In order to ensure safe landing and taking off of aircrafts, airports provide visual aids. These aids provide guidance to the pilot on the runway or taxiway. Airport aids include runway and taxiway markings and signs, navigation aids, edge lighting and runway light landing aids.
Runway markings, signs and lighting are important in enabling the airplane to navigate the surface and avoid incursions on the runway. They help the pilot in knowing his location on the runway or taxiway. These markings and signs provide useful information to a pilot when landing, taking off or taxiing. This paper explores the importance of these aids and the role of the airport manager in maintaining them in good condition.
Runway and Taxiway Markings
There are various types of airport markings. These include runway markings, taxiway markings, holding position markings, among others. Runway markings are white while those in taxiways are yellow (Horonjeff, McKelvey and Sproule, 2010).
There are three types of runways namely precision instrument runway, non-precision instrument runway and visual runway. These runway types have various marking elements which include runway designation, threshold markers, side stripes, centerline, touchdown zone and runway aiming point markings (Ashford, Mumayiz and Wright, 2011).
Runway designation markings are letters which differentiate right, left or center parallel runways. These letters are determined from the direction of approach. “L” “C” “R” is used to designate three parallel runways and two parallel runways are designated by “L” “R”. Runway centerline markings are used to identify the runway center in order to enable aircrafts to be properly guided into alignment when landing and taking off.
The centerline marking is a straight line with regularly spaced gaps and stripes. Runway aiming point marking provides a landing aircraft with a visual aiming point. These markings are two white rectangular stripes on each side of the runway centerline marking. They are positioned 1,000 feet away from the landing threshold (Steon, 2002).
The runway touchdown zone markings help the pilot to identify the landing touchdown zone. These markings are coded and provide information after every 500 feet. These markings are rectangular stripes that are grouped in ones, twos and threes and arranged about the runway centerline markings in pairs.
Runway side stripe markings are two white stripes on each side of the runway to identify the runway edges. This helps the pilot to see the edges of the runway and distinguish it from the surrounding areas. Runway shoulder markings are yellow stripes used to highlight the pavement areas that are next to the runway and are not supposed to be used by aircrafts (Horonjeff, McKelvey and Sproule, 2010).
The runway threshold markings are used by the pilot to identify where the runway available for landing begins. These markings can either be a pair of four lines on each side of the runway centerline, or the number of lines can depend on the runway width.
A runway demarcation bar is a three-feet wide yellow bar used to demarcate a runway with a threshold from a stop-way, taxiway or blast pad that precede the runway. This marking is located outside the runway. A runway threshold bar is a 10 feet wide marking used to demarcate the beginning of the available runway for landing in the event that the threshold has been displaced or relocated (Stanton, Ashford and Moore, 1998).
Whenever they intersect a runway, taxiways should have runway holding position markings and centerline markings. Taxiways have edge markings, holding position markings, shoulder markings and taxiway intersection markings. The taxiway centerline can either be normal or enhanced.
Normal Taxiway centerlines are single yellow continuous lines with a width of between six to twelve inches. During taxiing, aircrafts are supposed to be centered over this line. Enhanced taxiway centerlines found in larger airports are positioned on either side of a normal taxiway centerline as lines of yellow dashes.
These enhancements are found 150 feet before a runway holding position marking and their purpose is to alert the pilot that he/she is near a runway holding position marking and should therefore start preparing to stop if he/she is not cleared to enter across or onto the runway (Steon, 2002).
Taxiway edge markings identify the edges of the taxiway and demarcate it from the other parts of the pavement. Continuous double yellow markings are used to identify the taxiway edge and distinguish it from the shoulder or any other part of the pavement not meant to be used by aircrafts.
Dashed double yellow lines are used when it is necessary to demarcate the taxiway edge on a surface where the pavement next to the taxiway is meant to be used by aircrafts. Taxi shoulder markings are yellow markings used to identify shoulders that are used to prevent blast or water erosion. Shoulders are not meant to be used by aircrafts. Surface painted taxiway direction signs are used at intersections to provide taxiway direction signs or to supplement the signs.
