Safety Concerns Relating to the Class G Airspace
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
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
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.
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
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
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
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
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
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
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
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
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
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'.