A System of Maintenance is a regulatory requirement for the following reasons:
- Class A Aircraft. Transport Category aircraft and all aircraft over 5,700kg.
- ASEPTA Aircraft. Single Engine IFR Charter aircraft.
- PT6 Engine Aircraft wanting a 5,000 Hour TBO. AD/ENG/4 allows extended TBO.
These aircraft require a custom written System of Maintenance to allow operations with the type of aircraft involved. The SOM typically follows the aircraft manufacturers specific schedule with various options, plus addresses all the Australian requirements.