According to the International Civil Aviation Organization (ICAO), a runway is a “defined rectangular area on a land aerodrome prepared for the landing and takeoff of aircraft”. Runways may be a man-made surface (often asphalt, concrete, or a mixture of both) or a natural surface (grass, dirt, gravel, ice, or salt).
Structural design
Surface / substructure
Depending on the load, which is exposed to a runway in operation, different design principles come into consideration. While light aircraft can take off and land on simple short mowed grass tracks, most heavy commercial aircraft are unable to do so because their bogies would deform the ground too much. Most commercial airports therefore have at least one paved runway. The thickness of the covering extends from 25 cm up to 130 cm for heavily loaded railways as in the new southern runway of Berlin Brandenburg Airport. is used as covering either asphalt or concretefor use. Due to its longer service life of up to 40 years, concrete is mainly used at large airfields, the cheaper asphalt with a service life of 15 to 20 years at smaller airfields. Surfaces must have good frictional behavior in all expected weather conditions and be free from irregularities to ensure the best possible flight of the aircraft. For concrete runways, the soil is often grooved in the transverse direction (“grooving”), so that the water can flow away and no aquaplaning occurs.
Unpaved slopes consist of sod, gravel, dry soil or sand. Also, they are built as flat as possible and mowed briefly in grassy growth to ensure unimpeded taxiing of the aircraft. After heavy rainfall, they can be unusable. To prevent this, the ground can either be drained before the construction of the airfield or strengthened with inserted grid material (for example, at the airfield Speck-Fehraltorf in Switzerland).
The carrying capacity of runways can be classified with the Pavement Classification Number.
Also at landing sites for seaplanes one speaks in part of runways.
Length and Width
The length and width of the runway depends on the “design aircraft”. This is the aircraft most frequently operated on the corresponding runway. For larger aircraft, if necessary, a possible exemption will be granted. Thus, the use of large aircraft on intercontinental routes can lead to a very high maximum takeoff weight, which in turn may require a runway length of 3000 to 4000 m. Failure to provide the required length will result in aircraft restrictions on their weight and consequently their range. Location-related factors also influence the minimum length of the slopes. A reduced engine performance and a deteriorated buoyancy created by:
high temperatures at the location (warm air expands and is therefore thinner than cold). Therefore, the lengths have to be increased in percentage terms depending on the aerodrome reference temperature. This corresponds to the average daily high temperature of the hottest month of the year.
the high position of an airfield over the sea, resulting in lower air pressure.
The width of the runways is also influenced by the technical data of the aircraft. For most common, large aircraft types, the standard width of many 45 meter tracks is sufficient. A large-capacity aircraft such as the A380 requires a track width of 60 meters. However, given A380 Airport Compatibility Group an exemption for 45 m (AACG) for certain airfields wide runways.
At the military airfields, the runways are also built according to the types of aircraft they are to be used for. Many jet airplanes need a track length of about 2.5 kilometers, whereas numerous (especially smaller) propeller aircraft manage with very short distances.
For some ultralight aircraft, a take-off or landing distance of well under 100 m is sufficient. Ultralight airfields typically have grass tracks about 250 m in length.The longest railway in the world in civil aviation has a length of 5500 meters (14/32) at Qamdo-Bamda airport (ICAO code: ZUBD) and is located in the Tibet Autonomous Region (PRC) at 4334 m above sea level. The shortest rail line of an international jetliner commercial airport is Yap Airport (Micronesia) at 1469 meters. The Brazilian airport Rio de Janeiro-Santos Dumont, which is also used by jet planes, even has a length of only 1323 meters. Immediately around the runway around the security strip is approved by law. Depending on the size of the runway and use (instrument flight (IFR) / visual flight (VFR)), this has a width of 30 m (VFR) to the right and left of the track up to 150 m (IFR, code number 3 and 4) each Side and must be leveled and obstacle-free. Within the strip only allowed to be an obstacle from air traffic control reasons Gleitwegsendemastand the monitor mast are located. The strip begins at 30 m (VFR) to 60 m (IFR) in front of the track and ends at 30 m or 60 m after the end of the run. In front of and behind the strip is the RESA (Runway end safety area). The RESA has a length of min. 30 m (VFR) up to 90 m (IFR, recommended by ICAO 240 m at IFR). The width is that of the strip, but at least twice the width of the web.
