Runway
Overview
 

According to ICAO a runway is a "defined rectangular area on a land aerodrome
Aerodrome
An aerodrome, airdrome or airfield is a term for any location from which aircraft flight operations take place, regardless of whether they involve cargo, passengers or neither...

 prepared for the landing
Landing
thumb|A [[Mute Swan]] alighting. Note the ruffled feathers on top of the wings indicate that the swan is flying at the [[Stall |stall]]ing speed...

 and take-off of aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...

." Runways may be a man-made surface (often asphalt
Asphalt concrete
Asphalt concrete is a composite material commonly used in construction projects such as road surfaces, airports and parking lots. It consists of asphalt and mineral aggregate mixed together, then laid down in layers and compacted...

, concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...

, or a mixture of both) or a natural surface (grass
Sod
Sod or turf is grass and the part of the soil beneath it held together by the roots, or a piece of thin material.The term sod may be used to mean turf grown and cut specifically for the establishment of lawns...

, dirt
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

, gravel
Gravel
Gravel is composed of unconsolidated rock fragments that have a general particle size range and include size classes from granule- to boulder-sized fragments. Gravel can be sub-categorized into granule and cobble...

, ice
Ice
Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...

, or salt
Salt
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...

).
Runways are named by a number between 01 and 36, which is generally one tenth of the magnetic azimuth of the runway's heading
Course (navigation)
In navigation, a vehicle's course is the angle that the intended path of the vehicle makes with a fixed reference object . Typically course is measured in degrees from 0° clockwise to 360° in compass convention . Course is customarily expressed in three digits, using preliminary zeros if needed,...

: a runway numbered 09 points east (90°), runway 18 is south (180°), runway 27 points west (270°) and runway 36 points to the north (360° rather than 0°).
Encyclopedia

According to ICAO a runway is a "defined rectangular area on a land aerodrome
Aerodrome
An aerodrome, airdrome or airfield is a term for any location from which aircraft flight operations take place, regardless of whether they involve cargo, passengers or neither...

 prepared for the landing
Landing
thumb|A [[Mute Swan]] alighting. Note the ruffled feathers on top of the wings indicate that the swan is flying at the [[Stall |stall]]ing speed...

 and take-off of aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...

." Runways may be a man-made surface (often asphalt
Asphalt concrete
Asphalt concrete is a composite material commonly used in construction projects such as road surfaces, airports and parking lots. It consists of asphalt and mineral aggregate mixed together, then laid down in layers and compacted...

, concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...

, or a mixture of both) or a natural surface (grass
Sod
Sod or turf is grass and the part of the soil beneath it held together by the roots, or a piece of thin material.The term sod may be used to mean turf grown and cut specifically for the establishment of lawns...

, dirt
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

, gravel
Gravel
Gravel is composed of unconsolidated rock fragments that have a general particle size range and include size classes from granule- to boulder-sized fragments. Gravel can be sub-categorized into granule and cobble...

, ice
Ice
Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...

, or salt
Salt
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...

).

Orientation and dimensions

Runways are named by a number between 01 and 36, which is generally one tenth of the magnetic azimuth of the runway's heading
Course (navigation)
In navigation, a vehicle's course is the angle that the intended path of the vehicle makes with a fixed reference object . Typically course is measured in degrees from 0° clockwise to 360° in compass convention . Course is customarily expressed in three digits, using preliminary zeros if needed,...

: a runway numbered 09 points east (90°), runway 18 is south (180°), runway 27 points west (270°) and runway 36 points to the north (360° rather than 0°). When taking off from or landing on runway 09, a plane would be heading 90° (east). However, runways in North America that lie within the Northern Domestic Airspace
Canadian airspace
Canadian airspace is the region of navigable airspace above the surface of the Earth that falls within a region roughly defined by the Canadian land mass, the Canadian arctic, the Canadian archipelago, and areas of the high seas....

 of Canada are numbered relative to true north
True north
True north is the direction along the earth's surface towards the geographic North Pole.True geodetic north usually differs from magnetic north , and from grid north...

 because proximity to the magnetic North Pole makes the magnetic declination
Magnetic declination
Magnetic declination is the angle between magnetic north and true north. The declination is positive when the magnetic north is east of true north. The term magnetic variation is a synonym, and is more often used in navigation...

 large. A runway can normally be used in both directions, and is named for each direction separately: e.g., "runway 33" in one direction is "runway 15" when used in the other. The two numbers always differ by 18 (= 180°).
If there is more than one runway pointing in the same direction (parallel runways), each runway is identified by appending Left (L), Center (C) and Right (R) to the number — for example, Runways One Five Left (15L), One Five Center (15C), and One Five Right (15R). Runway Zero Three Left (03L) becomes Runway Two One Right (21R) when used in the opposite direction (derived from adding 18 to the original number for the 180 degrees when approaching from the opposite direction).