These are black inscriptions on a yellow background located next to the centerline indicating turns either to the right or left of the centerline. Surface painted location signs are used to supplement location signs and consist of a yellow inscription on a black background. These markings are positioned on the right side of the centerline and are used to confirm to the pilot the description of the taxiway on which the aircraft is located (Ashford, Mumayiz and Wright, 2011).
Geographic position markings are used during low visibility operations to help the pilot to identify the location of the taxiing aircraft. Low visibility operations occur when the runway visible range is less than 1200 feet. These marks are found on the left of the taxiway centerline. These markings comprise of a pink inner circle followed by a white ring and a black outer ring (Stanton, Ashford and Moore, 1998).
Holding Position Markings
These are markings on the runway which show where an aircraft is supposed to stop. These markings can be found on runways and taxiways and consist of two dashed and two solid yellow lines that cut across the runway width. They are spaced by between six to twelve inches. Runway holding position markings on taxiways indicate where an aircraft is supposed to stop on the taxiway if there is no clearance to enter the runway (Stanton, Ashford and Moore, 1998).
There are also holding position markings for taxiway intersections which consist of one dashed line running across the taxiway width. They are used to hold aircrafts short of taxiway intersections. Surface painted holding position signs are inscribed in red on a white background and are used to supplement the signs at the holding position (Stanton, Ashford and Moore, 1998).
These signs emphasize the markings on the pavement and show directions of various locations in the airport. The signs have standard color, shapes and meaning but have varied uses. The number of signs varies depending on the size of the airport, with the larger ones having more.
Airport signs will usually be positioned next to the taxiway, runway or ramp area, while the airport markings will be found painted on the pavement. There are various types of airport signs found in the airport. These include the location signs, mandatory instruction signs, direction signs, information sings, destination signs, and runway distance remaining signs (Steon, 2002).
The mandatory instruction signs are written in white on a red background and notify the pilot when entering a critical area, a runway or a prohibited area. These include the No Entry signs and the runway holding position signs. The runway holding position signs are found at the holding position on taxiways intersecting with runways.
They are marked with numbers signifying the direction of runways. For instance, “36-18” means that the departure end of runway 36 is to the left while that of runway 18 is to the right. Aircrafts are not supposed to cross the Holding Position markings until they get clearance. The holding position signs enable the pilot to know the position of the Holding Position Marking.
The No Entry sig n is used to prevent aircrafts from entering some areas, like on a one-direction taxiway or where taxiways or runways intersect with roadways or at points where it is hard to distinguish between taxiways and roadways (Ashford, Mumayiz and Wright, 2011).
Location signs are used in the identification of taxiway and runway locations. The background of the signs is black, written in yellow and with a yellow border. There are no arrows in these signs. The inscription on signs identifying runways is written in numbers while that identifying taxiways is in letters. Taxiway location signs can be combined with runway Holding Position signs, for instance, “T 36-18”. Direction signs are written in black on a yellow background.
They notify the pilot about the intersecting taxiways that lead out of an intersecting runway. These signs have arrows which point towards the direction of the intersecting taxiway. The background of destination signs is yellow with arrows and a black writing. These signs help the pilot to locate things like runways, fuel, parking, ramps, among others (Steon, 2002).
Runway distance remaining signs have white numbers written on a black background. The numbers on the signs signify remaining distance on the runway in thousands of feet. For instance, a sign reading 4 means that there are 4,000 remaining feet on the runway. Runway boundary signs help the pilot to know when the aircraft is leaving the runway safety area and is out of the runway. These signs have a black writing on a yellow background.
