It's a big red light placed near the runway where a pilot can see it. The control tower can turn it off and on. When it's on, takeoff has not been cleared. When it's off takeoff MAY have been cleared, so they need the usual radio clearance.-- Voice, Jan 27 2021 Baby Elephany walk -- Henry Mancini https://www.youtube...watch?v=b1z4JfxFb6c [Voice, Jan 27 2021] Why not a gate, like at a level crossing, but scaled up to aeroplane size?-- hippo, Jan 27 2021 Well I suppose once you have taken off the switch, then the light is not going to work, so you may as well take it off as well. Then you can use a single plate (or bit of parcel tape) to cover both mounting holes.-- pocmloc, Jan 27 2021 Why not use the very same traffic signal light fixtures we use out on the roadways? Everybody is already familiar with them, even the pilots (one would hope). Don't the Brits also have an audible chime that goes clang! when the lights change?-- whatrock, Jan 27 2021 No, it's a man in tudor robes and a wig ringing a handbell-- hippo, Jan 27 2021 Runway traffic signal lights could be mounted on tall poles, bringing them up to the eye level of the pilots of those really big planes. Of course, when the plane moved forward the wing would catch the pole and knock it over thus creating the necessary job of Air Traffic Takeoff Clearance Light Pole Restander Upper.-- whatrock, Jan 27 2021 Any increase in visual clutter around the runway threshold is not a good thing.
However, with the development of high-intensity LED lighting, which allows lamps to change their emitted colour as required, there is scope for changing the centreline lights between white (runway available) and red (runway in use) on command from the tower.
That would require agreement by the ICAO but it's probably being discussed already ... they have standing committees on all sorts of stuff like that.
// Air Traffic Takeoff Clearance Light Pole Restander Upper. //
On flattops, various bits of hardware hinge or drop down flush with the deck during operations. Doing the same with a set of traffic lights would be practical, but the mechanism would have to be very, very reliable. Existing light gantries, and antenna supports, that are positioned close to runways are specified as being frangible, so if they are hit, they just shatter, doing minimal damage - but it doesn't take much to damage the leading edge of a wing traveling at 150 kts*.
Interestingly, some early traffic lights were gas-lit.
*<Pause for reverie while contemplating the idea of piloting a plane capable of 150kts in anything less than a steep dive/>
<Further pause for reverie while contemplating the idea of flying in or out of an airfield that actually has runway lights, or indeed any facilities other than "a nasty little hut full of dead flies"./>-- 8th of 7, Jan 27 2021 //That would require agreement by the ICAO// - interestingly, in a previous job, I did actually get ICAO to agree to something I wrote-- hippo, Jan 27 2021 [hippo]: "Dear ICAO, I suspect I am an idiot. Is this correct ?"
[ICAO]: "Yes, we have checked our records and can confirm that you are an idiot."-- 8th of 7, Jan 27 2021 <cough!> //something I wrote//-- hippo, Jan 27 2021 <Queen Gertrude>
"The lady doth protest too much, methinks ..."
</Queen Gertrude>-- 8th of 7, Jan 27 2021 //[-] WKTE. Takeoff Hold Lights (part of runway status light system, linked) work pretty much as Voice described.//
No. The important part is they're controlled by the control tower. Thus automated systems, which may not be trusted, need not be relied upon.-- Voice, Jan 27 2021 // major airports //
<Bitter resentful rant about high landing fees, hangarage charges, limited landing slots, preferential treatment for 100-tonne passenger aircraft, and the vicissitudes of having to negotiate an "elephant walk" both in the air and on the ground, leading to unreasonable demands for unattainable approach speeds and subsequent laundry bills />-- 8th of 7, Jan 27 2021 A comparison of dictionary definitions and similies, plus consultation of a thesaurus, suggests that the precise term is "Aluminium alloy piggy bank"
It fulfills all the criteria, in that it just sits there while the owner stuffs money into it on a regular basis, said money being thereafter permanently inaccessible - unless the thing is broken up into component parts.-- 8th of 7, Jan 27 2021 I just wish we could fly somewhere. (Apply this comment to all other ideas about flying and planes till we can do that again in the future)-- blissmiss, Jan 28 2021 This might be a good visual indicator for individual commercial air passengers. Instead of conventional time and gate information, this would be a colored lantern issued to passengers upon check-in. The light starts out red and gradually shifts toward green as the passenger's departure time grows closer and/or if the passenger is becoming closer to their departure terminal, eventually becoming fully green when the passenger walks through the departure gate at the specified time. Passengers would locate their terminal by using a hot/cold search approach, walking in a direction and watching the color of their light. (For colorblind customers, a faint humming noisemaker would perform the same function instead.) If the light turns blue, this means that the passenger has missed their flight and needs to rebook and receive a new lantern.-- sninctown, Jan 29 2021 random, halfbakery