The Diploma of Aeroskills is a qualification under ASQA, who is Australia’s regulator for the VET system (Reference: https://training.gov.au/Training/Details/MEA50219[Mechanical] and https://training.gov.au/Training/Details/MEA50218 [Avionics]). 

A typical diploma qualification contains most of the same Units of Competency (“MEAs”) as required by CASA for a licence outcome. However, there are some exceptions. A common example is the B1.2 licence requirement to hold MEA362 (Maintain aircraft vapour cycle air conditioning systems). This unit of competency does not appear under any of the Diploma of Aeroskills qualifications, despite being a licence requirement of CASA.

N.B. Even if all the units of competency held under a Diploma of Aeroskills line up with the appropriate licence category, this only satisfies part of the CASA licence requirements. CASA still requires you to have completed the relevant experience and Part 66 Module examinations. 

To answer the second part of the question now. No, you do not need a Diploma of Aeroskills to get a CASA licence. However, it does streamline the path towards achieving the correct Units of Competency. The right way to view the ‘Diploma’ is that it is a formal qualification produced as an outcome of following the licencing pathway prescribed in the Part 66 MOS.

(please note that this refers to the licencing pathway outside the CASA self-study pathway. Please see related FAQ explaining the CASA self-study pathway)

See the FAQ What do I need to get an Aircraft Engineer’s Licence?.