Методические указания по изучению английского языка для специальности 270205. 65 «автомобильные дороги и аэродромы»

From an aeronautical viewpoint, the basic requirement of an airport is that it have a relatively flat area of land sufficiently large to accommodate the runways and other facilities and that this area be in a locality free from such obstructions to air navigation as mountains and tall buildings.From the viewpoint of air-transport needs, airport sites must be sufficiently close to population centres. Environmental considerations, on the other hand, dictate that the site should be far enough away from urban centres that noise and other harmful effects on the population should be kept to acceptable levels. Furthermore, the airport should not destroy areas of natural beauty.

The most modest airport facility-with a single runway, an apron, and a building that serves simultaneously as terminal, administration area, and control tower-can comfortably be built on a site as small as 75 acres, since it requires only a flat, well-drained area sufficient to accommodate a short runway and its surrounding safety strip. Larger and more modern airport facilities, on the other hand, require multiple runways of extended length, extensive terminal apron areas, and large areas of land for parking and access roads. For such an airport, a minimum area of 3,000 acres is likely to be required. Several major airports-such as Dallas-Fort Worth International Airport in Texas, King Abdul Aziz International Airport near Jiddah, Saudi Arabia, and Charles de Gaulle Airport near Paris-are built on sites well in excess of this figure.
NEW WORDS & EXPRESSIONS

1. site - стройплощадка

2. environmental factor - фактор окружающей среды, экологический фактор

3. to evaluate - оценивать

4. requirement - требование

5. flat - плоский, ровный

6. to accommodate -обеспечивать, снабжать , вмещать

7. locality - местность; район, участок; край, место

8. free - свободный, вольный, независимый

9. obstruction - затруднение продвижения, преграждение прохода, заграждение

10. air navigation - воздушная навигация, аэронавигация

11. harmful - вредный, пагубный

12. to destroy - разрушать, рушить,

13. modest - скромный

14. safety strip - полоса безопасности

15. access road - подъездной путь

First, the operational capability of the site is assessed with respect to weather conditions such as wind, snow, ice, fog, and low visibility and also with respect to obstructions to air navigation around the airport, particularly on the approach and takeoff paths. The location of the facility in relation to air-traffic-controlled airspace is also important. In addition, there must be an evaluation of the capacity of the available land to accommodate the expected configuration of runways and other facilities. Flat or very gently undulating land is necessary, because runways must be constructed according to restrictions on maximum allowable slopes--which, in turn, are governed by aircraft performance on landing and takeoff.

Ground access to the airport is also considered. An evaluation is made of the distance from population centres, the regional highway infrastructure, public transport facilities (including railways), and the availability of land for parking. Development costs are also estimated, taking into account the nature of the terrain, soil and rock conditions, drainage requirements, and local land values.

The environmental consequences of an airport development rank very high in any site-selection procedure. The impact of aircraft noise on the neighbouring population is often the most significant environmental factor, but in many countries account must also be taken of the impact on the flora and fauna of the area, pollution through chemical runoff into local groundwater, the presence of endangered species or significant cultural sites, and even undesirable changes in land use. Many governments now require that environmental analyses of airport development projects include evaluations of population relocation, changes in employment patterns, and distortion of existing regional land use and transportation planning.

operational capability - работоспособность; эксплуатационные качества

assess - оценивать, определять

location - размещение; местоположение

airspace - воздушное пространство
Airfield layout and configuration

Operational requirements
It is obvious even to the most casual observer that there is a large variation in the appearance and layout of airport facilities. Simple airports designed to accommodate light aircraft are essentially similar, but, as airports become larger and more complex, accommodating more passengers and cargo, their individual requirements affect their layouts and ensure that each becomes recognizably different.

The principal determinants of airport layout are the number of runways and their orientation, the shape of the available site, and constraints at the site both on the ground and in the air. The location and orientation of runways is governed in turn by the need to avoid obstacles, particularly during landing and takeoff procedures. For the largest airports, obstacles to air navigation must be considered up to 10 miles (15 kilometres) from the runways. Runway configurations must also ensure that, for 95 percent of the time, aircraft can approach and take off without either crosswinds or tailwinds that would inhibit operations. At the smallest airports, light aircraft are unable to operate in crosswinds greater than 10 knots; at all airports, operation in tailwinds in excess of 10 knots is not recommended by aircraft manufacturers (10 knots, or nautical miles per hour, is equal to about 12 statute miles per hour or 19 kilometres per hour).

