What level of maintenance involves disassembly of the compressor rotor?

The level of maintenance that involves disassembly of the compressor rotor is referred to as Engineering level maintenance. This type of maintenance typically includes comprehensive repairs and overhauls that go beyond routine service checks. Engineering level maintenance is performed by skilled technicians and engineers who have specialized training and equipment. It encompasses tasks such as the disassembly of complex components like the compressor rotor to inspect, repair, or replace necessary parts. This ensures that the aircraft's systems operate efficiently and safely.

The other choices do not specifically address the disassembly of intricate components like the compressor rotor. Maintenance levels such as 1st, 2nd, and 3rd degree maintenance usually focus on less complex tasks, including inspections, troubleshoots, adjustments, and minor repairs rather than extensive disassembly and detailed refurbishing undertaken in Engineering level maintenance.