At large airports with more than three parallel runways (for example, at Los Angeles
Los Angeles International Airport
Los Angeles International Airport is the primary airport serving the Greater Los Angeles Area, the second-most populated metropolitan area in the United States. It is most often referred to by its IATA airport code LAX, with the letters pronounced individually...

, Detroit Metropolitan Wayne County
Detroit Metropolitan Wayne County Airport
Detroit Metropolitan Wayne County Airport , usually called Detroit Metro Airport, Metro Airport locally, or simply DTW, is a major international airport covering in Romulus, Michigan, a suburb of Detroit. It is Michigan's busiest airport....

, Hartsfield-Jackson Atlanta
Hartsfield-Jackson Atlanta International Airport
Hartsfield–Jackson Atlanta International Airport , known locally as Atlanta Airport, Hartsfield Airport, and Hartsfield–Jackson, is located seven miles south of the central business district of Atlanta, Georgia, United States...

, Denver
Denver International Airport
Denver International Airport , often referred to as DIA, is an airport in Denver, Colorado. By land size, at , it is the largest international airport in the United States, and the third largest international airport in the world after King Fahd International Airport and Montréal-Mirabel...

, Dallas-Fort Worth
Dallas-Fort Worth International Airport
Dallas/Fort Worth International Airport is located between the cities of Dallas and Fort Worth, Texas, and is the busiest airport in the U.S. state of Texas...

, John F. Kennedy International Airport
John F. Kennedy International Airport
John F. Kennedy International Airport is an international airport located in the borough of Queens in New York City, about southeast of Lower Manhattan. It is the busiest international air passenger gateway to the United States, handling more international traffic than any other airport in North...

 and Orlando
Orlando International Airport
Orlando International Airport is a major international airport located southeast of the central business district of Orlando. It is the second busiest airport in Florida, after Miami International Airport...

) some runway identifiers are shifted by 10 degrees to avoid the ambiguity that would result with more than three parallel runways. For example, in Los Angeles, this system results in Runways 6L, 6R, 7L, and 7R, even though all four runways are exactly parallel (approximately 69 degrees). At Dallas-Fort Worth
Dallas-Fort Worth International Airport
Dallas/Fort Worth International Airport is located between the cities of Dallas and Fort Worth, Texas, and is the busiest airport in the U.S. state of Texas...

, there are five parallel runways, named 17L, 17C, 17R, 18L, and 18R, all oriented at a heading of 175.4 degrees.

For clarity in radio communications, each digit in the runway name is pronounced individually: runway three six, runway one four, etc. A leading zero, for example in "runway zero six" or "runway zero one left", is included for International Civil Aviation Organization
International Civil Aviation Organization
The International Civil Aviation Organization , pronounced , , is a specialized agency of the United Nations. It codifies the principles and techniques of international air navigation and fosters the planning and development of international air transport to ensure safe and orderly growth...

 (ICAO) and some United States military
United States armed forces
The United States Armed Forces are the military forces of the United States. They consist of the Army, Navy, Marine Corps, Air Force, and Coast Guard.The United States has a strong tradition of civilian control of the military...

 airports (such as Edwards Air Force Base
Edwards Air Force Base
Edwards Air Force Base is a United States Air Force base located on the border of Kern County, Los Angeles County, and San Bernardino County, California, in the Antelope Valley. It is southwest of the central business district of North Edwards, California and due east of Rosamond.It is named in...

). However in the United States at most civil aviation
Civil aviation
Civil aviation is one of two major categories of flying, representing all non-military aviation, both private and commercial. Most of the countries in the world are members of the International Civil Aviation Organization and work together to establish common standards and recommended practices...

 airports, the leading zero is often dropped. This also includes some military airfields such as Cairns Army Airfield
Cairns Army Airfield
Cairns Army Airfield is a military airport forming a part of Fort Rucker, in Dale County, Alabama, USA. It is owned by the United States Army. The airfield is south of the town of Daleville, which sits between it and the main post.-History:...

