For an airport to be classified as a Class C airport it must meet the following requirements:
Class C airports must also meet a minimum amount of operations annually. To receive Class C designation the airport must have at least one of the following:
Finally, the Class C designation must contribute to the efficiency and safety of operations. Class C designation must be necessary to correct a current situation or problem that cannot be solved without Class C designation.
Class C airspaces areas should be designated around a single primary airport, be simple in design, and follow the standard Class C lateral and vertical dimensions to the greatest extent possible.
Airspace designers are allowed to deviate from the standard vertical and lateral limits when justified and recommended.
However, containment of instrument procedures within Class C airspace is not required and may not be considered.
Class C airspace is designed as two concentric circles centered on the airport reference point.
The inner concentric circle, otherwise known as the surface area, should have a 5 NM radius.
The outer concentric circle should not extend beyond a 10 NM radius from the airport reference point.
Airspace planners also attempt, wherever possible, to use VOR radials and DME arcs to define Class C airspace boundaries and sun areas. Prominent visual landmarks are also considered to assist VFR traffic that prefers to remain clear of Class C airspace.
Generally, the inner-circle surface area of Class C airspace extends from the surface up to the upper limit of the airspace, typically 4,000ft AGL from the primary airport's field elevation.
The outer circle 5 - 10 NM from the primary airport may not be any lower than 1,200ft AGL and extends up to the upper limit (4,000ft AGL) of the airspace.
Operational requirements to operate within Class C airspace are found under Part 91.130.
To operate an aircraft within Class C airspace, pilots must meet the following two-way radio requirements:
Arrival and Transient Aircraft: Aircraft attempting to land at an airport within Class C airspace or pass through Class C airspace must establish two-way radio communications before entering Class C airspace and maintain communication while within Class C airspace.
Departing Aircraft: Aircraft departing from the primary airport or a satellite airport with an operating control tower must establish and maintain two-way radio communications with the control tower or as instructed while operating within Class C airspace.
Aircraft departing from a satellite airport without an operating control tower must establish and maintain two-way radio communications with the ATC facility having jurisdiction over the Class C airspace as soon as practicable after departing.
Traffic Pattern Aircraft: Aircraft performing take-offs or landings at a satellite airport within Class C airspace must comply with published FAA arrival and departure traffic patterns.
To operate in Class C airspace aircraft must be equipped with a transponder with Mode 3/A 4096 capability or Mode S capability with intermode capabilities, which replies to Mode 3/A interrogations with the code specified by ATC.
The aircraft must also be equipped with automatic pressure altitude reporting equipment with Mode C capability that automatically replies to Mode C interrogations in 100ft increments.
Additionally, when performing flight over Class C airspace at or below 10,000ft MSL, the previously mentioned transponder requirements still apply.
After January 1, 2020, unless authorized by ATC, all aircraft must be equipped with ADS-B out to operate within Class C airspace.
Additionally, ADS-B out is required to operate within the lateral boundaries of Class C airspace above the ceiling upwards to 10,000ft MSL.
Unlike Class B airspace, Class C airspace does not specify a minimum pilot certificate for any particular airspace.
However, student, sport, and recreational pilots are only allowed to enter all Class C airspace provided they receive an endorsement from an authorized instructor stating they received the required training to operate within Class C airspace.
Aircraft operating within Class C airspace under VFR must maintain at least a 3 statute mile forward visibility, and remain at least 1,000ft above, 500ft below, and 2,000ft horizontally from clouds at all times.
Unless otherwise authorized or required by ATC, no person may operate an aircraft at or below 2,500ft AGL within 4 nautical miles of the primary Class C airport at an indicated airspeed greater than 200 knots.