The National Airspace System (NAS) is the network of all components regarding airspace in the United States. This comprehensive label includes air navigation facilities, equipment, services, airports or landing areas, sectional charts, information/services, rules, regulations, procedures, technical information, manpower, and material. Many of these system components are shared jointly with the military. To conform to international aviation standards, the United States adopted the primary elements of the classification system developed by the International Civil Aviation Organization (ICAO). This chapter provides a general discussion of airspace classification. Detailed information on the classification of airspace, operating procedures, and restrictions is found in the Aeronautical Information Manual (AIM).

This handbook departs from the conventional norm, in that the airspace discussions are presented in reverse order, in the belief that it is much easier to learn the airspace from least complicated to most complicated; also, the information presented for basic visual flight rules (VFR) weather minimums is only that necessary for weight-shift control (WSC) aircraft operations.

The two categories of airspace are regulatory and nonregulatory. Within these two categories, there are four types: uncontrolled, controlled, special use, and other airspace.

Airspace is charted on sectional charts as shown in the some examples for the specific airspaces on the chapter. The specific airspace symbols are shown on the legend for each sectional chart. [Figure 8-1] The WSC aircraft pilot should study and refer to the specifics of the AIM; FAA-H-8083- 25, Pilot’s Handbook of Aeronautical Knowledge; and Title 14 of the Code of Federal Regulations (14 CFR) part 91 for additional information regarding airspace and operations within that airspace.

Figure 8-1. Each student, pilot, and instructor should have a current sectional chart for the flight area.

Uncontrolled and Controlled Airspace

Class G Airspace

Class G or uncontrolled airspace is the portion of the airspace that has not been designated as Class A, B, C, D, or E. Class G airspace extends from the surface to the base of controlled airspace (Class B, C, D, and E) above it as shown in Figures 8-2 and 8-3.

Figure 8-2. Class G uncontrolled airspace and Class E controlled airspace.Figure 8-3. Class G airspace extends from the surface to the base of controlled airspace (Class B, C, D, and E).

Most Class G airspace is overlaid with Class E airspace, beginning at either 700 or 1,200 feet above ground level (AGL). In remote areas of the United States, Class G airspace extends above 700 and 1,200 AGL to as high as 14,500 feet before the Class E airspace begins. [Figure 8-2] The pilot is advised to consult the appropriate sectional chart to ensure that he or she is aware of the airspace limits prior to flight in an unfamiliar area. [Figure 8-4]

Figure 8-4. Class G airspace as shown on a sectional chart.

There are no communications, entry, equipment, or minimum pilot certificate requirements to fly in uncontrolled Class G airspace unless there is a control tower. [Figure 8-5]

Figure 8-5. Requirements for airspace operation.

If operations are conducted at an altitude of < 1,200 feet AGL, the pilot must remain clear of clouds. If the operations are conducted more than 1,200 feet AGL but less than 10,000 feet mean sea level (MSL), cloud clearances are 1,000 feet above, 500 feet below, and 2,000 feet horizontally from any cloud(s). A popular mnemonic tool used to remember basic cloud clearances is “C152,” a popular fixed-wing training aircraft. In this case, the mnemonic recalls, “Clouds 1,000, 500, and 2,000.”

Visibility in Class G airspace below 10,000 MSL day flight is one statute mile (SM) for private pilots and three SM for sport pilots. See Figure 8-6 for specific Class G weather minimums for WSC pilots.

Figure 8-6. Basic weather minimums for WSC operations in the different classes of airspace.

Controlled Airspace

Controlled airspace is a generic term that covers the different classifications of airspace and defined dimensions within which ATC service is provided in accordance with the airspace classification. Controlled airspace consists of:

• Class E
• Class D
• Class C
• Class B
• Class A

Class E Airspace

Generally, if the airspace is not Class A, B, C, or D, and is controlled airspace, then it is Class E airspace. Class E airspace extends upward from either the surface or a designated altitude to the overlying or adjacent controlled airspace. [Figures 8-3 and 8-7] Also Class E is federal airways beginning at 1,200 feet AGL extending 4 nautical miles (NM) on each side, extending up to 18,000 feet.

