Restricted Area
FAA Acronyms and Initials Use to Abbreviate Altitude
It can be easy to get lost in the seemingly endless list of acronyms and initials used to abbreviate the many different altitudes associated with VFR and IFR operations. Here are a few brief descriptions of some of the common acronyms and initials the FAA has chosen to use to describe different VFR and IFR altitudes.
MSA - Minimum Safe Altitudes
Published for emergency use on instrument approach charts. For conventional navigation systems, the MSA is normally based on the primary omnidirectional facility on which the instrument approach is predicated. MSA's are expressed in MSL and normally have a 25 NM radius. They provide a 1,000 feet of clearance over all obstructions but do not assure acceptable navigation signal coverage. Found on Instrument Approach Charts. (See FAA-H-8261-1 Instrument Procedures Handbook)
ESA - Emergency Safe Altitude
Similar to an MSA but will provide 1000 of feet clearance in flat terrain and 2000 feet in designated mountainous terrain within 100 NM of the fix. Found on Instrument Approach Charts. (See AIM Glossary)
MEA - Minimum Enroute Altitude
The lowest published altitude that ensures a navigation signal strong enough for adequate reception by the aircraft navigation (NAV) receiver and adequate obstacle clearance along the airway. Communication is not necessarily guaranteed with MEA compliance. The obstacle clearance, within the limits of the airway, is typically 1,000 feet in non-mountainous areas and 2,000 feet in designated mountainous areas. Found on IFR Enroute Low Altitude Map. (See FAA Instrument Flying Handbook)
MOCA - Minimum Obstacle Clearance Altitude
Provides the same obstruction clearance as an MEA. However, navigation signal reception is only ensured within 22 NM of the closest NAVAID defining the route. The MOCA is listed below the MEA with an asterisk to the right of the altitude (*3400). Found on IFR Enroute Low Altitude charts. (See FAA Instrument Flying Handbook)
OROCA - Off-Route Obstacle Clearance Altitude
An OROCA is an off-route altitude that provides obstruction clearance with a 1,000-foot buffer in non-mountainous terrain and a 2,000-foot buffer in designated a mountainous areas within the U.S. This altitude may not provide signal coverage from ground-based navigation aids, air traffic control radar, or communications coverage. OROCAs are intended primarily as a pilot tool for emergencies and situational awareness. The large number represents thousands while the small number is representative of hundreds. Found on IFR Enroute Low Altitude charts. (See FAA-H-8261-1 Instrument Procedures Handbook)
MEF - Maximum Elevation Figure
The MEF represents the highest elevation, including terrain and other vertical obstacles (towers, trees, etc.), within a quadrant. A MEF is determined by taking the highest point within a quadrangle, adding 100 feet for vertical error, then adding the height of the highest obstacle in the quadrangle or 200 feet (whichever is higher), and then rounding up to the next hundred feet. Found on VFR Sectional Charts. (See Explanation of VFR Terms and Symbols)
MAA - Maximum Authorized Altitude
The highest altitude at which the airway can be flown without receiving conflicting navigation signals from NAVAIDs operating on the same frequency. Found on IFR Enroute Low Altitude charts. (See FAA Instrument Flying Handbook)
MCA - Minimum Crossing Altitude
The MCA is usually indicated prior to approaching steeply rising terrain, a changing obstacle clearance or to prevent signal reception being compromised. When indicated, the pilot is required to initiate a climb to reach the MCA by the time the intersection is crossed. Found on IFR Enroute Low Altitude charts. (See FAA Instrument Flying Handbook)
MRA - Minimum Reception Altitude
It is the lowest altitude on an airway segment at which an aircraft can be assured of receiving signals from navigation aids. If the reception is line-of-sight based, signal coverage will only extend to the MRA or above. (See FAA Instrument Flying Handbook)
MSA - Minimum Safe Altitudes
Published for emergency use on instrument approach charts. For conventional navigation systems, the MSA is normally based on the primary omnidirectional facility on which the instrument approach is predicated. MSA's are expressed in MSL and normally have a 25 NM radius. They provide a 1,000 feet of clearance over all obstructions but do not assure acceptable navigation signal coverage. Found on Instrument Approach Charts. (See FAA-H-8261-1 Instrument Procedures Handbook)ESA - Emergency Safe Altitude
Similar to an MSA but will provide 1000 of feet clearance in flat terrain and 2000 feet in designated mountainous terrain within 100 NM of the fix. Found on Instrument Approach Charts. (See AIM Glossary)
