Runway and Taxiway Marking

Runway and Taxiway Marking

In order to aid pilots in guiding the aircraft on runways and taxiways, pavements are marked with lines and numbers. These markings are of benefit primarily during the day and dusk. At night, lights are used to guide pilots in landing and maneuvering at the airport. White is used for all markings on runways and yellow is used on taxiways and aprons.

Runways

The FAA has grouped runways for marking purposes into three classes: (1) visual,cisionorinstrument?basic? runways, (2) runways, and (3) precision instrument runways. The visual runway is a runway with no straight-in instrument approach procedure and is intended solely for the operation of aircraft using visual approach procedures. The nonprecision instrument runway is one having an existing instrument approach procedure utilizing air navigation facilities with only horizontal guidance (typically VOR or GPS-based RNAV approaches without vertical guidance) for which a straight-in nonprecision approach procedure has been approved. A precision instrument runway is one having an existing instrument approach procedure utilizing a precision instrument landing system or approved GPS-based RNAV (area navigation) or RNP (required navigation performance) precision approach. Runways that have a published approach based solely on GPS-based technologies are known as GPS runways.

Runway markings include runway designators, centerlines, threshold markings, aiming points, touchdown zone markings, and side stripes. Depending on the length and class of runway and the type of aircraft operations intended for use on the runway, all or some of the above markings are required.

Runway Designators

The end of each runway is marked with a number, known as a runway designator, which indicates the approximate magnetic azimuth (clockwise from magnetic north) of the runway in the direction of operations.

The marking is given to the nearest 10 o with the last digit omitted. Thus a runway in the direction of an azimuth of 163 o would be marked as runway 16 and this runway would be in the approximate direction of south-south-east. Therefore, the east end of an east-west runway would be marked 27 (for 270 o azimuth) and the west end of an east-west runway would be marked 9 (for a 90 o azimuth). If there are two parallel runways in the east-west direction, for example, these runways would be given the designation 9L-27R and 9R-27L to indicate the direction of each runway and their position (L for left and R for right) relative to each other in the direction of aircraft operations. If a third parallel runway existed in this situation it has traditionally been given the designation 9C-27C to indicate its direction and position relative (C for center) to the other runways in the direction of aircraft operations. When there are four parallel runways, one pair is marked with the magnetic azimuth to the nearest 10 o while the other pair is marked with the magnetic azimuth to the next nearest 10 o . Therefore, if there were four parallel runways in the east-west direction, one pair would be designated as 9L-27R and 9R-27L and the other pair could be designated as either 10L-28R and 10R-28L or 8L-26R and 8R-26L. This type of designation policy is increasingly being applied to three parallel runway configurations, as well. For example, one pair would be designated as 9L-27R and 9R-27L and the third runway may be designated 10-28. Runway designation markings are white, have a height of 60 ft and a width, depending upon the number or letter used, varying from 5 ft for the numeral 1 to 23 ft for the numeral 7. When more than one number or letter is required to designate the runway the spacing between the designators is normally 15 ft. The sizes of the runway designator markings are proportionally reduced only when necessary due to space limitations on narrow runways and these designation markings should be no closer than 2 ft from the edge of the runway or the runway edge stripes.

Runway Threshold Markings

Runway threshold markings identify to the pilot the beginning of the runway that is safe and available for landing. Runway threshold markings begin 20 ft from the runway threshold itself.

Runway threshold markings consist of two series of white stripes, each stripe 150 ft in length and 5.75 ft in width, separated about the centerline of the runway. On each side of the runway centerline, a number of threshold marking stripes are placed, For example, for a 100-ft runway, eight stripes are required, in two groups of four are placed about the centerline. Stripes within each set are separated by 5.75 ft. Each set of stripes is separated by 11.5 ft about the runway centerline.

The above specifications for runway threshold markings were adapted by the FAA from ICAO international standards and made mandatory for United States civil use airports in 2008.

Centerline Markings

Runway centerline markings are white, located on the centerline of the runway, and consist of a line of uniformly spaced stripes and gaps. The stripes are 120 ft long and the gaps are 80 ft long. Adjustments to the lengths of stripes and gaps, where necessary to accommodate runway length, are made near the runway midpoint. The minimum width of stripes is 12 in for visual runways, 18 in for nonprecision instrument runways, and 36 in for precision instrument runways. The purpose of the runway centerline markings is to indicate to the pilot the center of the runway and to provide alignment guidance on landing and takeoff.

Aiming Points

Aiming points are placed on runways of at least 4000 ft in length to provide enhanced visual guidance for landing aircraft. Aiming point markings consist of two bold stripes, 150 ft long, 30 ft wide, spaced 72 ft apart symmetrically about the runway centerline, and beginning 1020 ft from the threshold.

