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Controlled airspace

From Wikipedia, the free encyclopedia
Not to be confused with area control center.

Schematic representation of the main controlled airspace types and the air traffic control offices that respectively provide control service inside these airspaces.

Controlled airspace is airspace of defined dimensions within which air traffic control (ATC) services are provided.[1][2][3][4] The level of control varies with different classes of airspace. Controlled airspace usually imposes higher weather minimums than are applicable in uncontrolled airspace.[5] It is the opposite of uncontrolled airspace.

Classes

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The International Civil Aviation Organization divides airspace into seven classes, from A to G, in order of decreasing ATC regulation of flights. Classes A to E are controlled airspace. Flight under instrument flight rules (IFR) is allowed in all controlled airspace. Some countries also permit IFR in uncontrolled airspace. Flight under visual flight rules (VFR) is permitted in all airspace except class A.[6][7]

Name Permitted flight rules Separation provided Services provided Radio required Requires ATC clearance to enter
Class A Only IFR All aircraft are separated from all others Air traffic control service to all flights Yes Yes
Class B IFR and VFR All aircraft are separated from all others Air traffic control service to all flights Yes Yes
Clas C IFR and VFR IFR flights separated from all others. VFR flights receive traffic information on IFR flights. Air traffic control service to all flights Yes Yes
Class D IFR and VFR IFR flights separated from other IFR flights and receive traffic information on VFR flights. VFR flights receive traffic information on all other flights. Air traffic control service to all flights Yes Yes
Class E IFR and VFR IFR flights separated from other IFR flights. All flights may receive traffic information when practical. Air traffic control service to IFR flights, traffic information to VFR flights when practical Yes Yes for IFR, no for VFR
[8]

Surrounding airports

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Certain special types of controlled airspace exist to protect aircraft in the vicinity of a busy airport.

Control Zone (CTR)

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A control zone is a volume of controlled airspace, normally around an airport, which extends from the surface to a specified upper limit, established to protect air traffic operating to and from that airport. Because CTRs are by definition controlled airspace, aircraft can only fly in them after receiving a specific clearance from air traffic control. This means that air traffic control at the airport know exactly which aircraft are in that airspace, and can take steps to ensure aircraft are aware of each other, either using separation or by passing traffic information.

A CTR requires permanent radio contact while being in it, and a clearance before entering. Certain activities such as making an approach, landing and taking off also require clearances. This implies that an aircraft flying in it must be equipped with a radio. There are procedures for radio failures.

In the USA the term control zone is no longer used[9] and has been replaced by airspace class D. Typically it extends 5 miles in diameter with a height of 2500 ft AGL (above ground level) around small commercial airports.

In the UK, control zones are normally class D airspace and usually extend from the surface to 2000 ft AGL. They can be observed to be usually rectangular, extending along the axis of the main runway, although irregular shapes may be used where more complex airspace dictates this (see Liverpool and East Midlands). A control area (CTA) is often placed between a CTR and nearby airways to give uninterrupted controlled airspace to airways arrivals and departures.

In Germany, control zones are a special type of class D airspace, called D (CTR). The main difference to the regular German class D airspace is, that within a CTR there is a minimum required cloud ceiling of 1500 ft AGL.[10]

Control area (CTA)

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A control area is a section of controlled airspace that extends upwards from a specified limit above the earth, which must be above 200m (700ft),[11] and are established in areas where the density of traffic is high. The upper limit of a control area is either when an air traffic control service will not be provided above, or there is another control area above.[12]

A control area usually is situated on top of a control zone (CTR) and provides protection to aircraft climbing out from the airport by joining the low-level control zone to the nearest airways. In the UK, they are generally class A, D or E.[13]

A terminal control area (TMA) is a control area established surrounding one or major airports at the confluence of airways. It typically sits above each individual airport's CTR.[14]

Terminal radar service area (TRSA)

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In the United States, a terminal radar service area is a section of airspace surrounding a busy airport where optional air traffic control services are provided. It is designated as Class E airspace.[15]

Aerodrome Traffic Zone (ATZ)

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An aerodrome traffic zone is a small section of airspace defined around an aerodrome to protect the traffic departing or arriving. The dimensions vary. In the UK, it is typically defined as:[16]

  • Extending from the surface to 2000ft and with a radius of 2.5NM around the longest runway when the longest runway is longer than 1850m
  • Extending from the surface to 2000ft and with a radius of 2.0NM around the longest runway when the longest runway is shorter than 1850m

See also

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References

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  1. ^ "Aviation Glossary C". Transport Canada. Retrieved 13 August 2012.
  2. ^ "Canadian Aviation Regulations (SOR/96-433) - Part I (General Provisions) - Subpart 1 (Interpretation)". Government of Canada. Archived from the original on 3 April 2012. Retrieved 30 November 2016.
  3. ^ ""PHAK Chapter 15"" (PDF). FAA. Retrieved 28 September 2025.{{cite web}}: CS1 maint: url-status (link)
  4. ^ "Controlled Airspace". CAA Infringement Tutorial. Retrieved 28 September 2025.
  5. ^ "Canadian Aviation Regulations - Part VI - Section 602.114 - General Operating and Flight Rules". Transport Canada. Archived from the original on 19 September 2012. Retrieved 13 August 2012.
  6. ^ "TP 14371 - Transport Canada Aeronautical Information Manual (TC AIM) - RAC - 2.0 AIRSPACE – REQUIREMENTS AND PROCEDURES". Transport Canada. 11 April 2012. Archived from the original on 18 February 2011. Retrieved 13 August 2012.
  7. ^ "Classification of Airspace | SKYbrary Aviation Safety". skybrary.aero. Retrieved 28 September 2025.
  8. ^ "Classification of Airspace | SKYbrary Aviation Safety". skybrary.aero. Retrieved 28 September 2025.
  9. ^ FAA: [1]
  10. ^ Deutsche Flugsicherung: Airspace Structure/Visual Flight Rules in the Federal Republic of Germany – Example Archived 2018-12-24 at the Wayback Machine
  11. ^ "Annex 11 to the Convention on International Civil Aviation: Air Traffic Services" (PDF) (15 ed.). International Civil Aviation Organization (ICAO). July 2018. Retrieved 28 June 2024.
  12. ^ Smith, David (2021). Air Traffic Control Handbook. Manchester, England: Crécy Publishing Ltd. ISBN 978-1-9108-0999-0.
  13. ^ "Understanding airspace | UK Civil Aviation Authority". www.caa.co.uk. Retrieved 8 September 2025.
  14. ^ "Terminal Control Area (TMA) | SKYbrary Aviation Safety". skybrary.aero. Retrieved 8 September 2025.
  15. ^ Institute, Pilot (1 February 2025). "TRSA Airspace Explained (Terminal Radar Service Area)". Pilot Institute. Retrieved 28 September 2025.
  16. ^ "Aerodrome Traffic Zone (ATZ) | SKYbrary Aviation Safety". skybrary.aero. Retrieved 28 September 2025.


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