MEA - Minimum Enroute Altitude
The lowest published altitude that ensures a navigation signal strong enough for adequate reception by the aircraft navigation (NAV) receiver and adequate obstacle clearance along the airway. Communication is not necessarily guaranteed with MEA compliance. The obstacle clearance, within the limits of the airway, is typically 1,000 feet in non-mountainous areas and 2,000 feet in designated mountainous areas. Found on IFR Enroute Low Altitude Map. (See FAA Instrument Flying Handbook)
MOCA - Minimum Obstacle Clearance Altitude
Provides the same obstruction clearance as an MEA. However, navigation signal reception is only ensured within 22 NM of the closest NAVAID defining the route. The MOCA is listed below the MEA with an asterisk to the right of the altitude (*3400). Found on IFR Enroute Low Altitude charts. (See FAA Instrument Flying Handbook)
OROCA - Off-Route Obstacle Clearance Altitude
An OROCA is an off-route altitude that provides obstruction clearance with a 1,000-foot buffer in non-mountainous terrain and a 2,000-foot buffer in designated a mountainous areas within the U.S. This altitude may not provide signal coverage from ground-based navigation aids, air traffic control radar, or communications coverage. OROCAs are intended primarily as a pilot tool for emergencies and situational awareness. The large number represents thousands while the small number is representative of hundreds. Found on IFR Enroute Low Altitude charts. (See FAA-H-8261-1 Instrument Procedures Handbook)MEF - Maximum Elevation Figure
The MEF represents the highest elevation, including terrain and other vertical obstacles (towers, trees, etc.), within a quadrant. A MEF is determined by taking the highest point within a quadrangle, adding 100 feet for vertical error, then adding the height of the highest obstacle in the quadrangle or 200 feet (whichever is higher), and then rounding up to the next hundred feet. Found on VFR Sectional Charts. (See Explanation of VFR Terms and Symbols)MAA - Maximum Authorized Altitude
The highest altitude at which the airway can be flown without receiving conflicting navigation signals from NAVAIDs operating on the same frequency. Found on IFR Enroute Low Altitude charts. (See FAA Instrument Flying Handbook)MCA - Minimum Crossing Altitude
The MCA is usually indicated prior to approaching steeply rising terrain, a changing obstacle clearance or to prevent signal reception being compromised. When indicated, the pilot is required to initiate a climb to reach the MCA by the time the intersection is crossed. Found on IFR Enroute Low Altitude charts. (See FAA Instrument Flying Handbook)MRA - Minimum Reception Altitude
Radio Calls Made Easy
A cheat sheet is an easy way to sound like a pro on the radio. Print this card off before your next flight. While this cheat sheet is geared for instrument flight it also works when contacting ATC while VFR. And remember ATC can't hear you reading but everyone can hear those long pauses as you try to spit out your request for a clearance.
Class A Airspace
Class A airspace overlies the 48 contiguous United States and Alaska, including airspace overlying waters within 12 NM of the coast.
Dimensions:
The vertical boundaries of Class A airspace are 18,000 feet MSL to 60,000 feet MSL (FL 600). Above FL600, the airspace reverts to Class E. Airspace in Alaska below 1500 AGL is not considered part of Class A airspace regardless of altitude.
Clearance:
All operations in Class A airspace must be conducted under IFR. VFR and SVFR flight in Class A airspace is prohibited.
Class B Airspace
Description:
Class B airspace is used to control the flow traffic around major airports.
VFR Sectional:
The airspace is charted on a VFR Sectional with a series of blue lines. Within these blue lines the floor and the ceiling of the Class B airspace is defined.
Dimensions:
The lateral boundaries of Class B airspace are individually tailored to facilitate arriving and departing traffic operating under IFR. Class B airspace extends from the surface to generally 10,000 feet MSL. In Denver and Salt Lake City the ceiling is at 12,000 feet MSL while in Phoenix the ceiling is at 9,000 feet MSL. Always consult your map for the most current floor and ceiling information.
Clearance:
Aircraft must establish two-way radio communication with ATC and obtain a clearance to enter the airspace.
Transponder:
All aircraft operating inside or within 30 NM of Class B airspace are required to have a transponder with Mode C. The 30 NM Mode C Veil is denoted on VFR charts by a thin magenta line.
Weather:
VFR traffic must remain clear of clouds and maintain 3 SM of visibility while operating within Class B airspace.
Class B airspace is used to control the flow traffic around major airports.