. This American anomaly may lead to inconsistencies in conversations between American pilots and controllers in other countries. It is very common in a country such as Canada for a controller to clear an incoming American aircraft to, for example, Runway 04, and the pilot read back the clearance as Runway 4. In flight simulation programs
Flight simulator
A flight simulator is a device that artificially re-creates aircraft flight and various aspects of the flight environment. This includes the equations that govern how aircraft fly, how they react to applications of their controls and other aircraft systems, and how they react to the external...

 those of American origin might apply U.S. usage to airports around the world. For example Runway 05 at Halifax will appear on the program as the single digit 5 rather than 05.
Runway designations change over time because the magnetic poles slowly drift on the Earth's surface and the magnetic bearing
Magnetic bearing
A magnetic bearing is a bearing which supports a load using magnetic levitation. Magnetic bearings support moving machinery without physical contact; for example, they can levitate a rotating shaft and permit relative motion with very low friction and no mechanical wear...

 will change. Depending on the airport location and how much drift takes place, it may be necessary over time to change the runway designation. As runways are designated with headings rounded to the nearest 10 degrees, this will affect some runways more than others. For example, if the magnetic heading of a runway is 233 degrees, it would be designated Runway 23. If the magnetic heading changed downwards by 5 degrees to 228, the Runway would still be Runway 23. If on the other hand the original magnetic heading was 226 (Runway 23), and the heading decreased by only 2 degrees to 224, the runway should become Runway 22. Because the drift itself is quite slow, runway designation changes are uncommon, and not welcomed, as they require an accompanying change in aeronautical chart
Aeronautical chart
An aeronautical chart is a map designed to assist in navigation of aircraft, much as nautical charts do for watercraft, or a roadmap for drivers...

s and descriptive documents. When runway designations do change, especially at major airports, it is often changed at night as taxiway
Taxiway
A taxiway is a path on an airport connecting runways with ramps, hangars, terminals and other facilities. They mostly have hard surface such as asphalt or concrete, although smaller airports sometimes use gravel or grass....

 signs need to be changed and the huge numbers at each end of the runway need to be repainted to the new runway designators. In July 2009 for example, London Stansted Airport
London Stansted Airport
-Cargo:-Statistics:-Infrastructure:-Terminal and satellite buildings:Stansted is the newest passenger airport of all the main London airports. The terminal is an oblong glass building, and is separated in to three areas: Check-in concourse, arrivals and departures...

 in the United Kingdom changed its runway designations from 05/23 to 04/22 after dark.

For fixed-wing aircraft
Fixed-wing aircraft
A fixed-wing aircraft is an aircraft capable of flight using wings that generate lift due to the vehicle's forward airspeed. Fixed-wing aircraft are distinct from rotary-wing aircraft in which wings rotate about a fixed mast and ornithopters in which lift is generated by flapping wings.A powered...

 it is advantageous to perform take-offs and landings into the wind to reduce takeoff roll and reduce the ground speed
Ground speed
Ground speed is the speed of an aircraft relative to the ground. Information displayed to passengers through the entertainment system often gives the aircraft groundspeed rather than airspeed....

 needed to attain flying speed
Airspeed
Airspeed is the speed of an aircraft relative to the air. Among the common conventions for qualifying airspeed are: indicated airspeed , calibrated airspeed , true airspeed , equivalent airspeed and density airspeed....

. Larger airports usually have several runways in different directions, so that one can be selected that is most nearly aligned with the wind. Airports with one runway are often constructed to be aligned with the prevailing wind
Prevailing winds
Prevailing winds are winds that blow predominantly from a single general direction over a particular point on Earth's surface. The dominant winds are the trends in direction of wind with the highest speed over a particular point on the Earth's surface. A region's prevailing and dominant winds...

.

Runway dimensions vary from as small as 245 m (804 ft) long and 8 m (26 ft) wide in smaller general aviation
General aviation
General aviation is one of the two categories of civil aviation. It refers to all flights other than military and scheduled airline and regular cargo flights, both private and commercial. General aviation flights range from gliders and powered parachutes to large, non-scheduled cargo jet flights...

 airports, to 5500 m (18,045 ft) long and 80 m (262 ft) wide at large international airport
International airport
An international airport is any airport that can accommodate flights from other countries and are typically equipped with customs and immigration facilities to handle these flights to and from other countries...

s built to accommodate the largest jets
Jet airliner
A jet airliner is an airliner that is powered by jet engines. This term is sometimes contracted to jetliner or jet.In contrast to today's relatively fuel-efficient, turbofan-powered air travel, first generation jet airliner travel was noisy and fuel inefficient...

, to the huge 11917 m (39,098 ft) x 274 m (899 ft) lake bed runway 17/35 at Edwards Air Force Base
Edwards Air Force Base
Edwards Air Force Base is a United States Air Force base located on the border of Kern County, Los Angeles County, and San Bernardino County, California, in the Antelope Valley. It is southwest of the central business district of North Edwards, California and due east of Rosamond.It is named in...

 in California – a landing site for the retired Space Shuttle
Space Shuttle
The Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...

.

Placement and grouping

Two runways pointing in the same direction are classed as dual or parallel runways depending on the separation distance. In some countries, flight rules mandate that only one runway may be used at a time under certain conditions (usually adverse weather
Weather
Weather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the troposphere, just below the stratosphere. Weather refers, generally, to day-to-day temperature and precipitation activity, whereas climate...

