What does the green arc on an aircraft temperature gauge indicate?

The green arc on an aircraft temperature gauge represents the desirable temperature range for the engine or system being monitored. This range indicates the temperatures at which the engine or system operates optimally, ensuring safe and efficient performance. When the temperature is within this green zone, it signifies that the aircraft is functioning as intended, allowing pilots to make informed decisions regarding the operation of the aircraft. Understanding this mark is crucial for pilots and technicians, as deviations from the green arc can signal potential issues that may need attention to avoid damage or reduced performance.