The operational capacity of an airport, which is usually defined as the maximum possible number of aircraft landings and takeoffs, is determined by the number of runways that are available for use at any one time. The vast majority of airports around the world have the simplest possible layout, a single runway. Where crosswinds would be high for an unacceptable proportion of operational time, a two-runway configuration is necessary, usually in the form of a main runway and an auxiliary crosswind runway. Depending on the shape of the site and the availability of land, the crosswind facility can take on a crossed configuration or an open or closed V layout. Where visibility is good and aircraft can operate under visual flight rules (VFR), operational capacity increases from the lowest level, crossed runways, through the closed V and open V configurations. However, in poor visibility or under certain conditions of very heavy air traffic, aircraft must operate under the strict instructions and rules of air traffic control and instrument operation; these are called instrument flight rules (IFR). Under such conditions, crosswind runways cannot be used simultaneously with main runways, so that the capacities of the crossed and V configurations are equivalent to that of a single runway.

An increase in operational capacity under VFR is possible with the use of a close parallel runway configuration. Most very large airports must be assured of adequate capacity even under IFR conditions, and this can be achieved by separating the parallel runways by a minimum of 5,000 feet (1,525 metres). This independent parallel configuration permits simultaneous independent landings and takeoffs on both runways. Munich Airport in Germany exemplifies this type of configuration. Even greater capacity is possible using a four-runway configuration of independent close parallels, as is the case at Los Angeles International Airport. With such a configuration, even under IFR, it is possible for two aircraft to land simultaneously while two other aircraft take off. A number of the world's largest airports have master plans that feature eight runways in the form of independent close parallels supplemented by other close parallels that are capable of crosswind operation. However, with passenger aircraft increasing in size, most can now operate in crosswinds of 20 knots and above. This reduces the likelihood that configurations with four crosswind runways will ever be constructed.

Parallel Runways Two parallel runways serve a major international airport. Narrow taxiways connect the runways and allow airplanes to move from the runway to the apron area near the terminal building, shown on the right. As jets leave the terminal, they travel along a taxiway to the end of a runway, where they wait in line for takeoff.

Intersecting Runways Some airports, like Louisville International Airport in Kentucky, have several intersecting runways. To coordinate traffic and ensure safety, air traffic controllers tell pilots which runways to use and notify them when it is safe to take off or land.

Until the introduction of heavy monoplane aircraft in the latter part of the 1930s, civil air-transport aircraft were able to operate from grass runways with takeoff distances of less than 650 yards. The advent of heavy aircraft such as the DC-3 required the provision of paved runways; at the same time, takeoff distances increased to more than 1,000 yards. The length requirements for runways continued to increase into the mid-1970s, when large civilian aircraft such as the Douglas DC-8 and some models of the Boeing 747 required almost 4,000 yards of runway at sea level. (Even longer runways were necessary at higher elevations or where high ambient air temperatures occurred during operations.) The trend toward increasing runway lengths caused many problems at existing civilian airports, where runways had to be extended in order to accommodate the new aircraft. Ultimately, pressure by airport operators and the development of turbofan jet engines arrested and finally reversed the trend. Since the 1970s, runway length requirements have actually decreased, and the takeoff and climb performance of civilian aircraft has improved substantially. This has brought a dual benefit in reducing the area of land required by an airport and also in reducing the area around the airport that is adversely affected by noise on takeoff.

At all but the smallest airports, pavements are now provided for runways, taxiways, aprons, and any other areas where aircraft are maneuvered. Pavements must be designed in such a way that they can bear the loads imposed by aircraft without failure. A pavement must be smooth and stable under conditions of loading during its expected or economic life. It should be free from dust and other particles that could be blown up and ingested into engines, and it must be capable of spreading and transmitting an aircraft's weight to the existing subsoil (or subgrade) in a manner that precludes subsoil failure. Another function of the pavement is to prevent weakening of the subsoil by moisture intrusion, especially from rainfall and frost.

