Interim Recommendation IR19980261

Interim Recommendation issued to: Civil Aviation Safety Authority

Recommendation details
Output No: IR19980261
Date issued: 08 December 1998
Safety action status:


Safety Concerns Relating to the Class G Airspace Demonstration.


Australia is harmonising with elements of the International Civil Aviation Organisation (ICAO) air traffic services standards and recommended practices. ICAO has developed an alphabetical airspace classification system ranging from A to G. Each classification indicates the level of air traffic control service provided, with Class G airspace having the least service.

The plan for Australia's move to this harmonised approach is known as 'Airspace 2000'. The implementation of Airspace 2000 commenced on 26 February 1998 with the demonstration of Class E airspace in the Canberra-Ballina region.

Airspace 2000 is altering some long-standing practices unique to the Australian aviation industry.

An important aspect of the Airspace 2000 program is its integration with The Australian Advanced Air Traffic System (TAAATS).

On 22 October 1998 the Civil Aviation Safety Authority (CASA) commenced a demonstration of new operating rules and procedures for Class G Airspace. The demonstration is being conducted in the Canberra-Ballina region in Class G Airspace below 8,500 feet.

Key features of the demonstration are that it:

removed directed traffic information (DTI) provided by flight service;

introduced a national advisory frequency (NAF); and

introduced a radar based traffic information service subject to radar coverage and air traffic controller workload.

The Bureau of Air Safety Investigation (BASI) is conducting a systemic investigation of the demonstration. The investigation is part of its normal systems safety investigation role.


The overall program management of the Class G Airspace Demonstration has been deficient because critical safety issues have not been addressed.


Related occurrences

9805078 - The crew of a BAe Jetstream was maintaining the aircraft at 5,000 ft for separation from a descending Beechcraft King Air. The sector controller transmitted radar information on the Jetstream to the pilot of the King Air. This transmission was not acknowledged by the King Air pilot and was subsequently reported to have been over-transmitted by another pilot. The King Air was observed on radar to descend through the level of the Jetstream. The two aircraft passed each other with approximately 600 ft vertical separation and 0.5 NM horizontal displacement. The investigation is continuing.

9804984 - Prior to departing Lismore the pilot of a Beechcraft King Air transmitted taxi and departure reports on the Lismore/Casino/Ballina mandatory broadcast zone frequency (MBZ) but received no replies. He then contacted Brisbane Centre for a radar information service and was advised that there was no radar observed traffic. The pilot of a SAAB 340, which had just departed Casino, was monitoring the Brisbane Centre frequency and heard this report. He then contacted the pilot of the King Air to arrange separation. Shortly after, the pilot of the King Air saw the SAAB 340 pass underneath his aircraft. Subsequently, the pilots established that they had both transmitted the required MBZ reports but neither had heard the other's transmissions. The SAAB 340 pilot was not required to monitor the Brisbane Centre frequency, but by doing so he enhanced the crew's situational awareness. The investigation is continuing.

In both of these incidents, prior to the introduction of the Class G Airspace Demonstration, the crews would have been alerted as to each other's existence through the provision of directed traffic information.

Project monitoring

As part of the Bureau's monitoring of the Class G Airspace Demonstration, an investigation team was formed to collect and analyse information relating to the development and conduct of the demonstration. The team conducted interviews with staff and obtained data from the Civil Aviation Safety Authority (CASA), Airservices Australia and the aviation industry.

The Bureau's investigation team has noted that CASA had a safety case process for the Class G Airspace Demonstration, and that CASA is closely monitoring the operational progress of the demonstration.

However, the Bureau's initial analysis of the information obtained identified a number of major safety concerns:

a) The independent review process for the introduction of airspace changes was removed when CASA, as the regulator and safety auditor of the airspace system, also actively assumed the primary role for the design, safety analysis, promotion and management of the Airspace 2000 program from Airservices Australia in late 1997.
Previously Airservices Australia conducted these airspace change activities and CASA had a clearly defined process for monitoring and evaluating this process. However, when CASA assumed the role formerly exercised by Airservices Australia, no system was put in place to ensure that CASA's own work was similarly evaluated for the Class G Airspace Demonstration. No such system is yet in place.

b) The CASA safety case process did not provide an integrated summary of all hazards considered, and their associated risk levels, mitigators, and anticipated effectiveness of the mitigators. In addition, the CASA safety case process did not include a 'full qualitative and quantitative evaluation by technical experts' of Airspace 2000 (which includes Class G Airspace). Such an evaluation was proposed by the acting Chairman of CASA in a letter to the Chairman of Airservices Australia following the CASA Board meeting of 25-26 September 1997.

c) The pilot education programs of both CASA and the aviation industry, as primary mitigators for hazards associated with the airspace changes, were not implemented effectively (in terms of the originally planned program, as well as the changes introduced subsequent to the issue of Aeronautical Information Publication Supplement 48/98). A lack of pilot knowledge continues to be a major operational safety concern.

