As far as I can see the choice of 6 a/c in the circuit was arbitrary, or at least made centrally by CASA bureaucrats. I deduce from the letter that after some sort of analsis of saftey data and some sort of consultation, they have now decided to increase the limit to 8, which I also suspect has a large degree of arbitraryness.
My question is this. CASA in one guise or another has been around for well over 60 years. Over all these years they have been (at our expense) collecting statistics of airport movements, accidents, and near misses & other incidentys via a number of different incident reporting mechanisms.
With all this taxpayer funded knowledge base, why can't they make better decisions that don't require modification within weeks or months of implementation. Indeed is this knowledge base usable or have we been funding all this activity for nothing?
I'd put the recent back track on base leg circuit entry in the same category. Why did they need to do a pilot survey? With 60 or 70 years of accumulated knowledge, why don't CASA better understand what works and what doesn't work and what's safe and not safe ?
How is traffic handling in the circuit different now to the sixties & seventies? Essentially all aircraft have radio now, and there is probably a smaller spread of ciruit speeds than there was with Tiger Moths & Comanche's sharing the circuit. Places like Moorabbin use 2 runways not 3. Shouldn't it be more straightforward now?