The point on the track at which a landing aircraft must touch down at the earliest is called the landing threshold (English Threshold hereinafter). The marking of this threshold looks like a crosswalk. This should be distinguished from the real touchdown point, which may be more or less far below the threshold depending on the length of the track, the aircraft and the wind conditions.
Depending on the obstacle situation, an open space (Clearway) may be set up at the end of the course. Their length results in the TODA (take off distance available) with the existing take-off run TORA. Likewise, a stopway could possibly be set up. This stopway adds to the existing TORA and gives the maximum ASDA (accelerate stop distance available).
Targeting
While in the early days of aviation the airfields in Germany were mostly round and could be used in every direction, today the runways are built in such a way that they are adapted in their direction to the local wind conditions. Aircraft always take off and land against the wind to generate maximum lift and to shorten the takeoff or landing distance. For this reason, the main line is ideally built after the main wind direction. Slight deviations from this can be caused by geographical conditions and approach proceduresbecome necessary. The location of other railways should be chosen so that the usability factor of the airport is at least 95%. If there is often such a strong crosswind at one site that the main line can not be operated permanently, there should be a crosswind in a crossed orientation. The smaller the aircraft that is to use the web, the lower the permissible transverse wind component. To plan the runway orientations, observations of the wind distribution should be made several times daily for at least five years in order to ensure the highest possible usability of the runways. [8th]
A particularly difficult situation arises when shear wind situations (English windshear) prevail on the runway. Shear winds are up-and-down rifts diverted through the ground, which appear as strong gusts. In the weather radar you can see bad weather areas well in advance and fly around, but shear winds are not displayed.
However, there is now a so-called windshear warning system, which detects not only a wind shear when it is currently occurring (caused by more than 15 kts vertical or 500 fpm horizontal deviation (Def.)), But also a so-called “Predictive Windshear System”, which also recognizes large upstream and downstream fields in front of the aircraft. If the risk becomes too great, you have to land at another airport.
Configurations
Meteorological and geographical factors at airfields require different configurations of runways. Possible configurations are the one-way, the parallel, the Kreuzbahn and the V-Bahn system as well as combinations thereof. The capacity, as the maximum possible number of flight movements is determined, but not exclusively by the railway system. Other capacity-limiting influencing factors are wind and visibility, delays in heavy traffic, grading, existing navigation aids, aircraft mix, approach and departure procedures, and the capacity of the aprons and taxiways, The capacity thus determined is not an absolute value but a simulated approximation.
The simplest variant is the one-way system, where there is only one runway in the main wind direction. It is v. a. used by smaller airfields that have no unfavorable cross winds. Depending on the ground equipment, this system can handle 180,000 to 230,000 aircraft movements a year.
In a parallel track system, there are two or more tracks in a parallel arrangement. As with the one-way system, this requires that there are hardly any strong headwinds at the locationthat would restrict the operation exist. The distance and the offset of the webs from each other are decisive for how many movements the capacity increases. This distance, which decides the operating mode, is measured by the distance of the track center lines from each other. There is a distinction between near, far and middle distance (“close”, “far”, “intermediate”). A distance of over 1,035 m means that the tracks can be operated independently under any conditions (exception: threshold offset of the two tracks). This results in a doubled capacity of a maximum of 120 movements per hour or 310,000 to 380,000 aircraft movements per year. At a distance of less than 1,035 m, no independent operation of both trains is possible.
The cross-web system is two tracks of different orientation, which intersect at one point. The different orientation of the webs is caused by winds from different directions. If only tracks of an orientation were present at such locations, this would lead to a capacity restriction under strong crosswind conditions. The tracks of different orientation ensures that a train always corresponds to the wind conditions. At low wind speeds even both lanes can be operated. The capacity is dependent on the cross-web system in addition to the operating direction strongly on the location of the intersection of both tracks. The smaller the distance of the intersection from the ends of the webs, the higher the capacity of the system.
The V-train system is similar in configuration to the cross-train system, but the two tracks of different geographic direction do not intersect. The lane with the prevailing operating direction is also referred to as the main lane, and the other accordingly as the cross-wind lane. In strong wind, the capacity is limited, since in this case only one lane can be operated. In contrast, both lanes can be used simultaneously in light wind. Higher capacity is achieved when the movements take place away from the V. In this case, up to 100 flight movements can take place every hour.