d) There has been a lack of support from elements of the aviation industry for the conduct of the demonstration. Such a lack of support had been recognised by CASA and a UK Civil Aviation Authority review team (engaged by CASA), as a significant risk to the success of the demonstration.

e) There are continuing problems associated with congestion of the NAF, a planned primary mitigator for hazards associated with the changes. This frequency congestion can prevent the transfer of vital information between pilots.

f) The Airspace 2000 plan proposed the introduction of Class E Airspace corridors through Class G airspace on any route where traffic density required, or where such corridors were requested by industry. These E corridors were a planned mitigator against the removal of DTI, but were not implemented for the Class G Airspace Demonstration.

g) There are safety deficiencies associated with the current frequency management procedures, particularly during departures and arrivals at uncontrolled aerodromes (as shown in the occurrences described above). Pilots are required to monitor a number of different frequencies during these high workload phases of flight and may consequently not receive critical radio transmissions, or may receive late advice of other traffic.

h) Pilots and air traffic services staff have been advised of changes to the demonstration through numerous Notices to Airmen, which have been issued in an ad hoc and reactive manner. This continues to cause confusion among pilots and air traffic services staff.

i) As yet, the investigation team has not found evidence to indicate that CASA's safety case process has considered the following safety issues associated with the Class G Airspace demonstration:

the full impact of each of the changes to the Class G Airspace Demonstration procedures and design that were implemented subsequent to the issue of Aeronautical Information Publication Supplement 48/98 on 13 August 1998;

the full impact of the removal of DTI, particularly the potentially detrimental effects on situational awareness for VFR pilots (for example a VFR pilot may now need to monitor two or three frequencies to maintain awareness of IFR traffic, when previously only one frequency was required); and

operational difficulties associated with two concurrent sets of procedures, one for the demonstration airspace and one for the existing system.

j) As yet, the investigation team has not found evidence to indicate that there was:

a clear transfer of roles and responsibilities from Airservices to CASA for the management of Airspace 2000 (which includes Class G Airspace);

a comprehensive and systematic analysis of pilot tasks under the Class G Airspace Demonstration model (including an examination of the combined effects of all the changes on workload, situational awareness and crew coordination, as well as the development and testing of specific operational procedures);

a systematic comparison of the Class G Airspace Demonstration model (including consideration of the Australian aviation system and environment) with appropriate overseas airspace systems;

a clear rationale for conducting the demonstration prior to the introduction of TAAATS; and

a proactive evaluation of the effectiveness of the pilot education program prior to the introduction of the demonstration.

It is not possible at this stage to compare the overall safety level of the Class G Airspace Demonstration with that of the previous system. However, due to the safety concerns listed above, the following interim recommendations are made.

For further information please see report `Systemic Investigation into the Class G Airspace Demonstration'.

Output text

The Bureau of Air Safety Investigation recommends that the Civil Aviation Safety Authority, the Department of Transport and Regional Services and Airservices Australia review and clarify the roles and responsibilities of the respective organisations in relation to the regulation, design and management of airspace to ensure the safety integrity of the aviation system.

Initial response
Date issued: 03 September 1999
Response from: Civil Aviation Safety Authority
Action status: Closed - Accepted
Response text:

I refer to your letter of 17 August 1999 regarding finalisation of the Class G Report and outstanding responses to IR980260 and IR980261.

CASA is still awaiting formal, consolidated advice on the results of the review conducted by the Secretary of DOTRS last December. However, certain aspects are becoming more lucid.

In a letter from the Assistant Secretary Aviation, DOTRS, to CASA, dated 29 June 1999, CASA was advised that the Government's decision is that'the regulatory responsibilities for the design, declaration and management of airspace are to remain with Airservices and not be transferred to CASK CASA understands that Airservices, in line with this decision, has been given direction by the Government to develop, by December 1999, a program for airspace reform.

In a draft working paper attached to the above mentioned letter, it was stated that before making a decision "Airservices would provide CASA with formal safety cases justifying any changes, including training and education of users'. CASA can review and, if necessary, veto the change. The paper went on to say that 'This acknowledges possible conflicts of interests which may arise were CASA to be both regulator and the initiator of airspace reforms".

The paper gave CASA's role as setting minimum standards to be applied to each particular class of airspace. It did not restrict CASA from initiating an upgrading of a class of airspace, however, it stated that CASA must identify "a clear safety justification" and "accompany any such proposal with evidence supporting the safety issue'. An overriding requirement was" 'When CASA seeks to change the classification of airspace, the DoTRS is to ensure an independent analyst is engaged to consider, and publish comments upon, the safety case made by CASK

CASA is willing to adopt the principles espoused in the above and believes that acceptance of them by the three parties would address the Interim Recommendations.


Last update 01 April 2011