阅读段落

　　Controlled airspace is divided into several different types, designated by letters of the alphabet. Uncontrolled airspace is designated Class F, while controlled airspace below 5,490 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 from the type of planes operating in them. Generally, Class E airspace is where one finds general aviation aircraft (few of which can climb above 5,490m anyway), and commercial turboprop aircraft. Above 5,490m is the realm of the heavy jets, since jet engines operate more efficiently 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 ATC control of the entire space is essential. Three other types of airspace, Class D, C and B, govern the vicinity of airports. These correspond roughly to small municipal, medium-sized metropolitan and major metropolitan airports respectively, and encompass an increasingly rigorous set of regulations. For example, all a VFR pilot has to do to enter Class C airspace is to establish two-way radio contact with ATC. No explicit permission from ATC to enter is needed, although the pilot must continue to obey all regulations governing VFR flight. To enter Class B airspace, such as on approach to a major metropolitan airport, an explicit ATC clearance is required. The private pilot who cruised without permission into this airspace risks losing their license.

　　段落大意

　　本段主要介绍了各种受控制的空域的各个等级，以及这些等级的区别和特点。

　　阅读笔记

　　Division of airspace: (designated by alphabetical letters)

　　1. Uncontrolled airspace: Class F

　　2. Controlled airspace:

　　Class E: controlled airspace & < 5490m, not in vicinity of airport (aviation aircraft)

　　Class A: > 5490m (heavy jets)

　　Difference of E & A: A – IFR, pilots instrument-rated

　　Class D=small municipal airports

　　C= medium-sized metropolitan airports (no need of permission from ATC to enter)

　　B=major metropolitan airports (explicit ATC clearance is required to enter)

　　逻辑关系

　　1. 因果(逻辑连接词: SINCE)

　　Jet engines operate more efficiently at higher altitudes.

　　Above 5,490m is the realm of the heavy jets.