) if the parallel runways are too close to each other.

Declared distances

TORA
Takeoff Run Available – The length of runway declared available and suitable for the ground run of an airplane taking off.


TODA
Takeoff Distance
Distance
Distance is a numerical description of how far apart objects are. In physics or everyday discussion, distance may refer to a physical length, or an estimation based on other criteria . In mathematics, a distance function or metric is a generalization of the concept of physical distance...

 Available
– The length of the takeoff run available plus the length of the clearway, if clearway is provided. 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 which is declared available and suitable for the ground run of an airplane landing.


EDA
Emergency Distance Available – LDA (or TORA) plus a stopway.

Sections of a runway


  • 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, 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
    Jet blast
    Jet blast is the phenomenon of rapid air movement produced by the jet engines of aircraft, particularly on or before takeoff.A large jet-engined aircraft can produce winds of up to 100 mph up to 200 feet behind it at 40% maximum rated power...

     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
    Rejected takeoff
    A rejected takeoff or RTO is the situation in which it is decided to abort the takeoff of an airplane...

     or a take-off 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
    Taxiing
    Taxiing refers to the movement of an aircraft on the ground, under its own power, in contrast to towing or push-back where the aircraft is moved by a tug...

    , 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
    Displaced threshold
    A displaced threshold is a runway threshold located at a point other than the physical beginning or end of the runway. The portion of the runway so displaced may be used for takeoff but not for landing...

     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.


History

The first runway lighting appeared in 1930 at Cleveland Municipal Airport
Cleveland Hopkins International Airport
Cleveland Hopkins International Airport is a public airport located nine miles southwest of the central business district of Cleveland, a city in Cuyahoga County, Ohio, United States. The airport lies just within the city limits of Cleveland...

 (now known as Cleveland Hopkins International Airport) in Cleveland, Ohio
Cleveland, Ohio
Cleveland is a city in the U.S. state of Ohio and is the county seat of Cuyahoga County, the most populous county in the state. The city is located in northeastern Ohio on the southern shore of Lake Erie, approximately west of the Pennsylvania border...

. 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 which allow night landings. Seen from the air, runway lights form an outline of the runway. A particular runway may have some or all of the following.
  • Runway End Identification Lights
    Runway End Identification Lights
    Runway end identifier lights are installed at many airports 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...

    (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
    Runway Edge Lights
    Runway Edge Lights are used to outline the edges of runways during periods of darkness or restricted visibility conditions. These light systems are classified according to the intensity they are capable of producing:...

    – white elevated lights that run the length of the runway on either side. On precision instrument runways, the edge-lighting becomes yellow in the last 2000 ft (610 m) of the runway, or last half 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 3000 ft (914 m), alternate white and red for next 2000 ft (610 m) and red for last 1000 ft (305 m).

  • Touchdown Zone Lights (TDZL) – rows of white light bars (with three in each row) at 100 ft (30 m) intervals on either side of the centerline over the first 3000 ft (914 m) (or to the midpoint, whichever is less) of the runway.

  • 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 about runway centerline to the position of first centerline light beyond holding position on taxiway.

  • Taxiway Centerline Lead-On Lights – installed the same way as taxiway centerline lead-off Lights.

  • Land and Hold Short Lights – a row of white pulsating lights installed across the runway to indicate hold short position on some runways which are facilitating land and hold short operations
    Land and hold short operations
    Land and Hold Short Operations is an aeronautical term for operations that involve aircraft landing and holding short of an intersecting runway, taxiway or some other designated point on a runway...

     (LAHSO).

  • Approach Lighting System
    Approach Lighting System
    An approach lighting system, or ALS, is a lighting system installed on the approach end of an airport runway and consisting of a series of lightbars, strobe lights, or a combination of the two that extends outward from the runway end...

    (ALS) – a lighting system installed on the approach end of an airport runway and consists of a series of lightbars, strobe light
    Strobe light
    A strobe light or stroboscopic lamp, commonly called a strobe, is a device used to produce regular flashes of light. It is one of a number of devices that can be used as a stroboscope...

    s, or a combination of the two that extends outward from the runway end.


According to Transport Canada
Transport Canada
Transport Canada is the department within the government of Canada which is responsible for developing regulations, policies and services of transportation in Canada. It is part of the Transportation, Infrastructure and Communities portfolio...

'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
Runway Status Lights
Runway Status Lights is a fully automatic advisory safety system as a part of an ongoing effort to explore new technologies to increase safety during airport ground operations.-Development:...

, 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 1400 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
Control tower
A control tower, or more specifically an Air Traffic Control Tower , is the name of the airport building from which the air traffic control unit controls the movement of aircraft on and around the airport. Control towers are also used to control the traffic for other forms of transportation such...