Touchdown Zone Markings

Runway touchdown zone markings are white and consist of groups of one, two, and three rectangular bars symmetrically arranged in pairs about the runway centerline. These markings begin 500 ft from the runway threshold. The bars are 75 ft long, 6 ft wide, with 5 ft spaces between the bars, and are longitudinally spaced at distances of 500 ft along the runway. The inner stripes are placed 36 ft on either side of the runway centerline. For runways less than 150 ft in width, the width and spacing of stripes may be proportionally reduced. Where touchdown zone markings are installed on both runway ends on shorter runways, those pairs of markings which would extend to within 900 ft of the runway midpoint are eliminated.

Side Stripes

Runway side stripes consist of continuous white lines along each side of the runway to provide contrast with the surrounding terrain or to delineate the edges of the full strength pavement. The maximum distance between the outer edges of these markings is 200 ft and these markings have a minimum width of 3 ft for precision instrument runways and are at least as wide as the width of the centerline stripes on other runways.

Displaced Threshold Markings

At some airports it is desirable or necessar threshold on a permanent basis. A displaced  threshold is one which has been moved a certain distance from the end of the runway. Most often this is necessary to clear obstructions in the flight path on landing. The displacement reduces the length of the runway available for landings, but takeoffs can use the entire length of the runway. T.

These markings consist of arrows and arrow heads to identify the displaced threshold and a threshold bar to identify the beginning of the runway threshold itself. Displaced threshold arrows are 120 ft in length, separated longitudinally by 80 ft for the length of the displaced threshold. Arrow heads are 45 ft in length, placed 5 ft from the threshold bar. The threshold bar is 5 ft in width and extends the width of the runway at the threshold.

Blast Pad Markings

In order to prevent erosion of the soil, many airports provide a paved blast pad 150 to 200 ft in length adjacent to the runway end. Similarly, some airport runways have a stopway which is only designed to support aircraft during rare aborted takeoffs or landing overruns and is not designed as a full strength pavement. Since these paved areas are not designed to support aircraft and yet may have the appearance of being so designed, markings are required to indicate this.

Centerline and Edge Markings

The centerline of the taxiway is marked with a single continuous 6-in yellow line. On taxiway curves, the taxiway centerline marking continues from the straight portion of the taxiway at a constant distance from the outside edge of the curve. At taxiway intersections which are designed for aircraft to travel straight through the intersection, the centerline markings continue straight through the intersection. At the intersection of a taxiway with a runway end, the centerline stripe of the taxiway terminates at the edge of the runway.

At the intersection between a taxiway and a runway, where the taxiway serves as an exit from the runway, the taxiway marking is usually extended on to the runway in the vicinity of the runway centerline marking. The taxiway centerline marking is extended parallel to the runway centerline marking a distance of 200 ft beyond the point of tangency. The taxiway curve radius should be large enough to provide a clearance to the taxiway edge and the runway edge of at least one-half the width of the taxiway. For a taxiway crossing a runway, the taxiway centerline marking may continue across the runway but it must be interrupted for the runway markings.

When the edge of the full strength pavement of the taxiway is not readily apparent, or when a taxiway must be outlined when it is established on a large paved area such as an apron, the edge of the taxiway is marked with two continuous 6-in wide yellow stripes that are 6 in apart.

Taxiway Hold Markings

For taxiway intersections where there is an operational need to hold aircraft, a dashed yellow holding line is placed perpendicular to and across the centerline of both taxiways.

When a taxiway intersects a runway or a taxiway enters an instrument landing system critical area, a holding line is placed across the taxiway. The holding line for a taxiway intersecting a runway consists of two solid lines of yellow stripes and two broken lines of yellow stripes placed perpendicular to the centerline of the taxiway and across the width of the taxiway. The solid lines are always placed on the side where the aircraft is to hold. The holding line for an instrument landing system critical area consists of two solid lines placed perpendicular to the taxiway centerline and across the width of the taxiway joined with three sets of two solid lines symmetrical about and parallel to the taxiway centerline.

Taxiway Shoulders

In some areas on the airfield, the edges of taxiways may not be welldefined due to their adjacency to other paved areas such as aprons and holding bays. In these areas, it is prudent to mark the edges of taxiways with shoulder markings. Taxiway shoulder markings are yellow in color, and are often painted on top of a green background.

The shoulder markings consist of 3-ft-long yellow stripes placed perpendicular to the taxiway edge stripes, On straight sections of the taxiway, the marks are placed at a maximum spacing of 100 ft. On curves, the marks are placed on a maximum of 50 ft apart between the curve tangents.

Distances shown above are for planning purposes only. must be placed in order to restrict the largest aircraft (tail or body) expected to use the runway from penetrating the obstacle-free zone.

For aircraft approach categories A and B, airplane design group III, this distance is increased 1 ft for each 100 ft above 5100 ft above sea level. For airplane design group IV, precision instrument runways, this distance is increased 1 ft for each 100 ft above sea level.

For aircraft approach category C, airport design group IV, precision instrument runways. This distance is increased 1 ft for each 100 ft above sea level. For airplane design group V, this distance is increased 1 ft for each 100 ft above sea level.

