AIRPORT LIGHTS AND MARKINGS

Have you ever wondered why there are so many brightly colored lights and painted symbols at airports? If you guessed that they are "road signs" for pilots, you were correct. They provide pilots with information necessary for taking off and landing.

The most predominant light, the rotating beacon, is usually located near the center of the airport. It allows pilots to locate the airport at night. These lights are green and white at civilian airports. Beacons that are green followed by two quick white flashes are found at airports located on military bases, while beacons for seaplane bases are yellow followed by white. Beacons generally operate from dusk until dawn. If lit during daylight hours, they signal that weather conditions require an instrument clearance for arrivals and departures.

Other airport lights also serve important functions. Providing outlines for taxiways are blue lights. Green lights indicate the start, or approach end, of the runway. The departure end is marked by red lights. Lights along the edges of the runway are white, changing to amber near the departure end of the runway. Recessed lights are located on the runway's centerline at most large airports. For most pilots, it is initially a bit unnerving to land on these. They are, however, safely situated under protective covers.

Sequenced flashing strobe lights line the approach threshold. Air traffic controllers can change the intensity of the lights from the tower at the pilot's request. The highest intensity is used to help incoming pilots locate the runway in times of reduced visibility. The lights are usually set at a low intensity at night so they won't interfere with the night vision of pilots.

Markings on taxiways and runways also have meaning. Taxiway centerlines are yellow while those on runways are white. A hold short line, consisting of two parallel solid lines and two parallel dashed lines, is located at the approach to each runway. This is the equivalent of a stop sign. An aircraft must be cleared by the tower to go beyond this point. Each taxiway intersection has a letter designation which allows pilots to advise the tower of their holding location.

Number designations are painted on each runway. These are determined by the runway's magnetic direction. Assume, for example, that a runway is oriented in a southeasterly direction with a compass heading of 145. This is rounded up to the nearest ten degree number (145 in this case becomes 150) and the final zero is dropped. This runway's number becomes 15. Similarly, if we consider the position that is 180 degrees opposite this, the resultant compass heading is 330. Because this number doesn't need to be rounded upward, we simply drop the final zero and the runway becomes number 33. An aircraft using this runway would be taking off in the opposite direction from that in the first example.

Also painted on the runway are touchdown zone markings. These provide a visual aiming point for approaching aircraft and are followed at fixed 500-feet intervals by pairs of one, two, or three bars on each side of the centerline. In times of reduced visibility, these markings assist the pilot in evaluating the remaining runway.

The next time you taxi, see how many of these "road signs" you can identify!