, a Flight Service Station
Flight service station
A Flight Service Station is an air traffic facility that provides information and services to aircraft pilots before, during, and after flights, but unlike air traffic control , is not responsible for giving instructions or clearances or providing separation...

 or another designated authority. Some airports/airfields (particularly uncontrolled ones
Non-towered airport
A non-towered airport, sometimes referred to as an uncontrolled airport, is an airport with no operating tower, or air traffic control unit...

) are equipped with Pilot Controlled Lighting
Pilot Controlled Lighting
Pilot Controlled Lighting , also known as Aircraft Radio Control of Aerodrome Lighting or Pilot Activated Lighting , is a system which allows aircraft pilots to control the lighting of an airport or airfield's approach lights, runway edge lights, and taxiways via radio. At some airfields, the...

, 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
Windsock
A windsock is a conical textile tube designed to indicate wind direction and relative wind speed. Windsocks typically are used at airports and at chemical plants where there is risk of gaseous leakage...

 beside a landing strip.

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 thousands of feet remaining, so 7 will indicate 7000 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, 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 1000 ft (305 m) mark (known as an aiming point, sometimes installed at 1500 ft (457 m)). They provide horizontal position guidance to planes on instrument approach via Non-directional beacon
    Non-directional beacon
    A non-directional beacon is a radio transmitter at a known location, used as an aviation or marine navigational aid. As the name implies, the signal transmitted does not include inherent directional information, in contrast to other navigational aids such as low frequency radio range, VHF...

     (NDB), VHF omnidirectional range
    VHF omnidirectional range
    VOR, short for VHF omnidirectional radio range, is a type of radio navigation system for aircraft. A VOR ground station broadcasts a VHF radio composite signal including the station's identifier, voice , and navigation signal. The identifier is typically a two- or three-letter string in Morse code...

     (VOR), Global Positioning System
    Global Positioning System
    The Global Positioning System is a space-based global navigation satellite system that provides location and time information in all weather, anywhere on or near the Earth, where there is an unobstructed line of sight to four or more GPS satellites...

    , 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), 1000 ft (305 m)/1500 ft (457 m), 2000 ft (610 m), 2500 ft (762 m), and 3000 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 all 3-stripe and 2-stripe touchdown zones for precision runways are replaced with one-stripe touchdown zones.
  • In Australia, precision runways consist of only an aiming point and one 1-stripe touchdown zone. Furthermore, many non-precision and visual runways lack an aiming point.
  • In some Latin America
    Latin America
    Latin America is a region of the Americas where Romance languages  – particularly Spanish and Portuguese, and variably French – are primarily spoken. Latin America has an area of approximately 21,069,500 km² , almost 3.9% of the Earth's surface or 14.1% of its land surface area...

    n countries like Colombia
    Colombia
    Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...

    , Ecuador
    Ecuador
    Ecuador , officially the Republic of Ecuador is a representative democratic republic in South America, bordered by Colombia on the north, Peru on the east and south, and by the Pacific Ocean to the west. It is one of only two countries in South America, along with Chile, that do not have a border...

     and Peru
    Peru
    Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....

     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 which end the zone is associated.

Runway safety

Types of runway safety
Air safety
Air safety is a term encompassing the theory, investigation and categorization of flight failures, and the prevention of such failures through regulation, education and training. It can also be applied in the context of campaigns that inform the public as to the safety of air travel.-United...

 incidents include:
  • Runway excursion - an incident involving only a single aircraft, where it makes an inappropriate exit from the runway.
  • Runway overrun - a type of excursion where the aircraft is unable to stop before the end of the runway (e.g. Air France Flight 358
    Air France Flight 358
    Air France Flight 358, a flight from Paris, France, to Toronto, Canada, using an Airbus A340 airliner, departed Paris without incident at 11:53 UTC 2 August 2005, later touching down on runway 24L-06R at Toronto Pearson International Airport at 20:01 UTC...

    ).
  • Runway incursion
    Runway incursion
    A runway incursion is an incident where an unauthorized aircraft, vehicle or person is on a runway. This adversely affects runway safety, as it creates the risk that an airplane taking off or landing will collide with the object...

     - an incident involving incorrect presence of a vehicle, person or another aircraft on the runway (e.g. Tenerife disaster).
  • Runway confusion - an aircraft makes use of the wrong runway for landing or take-off (e.g. Singapore Airlines Flight 006
    Singapore Airlines Flight 006
    Singapore Airlines Flight 006 was a scheduled passenger flight from Singapore Changi Airport to Los Angeles International Airport via Chiang Kai-shek Airport in Taiwan...

    ).

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
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...

