Controlled Airspace

Controlled Airspace is an airspace of defined dimensions within which air traffic control service is provided in accordance with the airspace classification.

Services

There are 3 services available in controlled airspace:

  • Flight Information Service
  • Alerting Service
  • Radar Control Service

Flight Information Service:

A Flight Information Service (FIS) is a non-radar service provided, either separately or in conjunction with other services, for the purposes of supplying information useful for the safe and efficient conduct of flights. Under a FIS the following conditions apply:

  • Provision of the service includes information about weather, changes of serviceability of facilities, conditions at aerodromes and any other information pertinent to safety.
  • The controller may attempt to identify the flight for monitoring and co-ordinationpurposes only. Such identification does not imply that a radar service is being provided or that the controller will continuously monitor the flight.
  • Pilots must be left in no doubt that they are not receiving a radar service.
  • Controllers are not responsible for separating or sequencing aircraft.

Alerting Service:

An alerting service is provided to notify appropriate organisations regarding aircraft in need of search and rescue aid, and assist such organisations as required.

Radar Control Service:

a) radar control service may be provided to aircraft operating IFR, SVFR or VFR. When providing the service controllers issue instructions to which:
a) pilots of aircraft operating IFR are required to comply; and
b) pilots of aircraft operating SVFR or VFR will comply unless they advise the controller otherwise.

Semi Cicular rule

Above FL 195 in Class C airspace the semi-circular rule shall apply. Flight levels 200, 220, 240, 260 and 280 shall be westbound; Flight levels 210, 230, 250 and 270 shall be eastbound. Above FL290, cruising levels are allocated according to the RVSM system.

Cruising levels at or above FL 410 up to FL 660 shall be selected according to the
semi-circular rule, therefore, flight levels available are:

  • Eastbound FL 410, FL 450, FL 490 etc.
  • Westbound FL 430, FL 470, FL 510 etc.

Uncontrolled Airspace

Within uncontrolled airspace in Australia, aircraft may operate free of the control of an ATC unit. However all aircraft are required at all times to conduct their activities with regard to the CASA Regulations.

When cruising in uncontrolled airspace pilots are advised to monitor continuously the emergency frequency 121.5, and 122.8

Services

There are 4 types of ATC service available to aircraft outside of controlled airspace:

  • Alerting Service
  • Basic Service
  • Traffic Service (Radar)
  • Deconfliction Service (Radar)

Alerting Service:

An alerting service is provided to notify appropriate organisations regarding aircraft in need of search and rescue aid, and assist such organisations as required.

Basic Service:

A Basic Service is a non-radar service provided, either separately or in conjunction with other services, for the purposes of supplying information useful for the safe and efficient conduct of flights. Under a Basic Service the following conditions apply:

  • Provision of the service includes information about weather, changes of serviceability of facilities, conditions at aerodromes and any other information pertinent to safety.
  • The controller may attempt to identify the flight for monitoring and co-ordinationpurposes only. Such identification does not imply that a radar service is being provided or that the controller will continuously monitor the flight. Pilots must be left in no doubt that they are not receiving a radar service.
  • Controllers are not responsible for separating or sequencing aircraft.

Traffic Service:

A Traffic Service is an air traffic radar service in which the controller shall inform the pilot of the bearing, distance and, if known, the level of the conflicting traffic. No avoiding action shall be offered. The pilot is wholly responsible for maintaining separation from other aircraft whether or not the controller has passed
traffic information. Under a Traffic Service the following conditions apply:

  • The service may be requested under any flight rules or meteorological conditions.
  • The controller shall only update details of conflicting traffic, after the initial warning, at the pilot’s request or if the controller considers that the conflicting traffic continues to constitute a definite hazard.
  • The controller may provide radar vectors for the purpose of tactical planning or at the request of the pilot. However, vectors shall not be provided to maintain separation from other aircraft, which remains the responsibility of the pilot. There is no requirement for a pilot to accept vectors.
  • The controller will be advised before a pilot changes level, level band or route.
  • Should a pilot request avoiding action, this shall be treated as a request for a change of radar service.