For aircraft approach category D, this distance is increased 1 ft for each 100 ft above sea level.

Enhanced Taxiway Markings

Beginning in 2008, all airports serving commercial air carriers are required to mark certain critical areas of the airfield with enhanced taxiway markings. These markings are designed to provide additional guidance and warning to pilots of runway intersections.

Enhanced markings consist primarily of yellow-painted lines, using paint mixtures with imbedded glass beads to enhance visibility. In addition, yellow markings must be marked on top of a darkened black background.

Taxiway centerlines are enhanced for 150 ft from the runway hold-short markings. The centerline enhancements include dashed yellow lines 9 ft in length, separated longitudinally by 3 ft. These yellow lines are placed 6 in from each end of the existing centerline.

Closed Runway and Taxiway Markings

When runways or taxiways are permanently or temporarily closed to aircraft, yellow crosses are placed on these trafficways. For permanently closed runways, the threshold, runway designation, and touchdown markings are obliterated and crosses are placed at each end and at 1000 ft intervals. For temporarily closed runways, the runway markings are not obliterated, the crosses are usually of a temporary type and are only placed at the runway ends. For permanently closed taxiways, a cross is placed on the closed taxiway at each entrance to the taxiway. For temporarily closed taxiways barricades with orange and white markings are normally erected at the entrances.

Airfield Signage

In addition to markings, signage is placed on the airfield to guide and direct pilots and ground vehicle operators to points on the airport. In addition some signage exists to provide the pilots with information regarding their position on the airfield, the distance remaining on a runway, the location of key facilities at the airport, and often informative signage ranging from voluntary procedures to mitigate noise impacts to warnings about nearby security sensitive areas

Runway Distance Remaining Signs

Runway distance remaining signs are placed on the side of a runway and provide the pilot with information on how much runway is left during takeoff or landing operations. These signs are placed at 1000 ft intervals along the runway is a descending sequential order.

In this configuration it is recommended that the signs be placed on the left side of the most frequently used direction of the runway.

The signs may be placed on the right side of the runway when necessary due to required runway-taxiway separations or due to conflicts between intersecting runways or taxiways. An alternative method is to provide a set of single-faced signs on either side of the runway to indicate the distance remaining when the runway is used in both directions. The advantage of this configuration is that the distance remaining is more accurately reflected when the runway length is not an even multiple of 1000 ft. Another alternative uses double-faced signs on both sides of the runway. The advantage of this method is that the runway distance is displayed on both sides of the runway in each direction which is an advantage when a sign on one side needs to be omitted because of a clearance conflict. When the runway distance is not an even multiple of 1000 ft, one half of the excess distance is added to the distance on each sign on each runway end.

Taxiway Guidance Sign System

The primary purpose of a taxiway guidance sign system is to aid pilots in taxiing on an airport. At controlled airports, the signs supplement the instructions of the air traffic controllers and aid the pilot in complying with those instructions. The sign system also aids the air traffic controller by simplifying  instructions for taxiing clearances, and the routing and holding of aircraft. At locations not served by air traffic control towers, or for aircraft without radio contact, the sign system provides guidance to the pilot to major destinations areas in the airport.

The efficient and safe movement of aircraft on the surface of an airport requires that a well-designed, properly thought-out, and standardized taxiway guidance sign system is provided at the airport. The system must provide the pilot with the ability to readily determine the designation of any taxiway on which the aircraft is located, readily identify routings to a desired destination on the airport property, indicate mandatory aircraft holding positions, and identify the boundaries for aircraft approach areas, instrument landing system critical areas, runway safety areas and obstacle free zones. It is virtually impossible, except for holding position signs, to completely specify the locations and types of signs that are required on a taxiway system at a particular airport due to the wide variation in the types of functional layouts for airports.

Taxiway Designations

Taxiway guidance sign systems are in a large part based on a system of taxiway designators which identify the individual taxiway components. While runway designators are based on the magnetic heading of the runway, taxiway designators are assigned based on an alphabetic ordering system, independent of the taxiways direction of movement. Taxiways are typically identified in alphabetic order from east to west or north to south (i.e., the northern or easternmost taxiway would be designatedthenext southern or western?A?,taxiway would be designated ?B,? and so forth). Entr perpendicular to main parallel taxiways are designated by the letter of the main parallel taxiway from which they spur, followed by a numeric sequence. For instance, the northernmost entrance taxiway off of taxiway A? would be designated ?A1,? and so forth. ?O? are not used as taxiway designators due to the numbers ?1? ands not?0used.?as a In addition the taxiway designator due to its similarity to a closed runway marking.

An example taxiway designation scheme is illustrated in Fig. 8-30. The taxiway guidance sign system consists of four basic types of signs: mandatory instruction signs, which indicate that aircraft should not proceed beyond a point without positive clearance, location signs, which indicate the location of an aircraft on the taxiway or runway system and the boundaries of critical airfield surfaces, direction signs, which identify the paths available to aircraft at intersections, and destination signs, which indicate the direction to a particular destination.