 . Although certain airports have used reinforcement in concrete pavements, this is generally found to be unnecessary, with the exception of expansion joint
Expansion joint
An expansion joint or movement joint is an assembly designed to safely absorb the heat-induced expansion and contraction of various construction materials, to absorb vibration, to hold certain parts together, or to allow movement due to ground settlement or earthquakes...

s across the runway where a dowel
Dowel
A dowel is a solid cylindrical rod, usually made of wood, plastic or metal. In its original manufactured form, dowel is called dowel rod.Dowel rod is employed in numerous, diverse applications. It is used to form axles in toys, as detents on gymnastics grips, as knitting needles, as structural...

 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 asphalt
Asphalt
Asphalt or , also known as bitumen, is a sticky, black and highly viscous liquid or semi-solid that is present in most crude petroleums and in some natural deposits, it is a substance classed as a pitch...

ic 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
Bearing capacity
In geotechnical engineering, bearing capacity is the capacity of soil to support the loads applied to the ground. The bearing capacity of soil is the maximum average contact pressure between the foundation and the soil which should not produce shear failure in the soil...

 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 (25.4 cm) 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
Coefficient
In mathematics, a coefficient is a multiplicative factor in some term of an expression ; it is usually a number, but in any case does not involve any variables of the expression...

 known as the K value
Hooke's law
In mechanics, and physics, Hooke's law of elasticity is an approximation that states that the extension of a spring is in direct proportion with the load applied to it. Many materials obey this law as long as the load does not exceed the material's elastic limit. Materials for which Hooke's law...

. 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
California Bearing Ratio
The California bearing ratio is a penetration test for evaluation of the mechanical strength of road subgrades and basecourses. It was developed by the California Department of Transportation before World War II....

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
Undercarriage
The undercarriage or landing gear in aviation, is the structure that supports an aircraft on the ground and allows it to taxi, takeoff and land...

. 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, every effort is made to minimize the stresses imparted to the pavement by aircraft. 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
Portland cement
Portland cement is the most common type of cement in general use around the world because it is a basic ingredient of concrete, mortar, stucco and most non-specialty grout...

 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
Frost heaving
Frost heaving results from ice forming beneath the surface of soil during freezing conditions in the atmosphere. The ice grows in the direction of heat loss , starting at the freezing front or boundary in the soil...

, 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
Airfield rubber removal
Airfield rubber removal, also known as runway rubber removal, is the use of high pressure water, abrasives, chemicals and/or other mechanical means to remove the rubber that builds up on airport landing strips...

 or hydrocleaning
Hydrocleaning
Hydrocleaning, high pressure cleaning or waterblasting is the use of water propelled at high speeds to clean surfaces and materials. By focusing and pressurizing the water stream, the force generated can remove, for example:...

 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
    Asphalt
    Asphalt or , also known as bitumen, is a sticky, black and highly viscous liquid or semi-solid that is present in most crude petroleums and in some natural deposits, it is a substance classed as a pitch...

  • BIT: Bitumenous Asphalt or Tarmac
  • BRI: Brick
    Brick
    A brick is a block of ceramic material used in masonry construction, usually laid using various kinds of mortar. It has been regarded as one of the longest lasting and strongest building materials used throughout history.-History:...

    s (no longer in use, covered with Asphalt or Concrete now)
  • CLA: Clay
    Clay
    Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...

  • COM: Composite
  • CON: Concrete
    Concrete
    Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...

  • COP: Composite
  • GRS: Grass
    Grass
    Grasses, or more technically graminoids, are monocotyledonous, usually herbaceous plants with narrow leaves growing from the base. They include the "true grasses", of the Poaceae family, as well as the sedges and the rushes . The true grasses include cereals, bamboo and the grasses of lawns ...

     or earth not graded or rolled
  • COR: Coral
    Coral
    Corals are marine animals in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.A coral "head" is a colony of...

     (Coral reef structures)
  • GRE: Graded or rolled earth, Grass on graded earth
  • GVL: Gravel
    Gravel
    Gravel is composed of unconsolidated rock fragments that have a general particle size range and include size classes from granule- to boulder-sized fragments. Gravel can be sub-categorized into granule and cobble...

  • LAT: Laterite
    Laterite
    Laterites are soil types rich in iron and aluminium, formed in hot and wet tropical areas. Nearly all laterites are rusty-red because of iron oxides. They develop by intensive and long-lasting weathering of the underlying parent rock...

  • ICE: Ice
    Ice
    Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...

  • MAC: Macadam
    Macadam
    Macadam is a type of road construction pioneered by the Scotsman John Loudon McAdam in around 1820. The method simplified what had been considered state-of-the-art at that point...

