and passenger enplanements (larger airline operations).  [Figures 8-3  and  8-9]  This airspace is charted in feet MSL,  and is generally of a five 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] Since Class C has significant air traffic, 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. Class B airspace is generally airspace from the surface to  10,000 feet MSL surrounding the nation’s busiest airports  in terms of IFR operations or passenger enplanements.  [Figures 8-3  and  8-10]  The configuration of each Class B  airspace area is individually tailored and consists of a surface  area and two or more additional layers (some Class B  airspace areas resemble upside-down wedding cakes), and  is designed to contain all published instrument procedures  once an aircraft enters the airspace. WSC aircraft can fly into Class C airspace by contacting  the control tower first, 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. Equipment requirements are the same as for Class C airspace;  however, due to air traffic congestion, the WSC aircraft pilot  requesting entry to Class B airspace may be denied entry.  Since aircraft operating in Class B airspace have a radar  signature and ATC provides aircraft separation, there is a  difference in the cloud clearance requirements. Visibility  remains three statute miles, but minimum cloud clearance  requirement is to remain clear of clouds.  [Figure 8-6] 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.  Class B Airspace Figure 8-10.  Class B airspace as shown on a sectional chart. Figure 8-9.  Class C airspace as shown on a sectional chart. 8-7