Deconfliction Service:

A Deconfliction Service is an air traffic radar service in which the controller shall provide advice necessary to maintain prescribed separation between aircraft participating in the advisory service, and in which he shall pass to the pilot the bearing, distance and, if known, level of conflicting non-participating traffic, together with advice on action necessary to resolve the confliction. Where time does not permit this procedure to be adopted, the controller shall pass advice on avoiding action followed by information on the conflicting traffic. Even though the service is an advisory one, controllers shall pass the 'advice' in the form of instructions. Under a Deconfliction Service the following conditions apply:

  • The service may be requested under any flight rules or meteorological conditions.
  • Controllers can expect the pilot to accept vectors or level allocations which may require flight in IMC. Controllers should be aware that pilots may not be qualified to fly in IMC. Should this situation arise the controller will be informed by the pilot.
  • There is no legal requirement for a pilot flying outside controlled airspace to comply with instructions because of the advisory nature of the service. However, should a pilot choose not to comply with advisory avoiding action then he will become responsible for his own separation and any avoiding action that may subsequently prove necessary.
  • The controller will be advised before a pilot changes heading or level.
  • Controllers shall pass avoiding action instructions to resolve a confliction with nonparticipating traffic and, wherever possible, shall seek to achieve separation which is not less than 5 nm or 3000 feet, except when specified otherwise by CASA. However, it is recognised that in the event of the sudden appearance of unknown traffic, and when unknown aircraft make unpredictable changes in flight path, it is not always possible to achieve these minima.
  • Controllers shall continue to provide information on conflicting traffic until the confliction is resolved.

Australian Airspace Classification System

Australia uses a unique (by world standards) airspace classification system although it has become largely aligned with the system used in the USA over recent years. There are four ICAO standard airspace classes (A, C, D, E), plus one uniquely Australian class (GAAP) of controlled airspace used in Australia. The special GAAP class of airspace which is currently used at the major, captial city general aviation aerodromes is scheduled to change to the ICAO standard Class D during 2010. The classes of airspace differ in that they have different operational requirements and / or operational restrictions.

Airspace Class Descriptions

Class A

Class A is high level enroute airspace that is used by high performance jet and turbo-prop airspace. VFR flights are not generally permitted withinin Class A airspace. Separation is provided between all aircraft operating in Class A and there are no speed restrictions.Clearance is required by all aircraft operating in Class A.

Class C

Class C surrounds major city airports starting at ground level and stepped up into mid-level Class C or the high-level Class A airspace. The control area steps above Class D aerodromes is also classified Class C as is airspace within radar coverage south of Sydney between FL125 and FL180. Military restricted areas at or below FL285 are classified as Class C whilst they are active.

IFR and VFR flights are permitted within Class C, VFR flights are limited to 250 kts indicated airspeed below 10,000 feet AMSL. (If you are a balloon pilot this will hopefully never be an issue for you). Air traffic services are required to provide separation between IFR and IFR and IFR and VFR traffic. Traffic information and traffic avoidance advice is provided for VFR to VFR traffic but a separation service is not.Clearance is required by all aircraft operating in Class C.

Class D

Class D airspace is used around the non-capital city controlled aerodromes. Protected airspace in the form of Class C steps are provided above Class D to allow high speed and heavy traffic to remain inside controlled airspace whilst arriving and departing the Class D area.

IFR and VFR flights are permitted within Class D, Non-military IFR and VFR aircraft are limited to 250 kts indicated airspeed below 10,000 feet AMSL.Traffic information is provided to IFR about VFR traffic and VFR flights recieve information about all flights. Clearance is required by all aircraft operating in Class D.

Class E

Class E is mid level airspace where IFR aircraft are provided with a separation service from other IFR aircraft and where workload permits IFR aircraft are given traffic information about known VFR traffic. VFR traffic only recieves a flight information service on request. IFR and VFR flights are restricted to 250kts indicated airspeed below 10,000 feet AMSL. In Class E airspace IFR aircraft must obtain a clearance but VFR flights do not require a clearance.

Class G

Class G is uncontrolled airspace and accounts for the majority of Australian airspace. There is no separation service provided to any aircraft operating in Class G but a flight information service is provided to IFR traffic and flight information and radar information services and flight following is provided on request to VFR flights.Speed is restircted to below 250 kts for all aircraft below 10,000 feet AMSL whilst within Class G. CLass G is the only airspace category in which 'no radio' flights may be conducted but these are restricted to below 5,000 feet AMSL, away from aerodromes that require the use of radio and in weather conditions than meet the standard VMC criteria.