  • PEM: Partially Concrete, Asphalt or Bitumen-bound Macadam
  • PER: Permanent Surface, Details unknown
  • PSP: Marsden Matting
    Marsden Matting
    Marsden Matting is standardized, perforated steel matting material originally developed by the United States at the Waterways Experiment Station shortly before World War II, primarily for the rapid construction of temporary runways and landing strips...

     (Derived from Pierced/Perforated Steel Planking)
  • SAN: Sand
    Sand
    Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...

  • SNO: Snow
    Snow
    Snow is a form of precipitation within the Earth's atmosphere in the form of crystalline water ice, consisting of a multitude of snowflakes that fall from clouds. Since snow is composed of small ice particles, it is a granular material. It has an open and therefore soft structure, unless packed by...

  • U: Unknown surface


Water runways do not have a type code as they don't have physical markings, and are thus not registered as specific runways.

Active runway

The active runway is the runway at an airport that is in use for takeoffs and landings. Since takeoffs and landings are usually done as close to "into the wind
Wind
Wind is the flow of gases on a large scale. On Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space...

" (see headwind) as possible, wind direction generally determines the active runway.

Selection of the active runway, however, depends on a number of factors. At a non-towered airport, pilots usually select the runway most nearly aligned with the wind, but they are not obliged to use that particular runway. For example, a pilot arriving from the east may elect to land straight in to an east-west runway despite a minor tailwind
Tailwind
A tailwind is a wind that blows in the direction of travel of an object, while a headwind blows against the direction of travel. A tailwind increases the object's speed and reduces the time required to reach its destination, while a headwind has the opposite effect...

 or significant crosswind
Crosswind
A crosswind is any wind that has a perpendicular component to the line or direction of travel. In aviation, a crosswind is the component of wind that is blowing across the runway making landings and take-offs more difficult than if the wind were blowing straight down the runway...

, in order to expedite his arrival, although it is recommended to always fly a regular traffic pattern
Airfield traffic pattern
An airfield traffic pattern is a standard path followed by aircraft when taking off or landing, while maintaining visual contact with the airfield....

 to more safely merge with other aircraft.

At controlled airports, the active is usually determined by a tower supervisor. However, there may be constraints, such as policy from the airport manager (calm wind runway selection, for example, or noise abatement guidelines) that dictate an active runway selection that is not the one most nearly aligned with the wind.

At major airports with multiple runways, the active could be any of a number of runways. For example, when O'Hare (ORD) is landing on 27L and 32L, departures use 28 and 32R, thus making four active runways. When they are landing on 14R and 22R, departures use 22L and 9R, and occasionally a third arrival runway, 14L, will be employed, bringing the active runway count to five.

At major airports, the active runway is based on weather conditions (visibility
Visibility
In meteorology, visibility is a measure of the distance at which an object or light can be clearly discerned. It is reported within surface weather observations and METAR code either in meters or statute miles, depending upon the country. Visibility affects all forms of traffic: roads, sailing...

 and ceiling
Ceiling (cloud)
- ICAO :The height above the ground or water of the base of the lowest layer of cloud below 6000 meters covering more than halfthe sky.- United Kingdom :...

, as well as wind, and runway conditions such as wet/dry or snow covered), efficiency (ORD can land more aircraft on 14R/32L than they can on 9R/27L), traffic demand (when a heavy departure rush is scheduled, a runway configuration that optimizes departures vs arrivals may be desirable), and time of day (ORD is obliged to use runway 9R/27L during the hours of roughly midnight to 6 a.m. due to noise abatement).

London Heathrow Airport
London Heathrow Airport
London Heathrow Airport or Heathrow , in the London Borough of Hillingdon, is the busiest airport in the United Kingdom and the third busiest airport in the world in terms of total passenger traffic, handling more international passengers than any other airport around the globe...

 in the United Kingdom has two runways which are parallel to each other, they are designated 09L/27R and 09R/27L. They are used in segregated alternate mode which means one runway is used only for arrivals and the other is only used for departures. The present pattern provides for one runway to be used by landing aircraft from 06:00 until 15:00 and then arrivals will switch to the other runway from 15:00 until after the last departure, after which landing aircraft use the first runway again until 06:00. However, on Sunday each week the runway used before midnight continues to be used for landings until 06:00. This means early morning arrivals before 06:00 use a different runway on successive weeks and that the runways used by landing aircraft before and after 15:00 also alternate on a weekly basis. This only applies to westerly operations as landing aircraft always use runway 09L.

