Why there are several runways

Planes always land and take off into the wind, for reasons explained in the a r t i c l e on PILOTING AN AIRPLANE; so at any airport there are as many runways, usually five, as there are directions from which the wind is likely to blow. Runways are numbered by the first two digits of their magnetic compass heading. A runway that is on a course of 320 magnetic would be called 32, and the number is painted at the end of the runway. Also, the length of the runway is painted on it and is shown by means of a white painted bar for each 1,000 feet, big enough so that the pilot can read it from the air.

Other marks are painted at the one-third and two-third distances. For planes without radios a tetrahedron ( w h i c h may be moved by the wind or mechanically, or a wind sock, tells the direction of the wind. At the large fields there are always several fire trucks, a crane, and an ambulance for use in case the pilot has an accident while he is landing or taking off. If the plane catches fire, or if anyone has been hurt in the crash, help is right there waiting. To get to the runway from the hangars, parking areas, or passenger terminal, there is a taxi way, which is just like a driveway for a car. Every large field has a central tower in which one or more men direct the traffic of planes at the field. When a pilot wishes to taxi from his parking place, he calls the tower on his radio, and the tower tells him which runway to use, the one that is most nearly in line with the direction of the wind. The man in the tower also tells him the altimeter setting—the barometric pressure at the moment.

The altimeter is the instrument for telling how high he is above sea level. He sets the current barometric pressure, and if the airport is 100 feet above sea level, since he is on the airport, his altimeter, when set correctly, will also tell him that. When the pilot gets to the starting end of the runway, after he was warmed up the plane and checked to see that everything about the plane is working right, he asks the tower for permission to take off, and if no one else is landing or taking off, the tower tells him to go ahead. The procedure is just reversed for landing. The pilot calls when he is about ten minutes away from the airport. Landing planes have priority, since they are usually low on fuel when returning.