Have you ever wondered what all the markings on airport runways mean and how the lighting assists pilots? Runway markings and lighting are essential for the safe operation of aircraft. The markings are used by pilots to determine the runway orientation, how much distance is remaining, and to make other critical judgments during takeoffs and landings. The lighting is used during the night and low visibility operations. Both the markings and lighting on a runway are highly standardized. This ensures that pilots, regardless of their experience or the airport at which they may find themselves, can easily interpret the visual cues and safely navigate the runway.
The number appearing on the runway denotes the magnetic heading to the closest 10 degrees and is used to identify that particular runway. For example, if the runway is labeled 36, then the bearing to that runway is 360 degrees. Conventionally, only two digits are used to mark a runway so the zero in 360 is dropped. Similarly, if the heading to the runway is 90 degrees, the last zero is dropped. However, in this case, a zero is added ahead of the number 9, making it runway 09. (This avoids confusion, as a heading of 900 degrees does not exist.) Magnetic runway markings are important to pilots because they provide a clear visual reference to the runway’s orientation based on magnetic north, allowing pilots to easily identify which runway they are approaching or departing from, especially in conditions with low visibility or at complex airports with multiple runways, by simply looking at the runway number which corresponds to its magnetic heading.
The runway threshold marks the start of the runway. The threshold strips are unofficially known as “piano keys” because that’s what they look like from above. In some airports, there exists a portion behind the runway threshold known as a displaced threshold. This area is marked with arrows pointing to the threshold. The displaced threshold is an area where aircraft are prohibited from landing, but in which takeoffs may be conducted, Displaced thresholds shorten the runway available for landings in order to protect an object or area off the end of the runway, such as a taxiway, a runway safety area, or a populated area. They may also be used to protect the runway surface from excessive wear and tear, such as from the repeated impact of landing aircraft or to mitigate noise pollution from aircraft landings.
The landing aiming point consists of two large white stripes marked on the runway. It’s the point on the runway where the pilots aim to touch down during their approach. The length, width, and distance from the threshold where the aiming point must be painted depends upon the runway length.The touch-down zone marking helps pilots quickly determine the runway distance remaining during the final parts of the landing. The markings consist of pairs of rectangular stripes drawn symmetrically about the runway center line. The number of touch-down zone markings that need to be painted on the runway depends on the landing distance available or the distance between the thresholds of the runways. When an airport has parallel runways (runways with the same bearing), the number is supplemented with a letter code. Most airports mark parallel runways as L for Left, R for Right, and C for Center. As it suggests, the runway to the right is labeled R, the one to the left is labeled L, and the center runway is labeled C.
As for runway lighting, edge lights are used to outline the edges of runways during periods of darkness or reduced visibility. These light systems are classified according to the intensity or brightness they are capable of producing. They are either High, Medium or Low Intensity Runway Lights. The first two systems have variable intensity controls, whereas the Low Intensity Lights normally have but one intensity setting. All runway edge lights are white, but on instrument runways, yellow replaces white on the last 2,000 feet or half the runway length, whichever is less, to form a caution zone for landings. The lights marking the ends of the runway emit red light toward the runway to indicate the end of runway to a departing aircraft and emit green outward from the runway end to indicate the threshold to landing aircraft.
The runway threshold lights mark the runway’s beginning. If there is a displaced threshold, at least six green lights are present and the distance between them depends upon the type of approach for which the runway is certified. Runway centerline lights are white lights spaced 50 feet apart which run down the middle of a runway to assist pilots when landing and taking off. Runway End Identifier Lights (REIL) are installed at many airfields to provide rapid and positive identification of the approach end of a particular runway. The system consists of a pair of synchronized flashing lights located laterally on each side of the runway threshold. Runway lights are incredibly important because they provide pilots with crucial visual cues to safely navigate and land on a runway, especially during low visibility conditions at night or in bad weather, allowing them to clearly see the runway boundaries, threshold, and centerline, which is essential for safe takeoff and landing operations.
Pilots are expected to pay attention to all the relevant runway markings and lights to ensure safe flight operations. Even a slight oversight can have disastrous consequences. An incident that highlights this is the tragic loss of Singapore Airlines Flight # 006 on October 31, 2000. It was a scheduled passenger flight from Singapore’s Changi Airport (SIN) to Los Angeles International (LAX) with an intermediate stop at Taiwan’s Taipei Airport (TPE). After its initial leg, the Boeing 747-400 pushed back at TPE at around 11:00 PM local time amid poor weather conditions, with heavy rain resulting from a typhoon passing overhead of the airport and in the general vicinity. The airport had two runways, 05L and 05R, which run parallel to each other. But, a section of runway 05R between two taxiways was closed for construction. The aircraft was cleared for takeoff on 05L, which the captain acknowledged, but he turned the plane 705 ft too soon and lined up with 05R by mistake. With no ground radar and poor visibility due to the weather, the tower controller could not spot the aircraft. The 747 eventually hit concrete barriers, excavators, and other equipment that had been parked overnight on the runway after about 41 seconds into its takeoff roll. Tragically, 83 people lost their lives that night. After the crash, many changes were made at the airport to prevent similar accidents. The Taiwanese Civil Aviation Administration increased airport inspections, new taxiway and runway markings were painted and runway guard lights were installed on both runways 05L and 23R. The first ground radar system was installed in 2007. Unfortunately, beneficial changes are often made only after an accident occurs.
Until next time…safe travels.
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