Airfield pavements are of two types, rigid and flexible. Rigid pavements are constructed of portland cement concrete slabs resting on a prepared subbase of granular material or directly on a granular subgrade. Load is transmitted through the slabs to the underlying subgrade by flexure of the slabs. Flexible pavements are constructed of several thicknesses of asphalt or bituminous concrete layers overlying a base of granular material on a prepared subgrade. They spread the concentrated aircraft wheel loads throughout their depth until the load at the base of the pavement is less than the strength of the in situ soil. At all depths the strength of the pavement should be at least equal to the loads placed upon it by aircraft wheels. The choice of pavement type is often determined by economics. In some parts of the world, portland cement concrete is cheaper than asphalt; in other parts, the converse is true. For certain parts of the airfield, however, asphaltic concrete is an unsuitable material for pavement construction because of its vulnerability to damage by aviation fuel. Therefore, even at airports where flexible airfield pavements are generally in use, it is usual for concrete pavements to be used where aircraft stand on the aprons and at runway ends where fuel spillage is frequent.

Only the simplest airfields are designed for operations conducted under visual meteorological conditions (VMC). These facilities operate only in daylight, and the only guidance they are required to offer is a painted runway centreline and large painted numbers indicating the magnetic bearing of the runway. Larger commercial airports, on the other hand, must also operate in the hours of darkness and under instrument meteorological conditions (IMC), when horizontal visibility is 650 yards or less and the cloud base (or "decision height") is 65 yards or lower. In order to assist aircraft in approaches and takeoffs and in maneuvering on the ground, such airports are equipped with sophisticated radio navigational aids (navaids) and visual aids in the form of lighting and marking.

The most common form of navaid used for the approach phase of aircraft descent is the instrument landing system (ILS). This is a radio signal that is beamed along the centreline of the runway and at the correct angle of approach (usually 3 above the horizontal). The beam is intercepted by an approaching aircraft up to 15 miles from the threshold of the runway. Information is given concerning position above and below the glide slope and deviation to the right or left of centreline; consequently, the pilot is able to determine from cockpit instruments a deviation of the aircraft from the proper approach.Additional approach information is given visually to the pilot in the form of lighting approach aids. Two systems of approach aids are in use: the visual approach slope indicator system (VASIS) and the more modern precision approach path indicator (PAPI). Both work on the principle of guiding lights that show white when the pilot is above the proper glide slope and red when below.

Visual guidance to approaching aircraft is also provided by approach lighting systems, a configuration of high-intensity white lights running along the centreline of the runway and extending up to 650 yards beyond the threshold. At airfields where aircraft operate in very poor visibility, touchdown-zone lighting is provided over the first 1,000 yards from the runway threshold. These lights, set in patterns flush with the runway pavement, provide guidance up to the final moment of touchdown.The runway itself is strongly delineated by a variety of guidance light systems. The threshold is designated by a line of green lights, and the edges and centreline are delineated by white lights that shine toward the maneuvering aircraft at regular intervals. The pilot is warned of the approaching runway end by a line of red lights at the end of the usable pavement. Taxiways are delineated by blue edge lights and by green centreline lights that also appear at regular intervals.

Considerable additional visual guidance is given to pilots by painted markings on the runway. The form of marking indicates at a glance whether radio instrument guidance is available at any particular airfield. On precision instrument runways, the runway edges are indicated by painted lines, and distances along the runway from the threshold are indicated by pavement markings. In addition, touchdown-zone markings are painted on the pavement immediately after the threshold, providing vital visual guidance during the moments immediately before touchdown when all lighting may be obscured by fog.

Large airports are actually urban complexes in which high-population activity centres are closely associated with very extensive paved areas. Typically a large airport can, on a daily basis, handle more than 100,000 passengers and support a working population of over 50,000 employees. The sewage system of such an airport must cope with large daily flows of sanitary sewage effluent and, in addition, must accommodate runoff from rain and snow accumulating over several hundred acres of impervious pavement. The scale of the sewage problem at many large airports is such that some facilities have their own sewage treatment plants, especially for sanitary sewage. Because many airports are situated on low-lying ground, which is more likely to provide the flat land necessary for airstrips, the sewage system must often include extensive pumping facilities.

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