Đường băng
Bách khoa toàn thư mở Wikipedia
Đường băng là một phần của sân bay, gọi chung các đường cất hạ cánh, đường lăn chính, đường lăn phụ, đường tắt (đường lăn cao tốc, đường lăn nối) và sân chuẩn bị cất cánh, hạ cánh của máy bay.
Thành phần chủ yếu của sân bay cố định là kích thước và chất lượng đường băng, phụ thuộc vào cấp sân bay và loại máy bay có thể cất hạ cánh. Mặt đường băng thường được làm bằng bê tông hoặc bê tông nhựa, mặt đường băng dã chiến bằng đất gia cố hoặc lát các tấm kim loại.
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[sửa] Hướng và kích thước
Đường băng được đánh số theo hướng từ trường mà nó hướng tới, làm tròn tới 10 và chia cho 10. Mỗi số sẽ được đọc riêng biệt để không nhầm lẫn khi giao tiếp bằng radio. Thí dụ, "Đường băng Ba Sáu" sẽ có hướng 360 độ (nghĩa là hướng Bắc), "Đường băng Chín" có thể dùng để chỉ đường băng có hướng 94 độ (nghĩa là gần hướng Đông), và "Đường băng Một Bảy" cho hướng 168 độ. Mỗi đường băng có thể dùng cả 2 hướng, và do đó nó có 2 số, mỗi số cách nhau 180°. Vì vậy, Đường băng Một Không (100°) trở thành đường băng Hai Tám (280°) khi dùng hướng ngược lại, và Đường băng Một Tám (180°) trở thành Đường băng Ba Sáu (360°).
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 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.
[sửa] "Các bộ phận" của một đường băng
[sửa] Dải đường chạy
Đây là một vùng quang đãng xung quanh đường băng. Nó phải không có bất kỳ một vật cản nào có thể cản trở việc bay hay chạy trên mặt đất của máy bay, dù nó không cần thiết phải ở tình trạng tốt. Nó được đánh dấu bởi các cột và/hay vật hình nón trắng. Thông thường đây là một vùng bề mặt cỏ mọc tự nhiên.
[sửa] Blast pads
Blast pads 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 may also be constructed as emergency space for aborted take-offs. 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.
[sửa] Điểm dời chuyển
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.
[sửa] Chiếu sáng đường băng
At bigger airports, runways use a standard lighting system to allow night landings. Seen from a landing plane, the runway starts with a strip of green lights (known as threshold lights) at the near end and stops with a strip of red lights at the far end. The runway itself is framed with white elevated edge lights, as opposed to the blue elevated edge lights of a taxiway. 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. The sides of the runway are marked by lines of bright white lights. Larger runways may have another line of dimmer white lights running down the centerline. According to Transport Canada's regulations, the runway-edge lights must be visible for at least 2 miles.
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.
[sửa] Dấu hiệu đường băng
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.
There are three types of runways:
[sửa] Visual Runways
Found at small airstrips, visual runways are usually just a strip of grass, gravel, or unmarked asphalt or concrete. They may also be marked asphalt or concrete. There are no markings on a visual runway; it is usually just 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.
[sửa] 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.
[sửa] 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.
[sửa] 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 175 ft/270 m of the midpoint are omitted, to avoid pilot confusion over which end the marking belongs to.
[sửa] Pavement
The choice of material used to construct the runway depends on the use and the local ground conditions. Generally speaking, 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, because of unstable ground conditions, that major settlements of the runway will occur over the years, 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.
The development of the pavement design proceeds along a number of paths. Exploratory borings are taken to determine the subgrade condition, and based upon relative bearing capacity of the subgrade, different pavement specifications are established. Typically, for heavy-duty commercial aircraft, the pavement thickness, no matter what the top surface, varies from as little as 10 in. (25 cm) to as much as 4 ft (1.2 m), including subgrade.
Historically, airport pavements have been designed by two methods. The first, Westergaard, is based upon 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 upon 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 predicated upon melding of these two design theories; they are empirical in nature and are not reliable. Another, 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. However, in the final analysis, if plane weights continue to increase as they have in the past, it will be necessary to provide substantially stronger pavements than those that are generally in use in Europe and the United States. Sometimes it is possible to reinforce a pavement for higher loading by applying an overlay of asphaltic concrete or portland cement concrete that is suitably bonded to the original slab.
Posttensioning 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.
[sửa] Đường băng hoạt động
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 as "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).
[sửa] Các đường băng dài nhất
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 (
30°33′N 97°06′E) - 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]
- Shigatse Peace Airport (日喀則和平機場), Tibet, China (
29°21′N 89°19′E) - 16,404 ft (5000 m) concrete, not in use, renovation starts in 2007 with projected completion in 2009. [3]
- Embraer Gaviao Peixoto, Brazil (
21°46′S 48°24′W) - 16,295 ft (4967 m) asphalt [4]
- Upington, South Africa (
28°24′S 21°16′E) - 16,076 ft (4900 m) asphalt [5]
- Denver International Airport, Colorado, USA (
39°52′N 104°40′W) - 16,000 ft (4877 m) concrete [6]
- Edwards Air Force Base, California, USA (
34°54′N 117°53′W) - 15,013 ft (4576 m) concrete [7] 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 (
34°44′N 120°35′W) - 15,000 ft (4572 m) concrete [8] 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 (
28°37′N 80°41′W) - 15,000 ft (4572 m) concrete [9] As a military installation, the runway is not normally available for use by air carrier or civilian aircraft.
40°38′N 73°47′W) - 14,572 ft (4441 m) concrete [10]
- McCarran International Airport, Las Vegas, Nevada, USA (
36°4′N 115°9′W) - 14,510 ft (4423 m) asphalt [11]
- Eielson Air Force Base, Alaska, USA (
64°40′N 147°6′W) - 14,500 ft (4420 m) concrete [12] As a military installation, the runway is not normally available for use by air carrier or civilian aircraft.
- Kirtland Air Force Base, New Mexico, USA (
35°2′N 106°37′W) - 13,793 ft (4204 m) [13] This military runway is also used jointly by the Albuquerque International Sunport.
- Rick Husband Amarillo International Airport, Texas, USA (
35°13′N 101°42′W) - 13,502 ft (4115 m) concrete [14]
- Colorado Springs Municipal Airport, Colorado, USA - 13,501 ft (4115 m) concrete [15]
- Dallas/Ft. Worth International Airport - Four parallel north/south runways of 13,400 ft (4084 m) concrete [16]. This is the only commercial airport in the world (as of June 2006) with four serviceable runways longer than 4000 m.
- Hurghada International Airport, Hurghada, Egypt 27°10′41.94″N, 33°47′57.97″E - 13,124 ft (4000 m, only 45 m wide) asphalt [17]
- El Alto International Airport, La Paz, Bolivia (
16°30′S 68°11′W) Runway 10/28 - 13,123 ft (4000 m) paved concrete at 13,125 ft (4001 m) altitude. [18]
13°41′N 100°44′E) - 13,120 ft (4000 m) asphalt [19]
41°59′N 87°54′W) - 13,000 ft (3962 m) concrete [20]
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