Figure 8-7. Class E airspace as shown on a sectional chart.

Unless designated at a lower altitude, Class E airspace begins at 1,200 AGL over the United States, including that airspace overlying the waters within 12 NM of the coast of the 48 contiguous states and Alaska, and extends up to but not including 18,000 feet.

There are no specific communications requirements associated with Class E airspace [Figure 8-5]; however, some Class E airspace locations are designed to provide approaches for instrument approaches, and a pilot would be prudent to ensure that appropriate communications are established when operating near those areas.

If WSC aircraft operations are being conducted below 10,000 feet MSL, minimum visibility requirements are three statute miles and basic VFR cloud clearance requirements are 1,000 feet above, 500 feet below, and 2,000 feet horizontal (remember the C152 mnemonic). Operations above 10,000 feet MSL for private pilots of WSC aircraft require minimum visibility of five statute miles and cloud clearances of at least 1,000 feet above, 1,000 feet below, and one statute mile horizontally. [Figure 8-5] See Figure 8-6 for specific VFR visibility requirements.

Towered Airport Operations

All student pilots must have an endorsement to operate within Class B, C, and D airspace and within airspace for airports that have a control tower, per 14 CFR section 61.94 or 14 CFR section 61.95. Only private pilot students can operate within Class B airspace with the proper endorsements per 14 CFR section 61.95. Sport pilots must also have an endorsement per 14 CFR section 61.325 to operate within Class B, C, and D airspace and within airspace for airports with a control tower. [Figure 8-5] All students and Sport pilots have further restrictions regarding the specific Class B airports out of which they may operate, per 14 CFR section 91.131.

Class D Airspace

Class D is that airspace from the surface to 2,500 feet AGL (but charted in MSL) surrounding smaller airports with an operational control tower. [Figures 8-3 and 8-8] The configuration of each Class D airspace area is individually tailored. When instrument procedures are published, the airspace is normally designed to contain the procedures.

Figure 8-8. Class D airspace shown on a sectional chart.

Unless otherwise authorized, each aircraft must establish two-way radio communications with the ATC facility providing air traffic services prior to entering the airspace and thereafter maintain those communications while in the airspace. Radio contact should be initiated far enough from the Class D airspace boundary to preclude entering the Class D airspace before two-way radio communications are established. It is important to understand that if the controller responds to the initial radio call without using the WSC aircraft’s call sign, radio communications have not been established, and the WSC aircraft may not enter the Class D airspace.

Many airports associated with Class D airspace do not operate a control tower on a 24-hour-a-day basis. When not in operation, the airspace will normally revert to Class E or G airspace, with no communications requirements. Refer to the AF/D for specific hours of operation airports.

The minimum visibility requirements for Class D airspace are three statute miles; cloud clearances are the 1,000 above, 500 below and 2,000 vertical. [Figure 8-6]

Class C Airspace

Class C airspace normally extends from the surface to 4,000 feet above the airport elevation surrounding those airports having an operational control tower, that are serviced by a radar approach control, and with a certain number of IFR and passenger enplanements (larger airline operations). [Figures 8-3 and 8-9] This airspace is charted in feet MSL, and is generally of a five NM radius surface area that extends from the surface to 4,000 feet above the airport elevation, and a 10 NM radius area that extends from 1,200 feet to 4,000 feet above the airport elevation. There is also a noncharted outer area with a 20 NM radius, which extends from the surface to 4,000 feet above the primary airport, and this area may include one or more satellite airports. [Figure 8-9]

Figure 8-9. Class C airspace as shown on a sectional chart.

WSC aircraft can fly into Class C airspace by contacting the control tower first, establishing communications (same as Class D), and having an altitude encoding transponder. Aircraft can enter Class C airspace without a transponder if prior permission from ATC is received 1 hour before entry, per 14 CFR section 91.215(d)(3). Aircraft may fly under the Class C upper tier of airspace without a transponder but not over the top of Class C airspace lateral boundaries.

Cloud clearances in Class C airspace are the same as Class D airspace: minimum visibility of three statute miles, and a minimum distance from clouds of 1,000 feet above, 500 feet below, and 2,000 feet horizontal.

