Runway
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A runway is a strip of land on an airport, on which aircraft can take off and land. Runways may be a prepared surface (often asphalt, concrete, or a mixture of both) or an unprepared surface (grass, dirt, or gravel).
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[edit] Orientation and dimensions
Runways are generally numbered according to the magnetic direction in which they point (referred to as the "runway heading"), rounded to the nearest ten degrees and then divided by ten. Each digit is pronounced separately for clarity in radio communications. For example, Runway Three Six would be aligned in roughly a 360 degrees direction (i.e. magnetic north), Runway Nine would be used for a runway with a 94 degree-alignment (i.e. close to magnetic east), and Runway One Seven for 168 degrees. Each runway can be used in either direction, and hence has two numbers, each 180° apart. Thus, Runway One Zero (100°) becomes Runway Two Eight (280°) when used in the opposite direction and Runway One Eight (180°) becomes Runway Three Six (360°). Runways in North America that lie within the Northern Domestic Airspace are, because of the magnetic north pole, usually numbered according to true north.
In United States civil aviation, numbers for runways less than 100° are often given as single digits; e.g. Runway Nine or Runway Four Right. In United States military and ICAO operations, numbers for runways less than 100° include the leading "zero", e.g. Runway Zero Two or Runway Zero One Left.
If there is more than one runway pointing in the same direction (parallel runways), each runway is identified by appending Left, Center and Right to the number — for example, Runways One Five Left (15L), One Five Center (15C), and One Five Right (15R). Runway Two Left (2L) becomes Runway Two Zero Right (20R) when used in the opposite direction.
At large airports with more than three parallel runways (for example, at Los Angeles International Airport in Los Angeles, California or Hartsfield-Jackson International Airport in Atlanta, Georgia), some runway identifiers are shifted by 10 degrees to avoid the ambiguity that would result with more than three parallel runways. In Los Angeles, this system results in Runways Six Left, Six Right, Seven Left, and Seven Right, even though all four runways are exactly parallel (approximately 69 degrees).
For fixed wing aircraft it is advantageous to perform take-offs and landings into the wind to reduce takeoff roll and reduce the ground speed needed to attain flying speed. 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.
Runway dimensions vary from as small as 800 feet (240 m) long and 25 feet (8 m) wide in smaller general aviation airports, to 16,000 feet (4,800 m) long and 250 feet (80 m) wide at large international airports built to accommodate large passenger jets. Runway dimensions are measured in feet in the United States and Canada, and meters are used elsewhere in the world.
[edit] "Sections" of a runway
[edit] Runway Strip
This is a cleared area around the runway itself. It is kept free from any obstacles that might impede flight or ground roll of aircraft, although it is not necessarily in good condition. It is marked with white cones and/or gables. It is usually left with a natural grass surface.
[edit] Blast pads/Overrun Area
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. They are also constructed as emergency space to slowly stop planes that overrun the runway on a landing gone wrong, or to slowy stop a plane on an aborted take-off or a take-off gone wrong. They are often not as strong as the main surface of the runway and are marked with yellow chevrons. It is illegal to taxi, take-off or land on them except in an emergency. Blast pads are suppose to be a minimum 1000ft long. The FAA has said that most airports don't meet that requirement.[citation needed]
[edit] Displaced threshold
The threshold of a runway is the point at the end of it. It is usually marked with white paint (or not at all on smaller runways). A displaced threshold (see diagram) is marked with arrows leading up to the threshold itself. A displaced threshold may be used for taxiing and takeoff but not for landing. This due to three main reasons: obstacles just before the runway, runway strength, or noise restrictions.
[edit] Runway lighting
Runway lighting is used at airports that wish to allow night landings. Seen from the air, runway lights form an outline of the runway. From a landing aircraft, the threshold is a strip of green lights (known as threshold lights) the far end is a strip of red lights. White elevated edge lights run the length of the runway on either side. Taxiways are differentiated by being bordered by blue lights. The centerline is often indicated by white lights, which may be coded alternately white and red and then purely red nearing the far end of the runway. Furthermore, many runways equipped with instrument landing systems feature touchdown zone lighting. This consists of rows of white light bars on either side of the centerline over the first 30 feet of the runway. According to Transport Canada's regulations, the runway-edge lights must be visible for at least 2 miles. Additionally, a new system of advisory lighting, Runway Status Lights, is being tested in 2006 in the United States.
