What is the outside air temperature threshold at which the PMU goes offline?

The correct answer indicates that the PMU (Power Management Unit) goes offline when the Inlet Outside Air Temperature (IOAT) exceeds 121 degrees Celsius. This threshold is significant because it protects the engine and associated systems from potential damage due to extreme temperatures. When the IOAT rises to a certain level, the PMU disables some functions to maintain engine performance and safety, ensuring that the aircraft operates within its safe operational limits.

Understanding this operational ceiling is crucial for pilots, as exceeding it could lead to decreased engine efficiency and increased risk of malfunction. Maintaining awareness of environmental conditions and how they affect the aircraft's systems is a fundamental aspect of safe flight operations.