Controlled Airspace is a generic term that covers the different classifications of airspace (Class A, B, C, D and E airspace) and defined dimensions within air traffic control service is provided to IFR flights and to VFR flights in accordance with the airspace classification.
Class A Airspace - Generally that airspace from 18,000 feet MSL up to and including FL 600, including the airspace overlying the waters within 12 nautical miles of the coast of the 48 contiguous States and Alaska; and designated international airspace beyond 12 nautical miles of the coast of the 48 contiguous States and Alaska within areas of domestic radio navigational signal or ATC radar coverage, and within which domestic procedures are applied.
Unless otherwise authorized, all persons must operate their aircraft under IFR.
Class B Airspace - Generally, that airspace from the surface to 10,000 feet MSL surrounding the nation’s busiest airports in terms of IFR operations or passenger enplanements. The configuration of each Class B airspace area is individually tailored and consists of a surface area and two or more 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.
An ATC clearance is required for all aircraft to operate in Class B Airspace, and all aircraft that so cleared receive separation services within the airspace. The cloud clearance requirement for VFR operations is “clear of clouds”.
Arriving or transiting aircraft must obtain an ATC clearance prior to entering Class B airspace on the appropriate frequency and relation to geographical fixes shown on local Class B charts. Departing aircraft require a clearance to depart Class B airspace and should advise clearance delivery of their intended altitude and route of flight.
Unless otherwise authorized by ATC, aircraft must be equipped with an operable two-way radio capable of communicating with ATC on appropriate frequencies for that Class B airspace. Also unless otherwise authorized by ATC the aircraft must be equipped with an operable radar beacon transponder with automatic altitude reporting equipment.
There are currently 12 airports with Class B airspace where the pilot in command must hold at least a private pilot certificate to take off and land. At other Class B airports a student pilot or recreational pilot who seeks private pilot certification may take off and land if certain requirements are met. The student or recreational pilot must receive ground and flight instruction from an authorized instructor and receive an endorsement from that instructor stating the student or recreational pilot is proficient to conduct solo operations at the specific Class B Airport & Airspace.
Mode C Veil A mode C transponder with altitude reporting is required within 30 nautical miles of a Class B airport from the surface to 10,000 feet MSL. An aircraft that was not originally certificated with engine driven electrical system or which has not subsequently been certified with a system installed may conduct operations within a Mode C veil provide the aircraft
remains outside Class A, B, or C airspace; and below the altitude of the ceiling of a Class B or Class C airspace area designated for an airport or 10,000 feet MSL, whichever is lower.
Class C Airspace
Class C Airspace is generally that airspace from the surface to 4,000 feet above the airport elevation (charted in MSL) surrounding those airports that have an operational control tower, are serviced by a radar approach control, and have a certain number of IFR operations or passenger enplanements.
Although the configuration of each Class C airspace area is individually tailored, the airspace usually consists of a 5 NM radius core surface area that extends from the surface up to 4,000 feet above the airport elevation, and a 10 NM radius shelf area that extends no lower than 1,200 feet up to 4,000 feet above airport elevation.
No specific pilot certification is required to operate in Class C airspace. A two way radio and unless otherwise authorized by ATC an operable radar beacon transponder with automatic altitude reporting equipment is required.
Two way radio communication must be established with the ATC facility providing ATC services prior to entry and thereafter maintain those communications while in Class C airspace. Pilots of arriving aircraft should contact the Class C airspace ATC facility on the publicized frequency and give their position, altitude, radar beacon code destination, and request Class C service.
Radio contact should be initiated far enough from the Class C airspace boundary to preclude entering Class C airspace before two way radio communications are established. If the controller responds to a radio call with, “aircraft call sign, standby” radio communications have been established and the pilot can enter the Class C airspace.
If workload or traffic conditions prevent immediate provision of Class C services, the controller will inform the pilot to remain outside the Class C airspace until conditions permit the services to be provided.
It is important to understand that if the controller responds to the initial radio call without using the aircraft call, radio communications have not been established and the pilot may not enter the Class C airspace.
Class D Airspace
Class D airspace is generally that airspace from the surface to 2,500 above the airport elevation (charted in MSL) surrounding those airports that have an operational control tower. The configuration of each Class D airspace area is individually tailored and when instrument procedures are published, the airspace will normally be designated to contain the procedures.
No specific pilot certification is required. Unless otherwise authorized by ATC, an operable two way radio is required.
Two way radio communication must be established with the ATC facility providing ATC services prior to entry and thereafter maintain those communications while in Class D airspace. Pilots of arriving aircraft should contact the control tower on the publicized frequency and give their position, altitude, destination, and any request(s). Radio contact should
be initiated far enough from Class D airspace boundary to preclude entering the Class D airspace boundary to preclude entering Class D airspace before two way radio communications are established.
If the controller responds to a radio call with, “aircraft call sign, standby,” radio communications have been established and the pilot can enter the Class D airspace. If workload or traffic conditions prevent immediate entry into Class D airspace, the controller will inform the the pilot to remain outside the Class D airspace until conditions permit entry.
Class E Airspace
Generally, if the airspace is not Class A, B, C, or D, and is controlled airspace it is Class E airspace. There are no specific pilot certification or equipment requirements to operate in Class E airspace. Special VFR operations are permitted but clearance must be obtained from the controlling facility.
Class E airspace is depicted in blue or magenta on sectional charts and white on low altitude enroute charts.
For VFR operations basic VFR visibility and distance from clouds must be maintained. Below 10,000 MSL feet this is 3 statute miles visibility and 500 feet below, 1000 feet above, and 2000 feet horizontally. Above 10,000 feet MSL this increases to 5 statute miles visibility, 1000 feet above, 1000 feet below and 1 mile horizontally.
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