The lights must be arranged such that:
- the minimum distance between lines is 75 feet, and maximum is 200 feet;
- the maximum distance between lights within each line is 200 feet;
- the minimum length of parallel lines is 1400 feet;
- the minimum number of lights in the line is 8.[1]
[edit] Runway markings
There are various runway markings and signs on any given runway. 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 7,000 feet remaining. The runway threshold is marked by a line of green lights.
Some airports/airfields (particularly uncontrolled ones) are equipped with Pilot Controlled Lighting, so that pilots can temporarily turn on the lights when they need them. 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 costs of having hundreds of lights on for extended periods.
Of course not all airports have lighted runways, and runways may not be marked at all. At small, particularly private airfields, there may be nothing more than a windsock, if that.
Runway Status Lights are being developed to give more information on runway movements.
There are three types of runways:
[edit] Visual Runways
Found at small airstrips, visual runways are usually just a strip of grass, gravel, asphalt or concrete. Although there are usually no markings on a visual runway there may have threshold markings, numbers, 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.
[edit] Non-precision runways
Often used at small-medium size airports, non-precision runways are always marked. They consist of threshold markings, numbers, centerlines, and sometimes an aiming point. They provide horizontal position guidance to planes on instrument approach via radio beacons.
[edit] Precision runways
Precision runways, found at medium and large size airports, consist of, in order, a blast pad/stopway (optional, for airports handling jets), threshold, number, centerline, one 3-stripe touchdown zone (All countries) or two three stripe touchdown zone (All except US), aiming point, two 2-stripe touchdown zones (All countries) or one 2-stripe touchdown zone (All except US), and two 1 stripe touchdown zones. They provide both horizontal and vertical guidance for instrument approaches.
[edit] Notes
- In Canada, Australia, 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 one 1-stripe touchdown zone, aiming point, and one 1-stripe touchdown zone. Furthermore, all non-precision and visual runways have no aiming point.
- Some European countries replace the aiming point with a 3-stripe touchdown zone.
- Runways may have different types on each end. Many real world airports do not install precision guidance equipment on both ends, in order to save money. 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. If a runway has Precision markings on both ends, touchdown zones within 900 ft/270 m of the midpoint are omitted, to avoid pilot confusion over which end the marking belongs to.
- Runways in Norway have yellow markings instead of the usual white ones.
[edit] Active runway
The active runway is the runway at an airport that is in current use for takeoffs and landings. Since takeoffs and landings are usually done as close to "into the wind" as possible, wind direction generally determines the active runway (or just the active in aviation slang).
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 or significant crosswind, in order to expedite his arrival, although it is recommended to always fly a regular traffic pattern 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 isn't 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 27R and 32L, departures use 27L and 32R, thus making four active runways. When they're landing on 14R and 22R, departures use 22L and 9L, 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 existing weather conditions (visibility and ceiling, as well as wind, and runway conditions such as wet/dry or snow covered), efficiency (ORD can land more aircraft on 14R-22R than they can on 27R-32L), 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 9L/27R during the hours of roughly midnight to 6 a.m. due to noise abatement).
[edit] Longest runways
Although runway length may be of some academic interest, in terms of usability for air carrier operations, a runway of at least 6,000 ft (1,820 m) in length is usually adequate for aircraft weights below approximately 200,000 lb (90,900 kg). Larger aircraft including widebodies (Boeing 747, 767, 777, and 787 (still in design)); Airbus A-340, A-330, A-350 (still in design), A-380 and A-310; McDonnell-Douglas DC-10 or MD-11; and the Lockheed L1011 will usually require at least 8,000 ft (2,430 m) at sea level and somewhat more at higher altitude airports. International widebody flights may also have landing requirements of 10,000 ft (3,048 m) or more and takeoff requirements of 13,000+ ft.
At sea level, 10,000 ft can be considered an adequate length to accommodate virtually any aircraft. For example, at ORD, when landing simultaneously on 22R and 27L or parallel 27R, it is routine for arrivals from the Far East which would normally be vectored for 22R (7,500 ft) or 27R (8,000 ft) to request 27L (10,000 ft). It is always accommodated, although occasionally with a delay.
