Compass headings, runway names change with Earth’s magnetic field

Mysteries
airplane compass

MYSTERY WIRE — The Earth’s magnetic field changes constantly, but on a very small scale. You may have read recent reports that the North Pole is gradually shifting toward Siberia.

Airport runway designations even change, since they reflect actual compass headings that are always in flux.

A recent article on the National Centers for Environmental Information website notes the changing runway names at Fairbanks International Airport in Alaska. Runway 1L-19R changed to runway 2L-20R in 2009, and the airport knows they will be changing it again in about 13 years. Airports nearer to the north and south poles see the effect much more often than airports near the equator.

READ: Airport runway names shift with magnetic field

McCarran International Airport in Las Vegas most recently changed its two longest runways in 2017, according to Public Information Administrator Christine Crews. Runway 7L/25R became Runway 8L/26R, and 7R/25L was renamed 8R/26L on Aug. 16, 2017. A news release from McCarran also mentions renumbering in Tampa, Florida, and Orange County, California, in 2017.

Aviation is affected by these miniscule changes, especially as they relate to navigation. Even your smartphone’s map app relies on a “map” of the magnetic field. That map is known as the World Magnetic Model, and it is updated every five years.

“The aviation industry relies on magnetic compasses as primary instruments for navigation, alongside GPS instruments, so shifts in Earth’s magnetic field affect many aspects of aircraft navigation, including instrument landing systems, air traffic procedures, and runway designations.”

FAA rules dictate that runways are numbered according to the points on a compass. Other designations reflect rounding to the nearest 10 degrees, so the names go from 1 to 36. The additional numbers designate headings.

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