A future concept is the circular “Endless Runway”, which is designed to significantly reduce land use, noise and the costs of future runways.
Declared distances
Runway dimensions vary from as small as 245 m (804 ft) long and 8 m (26 ft) wide in smaller general aviation airports, to 5,500 m (18,045 ft) long and 80 m (262 ft) wide at large international airports built to accommodate the largest jets, to the huge 11,917 m × 274 m (39,098 ft × 899 ft) lake bed runway 17/35 at Edwards Air Force Base in California – developed as a landing site for the Space Shuttle.
Takeoff and landing distances available are given using one of the following terms:
TORA
Takeoff Run Available – The length of runway declared available and suitable for the ground run of an airplane taking off.
TODA
Takeoff Distance Available – The length of the takeoff run available plus the length of the clearway, if clearway is provided.
(The clearway length allowed must lie within the aerodrome or airport boundary. According to the Federal Aviation Regulations and Joint Aviation Requirements (JAR) TODA is the lesser of TORA plus clearway or 1.5 times TORA).
ASDA
Accelerate-Stop Distance Available – The length of the takeoff run available plus the length of the stopway, if stopway is provided.
LDA
Landing Distance Available – The length of runway that is declared available and suitable for the ground run of an airplane landing.
EMDA
Emergency Distance Available – LDA (or TORA) plus a stopway.
Sections of a runway
There exist standards for runway markings.
The runway thresholds are markings across the runway that denote the beginning and end of the designated space for landing and takeoff under non-emergency conditions.
The runway safety area is the cleared, smoothed and graded area around the paved runway. It is kept free from any obstacles that might impede flight or ground roll of aircraft.
The runway is the surface from threshold to threshold, which typically features threshold markings, numbers, and centerlines, but not overrun areas at both ends.
Blast pads, also known as overrun areas or stopways, are often constructed just before the start of a runway where jet blast produced by large planes during the takeoff roll could otherwise erode the ground and eventually damage the runway. Overrun areas are also constructed at the end of runways as emergency space to slowly stop planes that overrun the runway on a landing gone wrong, or to slowly stop a plane on a rejected takeoff or a takeoff gone wrong. Blast pads are often not as strong as the main paved surface of the runway and are marked with yellow chevrons. Planes are not allowed to taxi, take off or land on blast pads, except in an emergency.
Displaced thresholds may be used for taxiing, takeoff, and landing rollout, but not for touchdown. A displaced threshold often exists because obstacles just before the runway, runway strength, or noise restrictions may make the beginning section of runway unsuitable for landings. It is marked with white paint arrows that lead up to the beginning of the landing portion of the runway.
Runway markings
There are runway markings and signs on most large runways. Larger runways have a distance remaining sign (black box with white numbers). This sign uses a single number to indicate the remaining distance of the runway in thousands of feet. For example, a 7 will indicate 7,000 ft (2,134 m) remaining. The runway threshold is marked by a line of green lights.
There are three types of runways:
Visual runways are used at small airstrips and are usually just a strip of grass, gravel, ice, asphalt, or concrete. Although there are usually no markings on a visual runway, they may have threshold markings, designators, and centerlines. Additionally, they do not provide an instrument-based landing procedure; pilots must be able to see the runway to use it. Also, radio communication may not be available and pilots must be self-reliant.
Non-precision instrument runways are often used at small- to medium-size airports. These runways, depending on the surface, may be marked with threshold markings, designators, centerlines, and sometimes a 1,000 ft (305 m) mark (known as an aiming point, sometimes installed at 1,500 ft (457 m)). They provide horizontal position guidance to planes on instrument approach via Non-directional beacon, VHF omnidirectional range, Global Positioning System, etc.
Precision instrument runways, which are found at medium- and large-size airports, consist of a blast pad/stopway (optional, for airports handling jets), threshold, designator, centerline, aiming point, and 500 ft (152 m), 1,000 ft (305 m)/1,500 ft (457 m), 2,000 ft (610 m), 2,500 ft (762 m), and 3,000 ft (914 m) touchdown zone marks. Precision runways provide both horizontal and vertical guidance for instrument approaches.
National variants
In Australia, Canada, Japan, the United Kingdom, as well as some other countries or territories (Hong Kong and Macau) all 3-stripe and 2-stripe touchdown zones for precision runways are replaced with one-stripe touchdown zones.
