What is 'Airspace'?
In the aviation context, airspace can be defined as any part of the earth's atmosphere that can be used by an aircraft. Airspace is a three-dimensional space, or volume, where aircraft (including rockets, balloons, gliders, etc) can operate.
The use of airspace is controlled by international rules and procedures in much the same way that shipping is controlled by laws of the sea. In practice, the rules and operating procedures are complex, particularly in the vicinity of major airports.
It is international practice to measure airspace in feet for altitude and nautical miles for distance. Metric equivalents are included below in brackets. Airspace volumes are defined by vertical boundaries expressed in feet above a datum, and horizontally by defined lines between, or bearings and distances from, known points on the ground or by latitude and longitude.
The following is a general and generic explanation of airspace elements and does not attempt to cover all the definitions and technical issues involved.
Controlled and Uncontrolled Airspace
Airspace is either controlled or uncontrolled. Controlled airspace in Australia is designated differently based on the level of air traffic service provided. To enter controlled airspace, an aircraft must first gain a clearance from the applicable air traffic service provider. No clearance is required to operate in uncontrolled airspace. Controlled airspace comprises terminal and en-route as described below.
Terminal airspace is the airspace surrounding a major airport, generally within 30 to 50 nautical miles (55 - 90 km). In the case of Sydney Airport, this airspace extends from ground level up to 18,000 feet (approximately 6,000 m) close to the airport. As the distance from the airport increases, the lower boundary of the zone rises in steps, beginning at 1,000 feet (300 m) and increasing to typically 7,500 feet (2,300 m) at the outer edges of the Sydney Basin. This enables other airspace users, such as gliders, balloons, etc, to operate safely underneath terminal airspace without requiring an air traffic clearance.
En-route airspace encloses the flight paths between airports where an air traffic service is provided.
Restricted airspace is defined as airspace within which the flight of aircraft is restricted in accordance with certain specified conditions. This designation is normally used whenever the activities within the airspace are a hazard to other users; or other users could constitute a hazard to the activities. Examples of restricted airspace would be airspace around a military installation or an explosives storage facility, or for high density flying operations at a big airshow.
Australian Airspace - the Relationships
Airspace is a national resource overlying territorial Australia and adjacent oceanic regions. The responsibility for managing that airspace outside its territorial boundaries is allocated to Australia by the International Civil Aviation Organization (ICAO).
Legislation and policy relating to airports and aviation, including Australia's participation in the work of ICAO, is overseen by the Department of Infrastructure and Regional Development.
CASA sets regulations and standards for civil aviation operations in Australia, with the Office of Airspace Regulation (OAR) regulating airspace aspects. The Department of Defence is responsible for military aviation operations.
The Australian airspace architecture is published in the Australian Aeronautical Information Publication (AIP) suite of documents by Australia's current Aeronautical Information Service provider, Airservices Australia.
Changes to the airspace architecture are published on an Aeronautical Information Regulation and Control (AIRAC) date, in accordance with the requirements of ICAO Annex 15. The changes become effective after promulgation in the AIP.
Airspace Management Principles
The operation of OAR, within CASA, is dictated by the overall principals or requirements placed on CASA itself.
- Safety - CASA must regard the safety of air navigation as the most important consideration.
- ICAO Obligations - CASA must perform its functions in a manner that is consistent with Australia's obligations under the Chicago Convention.
- Environment - CASA must exercise its powers and perform its functions in a manner that ensures that, as far as is practicable, the environment is protected from the effects of the operation and use of aircraft, and the effects associated with the operation and use of aircraft.
- Consultation and Cooperation - CASA must, where appropriate, consult with government, commercial, industrial, consumer and other relevant bodies and organisations (including ICAO and bodies representing the aviation industry).
- Government Policy - The Minister for Infrastructure, Transport, Regional Development and Local Government will, from time to time, issue CASA with an Australian Airspace Policy Statement. This statement provides CASA with direction and guidance on the administration of airspace. Relevant regulatory and other decisions made by CASA or its delegates must be consistent with this statement.
Key Policy Principles for Airspace Administration
Key principles have been developed by the Australian Government to guide the administration of airspace as a national resource. The principles are specified in the Australian Airspace Policy Statement (2012):
- shall consider the current and future needs of the Australian aviation industry;
- shall adopt proven international best practice airspace systems adapted to benefit Australia’s aviation environment; and
- shall take advantage of advances in technology wherever practicable.
CASA will take these principles into account in carrying out its airspace regulation activities.