VFR Sectional:
The airspace is charted on a VFR Sectional with a series of blue lines. Within these blue lines the floor and the ceiling of the Class B airspace is defined.Dimensions:
The lateral boundaries of Class B airspace are individually tailored to facilitate arriving and departing traffic operating under IFR. Class B airspace extends from the surface to generally 10,000 feet MSL. In Denver and Salt Lake City the ceiling is at 12,000 feet MSL while in Phoenix the ceiling is at 9,000 feet MSL. Always consult your map for the most current floor and ceiling information.
Clearance:
Aircraft must establish two-way radio communication with ATC and obtain a clearance to enter the airspace.
Transponder:
All aircraft operating inside or within 30 NM of Class B airspace are required to have a transponder with Mode C. The 30 NM Mode C Veil is denoted on VFR charts by a thin magenta line.
Weather:
VFR traffic must remain clear of clouds and maintain 3 SM of visibility while operating within Class B airspace.
Class C Airspace
Class C airspace is used around airports with moderate traffic levels.
VFR Sectional:
The airspace is charted on a VFR Sectional by 2 magenta circles. Within these magenta circles the floor and the ceiling of the Class C airspace is defined.Dimensions:
The airspace consists of 2 circles centered on the airport. The inner circle has a radius of 5 NM while the outer circle has a 10 NM radius. The inner circle begins at the surface and continues to 4000 ft AGL. The outer circle begins at 1200 ft AGL and continues to 4000 ft AGL. There is a 20 NM ring around all Class C airports referred to as the “Outer Area.” This area is not part of the Class C airspace. The outer area begins at the lower limit of radio/radar coverage and continues up to the upper limit of Approach Control's delegated airspace. As stated on VFR Sectional Charts you are asked to contact approach control within 20 NM of the airport.
Clearance:
Prior to entry, you must establish radio contact with ATC. If ATC responds with, "(Your aircraft call sign), standby," then contact has been established. If ATC does not use your call sign, contact has not been established.
Transponder:
A transponder with Mode C is required in and above all Class C airspace up to 10,000 ft MSL.
Weather:
VFR traffic must remain 500 ft below, 1000 ft above, and 2000 ft horizontal separation from clouds with 3 miles of visibility.
Class D Airspace
Class D airspace is generally pretty quiet but has the capacity and infrastructure to handle large volumes of traffic.
Sectional:
Class D airspace is charted on a VFR Sectional by a blue segmented line.
Dimensions:
The lateral dimensions of Class D airspace are individually tailored to facilitate IFR arrives and departures. The airspace begins at the surface and extends to 2,500 ft AGL. The MSL altitude of the ceiling is displayed as a two digit number within a dashed box. Some Class D airports have extensions protruding from the main airspace. These extensions are used for instrument approaches. If an extension is 2 NM or less, it is Class D airspace. If there is more than one extension and anyone of the extensions is greater than 2 NM, then all extensions are designated as Class E airspace.
Clearance:
Prior to entering Class D airspace, radio contact must be established with ATC. If ATC responds with, "(Your aircraft call sign), standby," then contact has been established. If ATC does not use your call sign, contact has not been established.
Class D airspace is only in effect when the tower is operational. When the tower is closed the airspace reverts to Class E and no clearance is required to enter. During these hours CTAF calls are over tower’s frequency.
Transponder:
A transponder is not required to operate within Class D airspace.
Weather:
VFR traffic must remain 500 ft below, 1000 ft above, and 2000 ft laterally from clouds with 3 miles of visibility while operating within Class D airspace.
Class E Airspace
Description:
All controlled airspace which is not Class A, B, C nor D is considered Class E airspace.
VFR Sectional:
Three types of Class E airspace are depicted on VFR Sectional Charts: surface based, transitional areas, and federal airway.
Surface based Class E airspace is depicted by a magenta segmented line. On occasion it is included as an extension of Class D airspace. These extensions are used facilitate instrument approaches. If the extension is 2 NM or less, it is Class D airspace. If anyone extension is greater than 2 NM, then all extensions are Class E airspace. (A clearance is not necessary to transition though Class E extensions.)
Transitional areas are used to transition between the terminal and en route environment. The airspace begins at either 700 feet AGL (fading magenta band) or 1200 feet AGL (fading blue band).
Federal airways below 18,000 feet MSL are Class E airspace. These airways are also known as Vector airways and begin at 1200 feet AGL.
Dimensions:
Surface based and transitional areas are individually tailored to fit the needs of the environment they serve.
Federal airways within Class E airspace begin at 1200 feet AGL and extend up to but not including 18,000 feet MSL. The width of a these airways is 8 NM. Airways exceeding 51 NM expand about 2 NM every 13 NM.