Within Class G, uncontrolled airspace some aerodromes operate a Common Traffic Advisory Frequency (CTAF) which imposes a requirement for radio to be carried and used but does not affect the operational services or requirements provided by air traffic services.

GAAP

GAAP airspace is uniquely Australian! The major capital city general aviation aerodrome aerodromes are currently classified GAAP but these are in the process of changing to Class D. In GAAP airspace IFR aircraft are provided a separation service when IMC conditions exist, and a special VFR to special VFR separation service is provided when visibility is less than VMC. An air traffic control serice is provided for take-off and landing.

Airspace Design Models

There are three general airspace design models used in Australia. There is one for use of the majority of the country where there is no radar coverage and two for use along the east and south east fringes of the country where there is radar coverage because a high percentage of the air traffic operates in those areas. Different models are used in the north and south because of the differing type of air traffic in those areas. From Sydney north, because of the larger distances that are generally flown there are comparitively few high performance piston engine aircraft used for commuter Regular Public Transport (RPT) operations so there is less traffic operating in the 8,000 - 10,000 foot altitude range. This means that there isn't sufficient demand for seperation services between instrument flight rules (IFR) and visual flight rules (VFR) traffic to warrant Class C airspace below the flight levels. In the southern part of Australia there is still quite a lot of short haul commuter aircraft operate between 8,000 and 10,000 feet so Class C is provided.

Airspace Depiction on Charts

Airspace categories and their lateral and vertical limits are depicted on ERC-L, ERC-H, TAC and VTC charts. Each chart has a legend which gives specific information about the way information is depicted on the chart.

The lower limits of airspace are shown on all charts by indicating the airspace class and the lower limit. Where a piece of airspace commences at the surface the lower limit is shown as 'SFC'. In areas where different classes of airspace are stacked vertically the labels are shown in layers

.Airspace lower limit

Boundaries of Class A, C and D controlled airspace are shown on charts as a SOLID BLUE line. Class E controlled airspace is shown on charts as a SOLID BROWN line and should not be confused with the dashed brown flight information area frequency boundary. Military controlled airspace and restricted areas are shown using MAGENTA lines.

RVSM

RVSM airspace was introduced throughout Australia in January 2002. It has also been implemented in North America, South America, Europe, Middle East, Africa, Parts of Asia and the Atlantic and Pacific Oceans.

RVSM means Reduced Vertical Separation Minima - or in plain english the reduction of the vertical separation required between FL290 and FL410 from 2000ft to 1000ft. By doing this you double the amount of airspace available, therefore doubling the traffic capacity. With the skies getting busier and busier every day the need for more room has become more and more important.

In the real world aircraft must have the following equipment aboard to be RVSM certified and therefore take advantage of the reduced separation minimum:

  • Two primary altitude reporting systems;
  • One automatic altitude-keeping device;
  • One altitude-alerting device.
  • In addition, while changing altitudes, the altitude holding device must not overshoot an assigned level by more than 150 feet.
  • Also, to gain certification for RVSM, each aircraft must overfly a stationary Height Monitoring Unit (HMU) or a portable Ground Monitoring Unit (GMU) unless flight test evidence can be supplied to the regulator that the airframe is compliant with Altimeter System Error (ASE) targets.

Aircraft who do not meet the standards are excluded from RVSM airspace except for the purpose of climbing or descending to/from the CVSM airspace above FL410. (Exceptions do exist though, see bottom of page for complete listing.)

In the real world this was a costly affair for operators who still had older aircraft in their fleet. On IVAO there isn't much to it, as any aircraft can be considered RVSM, or non-RVSM. There are however a few important procedures for pilots and ATC to follow. They are detailed below.

Altitudes

Pilots flying through RVSM airspace continue using the Odd-East / West-Even rule up to FL410, after which the airspace becomes CVSM.

