Runway lights

I often fly between my home in Houston and Tulsa. Often the plane will fly directly over Dallas and DFW airport. Last night was my first time to fly over the airport at night with clear visibility, and I was surprised not to see any runway lights. This was only around 9:00 - I’m know the airport was open and I even saw planes (or blinking lights at least) landing in the broad dark spaces where I know the runways to be at DFW. Obviously, the lights were on, but I couldn’t see them.

After I thought about it today, I realized that I have never seen any runway lights from the air. I know I’ve seen actual airports from the air because of the flashing white/green beacons, etc, but I’ve never seen runway lights.

So my question, of course, is why couldn’t I see the lights? How does the mechanism work? And why is it set up that way?

I dunno. I have no problem seeing runway lights at night, but you need to be kinda close to the airport - perhaps in a big jet you are too high/far away. Mostly you see the green/white beacon, and at larger airports the epilepsy inducing strobes that say “This way to the runway”.

Less busy airports turn their lights off to save energy - the pilot of a plane can turn them on by sending a radio signal - it’s like the clapper. They stay on for 15 minutes or so, then reset.

Just a WAG here. If you were flying over the airport, I’m assuming your plane was at cruising altitude. My guess is that the runway lights are designed such that they are best visible to a pilot who is low for landing and approaching.

P.S. Are you going to join us for a Houston SDMB gathering? There’s a couple in the works.

There can be lots of reasons. First, the controllers can turn the intensity of the lights up and down. I have had trouble finding an airport at night, and will ask the controller to turn the lights up.

And yes, the lights are really designed to be able to be seen when you are on final approach from landing. The controllers don’t want them too bright, because it can screw up the night vision for the pilots. But there are also ‘racetrack’ lights on the approach path that can strobe to indicate the approach, and when these are on they are often very bright.

For visual approaches to an airport at night, pilots rely on VASIS lights, which can only be seen when you are directly on approach for the active runway. They change color depending on whether you are too high or too low on approach.

If no aircraft are in the pattern and no flight plans are scheduled, the controllers may not even have the lights on.

Finally, some smaller airports use pilot-controlled lighting, which only come on when a pilot signals them with his aircraft radio. If no one is landing, the lights are off.

Maybe Johnny from Airplane! had unplugged the lights again. :slight_smile:

See photometric performance chart at link below.

This may be representative of lens design to minimize power consumption and maximize bulb life. No need to waste candelas shining at the moon.

A point in every direction is like no point at all

I live within spitting distance of DFW airport and I don’t remember a time that the lights aren’t on at night. But I think is is like beatle and dhanson said, they are much more visible from lower angles than flying over. As I recall, airports from above seem to have just a glow around the runways, not the colored markers that you see from the ground.

Oh, and by the way, don’t those little runway marker lights have little hats on top that would block almost all the light when viewed from above?

No, your typical runway light is simply a glass cylinder with a hemispherical top. However, never having looked straight down at one, I don’t know how much light transmits through the thick curved glass at the top.