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Controlled Airspace
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Introduction
Controlled airspace is the airspace within which air traffic control service is provided, and within which some, or all aircraft may be subjected to air traffic control.
Types of controlled airspace are High Level Airspace, and Low Level Airspace, both of which are described below.
High Level Airspace
All airspace 18 000ft and above is considered high level airspace.
The high level airspace is divided into 3 regions, depicted below.
- The Southern Control Area (SCA). The boundaries of the southern control area are the same as those of the Southern Domestic Airspace. Within the Southern Control Area all traffic is controlled.
- The Northern Control Area (NCA) Within the Northern Control Area all traffic above FL230 is controlled.
- The Arctic Control Area (ACA) Within the Arctic Control Area all traffic above FL270 is controlled.
In the Northern Domestic Airspace there is airspace between 18 000ft ASL and the floors of the NCA (FL230) and ACA (FL270) which is high level airspace but which is uncontrolled.
All high level airspace within the SCA is controlled airspace, designated class A.
Encompassed within the high level airspace are the following types of controlled high level airspace: high level airways and that portion of any Terminal control area (TCA), Control area extension, Class F CYA zones and Class F CYR zones that may extend above FL180.
Also there are high level air routes which are uncontrolled.
High Level airways are routes between points along which aircraft can navigate by following NDB or VOR signals. High level Jet airways are followed by reference to the radials projected by VORs located approximately 100nm apart along the airways.
High Level air-routes are prescribed tracks between specified nav-aids but along which Air traffic control is not provided. These High level air-routes exist only in Northern Domestic Airspace between FL180, and the bases of the Northern and Arctic Control Areas (see above).
Low Level Airspace
All airspace within the Canadian Domestic Airspace below 18 000ft is considered low level airspace.
Not all low level airspace is controlled. Boundaries of low level controlled airspace are indicated on indicated on the LO en-route charts.
Airspace that is uncontrolled from the ground to, but not including 18 000ft is shaded green, while airspace that is uncontrolled to 12 500ft is shaded green which white pinstripes.
Encompassed within the high level airspace are the following types of controlled low level airspace: low level airways, and that portion of any Terminal control area (TCA), Control area extension, Class F CYA and Class F CYR.
Also there are high level air routes which are uncontrolled.
Low Level Airways are routes between points along which aircraft can navigate by following NDB or VOR signals. Low level Victor airways are followed by reference to the radials projected by VORs located approximately 100nm apart along the airways.
MF/LF air-routes are routes between points along which aircraft can navigate by following NDB signals. They can be controlled, or uncontrolled.
(Hint: In most cases if the airway is coloured black on the LO en-route charts it is controlled, while if it is green it is an uncontrolled airway)
The basic width of a Victor airway is 4nm either side of the centerline; of a LF/MF air-route, 4.34nm either side of the centerline.
Unless otherwise published an airway is based at 2 200ft above ground level (AGL). It extends up to the base of the overlying High Level airspace.
That portion of a low level airway that extends upwards between 12 500ft and, but not including 18 000ft is designated class B. At and below 12 500ft a low level airway is designated class E airspace, except when passing through a TCA.
VFR aircraft operating below 12 500ft within a low level airway are not subject to air traffic control. However ATC control is provided for all IFR aircraft. (standard class E airspace)
Control Area extensions (CAE)
Control Area Extensions are established at some airports to provide additional controlled airspace to handle IFR traffic.
The CAE surrounds the core control zone (CZ) and IFR traffic is controlled by the appropriate Area Control Centre (ACC, call-sign xxxx_CTR). A cross section of such airspace is available in the section Airspace classification.
Control Zones (CZ)
Control Zones are designated around larger airports to keep IFR aircraft within controlled airspace, and to facilitate the control of VFR and IFR aircraft.
These control zones are established around airports which have control towers. The area of control begins at the surface of the earth. The upper limit is usually 3 000ft AAE (Above Aerodrome Elevation), but may vary.
Control zones associated with a TCA usually have a radius of 7nm, while others usually have a 5nm radius.
Military control zones usually have a radius of 10nm, and extend to 6 000ft AAE.Control zones will be classified as B, C, D or E depending on the classification of the surrounding airspace.
Terminal Control Areas (TCA)
Terminal control areas are established at airports with a high volume of traffic to provide IFR control service to arriving, departing and en-route aircraft.
Terminal control areas may be designated class A, B, C, D or E. TCAs usually extend into High Level airspace. That portion of a TCA that extends above 12 500ft is designated class B airspace regardless of the classification of the rest of the TCA. Any portion that may extend above 18 000ft (FL180) is designated class A airspace.
The TCA operating rules are established according to the classification of the airspace within the TCA. All traffic is normally controlled by the Terminal Control Unit (TCU, call-sign xxxx_DEP or xxxx_APP).The lateral and vertical dimensions of a TCA and it's control zone(s) are published on the Terminal Area charts in the CFS.
VFr traffic may operate in the uncontrolled airspace below the TCA without contacting ATC, however contact must be established prior to entering the controlled airspace.
Military Terminal Control Area (MTCA)
A MTCA is a Terminal Control Area in which air traffic control is provided by a military unit. Special provisions for military aircraft prevail, such as VFR above FL180.