When is ground power required to be applied to an aircraft with an INOP APU?

Ground power is required to be applied to an aircraft with an inoperative Auxiliary Power Unit (APU) prior to engine shutdown. This is essential because the APU typically provides electrical power to support the aircraft’s systems when the engines are not running. If the APU is inoperative, there will be no electrical power supply once the engines are turned off unless ground power is connected beforehand. Applying ground power ensures that critical systems such as lighting, avionics, and cabin services remain operational during and after the engine shutdown process. This practice is crucial for maintaining safety and operational integrity within the aircraft environment.