This angle is known as the magnetic heading of the runway. This line will make an opening angle with the runway, considering it as a line segment. Now imagine a line drawn from the magnetic north pole to the centre of an airport runway. Similar to a magnet, Earth’s magnetic field too has magnetic poles (see below). Long AnswerĪs we all know, Earth has a magnetic field around it. Great.Runways are numbered on the basis of the angle the runway makes in reference to the magnetic north pole, also known as the magnetic heading. Which it does every couple hundred thousand years or so, and we have no way of predicting when. 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. …unlike a real electromagnet, made of stable metal, all that swirling liquid iron inside the earth is not stable. If there’s one thing the indifferent Universe loves, it’s repeating the same patterns across scales and domains. Grey further delves into the properties of magnets, noting where and how magnets are formed, how they affect the Earth’s stability, and what might happen if the North and South Poles switch places. 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. Since runway numbers are derived from the heading on a compass, when the Magnet North moves the runway numbers need to change to match. This happens more in Canada than anywhere else in the world. If there is a magnetic field disruption, runway numbers must be changed. 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. …We draw a line about which this spin occurs, and name each end the North and South Pole. Runways numbers depend on where the North Pole …Okay, to find the North Pole, remember that the Earth is a sphere that spins. Grey also explains how the magnetic pull from the magnetic North Pole can mess things up a bit, particularly since it’s not at the actual North Pole. 225 and 45, round to ten again, drop the zeros for 23 and 5. Round to ten, for 320 and 140, then drop the zeros to get runways 32 and 14. 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. This low-tech check is useful as a fallback because a compass can see the way even when eyes and other equipment can not. The pilot can always confirm their doing it right by reading 360 on their ancient ancestor’s compass. Since airplanes are supposed to head into the wind for a smooth landing, it’s important for air traffic control to indicate at which degree of a 360° compass they should land. Grey then explains that, like pirates of the past, the airline industry relies on compasses to determine direction. Airport, in Nevada’s desert of nothing, there’s only two runways. 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. CGP Grey explains, in his rather frenetic manner, the purpose and the design of those seemingly random airport runway digits that are usually only seen out of a plane window.
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