Since Class C has significant air traffic, many with larger airplanes creating stronger vortices, the pilot must be aware that the chance of encountering catastrophic wingtip vortices is greater at airports with larger air traffic.

Class B Airspace

Class B airspace is generally airspace from the surface to 10,000 feet MSL surrounding the nation’s busiest airports in terms of IFR operations or passenger enplanements. [Figures 8-3 and 8-10] The configuration of each Class B airspace area is individually tailored and consists of a surface area and two or more additional 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.

Figure 8-10. Class B airspace as shown on a sectional chart.

Equipment requirements are the same as for Class C airspace; however, due to air traffic congestion, the WSC aircraft pilot requesting entry to Class B airspace may be denied entry. Since aircraft operating in Class B airspace have a radar signature and ATC provides aircraft separation, there is a difference in the cloud clearance requirements. Visibility remains three statute miles, but minimum cloud clearance requirement is to remain clear of clouds. [Figure 8-6]

Airspace Above 10,000′ MSL and Below 18,000′

For WSC aircraft flying above 10,000 feet MSL, the visibility must be greater than 5 SM and cloud clearances increase to 1,000 feet below, 1,000 feet above, and 1 SM horizontal. If the WSC aircraft was not certificated with an electrical system, an altitude encoding transponder is required per 14 CFR section 91.215.

Oxygen is required for the pilot above 12,500 MSL up to and including 14,000 feet MSL if the flight at those levels is more than 30 minutes duration. At altitudes above 14,000 feet MSL, oxygen is required for the pilot during the entire flight time at those altitudes. At altitudes above 15,000 feet MSL, each occupant of the aircraft must be provided with supplemental oxygen.

Class A Airspace

Class A airspace is generally the airspace from 18,000 feet MSL up to and including FL 600, including the airspace overlying the waters within 12 NM of the coast of the 48 contiguous states and Alaska. Unless otherwise authorized, all operations in Class A airspace are conducted under IFR. Class A airspace is not applicable to WSC pilots.

Special Use Airspace

Special use airspace is the designation for airspace in which certain activities must be confined, or where limitations may be imposed on aircraft operations that are not part of those activities.

Special use airspace usually consists of:

• Prohibited areas
• Restricted areas
• Warning areas
• Military operation areas (MOAs)
• Alert areas
• Controlled firing areas
• Parachute jump areas

Except for controlled firing areas, special use airspace areas are depicted on visual sectional charts. [Figure 8-11] Controlled firing areas are not charted because their activities are suspended immediately when spotter aircraft, radar, or ground lookout positions indicate an aircraft might be approaching the area. Nonparticipating aircraft are not required to change their flightpaths. Special use airspace areas are shown in their entirety (within the limits of the chart), even when they overlap, adjoin, or when an area is designated within another area. The areas are identified by type and identifying name or number, positioned either within or immediately adjacent to the area. [Figure 8-11]

Figure 8-11. Special use airspace designations as appear on sectional charts.

Prohibited, restricted or warning areas; alert areas; and MOAs are further defined with tables on sectional charts for their altitudes, time of use, controlling agency/contact facility and controlling agency contact frequency. [Figure 8-12]

Figure 8-12. Example of the additional information provided on sectional charts for special use airspace.

Prohibited Areas

Prohibited areas contain airspace of defined dimensions within which the flight of aircraft is prohibited. Such areas are established for security or other reasons associated with the national welfare. These areas are published in the Federal Register and are depicted on sectional charts. The area is charted as a “P” followed by a number (e.g., “P-56 A and B”). [Figure 8-13]

Figure 8-13. Prohibited area in Washington, D.C., on a sectional chart.

