What should be done after each 30-second ON operation interval?

After each 30-second ON operation interval, it is required to wait 5 minutes before conducting another operation cycle. This practice is essential to prevent overheating and ensure that components have time to cool down, which helps maintain the efficiency and longevity of the aircraft's systems.

Engaging in an operation without adhering to this cooling period could lead to potential damage or compromise the performance of critical components. The other options do not address the cooling requirement: increasing power could exacerbate thermal stresses, switching to reserve fuel is unrelated to operational intervals, and engaging autopilot is a tactical operation that does not pertain to the cooling cycle necessary after intervals of high power operation. Properly following the waiting period ensures safe and effective operation of the aircraft.