The normally separate worlds of geology and aviation intersected last week when Cork airport in Ireland changed the designation of its main runway.
Variation in the earth’s magnetic field (known as magnetic declination) meant that what had been opened in 1961 as Runway 17/35 is now better described as Runway 16/34.
Over the past 57 years, the Earth’s magnetic field lines have changed and shifted the magnetic headings of the runway. Runway headings are rounded to the nearest ten degrees and Cork’s latest magnetic headings of 164 degrees and 344 degrees magnetic required redesignation.
The formal redesignation took place early on 25 April before the first wave of departing flights.
Cork Airport’s safety lead Nathan Wall told the Irish Independent newspaper that work on the project started two years ago and included updating pilot charts and airport directories.
In Australia, aerodrome operators are responsible for ensuring that runway headings and designations are accurate. However, Geoscience Australia Branch Head of Observatories and Science Support, Guy Royal, said the rate of change in magnetic declination was slow in this part of the world. According to the declination data monitored by Geoscience Australia Geomagnetic observatories, declination changed about half a degree (0.5d) during the last 30 years.
He was not aware of any aerodrome having to redesignate its runways here.
Geoscience Australia publishes an updated model of Australia’s magnetic inclinations/declinations every five year and maintains a geomagnetic reference field values website where aerodrome operators can check the magnetic variation at their location.