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A An accident that occurred in the skies over the Grand Canyon in 1956 resulted in the establishment of the Federal Aviation Administration (FAA) to regulate and oversee the operation of aircraft in the skies over the United States, which were becoming quite congested. A1956年在大峡谷上空发生的一起事故导致了联邦飞行委员会（FAA）的成立以规范及监督日渐拥挤的美国领空的飞行行为。 The resulting structure of air traffic control has greatly increased the safety of flight in the United States, and similar air trafficcontrol procedures are also in place over much of the rest of the world. 随后制定的空中交通管制规划极大地增加了美国的飞行安全性，而相同的空中交通管制过程也被应用到了世界的其他国家和地区。

B Rudimentary air traffic control (ATC) existed well before the Grand Canyon disaster. B基础空中交通管制（ATC）在大峡谷灾难前运行良好。 As early as the 1920s, the earliest air traffic controllers manually guided aircraft in the vicinity of the airports, using lights and flags, while beacons and flashing lights were placed along cross-country routes to establish the earliest airways. 早在20世纪20年代，最早的空中交通控制员使用灯光和旗子亲自指引临近机场的飞机，而信号灯和闪灯被铺在野外的线路上，这便是最早的航道。 However, this purely visual system was useless in bad weather, and, by the 1930s, radio communication was coming into use for ATC. 不过这种纯粹的可视系统在坏天气时却失去作用，同时，在20世纪30年代，ATC开始使用无线信号进行通信。 The first region to have something approximating today's ATC was New York City, with other major metropolitan areas following soon after. 第一个使用类似今天的ATC的地区是纽约，很快这项技术在其他主要城市也投入使用。

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C In the 1940s, ATC 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 rudimentary. C在 20世纪 40年代，ATC 中心确实从新开发的雷达和在二战期间得到改善的无线通信中获得了益处，但这个系统还是比较基础的。 It was only after the creation of the FAA that full-scale regulation of America's airspace took place, and this was fortuitous, for the advent of the jet engine suddenly resulted in a large number of very fast planes, reducing pilots' margin of error and practically demanding some set of rules to keep everyone well separated and operating safely in the air. 紧随着FAA 的建立，美国空间的全面规范形成了，不过这只是偶然发生的事情。随着喷气式引擎的突然出现，大量高速飞机诞生了，从而减少了飞行员的边际错误，实际上确实需要一些规则将人们分开，使他们单独在空中安全操作。

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D Many people think that ATC consists of a row of controllers sitting in front of their radar screens at the nation's airports, telling arriving and departing traffic what to do. D很多人认为ATC 就是坐在国家机场的雷达屏幕前的一排控制员，并告诉到达和离开的飞机该做些什么。 This is a very incomplete part of the picture. 这是不全面的， 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 all of them. FAA 意识到在任何时刻美国领空上都有很多不同类型不同飞行目标的飞机在不同的气候条件下飞行，而它们需要相同的管制标准。

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E To meet this challenge, the following elements were put into effect. E为了迎接这种挑战，下列措施被付诸实施。 First, ATC extends over virtually the entire United States. 首先，ATC 的职责覆盖到了美国全境。 In general, from 365m above the ground and higher, the entire country is blanketed by controlled airspace. 通常情况下，地面上方365 米以上的区域都是飞行控制区域。 In certain 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. 在某一区域，尤其是靠近机场的区域，控制区域会下调到地面上方215 米以上，而在紧邻机场的区域，地面上空区域都受到管制。 Controlled airspace is that airspace in which FAA regulations apply. 这些提到的空中区域都受到FAA 的规范和监管。 Elsewhere, in uncontrolled airspace, pilots are bound by fewer regulations. 在其他不受管制的空间，飞行员受到的规范会少一些。 In this way, the recreational pilot who simply wishes to go flying for a while without all the restrictions imposed by the FAA has only to stay in uncontrolled airspace, below 365m, while the pilot who does want the protection afforded by ATC can easily enter the controlled airspace. 通过这种方式，一些只想飞一会儿而且不想受到FAA限制的业余飞行员就只能在非管制区域飞行了，也就是在低于365 米的空间飞行；而需要ATC 提供保护的飞行员无疑可以飞到管制空间中。