Restricted Areas

Restricted areas are areas where operations are hazardous to nonparticipating aircraft and contain airspace within which the flight of aircraft, while not wholly prohibited, is subject to restrictions. Activities within these areas must be confined because of their nature, or limitations may be imposed upon aircraft operations that are not a part of those activities, or both. Restricted areas denote the existence of unusual, often invisible, hazards to aircraft (e.g., artillery firing, aerial gunnery, or guided missiles). Penetration of restricted areas is illegal without authorization from the using or controlling agency may be extremely hazardous to the aircraft and its occupants. ATC facilities apply the following procedures:

1. If the restricted area is not active and has been released to the Federal Aviation Administration (FAA), the ATC facility will allow the aircraft to operate in the restricted airspace without issuing specific clearance for it to do so.
2. If the restricted area is active and has not been released to the FAA, the ATC facility will issue a clearance which will ensure the aircraft avoids the restricted airspace.

Restricted areas are charted with an “R” followed by a number (e.g., “R-4803 and R-4810”) and are depicted on the sectional charts. [Figure 8-14]

Figure 8-14. Special use airspace: restricted and MOA examples.

Warning Areas

Warning areas consist of airspace which may contain hazards to nonparticipating aircraft in international airspace. The activities may be much the same as those for a restricted area. Warning areas are established beyond the three-mile limit and are depicted on sectional charts.

Military Operations Areas (MOAs)

MOAs consist of airspace of defined vertical and lateral limits established for the purpose of separating certain military training activity from IFR traffic. There is no restriction against a pilot operating VFR in these areas; however, a pilot should be alert since training activities may include acrobatic and abrupt maneuvers. MOAs are depicted by name and with defined boundaries on sectional, VFR terminal area, and en route low altitude charts and are not numbered (e.g., “CHURCHILL HIGH MOA,” “CHURCHILL LOW MOA”). [Figure 8-14] MOA is further defined on sectional charts with times of operation, altitudes affected, and the controlling agency frequency for the MOA to contact for current activity. [Figure 8-15]

Figure 8-15. MOA is further defined on sectional charts with times of operation, altitudes affected, and the controlling agency to contact for current activity.

Alert Areas

Alert areas are depicted on sectional charts with an “A” followed by a number (e.g., “A-211” as in Figure 8-16) to inform nonparticipating pilots of areas that may contain a high volume of pilot training or an unusual type of aerial activity. Pilots should be particularly alert when flying in these areas. All activity within an alert area shall be conducted in accordance with regulations, without waiver. Pilots of participating aircraft, as well as pilots transiting the area, shall be equally responsible for collision avoidance.

Figure 8-16. Alert area (A-211).

Controlled Firing Areas

Controlled firing areas contain military activities, which, if not conducted in a controlled environment, could be hazardous to nonparticipating aircraft. The difference between controlled firing areas and other special use airspace is that activities must be suspended when a spotter aircraft, radar, or ground lookout position indicates an aircraft might be approaching the area.

Parachute Jump Areas

Parachute jump areas are published in the Airport/ Facility Directory (A/FD). Sites that are used frequently are depicted on sectional charts. Each pilot should listen to the appropriate airport radio frequency for parachute operations and be alert for aircraft which might be conducting parachute operations.

Other Airspace Areas

Other airspace areas is a general term referring to the majority of the remaining airspace. It includes:

• Airport advisory areas
• Military training routes (MTRs)
• Temporary flight restrictions (TFRs)
• Terminal Radar Service Areas
• National security areas

Local Airport Advisory

A local airport advisory is an area within 10 statute miles (SM) of an airport where a control tower is not operating, but where a flight service station (FSS) is located. At these locations, the FSS provides advisory service to arriving and departing aircraft. See AIM section 3-5-1 for more information on using the local airport flight station services.

Military Training Routes (MTRs)

National security depends largely on the deterrent effect of our airborne military forces. To be proficient, the military services must train in a wide range of airborne tactics. One phase of this training involves “low level” combat tactics. The required maneuvers and high speeds are such that they may occasionally make the see-and-avoid aspect of VFR flight more difficult without increased vigilance in areas containing such operations. In an effort to ensure the greatest practical level of safety for all flight operations, the Military Training Route (MTR) program was conceived.

