all?
Jeff: But before we get to that, what about the one tower I saw didn't have any lights that were blinking at all. And I zoomed in and I saw that there was a light on top, but it just wasn't doing anything.
Joe: Yeah. Well, and this is about daytime mode. So a tower that's painted, and that's legal for obstruction marking, and you don't have to light during the day. So at night, their lights would come on. So you can be in a situation where, like here, you could see three towers. One might be day and night with white light, and two of them might be red light day only, but one kicks on earlier than the other because of their exact photo cell triggering the lights.
Jeff: Or if the photo cell is covered by a layer of soot from 40 years...
Joe: Yeah. So that tower is probably in daytime mode, or it could be an AM tower. An AM tower below 200 feet doesn't have to be lit, so that's another one. In fact, all towers, I guess, under 200 feet, unless you're in a particular area where the FAA would require it.
Jeff: You always have to refer back to the documentation.
Joe: You always refer to the documentation.
Jeff: But what is the tower site that we went to for the hot dogs?
Joe: KHOJ? KHOJ, yeah. Those don't have lights. Those do not have lights.
Jeff: Because they're under 200 feet.
Joe: Yes, so they don't need lighting. So, and then they don't need painting either. So that's one of those things that, again, always refer to that because just because you have a tower that's under 200 feet doesn't mean you don't have to make sure it complies or you may have to paint it or you may have to light and paint.
Tower painting has changed a lot over the years. The older towers have lead in them. So whenever there's a project on the tower, it's not unusual to see the guys in some kind of a, what do they call those?
Jeff: A full ghillie suit? Or I don't know what they're called.
Joe: Yeah. Yeah. So they have that too. So anyway, that's the bottom line from then till now.
But some short towers do have lights...
Jeff: So far, we've been talking about radio and TV towers, the ones that are really big. But what about little small towers? I know I see a lot of cell towers that don't have any lights at all, but sometimes they do. They just have one little light bulb on top. Or even if they're 50 to 100 feet tall, I've seen it sometimes.
Joe: Yeah, and there's always a reason for seeing a light somewhere, almost always on structures, including buildings and so forth. But if you look around the area where you're seeing that tower that you know is not 200 feet and it's got a light on the top, look you're probably near an airport, a heliport, or somewhere where there's an aviation hazard. You know hospitals, they have their helipads there.
So everywhere there is a possible hazard for flight for aircraft is going to have lights involved, and that's why we see a lot of buildings even have lights.
FAA Rules
Jeff: So it sounds like we have towers and even buildings that have to have lights put up but who's in charge of all this? Like if I'm going to put up my own tower, who do I need to talk to to make sure that i'm doing it right and get it approved?
Joe: I think we go back to our friends at the FAA. They have that particular circular (AC 70/7460-1M - Obstruction Marking and Lighting). It describes all kinds of of places where lighting is need for air safety.
So that includes our broadcast towers, big chimney stacks, water towers, bridges, nuclear power plant cooling towers, wind turbines, tall electrical towers, you know, those ones that they cross a river, they'll have those extra tall ones with markings in the middle. Sometimes those are required to have lighting.
And there are also rules that even apply during construction projects. So you've got these big buildings going up And you'll notice the cranes will have lights on them. And there's a spec for that, how many lights have to be on the crane, what height it has to be at.
As you look around the next 12 months, look around at all those lights. You'll enjoy it like I do.
Jeff: You'll look like a radio engineer once you know about these things!
Estimating tower height by light
Jeff: So that's made me think, like, looking through these instructions, I did find this page. And I thought, like, could you use tower lights, the number of them, as a way to judge how tall a tower is? Kind of a rough estimate.
Joe: Yes, actually you can because the specifications, like for tall, these would apply to radio and TV towers. They require so many lights depending on the height.
Like around here, we would have the F4 version with four lights, four blinking light levels, a light at the top if the antenna here at the top is higher than 40 feet.
So you can kind of look and get an idea of whether you're looking at a 500-foot tower or a 1,000-foot tower. I don't think you could go like 700 versus 1,000 as easily.
But you can tell, and the guys know. I know a couple of pilots that are also engineers or selling in radio business, and they can do that. They'll tell you, you know, like I was passing a tower. What's a tower that's a 1,200-foot tower doing out here? So it's pretty fun, and you go to this document has everything you need if you want to take the time and study that and memorize it and then fly.
Monitoring and reporting outages (and NOTAMs)
Jeff: One other thing that since we've been running this channel I keep getting emails about, if someone sees that there's lights out on a tower, like let's say it's nighttime and you're out there and you notice like one of these towers for the past few days hasn't had a light on, can you do anything about that? What should you do?
Joe: Well, first of all, if it's required to be lit, every tower that's required to be lit is also required to be monitored.
So in radio, we put a monitoring circuit on the electrical feed to the filaments and you can measure how much current is going through there, right? So you've got to monitor it. You've got to get alarmed by that. The alarm can call you or reach you. But you also have to call every day, check your circuit, your system, and make sure the lights are on. So if you only are lit at night, that means that call has to happen after it's dark.
You've got to verify that your lighting is working, and you have to report it within 30 minutes. And you find that if a light's out, you've got to report it. And we call that a NOTAM, where the FAA puts it on a system that all the pilots can have access to. And they know that there's a tower there, but it's lights out. And they can use it in their flight planning.
Jeff: You're an engineer and you have the tie-in with the FAA or whatever. But what would I be able to do if I did see a tower that was out?
Joe: Well, you can do a NOTAM search. Try to look through and see if you see it. The other thing, you could contact the tower owner or the engineer at the site, the tower's engineer, and they can check into it. They should already know because they have their monitoring equipment, right?
Jeff: They should.
Joe: They should already know. They do.
And then, of course, if you're out there, usually the tower, either on the tower or in the fencing around it or on the building, will have an ASR number, which identifies that tower to the FAA and the FCC, actually. But that number would be the exact tower that you'd be reporting.
Jeff: So hopefully you learned a little bit more about why there are so many flashing lights around at night and not just for radio towers, but for bridges, buildings, and more. What other things do you want to know about towers? Let us know in the comments.