do a quick search (as below)and see if your aircraft/squadron etc is mentioned - if not, you will need to add more specific data to the search facility.
The National Archives | Search results:RAAF
when you go to TNA you will be able to see documents which have been digitally copied without the need to request documents to be brought in specially - if you need to see original Ops Books, records etc, then you will need a Reader's Ticket, which is issued at TNA. Its free, but before you go, def check their website for the bits you need to take to avoid a wasted journey. Nice café there, too!