A few other snippets from the joint review:
"The main difference between Class C and Class D airspace is ATC are not required to separate IFR and VFR aircraft. This could provide a certain level of flexibility for both the military and civil operators.
Class D is utilised at aerodromes where the majority of aircraft are of a similar type and speed range. This is the case at aerodromes with a high proportion of GA VFR aircraft such as Bankstown and Camden.
The purpose of Class D procedures is to address the risk without major impact on the efficiency of aviation activities which is beneficial at high-density traffic locations. Critical to Class D operations is the principle of see and avoid which has several limitations14. Class D procedures provide assisted traffic de-confliction to enhance see and avoid between IFR and VFR aircraft. The main users of Williamtown airspace are high speed low visibility military aircraft operating in large numbers, quite often in formation, with limited ability to be sighted and avoided in a timely manner by civil aircraft."
"Class D airspace has reduced VFR horizontal distance and altitude below cloud requirements compared to Class C airspace. This factor combined with low visibility paint schemes and higher speeds of military aircraft further limit the ability for civil aircraft to see and avoid traffic.
The geographical position and runway orientation often puts terminal traffic in conflict with the popular coastal route. This circumstance is exacerbated by the critical stage of flight for arriving and departing aircraft which will put VFR aircraft in conflict with PT and military aircraft. Many of the PT aircraft at Williamtown are of a medium wake turbulence category which may create an unrecoverable hazard for light aircraft in a near miss situation. Therefore, the geographical proximity of the aerodrome relative to the coast creates risks that require some form of additional control measures.
However, considering that the annual number of passengers already exceeds the AAPS threshold for consideration of Class C airspace and under the Civil Aviation Act 1988, CASA must regard the safety of air navigation as the most important consideration, it would be difficult to justify Class D airspace given the number of PT passengers and potential issues of see and avoid."
"When military aircraft are operating Williamtown can be one of the busiest and most complex volumes of airspace in Australia due to the diverse types of aircraft and differing operations that must be managed by ABATS. The Class C service provides clear instruction to ABATS on the processing of PT and other civil operations. Additionally, Class C airspace allows the RAAF to tailor separation standards for its use while still affording an acceptable level of safety to PT aircraft.
The only sector of the aviation community that was dissatisfied with the current Class C service was a small number of GA pilots. The main source of dissatisfaction was perceived unreasonable delays due to the need for ABATS to separate them in accordance with Class C procedures. During observations covering a period of several weeks at Williamtown the team observed only minor delays to GA aircraft all of which were justifiable as a result of arriving or departing PT aircraft not military traffic. Of note, stepped airspace would also resolve some of the need to apply restrictive separation standards as some transit aircraft could remain in Class G airspace."