Unless designated at a lower altitude, Class E airspace begins at 14,500 feet MSL and continues up to but not including 18,000 feet MSL over the 48 contiguous States and Alaska.
Clearance:
A clearance is not required to enter Class E airspace.
Transponder:
A transponder is not required to operate within Class E airspace.
Weather:
VFR visibility and cloud clearance requirements are the same as Class C and Class D when below 10,000 feet MSL. Above 10,000 feet MSL, the visibility requirement is extended to 5 SM and the cloud clearance requirement is extended to 1,000 feet below, 1,000 feet above, and 1 SM laterally from clouds.
All controlled airspace which is not Class A, B, C nor D is considered Class E airspace.
Three types of Class E airspace are depicted on VFR Sectional Charts: surface based, transitional areas, and federal airway.
Surface based Class E airspace is depicted by a magenta segmented line. On occasion it is included as an extension of Class D airspace. These extensions are used facilitate instrument approaches. If the extension is 2 NM or less, it is Class D airspace. If anyone extension is greater than 2 NM, then all extensions are Class E airspace. (A clearance is not necessary to transition though Class E extensions.)
Transitional areas are used to transition between the terminal and en route environment. The airspace begins at either 700 feet AGL (fading magenta band) or 1200 feet AGL (fading blue band).
Federal airways below 18,000 feet MSL are Class E airspace. These airways are also known as Vector airways and begin at 1200 feet AGL.
Dimensions:
Surface based and transitional areas are individually tailored to fit the needs of the environment they serve.
Federal airways within Class E airspace begin at 1200 feet AGL and extend up to but not including 18,000 feet MSL. The width of a these airways is 8 NM. Airways exceeding 51 NM expand about 2 NM every 13 NM.
Unless designated at a lower altitude, Class E airspace begins at 14,500 feet MSL and continues up to but not including 18,000 feet MSL over the 48 contiguous States and Alaska.
Clearance:
A clearance is not required to enter Class E airspace.
Transponder:
A transponder is not required to operate within Class E airspace.
Weather:
VFR visibility and cloud clearance requirements are the same as Class C and Class D when below 10,000 feet MSL. Above 10,000 feet MSL, the visibility requirement is extended to 5 SM and the cloud clearance requirement is extended to 1,000 feet below, 1,000 feet above, and 1 SM laterally from clouds.
Class G Airspace
Description:
All uncontrolled airspace is considered Class G.
Sectional:
Not depicted
Dimensions:
All airspace outside of controlled airspace.
Clearance:
A clearance is not required to operate VFR within Class G airspace.
Transponder:
A transponder is not required to operate VFR within Class G airspace.
Weather:
All uncontrolled airspace is considered Class G.
Sectional:
Not depicted
Dimensions:
All airspace outside of controlled airspace.
Clearance:
A clearance is not required to operate VFR within Class G airspace.
Transponder:
A transponder is not required to operate VFR within Class G airspace.
Weather:
1200 feet AGL or less above the surface (regardless of MSL altitude).
|
||
| Visibility | Clouds | |
| Day | 1 statute mile | Clear of clouds |
| Night | 3 statute mile | 500 feet below
1,000 feet above 2,000 feet horizontal |
| More than 1,200 feet AGL but less than 10,000 feet MSL. | ||
| Visibility | Clouds | |
| Day | 1 statute mile | 500 feet below 1,000 feet above 2,000 feet horizontal |
| Night | 3 statute miles | 500 feet below 1,000 feet above 2,000 feet horizontal |
| More than 1,200 AGL and at or above 10,000 feet MSL. | ||
| Visibility | Clouds | |
| Day/Night | 5 statute miles | 1,000 feet below 1,000 feet above 1 statute mile horizontal |
Terminal Radar Service Area (TRSA)
Terminal Radar Service Areas (TRSA) are pockets of airspace surrounding some Class D airports. Within a TRSA radar services such as traffic advisories and flight following are offered. Unlike other classes of airspace that offer similar services, pilot participation is within a TRSA is voluntary.
Charts:
A TRSA is depicted on a VFR sectional and terminal area charts by solid black lines with ceiling and floor altitudes included for each segment. All TRSAs include a Class D airport depicted with a blue segmented line.
Clearance:
A clearance is not required to operate VFR within a TRSA. However, pilots are highly encouraged to contact the controlling agency for advisories.
Transponder:
A transponder is not required to operate VFR within a TRSA.
Weather:
TRSA weather minimums are the same as those in Class E airspace. Class D airspace weather minimums apply within the Class D airspace.
Reference: AIM 3-5-6