They also have a graphic signifying the Holding Position Marking. The pilot can see the sign as he exits the runway. These signs are positioned next to the Holding Position Marking. There are also other information signs which give certain information to the pilot on things such as procedure for reducing noise and the radio frequencies that are applicable. These signs vary in location and size depending on the airport operator (Stanton, Ashford and Moore, 1998).
Lighting is very important in guiding aircrafts through runways and taxiways at night or when there is fog or rain. There are green runway threshold lights signifying the beginning of the runway and red runway end lights indicating the end. There are also runway edge lighting which comprise of white lights on both edges of the runway. These indicate the runway edges. Some runways also have lights along the runway centerline to identify the centerline. Others have lights indicating the approach (Stanton, Ashford and Moore, 1998).
Touchdown zone lighting is used to enhance identification of the touchdown zone in low visibility conditions. Caution zone lighting is used on runways that do not have centerline lighting to provide the pilot with a visual alert of the approaching runway end. Taxiways have blue lights indicating the edges of the taxiway and green lights highlighting the centerline. Taxiway turnoff lights enable the pilot to turn off runways (Ashford, Mumayiz and Wright, 2011).
There are other aids used to enable pilots to land safely. Visual approach slope indicators help the pilots in flying the approach for landing. VHF Omni-directional range enables the pilots in determining the direction of the airport. There is also distance measuring equipment used to determine the distance to the airport.
An instrument landing system is used by pilots in poor weather to find the runway and land safely since they cannot see the ground. Precision approach radar is used to notify the pilot of his position relative to the approach slope (Horonjeff, McKelvey and Sproule, 2010).
Maintenance and Upkeep of Airport Landing Aids
The airport manager is in charge of managing the overall coordination, direction and evaluation of the airport operations. In order to prevent any incursions, the airport manager must ensure that the landing aids are maintained in good condition.
The airport manager should ensure that the runway markings and signs are not confusing or deteriorating. Airport diagrams and signs should also be accurate. The manager also ensures that the airport lighting is in operation and has the right intensity. Poorly illuminated areas should be corrected immediately (Wells and Young, 2004).
The airport manager should ensure that all the landing aids are functioning and if they are not, he/she is supposed to take the necessary actions to make them functional. He/she ensures that all the markings and signs are inspected and repaired if they are not in good condition. The manager should also ensure that there are appropriate signs and markings at confusing intersections. Missing or rubbed out markings and signs should be replaced immediately.
He/she must ensure that closed runways or taxiways are marked clearly. The manager also ensures that he /she is in constant communication with the co-workers, pilots, and other workers so that he can be aware of any problems with the landing aids. The manager should ensure that all the navigation aids like the precision approach radar and visual approach slope indicator are functional (Wells and Young, 2004).
The airport manager formulates policies and procedures to ensure that all the runway and taxiway aids are in good condition. He/she ensures that these aids comply with the State and local laws, and in accordance with the Federal Aviation Administration (Wells and Young, 2004).
In order to ensure safe landing and taking off without any incursions, all airports must have landing aids. These include various markings and signs that direct the pilot on the runway and taxiway. Lighting also helps the pilots to be able to see the runway clearly especially at night and during bad weather conditions.
There are also other navigation aids which give the pilot specific runway information. The airport manager should ensure that all the necessary landing aids are available on the runway and taxiways and that they are in a good condition and unambiguous. He/she should ensure that the runway/taxiway lighting is in good condition. This will ensure that all airport incursions are avoided.
Ashford, N. J., Mumayiz, S. and Wright, P.H. (2011). Airport engineering: Planning, design and Development of 21st century airports. USA: John Wiley and Sons.
Horonjeff, R., McKelvey, F. and Sproule, W. (2010). Planning and Design of Airports. USA: McGraw-Hill.
Stanton, M., Ashford, N. and Moore, C.A. (1998). Airport operations. USA: McGraw-Hill Professional.
Steon, H. (2002). Runways and taxiways. Web.
Wells, A. T. and Young, S. B. (2004). Airport planning & management. USA: McGraw-Hill.