VATUSA
Virtual Air Traffic Simulation - USA Division
The National Airspace System
Airspace over the United States is a complex, intertwining road map that is often described as several puzzles stacked atop one another. For this reason, the FAA has created classifications of airspace based on their location, size, services provided and aircraft operation and equipage requirements. The airspace on VATSIM is managed in much the same way. Below we are going to discuss the various classifications of airspace, what they look like on a sectional chart, and what are the pilot requirements for them to enter.
Class A Airspace (Alpha)
What is it?
Class A airspace is all airspace extending upward from 18,000 feet Mean Sea Level (MSL) up to and including 60,000 feet MSL within the 48 Contiguous States, most of Alaska and the airspace included within a 12NM offâ€shore perimeter. For all you HCF bound controllers, know that there is no Class Alpha airspace over the Hawaiian Islands.
Whats it look like? (Sectional)
There is no sectional picture here, because Class Alpha airspace is the only classification of airspace not depicted on a sectional chart.
Pilot Requirements
The pilots requirements for to enter Class Alpha airspace are as follows:
- Flying under Instrument Flight Rules (IFR)
- Two way communications
- Operating Mode C Transponder
Class B Airspace (Bravo)
This class of airspace encompasses the busiest of airports. It generally extends up from the surface to 10,000 feet MSL. Think “B†for “Boeing†or “Busyâ€. This airspace includes airports such as: Chicago's O'Hare (KORD), Los Angeles International (KLAX), and Miami International (KMIA), to name a few.
Whats it look like? (Sectional)
Above is an excerpt from a sectional chart depicting Class Bravo airspace. Note the solid blue lines on the sectional. This indicates that it is a class bravo airspace. This classification of airspace is made up of various shelves that resemble an upside down wedding cake. You can tell the dimensions of each shelf by looking for the altitude indicators which look like
Why would Air Traffic Controllers want to control certain aircraft/airports but not others?
Simple, controllers working Class Bravo airspace are usually very busy directing aircraft into the primary airport. Allowing smaller aircraft to fly under the airspace frees the pilot from waiting for clearance to the nearby airport and frees the controller to concentrate on aircraft going into the primary airport.
Pilot Requirements
- VFR Aircraft operating into/out of/through Class Bravo airspace require an explicit clearance.
- Two way communications
- Operating Mode C Transponder within the confines of the Mode C Veil.
Class C Airspace (Charlie)
This class of airspace surrounds crowded airspace that does not get the traffic that a Bravo airport does. Think of “C†as meaning “Crowded†or “Congestedâ€. Typically the airspace extends 10 miles out and up to 4000 AGL (Above Ground Level).
Whats it look like? (Sectional)
Here is a picture of the sectional chart depicting Class Charlie airspace. Notice how the Class Charlie airspace is defined by a solid magenta line. As you can see here, the airspace does extend out in various shelves similar to a Bravo. In this example above, the inner ring goes from SFC (Surface) up to 4,800 MSL and the outer ring goes from 2,500 ft to 4,800 ft MSL.
Pilot Requirements
- Two Way Radio Communications
- Operating Mode C Transponder within the confines of the Class Charlie Airspace
Class D Airspace (Delta)
Class D airspace provides ATC service for aircraft on the airport surface and in the airspace immediately surrounding the airport to control air traffic flow. ATC services typically provided at a Class D airport is via a Control Tower.
Whats does it look like? (Sectional)
Class D airspace extends from the surface to 2,500 feet AGL. It is individually tailored for each airport but typically extends out 4 Nautical Miles from the primary airport.
Pilot Requirements
- Two Way Radio Communications
I keep seeing "Two Way Radio Communications", but what does it mean?
For example, if a controller tells a calling aircraft, "Aircraft calling, standby", twoâ€way communication has NOT been established because the callsign was not used. If the controller tells the aircraft calling, "N5204N, standby", twoâ€way communication has been established.
Class E Airspace (Echo)
This class of airspace covers the majority of our sky and extends from 1200 ft AGL and up to but not including FL180. The class echo also extends down to 700 ft AGL around both uncontrolled fields that are serviced by an instrument approach. This extension places the airports traffic pattern within the confines of the class echo so we are able to control and separate IFR aircraft from local VFR aircraft. Echo airspace may even extend to the surface is some cases. Now lets look at the sectional chart below and see how we can determine the altitudes of the class echo airspace.
Whats it look like? (Sectional)
Lets start by looking at the image on the left. On the inside of the magenta circle (The 'fuzzy' side), Class Echo airspace begins at 700 ft AGL on the inside of the fading magenta circle, where as on the outside of the magenta circle, the Class Echo airspace begins at 1200 ft AGL.
On the right side of the picture, notice the dashed magenta line on the inside of the magenta circle. Inside of this dashed magenta line indicates that the airspace extends completely down to the surface. Also any Class Delta tower that does not operate continuously become class echo airspace to the surface level during the closed hours. These hours are posted in the Airport Facility Directory, which can also be found at Skyvector.com.
Pilot Requirements
- There are no requirements for an aircraft to operate in Class Echo airspace other then weather minimums (Which we'll discuss later)
Umm...You skipped Foxtrot! Why?
Well it is not because the members of the VATUSA Training Department are lazy! In the National Airspace System, there is no classification of airspace known as Foxtrot.
Class G Airspace (Golf)
Class golf airspace is uncontrolled airspace. We as air traffic controllers are unable to control an aircraft while they are inside the confines of the Class Golf airspace. You may think of Class Golf airspace as "government free" or "go anywhere." The Class Golf airspace begins at surface level and extends up to the Echo above it (700AGL or 1200AGL). In some locations the Class Golf airspace extends as high as 14,500 ft MSL.
Summary of Airspace (Alpha - Golf)
Below is an image of the national airspace system which puts what you've read into a nice easy to view graphic:
Special Use Airspace
Special Use Airspace is airspace that has been defined to support the critical mission requirements of other government agencies, protect vital national facilities, or is otherwise necessary for the safety and security of both the airspace and surface installations.
Alert Areas †These areas are depicted on aeronautical charts to inform nonparticipating pilots of areas that may contain a high volume of pilot training or unusual types of aerial activity.
Military Operations Areas (MOA) †These areas consist of airspace with defined vertical and lateral limits established for the purpose of separating certain military training activities from civilian air traffic.
Prohibited Areas †These areas contain airspace of defined dimensions identified by an area on the surface of the earth within which the flight of aircraft is prohibited. Pâ€56 which covers the National Mall in Washington, D.C. is the most well known Prohibited Area in the United States.
Restricted Areas †These areas contain airspace identified by an area on the surface of the earth within which the flight of aircraft, while not wholly prohibited, is subject to restrictions. Restricted Areas denote the existence of unusual, often invisible hazards to aircraft such as artillery firing, aerial gunnery, or guided missiles.
Warning Areas †These are airspaces extending three nautical miles outward from the coast of the United States. A Warning Area contains activity deemed hazardous to nonparticipating aircraft. Furthermore, a Warning Area may be established over domestic waters, international waters or a combination of both.
