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Class D -- Airports with Control Tower
The lowest level of control is at airports with a low volume of traffic. It has a control tower and is depicted on the
aeronautical charts as shown below.
Class D airports are depicted on aeronautical charts by a blue dashed circle around the airport symbol. Within the
dashed circle is a number enclosed in a dashed square. This number indicates the top of the Class D airspace,
expressed in hundreds of feet (MSL). In the diagram, the top is 4,600 feet MSL This airspace may have a Class E
extension as shown in the diagram for an IFR approach transition area.
The control tower has jurisdiction within the Class D airspace which is 5 Statute Miles radius around the control
tower. The top of the Class D airspace extends 2500 feet above the surface of the airport. Two way radio contact
must be maintained with the Control Tower while in this airspace. The pilot should contact the control tower
prior to entering the airspace.
See AIM Chapter 3 for further data on Class D Airspace
Terminal Radar Service Areas (TRSA)
Some Class D airports have a local radar service called a Terminal Radar Service Area.(TRSA). The service is
available for conflict resolution and traffic sequencing to departing and arriving aircraft. However contact with
the radar is not mandatory and the pilot may decline the service.
These airports are depicted on the aeronautical charts in the normal Class D manner, but have a dark gray circular
line around the airport out at the boundary of the radar service range. Wilmington N.C. and Augusta Ga. are
examples of airports with TRSA. There is no specified regulatory radius for the radar service.
See AIM Chapter 3 for further data on Terminal Radar Service Area
Class C Airspace (Mandatory Radar)
Class C airspace has two concentric tiers. The inner circle is 5 nautical mile core area extending to 4000 feet
above the surface. It is similar in function to Class D airspace where the tower usually maintains jurisdiction.
A shelf area with an outer radius of 10 nautical miles surrounds the core area. It extends from 1200 feet AGL to
4000 feet AGL. The airspace is depicted on charts as 2 concentric magenta circles.
For example, an airport with a surface altitude of 500 feet MSL is depicted above. The left diagram is a side
profile of the airspace. The right diagran shows how the airspace is depicted on the aeronautical chart.
The ceiling of the Class C airspace is 4,500 feet (MSL). This is calculated as runway altitude of 500 feet plus
4000 feet. The floor of the outer shelf is 1,700 feet MSL. (1200 + 500 feet). The space under the shelf is Class G.
These altitudes are indicated by 45 over SFC for the core circle, and 45 over 17 on the outer shelf.
AIRSPACE AND AIRPORT TYPES
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Contact with Approach and Departure Radar Control is mandatory within the core and shelf airspace. During
takeoff and landing, the tower and radar controller coordinate their activity. You will be told by either controller
when to switch frequency to the other controller. Aircraft must be capable of two-way communication with the
radar facility and the tower. A 4096 Altitude Reporting (Mode C) Transponder is required when operating within,
under or above Class C airspace.
Before entering Class C airspace, the pilot MUST establish communication with the radar service. Radio contact
with radar and/or tower must be maintained when in this airspace.
You may request Flight Following Radar Service outside the 10 mile shelf. It may be granted on a workload
permitting basis. The service can usually be provided to about a 20 NM radius of the airport.
See AIM Chapter 3 for further data on Class C Airspace
Class B -- Large Terminal Airports
Large terminal areas such as the New York, Chicago, and Los Angeles areas have a high volume of air traffic.
The airspace around these airports is under rigid control of ATC, and are called Class B airspace.
AIRCRAFT MUST HAVE ATC CLEARANCE PRIOR TO ENTRY INTO THIS AIRSPACE.
The airspace is composed generally of three concentric tiers. A core area around the airport is generally is
surrounded by two additional shelf areas extending approximately 30 nautical mile radius from the primary
airport.
The core area extends from the surface to 10,000 feet AGL. The second shelf has a wider radius and has both a
floor and a ceiling. The ceiling is the same as the inner circle. The floor may vary at differing altitudes in various
sections to accommodate smaller airports that underlie the middle tier of airspace.
The third shelf extends out approximately 30 Nm from the airport. It has the same ceiling as the other two tiers,
but has a higher floor than the middle shelf. This floor may also be variable in altitude to accommodate airports
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