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The Civil Aviation Safety Authority (CASA) recently commissioned two reviews into operations at GAAP aerodromes, following a number of mid-air collisions at major general aviation airports (in particular at Moorabbin and Bankstown).


The final report on one of the reviews, carried out by aviation consultants Ambidji Group Pty Ltd, looking into airspace managements at GAAP aerodromes, was released on 15 July 2009.


The Ambidji Report examined GAAP procedures used at six aerodromes around Australia: Melbourne’s Moorabbin, Adelaide’s Parafield, Perth’s Jandakot, Brisbane’s Archerfield, and Sydney’s Bankstown and Camden.


GAAP was originally introduced at these airfields between 1978-1982 (it was introduced at Moorabbin in June 1980).  The procedures, now 30 years old, were introduced before the large growth in recorded air movements in recent years – especially since the rapid increase in flying training by overseas students since 2007.


GAAP procedures place prime responsibility for aircraft separation on the pilot in command when operating in a GAAP control zone.  Within the GAAP environment, Air Traffic Control (during operational hours) provides aircrew with information about the movements of other relevant aircraft and delivers traffic sequencing. ATC also provide clearances to land or take-off at GAAP aerodromes.


Report findings

The ‘Ambidji Report’ – a 180 page review, plus a 140 page appendix to the review – was released on 15 July 2009.


Among the findings of the review:


Moorabbin Airport experienced 335,000 aircraft movements during 2007/08, and recorded two Mid-Air Collisions (MACs) between 1999-2008 (see Table 3.2, p. 21).


Figures sourced from Airservices Australia, who operate the Moorabbin Air Traffic Control (ATC) tower, indicate that Moorabbin had about 310,000 aircraft movements during GAAP hours in FY 2006/07, which increased to 350,000 movements during FY 2007/08 (Figure 4.1, p. 25)  


The review highlighted a number of serious accidents and incidents involving planes using the busy aerodromes at Moorabbin and Bankstown over the last 10 years.


A study of Electronically Submitted Incident Reports (ESIRs) submitted from GAAP aerodromes from January 2001-March 2009, shows that Moorabbin had two Mid-Air Collisions (MACs), and an estimated 25 Accidents, 240 Runway Incursions, and 80 Failures to Comply with instructions issued by ATC (Figure 4.3, p. 29).


Two MACs have occurred in or within the vicinity of Moorabbin aerodrome in the last 10 years, both involving aircraft in flying training circuits.  Fatal accidents occurred on 29 July 2002 and 27 August 2008 (Table 10.3, pp 110-111).  Actual collision rates for Moorabbin have increased in the last 10 years compared to the previous 10 year period.


Out of the six surveyed GAAP aerodromes, Moorabbin recorded the worst figures for Runway Incursions between 2000-2009 (60 incursions in 2007, and 60 in 2008).  This is far ahead of Bankstown (40 in 2007, and 38 in 2008) (Figure 4.6, p. 43).  Airservices and CASA rate runway incursions among the most serious threats to operational safety.


A clear rising trend in the number of Failure to Comply incidents is evident when all locations are combined, and is clearly evident at Moorabbin, Bankstown and Parafield (Figure 10.13, p. 134).


Ambidji recognises that Airservices ATC personnel submit the majority of safety occurrence reports within the GAAP environment, while Aircrew submit relatively few safety incident reports.  The Ambidji Report found that safety incidents are being under-reported, and this failure to report incidents is an untenable situation in 2009 (p. 32).


Ambidji concludes that the current risks at GAAP aerodromes are unacceptable:


“Risks associated with light aircraft collisions are currently intolerable at Moorabbbin, Bankstown and Jandakot” (Figure 11.7, p. 147).


“The societal risk analysis shows that risk reduction measures are required (irrespective of costs) at Moorabbin, Jandakot, Bankstown and Parafield

due to the tolerability limits being reached / exceeded” (p. 148).


“Baseline societal risks are shown to be intolerable at Moorabbin, Bankstown and

Jandakot aerodromes ….. Immediate risk reduction measures to reduce risk to tolerable levels are required” (p. 160).


“Current (baseline) societal risks associated with GAAP operations at Bankstown, Jandakot and Moorabbin are intolerable when compared with the CASA risk criteria” (p. 167).


In summary, the Ambidji Report identifies major deficiencies in current airspace and aerodrome procedures, an unacceptable level of safety risk (particularly concerning mid-air collisions), and an urgent need to reduce these risks.




The Ambidi Report stresses the need for immediate action to improve airspace management and improve safety at GAAP aerodromes, and identifies a long list of 24 recommendations to reduce existing safety risks (pp 6-9). The authors state that a range of recommendations need to be implemented in order to bring risks at these aerodromes to within tolerable risk limits.  Immediate intervention is required at Moorabbin, Bankstown and Jandacot (p. 4).


The report (dated 30 June 2009) was submitted to CASA – OAR for consideration.




The alarming nature of the Ambidji Report forced CASA to act promptly, and on 15 July 2009, CASA Director of Aviation Safety, John McCormick, was left with no choice than to order immediate changes to a number of procedures and new initiatives to improve safety.  Priority was given to dealing with the high risk of mid-air collisions in circuits at GAAP aerodromes, and the likelihood of runway incursions.


Sweeping new legal directions to Airservices Australia and all pilots came into effect on 21 July 2009.  Immediate changes relate to three main procedures at GAAP aerodromes.  New instructions specify that a maximum number of six aircraft are permitted within the circuit area at GAAP aerodromes at any one time; that pilots in command of an aircraft must obtain ATC clearance before entering, crossing or taxiing along a runway; and Airservices is required to provide air traffic services at all six airports daily in all hours of daylight without any reduction in present night services.


The CASA directions also require these six aerodromes to phase out GAAP procedures, and move towards internationally-recognised Class D air traffic controls by 21 April 2010.


Note: As we know, Moorabbin Airport only operates under GAAP procedures when Air Traffic Control (ATC) is open between the hours of 0900-1900 during daylight saving time (November-March) and 0800-1800 at other times (  Outside of these hours, there is no ATC surveillance.  The Ambidji Report and CASA directions only address GAAP operations, and still fail to address the intolerable risks of large numbers of aircraft operating in the hours of darkness (esp. student pilot circuit training every evening).



Ambidji Group Pty Ltd. 2009. Utility of General Aviation Aerodrome Procedures to Australian-Administered Airspace. Report to CASA – Office of Airspace Regulation. 180 page report, plus 140 page appendix to the review. Full report available to download at:


CASA. 2009. GAAP changes booklet. Available to download at:   


CASA. 2009. Revised procedures at GAAP aerodromes. Online at: