You know Herman, I was looking out the window last night at the city lights and it made me think of that audio clip Daniel sent us. Our housemate has been on a bit of an aviation kick lately, and he brought up something that I think most people only see for about ten seconds from a tiny airplane window, if they see it at all. He called them the lighthouses of the airport.
Oh, I know exactly what he is talking about. Herman Poppleberry here, and I have been waiting for someone to ask about approach lighting systems. It is one of those classic examples of hidden in plain sight infrastructure. You see them when you are landing, those long rows of glowing bars and flashing white lights that seem to lead you right onto the tarmac, but the engineering behind them is actually incredible.
It really is. Daniel mentioned growing up as a plane spotter, watching these massive systems that can be two meters tall and stretch for hundreds of meters. He was particularly curious about how they work, who manages them, and honestly, what it is like to actually live next to them. I mean, imagine having a high intensity strobe light in your backyard every time a Boeing seven forty seven comes in for a landing at three in the morning.
That is the reality for a lot of people near major hubs. But before we get into the neighborhood drama, we should probably talk about why they exist in the first place. You know, we touched on airport infrastructure way back in episode eighty when we talked about why smart homes are not built like airports, and we did a deep dive into networking at J-F-K International in episode one eighty six. But the lighting? That is a whole different beast. It is not just about being bright. It is about information.
Right, because when a pilot is coming in, especially in low visibility, they are transitioning from flying purely by instruments to flying by what they can see. That transition is the most critical part of the flight.
Exactly. It is called the visual segment. Even with all the modern G-P-S and Instrument Landing Systems we have today, for most landings, the pilot still needs to see the runway environment to actually touch down. The approach lighting system, or A-L-S, is the bridge between the digital world of the cockpit instruments and the physical world of the pavement.
So, let us break down the hardware. Daniel mentioned these can be huge. When you see them at the end of a runway, they are not just light bulbs on sticks. What are we actually looking at?
Well, it depends on the category of the runway. If you are at a major international airport, you are likely looking at an A-L-S-F dash two. That stands for Approach Lighting System with Sequenced Flashing Lights, High Intensity, Category Two. This system is a forest of lights. It starts almost three thousand feet from the runway threshold. Think about that, Corn. That is over half a mile of lights before you even reach the start of the runway.
Half a mile. And they are arranged in a very specific pattern, right? It is not just a straight line.
No, it is a very precise geometry. A full A-L-S-F dash two has two hundred and forty seven steady burning lights and fifteen sequenced flashers. You have the centerline lights, which are white. Then you have these crossbars. The big one is the thousand foot bar. When a pilot sees that, they know exactly how much distance they have left. Then, as you get closer to the runway, you start seeing red side row lights. Those are a huge warning sign. If you see red, you are getting very close to the ground and you better be lined up.
And then there is the rabbit. Daniel mentioned the power of these systems, and I think the sequenced flashers are what people notice most. It looks like a ball of light sprinting toward the runway.
I love the rabbit! Technically, those are the sequenced flashers. They fire one after another, starting from the furthest light and moving toward the runway, twice every second. It is a psychological trick, really. In heavy fog or rain, your brain might struggle to identify a static light, but it is very good at tracking motion. That moving flash points your eyes exactly where they need to go. It says, hey, the runway is this way!
It is fascinating because even with all the technology in the cockpit, we still rely on these basic human evolutionary traits, like tracking movement in the dark. But let us talk about the intensity. Daniel asked about the brightness, and I have read that these lights can be adjusted based on the weather.
Oh, they have to be. If you turned an A-L-S-F dash two system up to full intensity on a clear, dark night, you would probably blind the pilot. It would be like staring into a supernova. These systems usually have five different brightness settings, or steps. On a clear night, they might be on step one or two. But when the fog rolls in and the visibility drops to less than half a mile, they crank it up to step five. We are talking about twenty thousand candelas of light per bulb.
And that brings up the question of power. In episode one twelve, we talked about industrial strength reliability and why airports do not use consumer grade smart bulbs. I imagine the power requirements for a half mile of high intensity lights are significant.
They are massive. And more importantly, they are redundant. Every major airport has a dedicated vault for lighting power. They use constant current regulators rather than constant voltage. In an airport lighting circuit, they keep the current at exactly six point six amps across the whole loop. This ensures that every single bulb in that half mile stretch has the exact same brightness. If one bulb burns out, the rest stay at the perfect intensity.