Some of the longest runways include:
- Qamdo Bamda Airport (昌都邦達機場), Tibet, China () - 18,045 ft (5500 m) concrete, of which 13,779 ft (4200 m) currently meets 4D standard. Bamda's runway is also the highest in world, with altitude at 14,219 ft (4334 m). [1] [2]
- Ulyanovsk-Vostochny International Airport (Международный аэропорт Ульяновск-Восточный), Ulyanovsk, Russia () - 16,404 ft (5000 m) concrete [3] [4]
- Shigatse Peace Airport (日喀則和平機場), Tibet, China () - 16,404 ft (5000 m) concrete, not in use, renovation starts in 2007 with projected completion in 2009. [5]
- Embraer Gaviao Peixoto, Brazil () - 16,295 ft (4967 m) asphalt [6]
- Upington, South Africa () - 16,076 ft (4900 m) asphalt [7]
- Denver International Airport, Colorado, USA () - 16,000 ft (4877 m) concrete [8]
- Southern California Logistics Airport, Victorville, California, USA () - 15,050 ft (4587 m) asphalt/concrete [9]
- Edwards Air Force Base, California, USA () - 15,013 ft (4576 m) concrete [10] The famous dry lake bed "runways" are of considerable length (the longest is 39,000 feet by 900 feet), but have little improvement other than markings and are not comparable to other runways in this category. As a military installation, the runways are not normally available for use by air carrier or civilian aircraft.
- Vandenberg Air Force Base, California, USA () - 15,000 ft (4572 m) concrete [11] As a military installation, the runway is not normally available for use by air carrier or civilian aircraft.
- Kennedy Space Center, Shuttle Landing Field, Florida, USA () - 15,000 ft (4572 m) concrete [12] As a military installation, the runway is not normally available for use by air carrier or civilian aircraft.
- John F. Kennedy International Airport, New York, New York, USA () - 14,572 ft (4441 m) concrete [13]
- Arakkonam in India has the longest runway in South Asia (4500 meters) at INS Rajali, a naval Air base of the Indian Navy.
- McCarran International Airport, Las Vegas, Nevada, USA () - 14,510 ft (4423 m) asphalt [14]
- Eielson Air Force Base, Alaska, USA () - 14,500 ft (4420 m) concrete [15] As a military installation, the runway is not normally available for use by air carrier or civilian aircraft.
- Mandalay International Airport, Mandalay, Myanmar () - 14,003 ft (4,268 m) Southeast Asia's longest runway.
- Kirtland Air Force Base, New Mexico, USA () - 13,793 ft (4204 m) [16] This runway is used jointly with the Albuquerque International Sunport.
- Grant County International Airport, Moses Lake, Washington, USA () -13,503 ft (4,116 m) concrete/asphalt [17]
- Rick Husband Amarillo International Airport, Texas, USA () - 13,502 ft (4115 m) concrete [18]
- Colorado Springs Airport, Colorado, USA - 13,501 ft (4115 m) concrete [19] This runway is jointly used with Peterson Air Force Base
- Dallas-Fort Worth International Airport - Four parallel north/south runways of 13,400 ft (4084 m) concrete [20]. This is the only commercial airport in the world (as of June 2006) with four serviceable runways longer than 4000 m.
- El Alto International Airport, La Paz, Bolivia () Runway 10/28 - 13,123 ft (4000 m) paved concrete at 13,125 ft (4001 m) altitude. [21]
- Athens International Airport, Athens, Greece - 13,123 ft (4000m) asphalt [22]
- Hurghada International Airport, Hurghada, Egypt () - 13,123 ft (4000 m, only 45 m wide) asphalt [23]
- Galeão - Antônio Carlos Jobim International Airport, Rio de Janeiro, Brazil Runway 10/28 - 13,123 ft (4000 m) concrete [24]
- Kuala Lumpur International Airport, Kuala Lumpur, Malaysia () Runway 14L/32R and 14R/32L - 13,123 ft (4000 m) concrete [25]
- Singapore Changi Airport, Singapore ()- 13,123 ft (4000m) asphalt [26]
- Suvarnabhumi Airport, Bangkok/Samut Prakan, Thailand () - 13,123 ft (4000 m) asphalt [27]
- O'Hare International Airport, Chicago, Illinois, USA () - 13,000 ft (3962 m) concrete [28]
[edit] Notes
- ^ http://www.tc.gc.ca/CivilAviation/publications/tp14371/AGA/7-1.htm#7-8 Transport Canada Aeronautical Information Manual