These routes are usually established below 10,000 feet MSL for operations at speeds in excess of 250 knots. Some route segments may be defined at higher altitudes for purposes of route continuity. Routes are identified as IFR (IR), and VFR (VR), followed by a number. MTRs with no segment above 1,500 feet AGL are identified by four numeric characters (e.g., IR1206, VR1207). MTRs that include one or more segments above 1,500 feet AGL are identified by three numeric characters (e.g., IR206, VR207). IFR Low Altitude En Route Charts depict all IR routes and all VR routes that accommodate operations above 1,500 feet AGL. IR routes are conducted in accordance with IFR regardless of weather conditions.

MTRs are usually indicated with a gray line on the sectional chart. A WSC aircraft pilot flying in the area of VRs or IRs should question the briefer during the weather brief to find out if any of the routes are in use, and a possible time frame for opening and closing. While it is true that the WSC aircraft pilot has the right of way, the WSC aircraft will generally come out worse in a midair conflict with a fast-moving military aircraft. MTRs, such as the example depicted in Figure 8-17, are also further defined on sectional charts.

Figure 8-17. MTR chart symbols.

Temporary Flight Restrictions (TFRs)

TFRs are put into effect when traffic in the airspace would endanger or hamper air or ground activities in the designated area. For example, a forest fire, chemical accident, flood, or disaster-relief effort could warrant a TFR, which would be issued as a Notice to Airmen (NOTAM). The NOTAM begins with the phrase “FLIGHT RESTRICTIONS” followed by the location, effective time period, area defined in statute miles, and altitudes affected, which aircraft flying in the area must avoid. The NOTAM also contains the FAA coordination facility and telephone number, the reason for the restriction, and any other information deemed appropriate. The pilot should check NOTAMs as part of flight planning.

The reasons for establishing a temporary restriction are to:

• Protect persons and property in the air or on the surface from an existing or imminent hazard;
• Provide a safe environment for the operation of disaster relief aircraft;
• Prevent unsafe congestion of sightseeing aircraft above an incident or event, which may generate a high degree of public interest;
• Protect declared national disasters for humanitarian reasons;
• Protect the President, Vice President, or other public figures; and
• Provide a safe environment for space agency operations.

It is a pilot’s responsibility to be aware of TFRs in his or her proposed area of flight. One way to check is to visit the FAA website, www.tfr.faa.gov, and verify that there is not a TFR in the area. Another resource is to ask the flight briefer at 800-WX-BRIEF during the preflight briefing.

Terminal Radar Service Areas (TRSA)

Terminal Radar Service Areas (TRSA) are areas where participating pilots can receive additional radar services. The purpose of the service is to provide separation between all IFR operations and participating VFR aircraft.

The primary airport(s) within the TRSA become(s) Class D airspace. The remaining portion of the TRSA overlies other controlled airspace, which is normally Class E airspace beginning at 700 or 1,200 feet and established to transition to/ from the en-route terminal environment. TRSAs are depicted on VFR sectional charts and terminal area charts with a solid black line and altitudes for each segment. The Class D portion is charted with a blue segmented line. Participation in TRSA services is voluntary; however, pilots operating under VFR are encouraged to contact the radar approach control and take advantage of TRSA service. Operations inside the TFR area must be conducted under the provisions of a waiver. Should such an operation be contemplated, the WSC aircraft pilot should consult with the local Flight Service District Office (FSDO) well in advance of the event.

National Security Areas (NSAs)

NSAs consist of airspace with defined vertical and lateral dimensions established at locations where there is a requirement for increased security and safety of ground facilities. Flight in NSAs may be temporarily prohibited by regulation under the provisions of 14 CFR part 99, and prohibitions are disseminated via NOTAM.

Published VFR Routes

Published VFR routes are for transitioning around, under, or through some complex airspace. Terms such as VFR flyway, VFR corridor, Class B airspace, VFR transition route, and terminal area VFR route have been applied to such routes. These routes are generally found on VFR terminal area planning charts.

Flight Over Charted U.S. Wildlife Refuges, Parks, and Forest Service Areas

The landing of aircraft is prohibited on lands or waters administered by the National Park Service, U.S. Fish and Wildlife Service, or U.S. Forest Service without authorization from the respective agency. Exceptions include:

1. When forced to land due to an emergency beyond the control of the operator;
2. At officially designated landing sites; or
3. An approved official business of the Federal Government.