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F The FAA then recognised two types of operating environments. FFAA 随即认定了两种操作环境。 In good meteorological conditions, flying would be permitted under Visual Flight Rules (VFR), which suggests a strong reliance on visual cues to maintain an acceptable level of safety. 在气候条件良好的情况下，符合可视飞行规则（VFR）的飞行是被允许的，这个规则建议飞行员强烈依赖可视信号以保持较强的安全性。 Poor visibility necessitated a set of Instrumental Flight Rules (IFR), under which the pilot relied on altitude and navigational information provided by the plane's instrument panel to fly safely. 在可视条件差的情况下则需要运用仪器飞行规则（IFR）。在这项规则下飞行员需要依靠飞机仪表盘上提供的海拔和导航信息进行安全性飞行。 On a clear day, a pilot in controlled airspace can choose a VFR or IFR flight plan, and the FAA regulations were devised in a way which accommodates both VFR and IFR operations in the same airspace. 天气晴朗的时候，在管制区域的飞行员可以选择VFR 或IFR 飞行计划，而在同一片区域，FAA 规则中的VFR 和IFR 操作都是适用的。 However, a pilot can only choose to fly IFR if they possess an instrument rating which is above and beyond the basic pilot's license that must also be held. 不过，如果飞行员的仪器等级超过或不足于必须持有的基础飞行员执照时，他们只能选择IFR 模式进行飞行。

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G Controlled airspace is divided into several different types, designated by letters of the alphabet. G管制区域根据字母分为几种不同的类型。 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. 不受管制区域被称为F 类，海平面到5,490 米以下并且不紧邻机场的管制空间被称为E 级。 All airspace above 5,490m is designated Class A. 所有5,490 米以上的空间被称为A 级。 The reason for the division of Class E and Class A airspace stems from the type of planes operating in them. 如此区分E 级和A 级空间源于在它们中飞行的飞机类型。 Generally, Class E airspace is where one finds general aviation aircraft (few of which can climb above 5,490m anyway), and commercial turboprop aircraft. 通常情况下，人们在E级空间看到的是通用飞行器（几乎不可能飞到5,490 米以上）以及商用涡轮式螺旋桨飞机。 Above 5,490m is the realm of the heavy jets, since jet engines operate more efficiently at higher altitudes. 而5,490 米以上则是重型喷气式飞机的王国，因为喷气式引擎在高海拔区域的效率更高。 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. 而E 级和A 级区域的不同是在A 级所有操作必须符合IFR，而飞行员必须具有仪器导航飞行执照，也就是说在仪器化方面得到训练及拿到执照。 This is because ATC control of the entire space is essential. 这是因为ATC 对整个空间的控制是非常重要的。 Three other types of airspace, Classes D, C and B, govern the vicinity of airports. 另外三种空间级别是D 级、C 级和B 级，它们均控制着紧邻机场的区域。 These correspond roughly to small municipal, medium-sized metropolitan and major metropolitan airports respectively, and encompass an increasingly rigorous set of regulations. 它们大致分别对应着小型自治区、中型城市及主要城市的机场，它们也包含了日渐严格的飞行规则。 For example, all a VFR pilot has to do to enter Class C airspace is establish two-way radio contact with ATC. 比如，所有的VFR 飞行员进入C 级区域时都需要与ATC 建立双向无线联系。 No explicit permission from ATC to enter is needed, although the pilot must continue to obey all regulations governing VFR flight. 而进入时不再需要ATC 的明确允许，尽管飞行员还是必须遵守所有VFR 飞行要求的规则。 To enter Class B airspace, such as on approach to a major metropolitan airport, an explicit ATC clearance is required. 如要进入B 级区域，如要接近一个主要城市的机场时需要ATC 的明确批准。 The private pilot who cruises without permission into this airspace risks losing their license. 在未经允许的情况下飞入这片区域的私人飞行员将面临着可能被吊销执照的风险。