In some South American countries like Colombia, Ecuador and Peru one 3-stripe is added and a 2-stripe is replaced with the aiming point.
Some European countries replace the aiming point with a 3-stripe touchdown zone.
Runways in Norway have yellow markings instead of the usual white ones. This also occurs in some airports in Japan, Sweden, and Finland. The yellow markings are used to ensure better contrast against snow.
Runways may have different types on each end. To cut costs, many airports do not install precision guidance equipment on both ends. Runways with one precision end and any other type of end can install the full set of touchdown zones, even if some are past the midpoint. Runways with precision markings on both ends omit touchdown zones within 900 ft (274 m) of the midpoint, to avoid ambiguity over the end with which the zone is associated.
Runway lighting
The first runway lighting appeared in 1930 at Cleveland Municipal Airport (now known as Cleveland Hopkins International Airport) in Cleveland, Ohio. A line of lights on an airfield or elsewhere to guide aircraft in taking off or coming in to land or an illuminated runway is sometimes also known as a Flare Path.
Technical specifications
Runway lighting is used at airports that allow night landings. Seen from the air, runway lights form an outline of the runway. A runway may have some or all of the following:
Runway end identifier lights (REIL) – unidirectional (facing approach direction) or omnidirectional pair of synchronized flashing lights installed at the runway threshold, one on each side.
Runway end lights – a pair of four lights on each side of the runway on precision instrument runways, these lights extend along the full width of the runway. These lights show green when viewed by approaching aircraft and red when seen from the runway.
Runway edge lights – white elevated lights that run the length of the runway on either side. On precision instrument runways, the edge-lighting becomes amber in the last 2,000 ft (610 m) of the runway, or last third of the runway, whichever is less. Taxiways are differentiated by being bordered by blue lights, or by having green centre lights, depending on the width of the taxiway, and the complexity of the taxi pattern.
Runway centerline lighting system (RCLS) – lights embedded into the surface of the runway at 50 ft (15 m) intervals along the runway centerline on some precision instrument runways. White except the last 900 m (3,000 ft): alternate white and red for next 600 m (1,969 ft) and red for last 300 m (984 ft).
Touchdown zone lights (TDZL) – rows of white light bars (with three in each row) at 30 or 60 m (98 or 197 ft) intervals on either side of the centerline for 900 m (3,000 ft).
Taxiway centerline lead-off lights – installed along lead-off markings, alternate green and yellow lights embedded into the runway pavement. It starts with green light at about the runway centerline to the position of first centerline light beyond the Hold-Short markings on the taxiway.
Taxiway centerline lead-on lights – installed the same way as taxiway centerline lead-off Lights, but directing airplane traffic in the opposite direction.
Land and hold short lights – a row of white pulsating lights installed across the runway to indicate hold short position on some runways that are facilitating land and hold short operations (LAHSO).
Approach lighting system (ALS) – a lighting system installed on the approach end of an airport runway and consists of a series of lightbars, strobe lights, or a combination of the two that extends outward from the runway end.
According to Transport Canada’s regulations, the runway-edge lighting must be visible for at least 2 mi (3 km). Additionally, a new system of advisory lighting, runway status lights, is currently being tested in the United States.
The edge lights must be arranged such that:
the minimum distance between lines is 75 ft (23 m), and maximum is 200 ft (61 m);
the maximum distance between lights within each line is 200 ft (61 m);
the minimum length of parallel lines is 1,400 ft (427 m);
the minimum number of lights in the line is 8.
Control of lighting system
Typically the lights are controlled by a control tower, a flight service station or another designated authority. Some airports/airfields (particularly uncontrolled ones) are equipped with pilot-controlled lighting, so that pilots can temporarily turn on the lights when the relevant authority is not available. This avoids the need for automatic systems or staff to turn the lights on at night or in other low visibility situations. This also avoids the cost of having the lighting system on for extended periods. Smaller airports may not have lighted runways or runway markings. Particularly at private airfields for light planes, there may be nothing more than a windsock beside a landing strip.
Runway safety
Types of runway safety incidents include:
Runway excursion – an incident involving only a single aircraft, where it makes an inappropriate exit from the runway (e.g. Thai Airways Flight 679).
Runway overrun (also known as an overshoot) – a type of excursion where the aircraft is unable to stop before the end of the runway (e.g. Air France Flight 358, TAM Airlines 3054).