That is a great detail. It prevents a situation where the lights near the power source are blinding and the ones at the end are dim. But what happens if the grid goes down?
That is where the backup systems come in. These systems are required to have secondary power, usually massive diesel generators, that can kick in within seconds. For Category Two and Three runways, the switchover has to be almost instantaneous. You cannot have a pilot on a three mile final approach in a fog bank suddenly lose their visual reference.
So, we have this massive, powerful, half mile long system. Now, let us address the part of Daniel's prompt that really intrigued me: the geography of it. These things do not care what is in their way. If the runway ends and there is a neighborhood or an ocean, the lights keep going.
This is where the engineering gets really wild. If you look at an airport like J-F-K in New York, which we discussed in episode one eighty six, some of those runways point right out into Jamaica Bay. You cannot just float the lights. You have to build massive piers. These are heavy duty wooden or steel structures that extend hundreds of feet into the water, just to hold a few rows of lights at the exact correct elevation.
And they have to be at the exact elevation of the runway, right? They cannot just follow the slope of the land.
Exactly. They have to be level with the runway surface or on a very specific, slight upward slope. This means if the ground drops away at the end of the runway, the light masts get taller and taller. You might start with a light that is only six inches off the ground near the pavement, but by the time you get to the end of the system, the lights are on towers thirty or forty feet in the air.
Daniel mentioned seeing them in people's backyards in places like Cork, Ireland. I can only imagine the legal and logistical nightmare of telling a homeowner, hey, we need to put a twenty foot steel tower with a strobe light in your garden.
It is usually handled through something called an avigation easement. The airport or the government essentially buys the right to use the airspace over your property and the right to install and maintain those structures. In some cases, they just buy the houses and tear them down to create a clear zone, but in older, more cramped cities, you really do see these lights standing right next to someone's swing set.
What is the maintenance like for those? I mean, who is the person whose job it is to go into someone's backyard and change a lightbulb on a thirty foot mast?
In the United States, it is usually the F-A-A. They have technicians who specialize in Navigational Aids, or N-A-V-A-I-D-S. These folks are officially called Airway Transportation Systems Specialists. They are the unsung heroes of aviation. They are out there in the middle of snowstorms, in the middle of the night, climbing these towers to make sure the lights are working. Because if a certain percentage of the lights are out, the runway's category gets downgraded. That means planes might not be allowed to land there in bad weather, which causes delays that ripple across the entire country.
That is a huge responsibility. If you do not fix that one light in a backyard in Queens, a flight from London might have to divert to Philadelphia.
Precisely. And the hardware itself is designed for this. We should talk about frangibility. This is a word that engineers love.
Frangibility. Like, it is designed to break?
Yes! If a plane undershoots the runway, the last thing you want is for it to hit a massive, rigid steel beam. That would be catastrophic. So, all these light masts are designed with frangible couplings. They are strong enough to withstand high winds and ice, but if an aircraft strikes them, they snap off cleanly at the base. They basically disintegrate to minimize damage to the plane.
That is brilliant. It is a safety system designed to destroy itself to save lives. You know, Daniel also asked about the experience of living around these lights. We talked about the physical towers, but the light itself is another story. I was reading some forums from people who live near Heathrow and Chicago O'Hare. They talk about the glow.
Oh, the light pollution is incredible. When those systems are on high intensity, they create a literal pillar of light in the sky. If you are a neighbor, it is not just a light in your window; it is the entire atmosphere turning white every few seconds because of the rabbit.
Does the airport provide anything for these people? Daniel joked about blackout curtains. Is that a real thing?
In some cases, yes! Many airports have noise and light mitigation programs. They might pay for triple pane windows to block the sound of the engines and heavy duty industrial blackout shutters for the residents most affected by the approach lights. But for a lot of people, you just kind of get used to it. It becomes part of the rhythm of the house.
It reminds me of people who live near train tracks. Eventually, your brain just filters it out. But I wonder about the wildlife. You have these incredibly bright, flashing lights in areas that are often semi rural or near water.
That is actually a significant area of study. Migrating birds are often disoriented by high intensity lights. There have been cases where birds circle the light towers until they drop from exhaustion. Interestingly, the F-A-A has been moving away from static red lights on towers because research shows they disorient birds more than flashing ones. Modern systems are also trying to use different wavelengths or shielding the light so it only shines upward toward the pilots, not out toward the surrounding environment.
