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Why is magnetism forcing changes to airport runway numbering?
Runway 36
CC BY S.A 4.0, via wikimedia commons
Rafael Ramos
9/20/2022
Changes in Earth's magnetism are happening all the time, impacting aircraft operations. Thus, at the beginning of this month, some operational changes were made, but notably, the change of the numbering of the Guarulhos lanes.
Airplanes have a large part of their operations based on compasses and changes in magnetism directly impact the way runway numbering is done, so that with compass guidance, pilots can align the plane perfectly with the runway. In the case of Guarulhos, the two runways were marked 09/27R and 09/17L. It is now 10L/28R and 10R/28L.
The numbering of the tracks varies from 01 to 36, according to the compass indication. If the compass points to 128°, the track number will be 13 (always exclude the last digit, respecting the rounding).
The change in the indication of the tracks of Guarulhos happened after 5 years, the indications changed from 95° to 96° and from 275° to 276°. The change itself is small, but it influences the roundness, which could make a difference in the case of an approach with low visibility. In addition, documentation and navigation systems also had to be changed.
To simplify and understand, these changes occur because the Earth's layers below the surface behave like a fluid and are in constant motion. Some of this fluid has iron and other magnetic materials. Thus, the electrons are moving and, consequently, we have the formation of a magnetic field. However, the fields are not fixed. For example, magnetic north and magnetic south are not perfectly aligned, as we often see in books.
Changes are happening much faster than anticipated. The magnetic motion has accelerated from its speed of 0 to 15 km per year to the 50 to 60 km per year currently observed.
There are two "norths". The magnetic north, generated by the magnetic fields formed by the movement of fluids; and geographic north, a result of the Earth's rotation movement. Aviation uses magnetic north to guide itself. 0° or 360° shows north, 180° shows south, 90° shows east, and 270° shows west.
Image: GRU Airport
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Rafael Ramos
Aviation enthusiast from an early age, he had his first contacts with the area developing that good old habit of spending dozens of hours in front of the screens of Micrsoft Flight Simulator and other simulators. With a solid background in various technological areas, including engineering and chemistry, Rafael has rejoined aviation as editor and author of articles and materials on our portal, providing invaluable help to the dynamics and expansion of the website and the aeronautical community, bringing us the news and updates so indispensable for us to remain current in our area of operation.
   
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