How Do Airport Runway Lights Work?
Have you ever wondered about the meaning behind the different colored runway lights at an airport? These lights play a crucial role in flight safety and are thus heavily regulated. In fact, every airport supporting takeoff and landing operations is required to have an International Civil Aviation Organization (ICAO) approved lighting system. In this blog, we will discuss the various types of runway lights and how they contribute to the safety of aircraft takeoff, landing, and towing operations.
The primary function of runway lights, regardless of their color, is to illuminate and identify the beginning and end of the runway. In order to help pilots identify these landmarks, various colors are used at different locations on the runway and will be explained in the following sections.
Approach Lights: The first set of lights that the pilot will see upon landing is the approach lights. Consisting of 17 white lights, approach lights are all positioned to face the same direction and are typically arranged in a cross shape. Regardless of their configuration, approach lights’ primary function is to communicate to the pilot which direction the runway is oriented.
Runway End Identification Light: The next pair of lights that will appear as the plane approaches the surface are the runway end identification lights (REIL). These two unidirectional flashing lights help identify the beginning of the runway. The bright REILs can be seen as far away as 3 miles in the day and up to 20 miles at night.
Threshold Lights: Threshold lights line the first part of the runway and indicate that it is safe for the pilot to land. While it is safe to begin touchdown here, it is typically only used in emergency situations, as it is very close to the edge of the runway. These unidirectional green lights are angled so that they are only visible upon approach.
Runway Edge Light: Accounting for the greatest portion of the lighting system, runway edge lights perform the important function of illuminating and defining the sides of the runway. These lights are bidirectional and come in various color patterns, including white/white, white/red, and yellow/red.
Runway End Light: Marking the end of the physical runway, the red runway lights warn pilots to prevent the aircraft from going beyond the runway boundaries. If the pilot recognizes that they cannot slow the plane to a stop before the end lights, they will have enough time to take off again and plan a recourse. Airports that support landing from both directions will usually merge the threshold and runway end lights, which will appear green from one direction and red from the other.
Taxiway Lights: While not part of the runway, the blue taxiway lights mark the lanes on which the aircraft travels after it lands. These lights are much dimmer than the others and can only be seen on the ground.
PAPI Lights: Precision Approach Path Indicator (PAPI) lights help pilots approach the runway at the appropriate altitude. Depending on the aircraft's approach altitude, the pilot may see up to four lights. If the plane is too high, more than two lights will be visible, and if it is too low, the pilot will see less than two.
Obstruction Aviation Lights: The red omnidirectional aviation lights alert pilots to nearby buildings, inaccessible areas, or other hazards that must be avoided.
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