It is interesting that we are still using these big, hot, incandescent or halogen bulbs in many places. With everything moving to L-E-D, is the airport lighting world changing too?
It is, but it is slower than you might think. We talked about this a bit in episode one twelve, the idea that industrial systems value proven reliability over the latest tech. But L-E-D-s are finally taking over. They last much longer, which is great because it means fewer trips into people's backyards or out onto those piers to change bulbs. And they use a fraction of the power.
But there is a catch with L-E-D-s, right? I remember you telling me something about heat.
You have a great memory, Corn. Yes, the old halogen bulbs got very hot. In a snowstorm, that heat was actually a feature because it melted the snow and ice off the lens of the light. L-E-D-s stay cool. So, engineers had to actually add heating elements back into the L-E-D light fixtures just to melt the snow. They call these arctic kits. It is one of those funny circular problems in engineering. We saved energy on the light, so now we have to spend energy on a heater.
That is classic. You solve one problem and create another. I want to go back to the pilot's perspective for a second. We talked about how these lights help them find the runway. But there is also the P-A-P-I, right? P-A-P-I. Daniel didn't mention it by name, but it is part of that lighthouse system.
Oh, the Precision Approach Path Indicator. Those are my favorite. If you have ever looked at the side of a runway and seen four lights that are either red or white, that is the P-A-P-I.
Right, and there is a little rhyme for it, isn't there?
Yeah, pilots say, white on white, check your height. Red on white, you are alright. Red on red, you are dead.
Well, that is a bit morbid, but I guess it gets the point across.
It is effective! Basically, if you see two white lights and two red lights, you are on the perfect three degree glide path to the runway. If you see four whites, you are too high. If you see four reds, you are dangerously low. It is a purely optical system. There are no moving parts, no electronics involved in the signaling. It is just lenses and filters. As you change your angle relative to the light, the color you see changes.
It is so simple, yet so critical. It is like a visual docking system for a giant metal tube moving at a hundred and fifty miles per hour. And you know, Herman, I think we have covered the what and the how, but I am still stuck on the who. We mentioned the F-A-A, but on a global scale, this is all standardized by I-C-A-O, the International Civil Aviation Organization.
Right, that is why an airport in Jerusalem looks remarkably similar to an airport in New York or Tokyo or Cork. These standards are universal. The spacing of the bars, the color of the lights, the frequency of the flashes... it is a global language. A pilot from any country can land at any international airport because they all speak the same visual language of lights.
It is one of the few things the whole world actually agrees on. Gravity and the need to not hit the ground too hard are universal constants.
Pretty much! And for the plane spotters like Daniel, those lights are part of the magic. There is nothing quite like standing under the approach path at night when the rabbit is running and a heavy jet passes just a few hundred feet over your head. You can feel the air vibrating, you can see the vortexes in the fog created by the wingtips, and those lights are illuminating the whole thing like a stage play.
It really is a performance. Before we head out, Herman, I have to ask about something I read. Can pilots actually turn these lights on themselves?
Yes! It is called Pilot Controlled Lighting. At smaller airports without a twenty four hour tower, a pilot can click their microphone button on the radio frequency. Three clicks for low intensity, five for medium, and seven for high. You could be flying over a dark field, click your mic seven times, and the whole runway lights up like a Christmas tree. It saves a ton of energy because the lights only run when someone is actually there to use them.
That sounds like magic. Well, Herman, I think we have given Daniel a pretty deep look into his lighthouses of the airport. It is a lot more than just some bright bulbs. It is a massive, coordinated, global effort of engineering, law, and maintenance.
It really is. And hey, if any of our listeners live near a major approach path and have some stories about the glow or the rabbit in their backyard, we would love to hear about it.
Definitely. You can get in touch with us through the contact form at myweirdprompts dot com. And while you are there, you can search our archive of over four hundred episodes. We have covered everything from industrial lighting to the deep networking of J-F-K.
Yeah, and if you are enjoying these deep dives into the weird infrastructure of our world, we would really appreciate it if you could leave us a review on Spotify or whatever podcast app you are using. It actually makes a huge difference in helping other curious people find the show.
It really does. Thanks to Daniel for sending in this prompt. It was a fun one to dig into. This has been My Weird Prompts. Thanks for listening.
Until next time, keep your eyes on the lights. Bye now!
Take care.