Runway incursion – an incident involving incorrect presence of a vehicle, person or another aircraft on the runway (e.g. Tenerife airport disaster (Pan American World Airways Flight 1736 and KLM Flight 4805)).
Runway confusion – an aircraft makes use of the wrong runway for landing or takeoff (e.g. Singapore Airlines Flight 006, Western Airlines Flight 2605).
Runway undershoot – an aircraft that lands short of the runway (e.g. British Airways Flight 38, Asiana Airlines Flight 214).
Pavement
The choice of material used to construct the runway depends on the use and the local ground conditions. For a major airport, where the ground conditions permit, the most satisfactory type of pavement for long-term minimum maintenance is concrete. Although certain airports have used reinforcement in concrete pavements, this is generally found to be unnecessary, with the exception of expansion joints across the runway where a dowel assembly, which permits relative movement of the concrete slabs, is placed in the concrete. Where it can be anticipated that major settlements of the runway will occur over the years because of unstable ground conditions, it is preferable to install asphaltic concrete surface, as it is easier to patch on a periodic basis. For fields with very low traffic of light planes, it is possible to use a sod surface. Some runways also make use of salt flat runways.
For pavement designs, borings are taken to determine the subgrade condition, and based on the relative bearing capacity of the subgrade, the specifications are established. For heavy-duty commercial aircraft, the pavement thickness, no matter what the top surface, varies from 10 in (250 mm) to 4 ft (1 m), including subgrade.
Airport pavements have been designed by two methods. The first, Westergaard, is based on the assumption that the pavement is an elastic plate supported on a heavy fluid base with a uniform reaction coefficient known as the K value. Experience has shown that the K values on which the formula was developed are not applicable for newer aircraft with very large footprint pressures.
The second method is called the California bearing ratio and was developed in the late 1940s. It is an extrapolation of the original test results, which are not applicable to modern aircraft pavements or to modern aircraft landing gear. Some designs were made by a mixture of these two design theories. A more recent method is an analytical system based on the introduction of vehicle response as an important design parameter. Essentially it takes into account all factors, including the traffic conditions, service life, materials used in the construction, and, especially important, the dynamic response of the vehicles using the landing area.
Because airport pavement construction is so expensive, manufacturers aim to minimize aircraft stresses on the pavement. Manufacturers of the larger planes design landing gear so that the weight of the plane is supported on larger and more numerous tires. Attention is also paid to the characteristics of the landing gear itself, so that adverse effects on the pavement are minimized. Sometimes it is possible to reinforce a pavement for higher loading by applying an overlay of asphaltic concrete or portland cement concrete that is bonded to the original slab. Post-tensioning concrete has been developed for the runway surface. This permits the use of thinner pavements and should result in longer concrete pavement life. Because of the susceptibility of thinner pavements to frost heave, this process is generally applicable only where there is no appreciable frost action.
Pavement surface
Runway pavement surface is prepared and maintained to maximize friction for wheel braking. To minimize hydroplaning following heavy rain, the pavement surface is usually grooved so that the surface water film flows into the grooves and the peaks between grooves will still be in contact with the aircraft tires. To maintain the macrotexturing built into the runway by the grooves, maintenance crews engage in airfield rubber removal or hydrocleaning in order to meet required FAA friction levels.
Surface type codes
In aviation charts, the surface type is usually abbreviated to a three-letter code.
The most common hard surface types are asphalt and concrete. The most common soft surface types are grass and gravel.
* ASP Asphalt
* BIT Bitumenous asphalt or tarmac
* BRI Bricks (no longer in use, covered with asphalt or concrete now)
* CLA Clay
* COM Composite
* CON Concrete
* COP Composite
* COR Coral (fine crushed coral reef structures)
* GRE Graded or rolled earth, grass on graded earth
* GRS Grass or earth not graded or rolled
* GVL Gravel
* ICE Ice
* LAT Laterite
* MAC Macadam
* PEM Partially concrete, asphalt or bitumen-bound macadam
* PER Permanent surface, details unknown
* PSP Marston Matting (derived from pierced/perforated steel planking)
* SAN Sand
* SMT Sommerfeld Tracking
* SNO Snow
* U Unknown surface
Water runways do not have a type code as they do not have physical markings, and are thus not registered as specific runways.
Source from Wikipedia