CHAPTER 8. The National Airspace System

Towered Airport Operations

All student pilots must have an endorsement to operate within Class B, C, and D airspace and within airspace for airports that have a control tower, per 14 CFR section 61.94 or 14 CFR section 61.95. Only private pilot students can operate within Class B airspace with the proper endorsements per 14 CFR section 61.95. Sport pilots must also have an endorsement per 14 CFR section 61.325 to operate within Class B, C, and D airspace and within airspace for airports with a control tower. [Figure 8-5] All students and Sport pilots have further restrictions regarding the specifi c Class B airports out of which they may operate, per 14 CFR section 91.131.

Class D Airspace

Class D is that airspace from the surface to 2,500 feet AGL (but charted in MSL) surrounding smaller airports with an operational control tower. [Figures 8-3 and 8-8] The confi guration of each Class D airspace area is individually tailored. When instrument procedures are published, the airspace is normally designed to contain the procedures.

Unless otherwise authorized, each aircraft must establish twoway radio communications with the ATC facility providing air traffi c services prior to entering the airspace and thereafter maintain those communications while in the airspace. Radio contact should be initiated far enough from the Class D airspace boundary to preclude entering the Class D airspace before two-way radio communications are established. It is important to understand that if the controller responds to the initial radio call without using the WSC aircraft’s call sign, radio communications have not been established, and the WSC aircraft may not enter the Class D airspace.

Many airports associated with Class D airspace do not operate a control tower on a 24-hour-a-day basis. When not in operation, the airspace will normally revert to Class E or G airspace, with no communications requirements. Refer to the AF/D for specifi c hours of operation airports.

The minimum visibility requirements for Class D airspace are three statute miles; cloud clearances are the 1,000 above, 500 below and 2,000 vertical. [Figure 8-6]

Class C Airspace

Class C airspace normally extends from the surface to 4,000 feet above the airport elevation surrounding those airports having an operational control tower, that are serviced by a radar approach control, and with a certain number of IFR and passenger enplanements (larger airline operations). [Figures 8-3 and 8-9] This airspace is charted in feet MSL, and is generally of a fi ve NM radius surface area that extends from the surface to 4,000 feet above the airport elevation, and a 10 NM radius area that extends from 1,200 feet to 4,000 feet above the airport elevation. There is also a noncharted outer area with a 20 NM radius, which extends from the surface to 4,000 feet above the primary airport, and this area may include one or more satellite airports. [Figure 8-9]

WSC aircraft can fl y into Class C airspace by contacting the control tower fi rst, establishing communications (same as Class D), and having an altitude encoding transponder. Aircraft can enter Class C airspace without a transponder if prior permission from ATC is received 1 hour before entry, per 14 CFR section 91.215(d)(3). Aircraft may fl y under the Class C upper tier of airspace without a transponder but not over the top of Class C airspace lateral boundaries.

Cloud clearances in Class C airspace are the same as Class D airspace: minimum visibility of three statute miles, and a minimum distance from clouds of 1,000 feet above, 500 feet below, and 2,000 feet horizontal.

Since Class C has signifi cant air traffi c, many with larger airplanes creating stronger vortices, the pilot must be aware that the chance of encountering catastrophic wingtip vortices is greater at airports with larger air traffi c.

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