Use the following table for reference:

RVSM airspace (the new way)
West track (180°-359°)
Even Altitudes
East track (000°- 179°)
Odd Altitudes
4,000 ft
6,000 ft
8,000 ft
10,000 ft
12,000 ft
14,000 ft
16,000 ft
FL 180
...
FL 280
-------------
FL 300
FL 320
FL 340
FL 360
FL 380
FL 400

FL 430
FL 470
FL 510
...
5,000 ft
7,000 ft
9,000 ft
11,000 ft
13,000 ft
15,000 ft
17,000 ft
FL 190
...
FL 290
-------------
FL 310
FL 330
FL 350
FL 370
FL 390
FL 410

FL 450
FL 490
FL 530
...
CVSM airspace (the old way)
West track (180°-359°)
Even Altitudes
East track (000°- 179°)
Odd Altitudes
4,000 ft
6,000 ft
8,000 ft
10,000 ft
12,000 ft
14,000 ft
16,000 ft
FL 180
...
FL 280
-------------
FL 310
FL 350
FL 390

FL 430
FL 470
FL 510
...
5,000 ft
7,000 ft
9,000 ft
11,000 ft
13,000 ft
15,000 ft
17,000 ft
FL 190
...
FL 290
-------------
FL 330
FL 370
FL 410

FL 450
FL 490
FL 530
...

Changes to cruise direction from the old system to the new RVSM system are highlighted in red.

Pilot Guidelines

All pilots operating within RVSM airspace are to comply with the following guidelines:

  • Pilots flying RVSM certified aircraft are expected to file altitudes appropriate for the direction of flight in compliance with the previous table.
  • The equipment suffix W shall be filed in the flight plan to indicate RVSM certification.
  • Autopilot must be used to maintain altitude in level cruise flight. Manual trimming of the aircraft is not acceptable. If the autopilot does not work or the altitude hold mode is known to be inaccurate, the aircraft will be considered non-RVSM, and therefore not allowed into RVSM airspace. The equipment suffix "W" is not to be used on such aircraft.
  • If a pilot notices his aircraft is unable to accurately maintain altitudes with the autopilot altitude hold he/she is to consider the aircraft as not up to RVSM standards and notify ATC at once. This applies regardless of whether the aircraft is already in, or cleared to enter RVSM airspace. ATC may instruct pilots of such aircraft to leave RVSM airspace if traffic requires.
  • Pilots are to report any encounters with turbulence greater than moderate. By its nature, severe turbulence means that control of the aircraft is affected, and RVSM procedures can no longer be maintained.

ATC Guidelines

All controllers operating positions involving RVSM airspace are to follow the following guidelines:

  • All aircraft having filed /W equipment suffix will be considered RVSM certified and equipped, unless there it is apparent that the aircraft is unable to hold altitude with reasonable accuracy.
  • Aircraft not having filed /W equipment suffix, will not be cleared to enter RVSM airspace except for those aircraft meeting the conditions described in the exceptions listed below.
  • Aircraft operating in RVSM Airspace who indicate an inability to maintain altitude correctly shall be considered non-RVSM compliant. Separation for such aircraft shall be immediately increased to 2,000 feet vertically, and the aircraft shall be cleared to climb or descend out of the RVSM airspace as soon as practicable. Aircraft who are unable to make destination due to fuel requirements at lower levels will not be required to descend below RVSM airspace, but 2000ft separation will have to be maintained at all times. The idea is to remain within the rules of RVSM while not creating a fuel shortage for the aircraft involved. It is essential to pass this information to adjacent sectors/units.
  • Use of altitudes inappropriate to direction of flight (wrong-way) in RVSM airspace remain the same as outside of RVSM airspace. Aircraft cruising at such altitudes should be cleared back to correct altitudes as soon as practicable.
  • If an aircraft reports greater than moderate turbulence, use of 2,000 feet vertical separation will be required. Immediate action must be taken to provide another form of separation, including changing of altitudes, use of speed control, or re-routing.

Exceptions

There are a few exceptions which may allow a non-RVSM certified aircraft to operate with RVSM exclusionary airspace. For those who do get clearance into it, the following rules apply:

  • RVSM certified aircraft will receive priority for altitude assignment over non-RVSM aircraft. (see example above)
  • Vertical separation of 2,000 feet will be maintained between non-RVSM aircraft and all other aircraft.
  • Aircraft wishing to climb or descend through RVSM airspace are to be granted clearance provided they do not level off within RVSM airspace, should maintain a normal rate of climb or descent (no cruise climbs/descents allowed).
  • Aircraft used by military, police and customs services are exempt from RVSM certification requirements, do not require advance approval, and will be provided with 2,000 feet separation from all other aircraft in RVSM airspace.