Runway length

A runway of at least 6000 ft (1,828.8 m) in length is usually adequate for aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...

 weights below approximately 200000 lb (90,718.5 kg). Larger aircraft including widebodies
Wide-body aircraft
A wide-body aircraft is a large airliner with two passenger aisles, also known as a widebody aircraft or twin-aisle aircraft. The typical fuselage diameter is . In the typical wide-body economy cabin, passengers are seated seven to ten abreast, allowing a total capacity of 200 to 850 passengers...

 will usually require at least 8000 ft (2,438.4 m) at sea level and somewhat more at higher altitude
Altitude
Altitude or height is defined based on the context in which it is used . As a general definition, altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The reference datum also often varies according to the context...

 airports. International widebody flights, which carry substantial amounts of fuel and are therefore heavier, may also have landing requirements of 10000 ft (3,048 m) or more and takeoff requirements of 13000 ft (3,962.4 m)+.

At sea level
Sea level
Mean sea level is a measure of the average height of the ocean's surface ; used as a standard in reckoning land elevation...

, 10000 ft (3,048 m) can be considered an adequate length to land virtually any aircraft. For example, at O'Hare International
O'Hare International Airport
Chicago O'Hare International Airport , also known as O'Hare Airport, O'Hare Field, Chicago Airport, Chicago International Airport, or simply O'Hare, is a major airport located in the northwestern-most corner of Chicago, Illinois, United States, northwest of the Chicago Loop...

, when landing simultaneously on 22R and 28 or parallel 27L, it is routine for arrivals from the Far East
Far East
The Far East is an English term mostly describing East Asia and Southeast Asia, with South Asia sometimes also included for economic and cultural reasons.The term came into use in European geopolitical discourse in the 19th century,...

 which would normally be vectored for 22R (7500 ft (2,286 m)) or 27L (7967 ft (2,428 m)) to request 28 (13001 ft (3,963 m)). It is always accommodated, although occasionally with a delay. Another example is that the Luleå Airport
Luleå Airport
Luleå Airport is located about 5 km south-southeast of Luleå, Sweden, near the village of Kallax. The airport had a 995,581 passenger total in 2008, and is thus Sweden's sixth largest airport...

 in Sweden was extended to 10990 ft (3,350 m) to allow any fully loaded freight aircraft to take off.

An aircraft will need a longer runway at a higher altitude due to decreased density
Density
The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...

 of air at higher altitudes, which reduces lift and engine power, requiring higher take-off and landing speed. An aircraft will also require a longer runway in hotter or more humid conditions (see density altitude
Density altitude
Density altitude is the altitude in the International Standard Atmosphere at which the air density would be equal to the actual air density at the place of observation, or, in other words, the height when measured in terms of the density of the air rather than the distance from the ground...

). Most commercial aircraft carry manufacturer's tables showing the adjustments required for a given temperature.

See also

  • Instrument landing system
    Instrument Landing System
    An instrument landing system is a ground-based instrument approach system that provides precision guidance to an aircraft approaching and landing on a runway, using a combination of radio signals and, in many cases, high-intensity lighting arrays to enable a safe landing during instrument...

     (ILS)
  • Aviation
    Aviation
    Aviation is the design, development, production, operation, and use of aircraft, especially heavier-than-air aircraft. Aviation is derived from avis, the Latin word for bird.-History:...

  • Engineered materials arrestor system
    Engineered Materials Arrestor System
    An engineered materials arrestor system or engineered materials arresting system is a bed of engineered materials built at the end of a runway. Engineered materials are defined in FAA Advisory Circular No 150/5220-22A as "high energy absorbing materials of selected strength, which will reliably...

  • List of airports
  • Pavement Classification Number
    Pavement Classification Number
    The Pavement Classification Number is an International Civil Aviation Organization standard used in combination with the Aircraft Classification Number to indicate the strength of a runway, taxiway or airport ramp...

     (PCN)
  • Precision Approach Path Indicator
    Precision Approach Path Indicator
    Precision approach path Indicator is a visual aid that provides guidance information to help a pilot acquire and maintain the correct approach to an aerodrome or an airport. It is generally located beside the runway approximately 300 metres beyond the landing threshold of the runway...

  • Runway safety area
    Runway safety area
    A runway safety area or runway end safety area is defined as "the surface surrounding the runway prepared or suitable for reducing the risk of damage to airplanes in the event of an undershoot, overshoot, or excursion from the runway."Past standards called for the RSA to extend only 60m from the...

  • Runway visual range
    Runway visual range
    Runway Visual Range is a term used in aviation meteorology to define the distance over which a pilot of an aircraft on the centreline of the runway can see the runway surface markings delineating the runway or identifying its centre line...

  • Visual Approach Slope Indicator
    Visual Approach Slope Indicator
    The visual approach slope indicator is a system of lights on the side of an airport runway threshold that provides visual descent guidance information during the approach to a runway...

  • Tabletop runway
    Tabletop runway
    A tabletop runway is a runway that is located on the top of a plateau with either end stopping abruptly and dropping into deep gorges. These type of runways create an optical illusion that requires a very precise approach from the pilot....

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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