Airspace And Airport Types (part 1)

Airspace And Airport Types

In September of 1993, the FAA adopted the International Civil Aviation Organization (ICAO) definition of airspace segments. The ICAO classifications of airspace are named A through G. The classification of “F” is not used in the USA.

NOTE: It will be helpful while studying this section to have a Sectional Aeronautical Chart available. Refer to the front panel of the chart as well as to content of the chart as you study this chapter.

The 3 predominant types of airspace are:

Positive Control (Class A) - White
Controlled (Class E - Yellow )
Uncontrolled (class G) - Magenta


Class G Airspace
ATC exercises no jurisdiction over Class G airspace. It is the airspace shown in magenta at left, and generally extends from the ground up to 1200 feet above ground level (AGL). As such it is classified as Uncontrolled airspace.





ATC exercises some jurisdiction, at varying degrees to all other airspace. Thus all other airspace is classifies as Controlled airspace.

Class A - Positive Control
ATC exercises complete control in the Positive Controlled airspace. Jets are the primary user of Class A airspace. It ranges from 18,000 feet (Flight Level 180) to 60,000 feet (FL600). Altitudes 18,000 feet and above are called Flight Levels (FL).

Class A airspace is not specifically charted on aeronautical charts. Operation is in accordance to Instrument Flight Rules (IFR). The aircraft must be equipped with appropriate IFR instrumentation, including a Mode C altitude reporting transponder. The pilot must be instrument rated. An IFR flight plan is required. ATC exercises full control of route, speed, and altitude. ATC is responsible for aircraft separation in Class A airspace.

Class E - Controlled
Class E airspace is from altitude 1200 feet Above Ground Level (AGL) up to 18,000 feet. All airspace from 14,500 feet (MSL) to 18,000 feet (MSL) is Class E. It contains the Low Altitude Victor airway system. These airways are designated on the aeronautical charts as blue lines about 1/16 inch wide, and have numbers like V12, V245, etc. written on them. They are roads in the sky. All Victor airways are Class E extending 6 nautical miles each side of the airway centerline. In mountainous terrain, class G airspace may exist from the surface to 14,500 feet outside the boundaries of the airway. In non-mountainous terrain (such as Eastern US), all the airspace above 1200 AGL is Class E unless specified otherwise.

ATC exercises no control over flights operating under Visual Flight Rules (VFR) in Class E airspace. Radio communication and transponder are not required. Specific cloud clearance and visibility requirements apply to Class E airspace. These are listed in the chart at the end of this section. ATC does exercise control of aircraft operating under Instrument Flight Rules (IFR). IFR flights must maintain altitudes, routes and speeds a directed by ATC. IFR flights must be capable of communicating with ATC, and must be Mode C Transponder equipped (capable of reporting altitude to the radar scope).

There are no specific certification requirements, other than normal pilot certificates. Class E airspace may be designated from the surface upward as extension to class B, C, and D airspace (defined later) to accommodate IFR traffic requirements. Class E airspace will extend downward to 700 feet AGL around uncontrolled airports that have published instrument approach procedures.

These areas around uncontrolled airports where the Class E airspace goes down to 700 feet AGL instead of the standard 1200 feet AGL are depicted on aeronautical charts by a wide shaded magenta colored band around the airport. The reason the Class E airspace extends nearer to the ground is to provide a controlled airspace transition area for aircraft operating IFR and making an IFR approach.

Class G - Uncontrolled
Most Class G airspace is that space from the surface up to 1200 feet. However, there are areas in mountainous terrain where airspace outside the Victor Airways is Class G from the ground to 14,500 feet AGL. Class G space may underlie Classes B, C, and D, but has no specific symbol indicated on the chart. The presence of the airspace is implied. Less stringent minimum cloud clearance and visibility requirements apply to VFR flight in Class G space since ATC does not maintain jurisdiction over this airspace. See last page of this section.

As mentioned in the Class E section, airports with published instrument approached have class E airspace extending down to 700 feet AGL. Obviously, in these areas, Class G only extends from the surface to 700 feet AGL.

Uncontrolled Airports
Airports without a control tower are classifies as uncontrolled. Three types of uncontrolled airports are shown below.



The airport on the right does not have an instrument approach or a control zone around the airport. The airspace overlying this type airport is Class G up to 1200 feet, then Class E above. It is depicted on the charts as a magenta circle (unpaved) or a solid circle with white runways (paved).

The airport in the middle has a Class E Control Zone around it, depicted by the dotted circle around it. If the line is magenta in color, it is a control zone at an airport where an FAA Flight Service Station (FSS) is on the field but no control tower. The FSS provides airport traffic advisory service. Class E airspace extends down to the surface. The zone is depicted on charts as a dashed MAGENTA circle around the airport. These airports usually have instrument approach procedures as well.

The airport at left has an instrument approach procedure for the airport. Such airports have a broad lightly shaded magenta band around them. Within the outer edge of the band, Class G airspace only extends up to 700 feet AGL. Class E extends down to 700 feet to provide a transition zone for aircraft making instrument approaches to the airport. The transition area is approximately 5 miles in radius.



Controlled Airports
These are airports that have sufficient air traffic to warrant a Control Tower, and in some cases Approach Control and Ground Control Radar. They are used by air carrier operations, and can have a mix of jet, high performance piston and turbine aircraft, as well as smaller single engine aircraft. The control tower is responsible for aircraft separation within its jurisdiction. Certain clearances must be obtained from ATC for operations on the airport surface, and within the controlled airspace around the airport.

There are 3 Classes of airspace around controlled airports. The type of airspace depends upon the traffic volume and types of flight. These Classes are B, C, and D airspace

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.

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 NC and Augusta Ga. are examples of airports with TRSA. There is no specified regulatory radius for the radar service.


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 diagram 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.

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.