Avionics Mandates: ADSB and GPS
If your aircraft is to be operated IFR, then the answer is one simple word: Yes.
As from February 2017 all IFR Airwork, Charter, or RPT aircraft must be equipped with ADSB out.
Aircraft that are solely operated in Private category IFR, may continue to operate without ADSB out fitted until 1 January 2020. Restrictions apply for entry into controlled airspace.
Airservices has some very useful information on ADSB and GPS mandates here.
There is currently no ADSB requirement for VFR aircraft. However if you fly regularly in controlled airspace, ADSB equipped aircraft will get a much easier run, because ATC have a very accurate picture of who you are, where you are, and which way you are moving.
Do I need ADSB?
Is my GPS OK for IFR?
As from February 2016, all IFR aircraft must be GPS equipped. This means that the GPS must have an appropriate TSO rating, and be installed to IFR standards.
The full requirements can be found in CAO 20.18 para 9D. This is somewhat convoluted to interpret, but what it boils down to is that IFR Charter and RPT aircraft must have at least one TSO c 145 or 146 approved GPS system (new generation WAAS systems).
Private and Airwork IFR aircraft may have other options to allow continued use of an existing TSO c 129 (older spec) GPS system, however this will not be suitable for ADSB position reference. Add to this the fact that these units are getting older, and support from the manufacturers is being phased out, and in many cases an upgrade to the new spec is a better decision.
Brisbane, Sydney, Melbourne and Perth International Airports now require all aircraft landing at these airport be equipped with Mode "S" transponders. This mandate is all about tracking surface movements of aircraft. Any modern ADSB transponder will meet this requirement.