Pilots are requested to maintain a minimum altitude of 2,000 feet above the surface of the following: national parks, monuments, seashores, lakeshores, recreation areas, and scenic riverways administered by the National Park Service, National Wildlife Refuges, Big Game Refuges, Game Ranges, and Wildlife Ranges administered by the U.S. Fish and Wildlife Service and wilderness and primitive areas administered by the U.S. Forest Service.

WSC Operations

WSC preflight planning should include a review of the airspace that is flown. A local flight may be close to the field and include only Class G and Class E airspace. Minimum visibility and cloud clearance may be the only requirements to be met. However, a radio to communicate to the airport traffic and an altimeter to fly at the proper airport pattern altitude is recommended.

If flying to control tower airports or through Class B, C, or D airspace, determine if the WSC meets all of the equipment requirements of that airspace. [Figure 8-5] Also review qualifications to determine if the minimum pilot requirements of the airspace are met. If the minimum aircraft and/or pilot requirements of the airspace are not met, then the preflight planning should include a course around the airspace. Extra time and fuel is required for the circumnavigation and should be taken into consideration prior to departure.

Figure 8-5. Requirements for airspace operation.

WSC and Air Traffic Control

In nontowered airspace, airspace separation from other aircraft is the responsibility of the pilot. Separation from higher speed traffic may require flightpaths different than faster traffic. For flight and communicating with a control tower, the WSC pilot may be asked to expedite or deviate from a traditional course. The WSC pilot must work with ATC in advising of the airspeed and surface wind limitations. Safe operation in controlled airspace requires that the controller understand the performance and limits of the WSC aircraft.

Navigating the Airspace

Knowledge of airspace dimensions, requirements to enter the airspace, and geographical location of the airspace is the responsibility of all pilots. The current sectional chart is the primary official tool to determine the airspace flying within or avoiding.

Pilotage is navigation by reference to landmarks to determine location and the location of airspace. Pilotage is the best form of navigation to ensure that you avoid airspace not authorized to enter. Locating your position on the sectional chart and locating/identifying the airspace you want to enter/avoid requires preflight planning on the ground and situational awareness in the air.

For all flights, pilots must be sure to have enough fuel to complete the flight. For longer cross-country flights, this requires the pilot to check winds aloft and calculate the groundspeed for the planned altitude and forecast wind. The resultant time to the destination and the fuel consumption determines the fuel required to make the flight. This preflight planning is especially important for slower WSC aircraft because increased headwind components provide significant time increases to get to fuel stops than faster aircraft. Although 14 CFR section 91.151 requires airplanes to have at least 30 minutes of reserve fuel for an intended fuel stop; this minimum is also recommended for WSC aircraft. The Pilot’s Handbook of Aeronautical Knowledge chapter on navigation provides procedures in navigation, plotting a course, determining groundspeed for the predicted wind, headings and the required fuel for intended legs of the flight. For any cross-country flight, a flight log should be used and the planned groundspeed should be compared to the actual GPS groundspeed measured in flight. If the GPS groundspeed is lower than the planned groundspeed, the time en route and the fuel reserves must be evaluated to assure the WSC aircraft does not run out of fuel during the flight.

GPS is a very popular form of navigation used by WSC pilots. The GPS receiver is small, simple to use, and inexpensive compared to other forms of electronic (radio) navigation. Simple modes of operation provide actual groundspeed and time to a waypoint. More sophisticated GPSs have aviation databases and provide the pilot a considerable amount of information about airports and airspace. When using GPS to determine airspace or airport position, boundaries, and/ or information, the aviation database in the GPS may not exactly match the information as depicted on the sectional chart. If there is a difference between the sectional chart and GPS information, the sectional chart should be considered correct.

A WSC pilot using GPS should ensure that the batteries are fresh and the aviation database is current. Never rely on the GPS as a primary navigation system. Pilotage using the sectional chart is the primary navigation system when flying beyond visual range of a familiar airport. The GPS is used only as a backup aid for navigation. With proper preflight planning and constant evaluation of the planned verses actual flight performance, cross-country flight is practical in the NAS for WSC pilots.