THE REAL MEANING BEHIND AIRPORT RUNWAY DIGITS
Have you ever seen the airplane runway at an airport? Have you noticed the strange numbers painted on the runway? In an very informative video, CGP Grey explains the purpose and the design of those seemingly random airport runway digits.
“While waiting on a plane during taxi ’till takeoff, looking out the window, you may have noticed the giant number numbering the runway, say eight, which implies seven others exist, at least, but this is a flight out of L.O.L. Airport, in Nevada’s desert of nothing, there’s only two runways.”
Just like pirates in the past, Grey went on to explain that the airline industry relies on compasses to determine direction. It is important for air traffic control to indicate the correct degree of a 360° compass the airplane should land. The number of degrees the plane should come in, is rounded to the nearest ten, dropping the zero.
To give you an example, the number 8 on the runway simply means that the plane should come in and land with 80°. Since the pilots are coming from the opposite direction, their compasses will read 260°, and the number on the far side of the runway will read 26.
“The pilot can always confirm their doing it right by reading 360 on their ancient ancestor’s compass. This low-tech check is useful as a fallback because a compass can see the way even when eyes and other equipment can not. As a two-runway example…gives 315 for one end because that’s the way the pilot needs to point and 135 at the other. Round to ten, for 320 and 140, then drop the zeros to get runways 32 and 14. On the other side. 225 and 45, round to ten again, drop the zeros for 23 and 5. “
However, things can still go a bit sideways with a compass. Grey explained how the magnetic pull from the magnetic North Pole, particularly since it’s not at the actual North Pole, can mess things up a bit. "Runways numbers depend on where the North Pole …Okay, to find the North Pole, remember that the Earth is a sphere that spins. …We draw a line about which this spin occurs, and name each end the North and South Pole. Starting with these poles, we clever humans created a square-ish co-ordinate system for our spherical earth, …This grid is what every modern navigational system uses to get around with the GPS, global positioning, coordinates it gives.”
When ever a magnetic field disruption is experienced, the runway numbers must be changed. This happens more in Canada than anywhere else in the world. “Since runway numbers are derived from the heading on a compass, when the Magnet North moves the runway numbers need to change to match. And the closer your airport is to a magnet pole, the bigger a difference its movement makes, and thus the more frequently you need to update the number.”
Grey further continues in the video to explain the properties of magnets. He also notes how magnets are formed, and how this affect the Earth’s stability. More interestingly, he delves deeper into what might happen if the North and South Poles switch places.
“If there’s one thing the indifferent Universe loves, it’s repeating the same patterns across scales and domains. …unlike a real electromagnet, made of stable metal, all that swirling liquid iron inside the earth is not stable. So at any moment, the field can split into multiple magnetic poles, roam randomly, or diminish entirely before flipping north to south and south to north. Which it does every couple hundred thousand years or so, and we have no way of predicting when. Great.”