"Cleared for takeoff three one, American One Three Niner." One of the pilots on AA139 will read back this instruction in their best pilot's voice: "American One Three Niner, cleared for takeoff, runway three one." In spoken language, pilots and LaGuardia's Air Traffic Control Tower will call out each number individually when referencing the runway in use. We're lined up correctly, and no, there aren't that many planes at LGA waiting to go. Here, one plane is lined up ready for departure on Runway 31 the heading indicator shows 315 degrees. Heading indicators, as seen from the pilot's point of view. Wind rushing over the wings provided by Mother Nature is free, unlike anything else in aviation. Planes depart and land into the wind in order to maximize lift when taking off and drag while landing, and to minimize ground roll. Which direction the runways are built is determined as a part of airport design, where the designers research the prevailing winds-the direction of wind generally speaking-specific to the area. In the US that would simply be Runway 9L, but each departs to the east. So, at London Heathrow (LHR) you'll spot runway 09L. (Just remember that you're facing outward from the compass.) In the US, our runways omit the leading zero for runway 01, which is not the case in much of the world. If there is a giant 19 painted on one end of the runway, there is a giant number 1 painted on the other side. (More about the wind in a moment.)Īs you might guess, the numbers are the reciprocals of each other. It makes sense then that runways and magnetic headings generally work hand in hand to this day.Ī runway will be numbered at both ends, offering two potential directions from which airplanes may depart and land, as decided by Air Traffic Control, which is mindful of the wind and weather at the time. Importantly, this direction-the magnetic heading-is made in reference to magnetic north rather than geographic north (the north used on road maps, for example.) Aviation has long used compasses which require no power, only the earth's magnetic field. The giant numbers painted on the runway correspond to the direction the runway points, as indicated on a 360-degree compass. It's the direction from the approach to landing that is painted on the runway.Īny runway- say, runway 4 -could be oriented between 035 degrees and 045 degrees magnetic and still be named Runway 4, departing to the northeast. Extend a line outward from that notch away from the compass, and presto, you've drawn runway 34, jetting off to the North-Northwest. On the compass above, find approximately 342 degrees.
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