Which statement best describes the purpose of disconnecting external power?

Disconnecting external power is primarily a safety and operational procedure designed to enable onboard systems to operate independently. This ensures that the aircraft’s internal systems, including essential navigation and communication equipment, are functioning as intended without reliance on external sources of power. It is a standard practice in aviation to verify that internal systems are operational and can support the aircraft in all situations, especially during engine start-up and other critical phases of flight.

While checking battery health could be one outcome of disconnecting external power, the main purpose centers around ensuring that onboard systems are fully operational and not dependent on external sources during critical phases. Understanding this distinction is crucial, as it highlights the importance of aircraft independence and reliability in its operations.