Air Traffic Control in the USA
Kiểm soát đường hàng không ở Mỹ
A An accident that occurred in the skies over the Grand Canyon in 1956 resulted(dẫn tới) in the establishment(sự thành lập) of the Federal Aviation Administration (FAA)(Cục quản lí hàng không liên bang) to regulate and oversee the operation(vận hành, hoạt đông) of aircraft in the skies over the United States, which were becoming quite congested(chật chội). The resulting structure of air traffic control has greatly increased the safety of flight in the United States, and similar air traffic control procedures(thủ tục) are also in place over much of the rest of the world.
B Rudimentary(sơ bộ) air traffic control (АТС) existed well before the Grand Canyon disaster. As early as the 1920s, the earliest air traffic controllers manually(điều khiển bằng tay) guided aircraft in the vicinity(vùng lân cận) of the airports, using lights and flags, while beacons(đèn tín hiệu) and flashing lights were placed along cross-country routes(tuyến đường xuyên quốc gia) to establish the earliest airways(chiến tranh trên không). However, this purely(hoàn toàn) visual system was useless in bad weather, and, by the 1930s, radio communication was coming into use for АТС. The first region to have something approximating today’s АТС was New York City, with other major metropolitan(khu đô thị) areas following soon after.
C In the 1940s, АТС centres could and did take advantage of the newly developed radar and improved radio communication brought about by the Second World War, but the system remained(vẫn còn) rudimentary(thô sơ). It was only after the creation of the FAA that full-scale regulation of America’s airspace took place, and this was fortuitous(bất ngờ), for the advent(sự đến) of the jet engine(động cơ) suddenly resulted in a large number of very fast planes, reducing pilots’ margin of error(lỗi sai của phi công) and practically demanding some set of rules to keep everyone well separated and operating safely in the air.
D Many people think that АТС consists(bao gồm) of a row of controllers sitting in front of their radar screens at the nation’s airports, telling arriving and departing(khởi hành) traffic what to do. This is a very incomplete part of the picture. The FAA realised that the airspace over the United States would at any time have many different kinds of planes, flying for many different purposes, in a variety of weather conditions, and the same kind of structure was needed to accommodate(dàn xếp) all of them.
E To meet this challenge, the following elements(yếu tố) were put into effect. First, АТС extends(mở rộng) over virtually(gần như) the entire(toàn bộ) United States. In general, from 365m above the ground and higher, the entire country is blanketed(bao phủ) by controlled airspace. In certain(đặc biệt) areas, mainly near airports, controlled airspace extends down to 215m above the ground, and, in the immediate vicinity of an airport, all the way down to the surface. Controlled airspace is that airspace in which FAA regulations apply. Elsewhere, in uncontrolled airspace, pilots are bound by fewer regulations. In this way, the recreational(giải trí) pilot who simply wishes to go flying for a while without all the restrictions(giới hạn) imposed(chịu) by the FAA has only to stay in uncontrolled airspace, below 365m, while the pilot who does want the protection afforded(được cho) by АТС can easily enter the controlled airspace.
F The FAA then recognised two types of operating environments. In good meteorological(thuộc thời tiết) conditions, flying would be permitted under Visual Flight Rules (VFR), which suggests a strong reliance(tin cậy, phụ thuộc) on visual cues to maintain an acceptable(chấp nhận được) level of safety. Poor visibility necessitated a set of Instrumental Flight Rules (IFR), under which the pilot relied on altitude and navigational information(thông tin đường biển) provided by the plane’s instrument panel(bảng điều khiến) to fly safely. On a clear day, a pilot in controlled airspace can choose a VFR or IFR flight plan, and the FAA regulations were devised(phát minh, đưa ra) in a way which accommodates both VFR and IFR operations in the same airspace. However, a pilot can only choose to fly IFR if they possess(có) an instrument rating which is above and beyond(vượt quá) the basic pilot’s license(giấy phép) that must also be held.
G Controlled airspace is divided into several different types, designated by letters of the alphabet. Uncontrolled airspace is designated Class F, while controlled airspace below 5,490m above sea level and not in the vicinity of an airport is Class E. All airspace above 5,490m is designated Class A. The reason for the division of Class E and Class A airspace stems(bắt nguồn) from the type of planes operating in them. Generally, Class E airspace is where one finds general aviation(hàng không) aircraft (few of which can climb above 5,490m anyway), and commercial turboprop(phản lực) aircraft. Above 5,490m is the realm(vương quốc) of the heavy jets, since jet engines operate more efficiently(hiệu quả) at higher altitudes. The difference between Class E and A airspace is that in Class A, all operations are IFR, and pilots must be instrument-rated, that is, skilled and licensed in aircraft instrumentation. This is because АТС control of the entire(thành một khối) space is essential. Three other types of airspace, Classes D, С and B, govern(kiểm soát) the vicinity of airports. These correspond(tương đương) roughly(nhiều, mạnh) to small municipal(thuộc thành phố), medium-sized metropolitan and major metropolitan airports respectively(tương ứng), and encompass(bao gồm) an increasingly rigorous(khắt khe) set of regulations. For example, all a VFR pilot has to do to enter Class С airspace is establish two-way radio contact with АТС. No explicit(rõ ràng) permission from АТС to enter is needed, although the pilot must continue to obey(tuân lệnh) all regulations governing VFR flight. To enter Class В airspace, such as on approach(tiếp canahj) to a major metropolitan airport, an explicit АТС clearance(sự cho phép, thông qua) is required. The private pilot who cruises without permission into this airspace risks losing their license.