Class C Airspace

AIM ¶ 3-2-4 Class C Airspace

AIM 3-2-4 explains Class C airspace dimensions, two-way radio and transponder/ADS-B requirements, entry procedures, speed limits, and ATC services for pilots.

In Plain English

Class C airspace surrounds busier airports that have an operational control tower, radar approach control, and meet certain IFR/passenger thresholds. Although tailored to each location, the typical shape is:

  • A 5 NM radius surface core from the surface up to 4,000 feet AGL (charted in MSL)
  • A 10 NM radius shelf from 1,200 feet AGL up to 4,000 feet AGL
  • A 20 NM procedural Outer Area (not charted) where Class C services are also available

Pilot/equipment requirements:

  • No specific pilot certification required
  • Two-way radio communication established with ATC before entry, and maintained while inside
  • Operable Mode C transponder with altitude reporting and ADS-B Out (unless ATC authorizes otherwise)

Communication tip: If ATC replies using your callsign (even just "N123AB, standby"), two-way comms are established and you may enter. If they say "aircraft calling, standby" without your callsign, you may not enter.

Speed: Below 2,500 ft AGL within 4 NM of the primary airport, max 200 knots indicated.

Within Class C, ATC sequences VFR traffic to the primary airport and separates VFR from IFR using visual separation, 500 ft vertical, or target resolution. Pilots remain responsible for see-and-avoid, terrain/obstacle clearance, wake turbulence avoidance, and VFR weather minimums per 14 CFR 91.155.

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AIM Source Text
FAA AIM ¶ 3-2-4
Definition. 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 that 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 the airport elevation. Charts. Class C airspace is charted on Sectional Charts, IFR En Route Low Altitude, and Terminal Area Charts where appropriate. Operating Rules and Pilot/Equipment Requirements: Pilot Certification. No specific certification required. Equipment. Two-way radio; and Unless otherwise authorized by ATC, an operable radar beacon transponder with automatic altitude reporting capability and operable ADS-B Out equipment. Arrival or Through Flight Entry Requirements. 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. Departures from: A primary or satellite airport with an operating control tower. Two-way radio communications must be established and maintained with the control tower, and thereafter as instructed by ATC while operating in Class C airspace. A satellite airport without an operating control tower. Two-way radio communications must be established as soon as practicable after departing with the ATC facility having jurisdiction over the Class C airspace. Aircraft Speed. Unless otherwise authorized or required by ATC, no person may operate an aircraft at or below 2,500 feet above the surface within 4 nautical miles of the primary airport of a Class C airspace area at an indicated airspeed of more than 200 knots (230 mph). Air Traffic Services. When two-way radio communications and radar contact are established, all VFR aircraft are: Sequenced to the primary airport. Provided Class C services within the Class C airspace and the outer area. Provided basic radar services beyond the outer area on a workload permitting basis. This can be terminated by the controller if workload dictates. Aircraft Separation. Separation is provided within the Class C airspace and the outer area after two-way radio communications and radar contact are established. VFR aircraft are separated from IFR aircraft within the Class C airspace by any of the following: Visual separation. 500 feet vertical separation. Target resolution. Wake turbulence separation will be provided to all aircraft operating: Behind and less than 1,000 feet below super or heavy aircraft, To small aircraft operating behind and less than 500 feet below B757 aircraft, and To small aircraft following a large aircraft on final approach. Secondary Airports In some locations Class C airspace may overlie the Class D surface area of a secondary airport. In order to allow that control tower to provide service to aircraft, portions of the overlapping Class C airspace may be procedurally excluded when the secondary airport tower is in operation. Aircraft operating in these procedurally excluded areas will only be provided airport traffic control services when in communication with the secondary airport tower. Aircraft proceeding inbound to a satellite airport will be terminated at a sufficient distance to allow time to change to the appropriate tower or advisory frequency. Class C services to these aircraft will be discontinued when the aircraft is instructed to contact the tower or change to advisory frequency. Aircraft departing secondary controlled airports will not receive Class C services until they have been radar identified and two-way communications have been established with the Class C airspace facility. This program is not to be interpreted as relieving pilots of their responsibilities to see and avoid other traffic operating in basic VFR weather conditions, to adjust their operations and flight path as necessary to preclude serious wake encounters, to maintain appropriate terrain and obstruction clearance or to remain in weather conditions equal to or better than the minimums required by 14 CFR section 91.155. Approach control should be advised and a revised clearance or instruction obtained when compliance with an assigned route, heading and/or altitude is likely to compromise pilot responsibility with respect to terrain and obstruction clearance, vortex exposure, and weather minimums. Class C Airspace Areas by State. These states currently have designated Class C airspace areas that are depicted on sectional charts. Pilots should consult current sectional charts and NOTAMs for the latest information on services available. Pilots should be aware that some Class C airspace underlies or is adjacent to Class B airspace. (See TBL 3-2-1 .) TBL 3-2-1 Class C Airspace Areas by State
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What is required before you may operate an aircraft within Class B airspace?

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Oral Exam Questions a DPE Might Ask
Q1What are the typical dimensions of Class C airspace?
Per AIM 3-2-4, Class C generally consists of a 5 NM radius surface core from the surface up to 4,000 ft above airport elevation, and a 10 NM radius shelf from 1,200 ft up to 4,000 ft above airport elevation. There is also a 20 NM procedural Outer Area that is not charted.
Q2What equipment and communication requirements must be met to enter Class C airspace?
Per AIM 3-2-4, you need a two-way radio and, unless otherwise authorized by ATC, an operable Mode C transponder with altitude reporting and operable ADS-B Out. Two-way radio communication must be established with the controlling ATC facility prior to entry — meaning the controller responds using your aircraft callsign — and maintained while inside.
Q3What is the maximum indicated airspeed allowed near a Class C primary airport, and where does it apply?
Per AIM 3-2-4, unless otherwise authorized or required by ATC, no person may operate an aircraft at or below 2,500 feet above the surface within 4 NM of the primary Class C airport at an indicated airspeed greater than 200 knots (230 mph).
Related Paragraphs in Chapter 3
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