What is the purpose of a standby instrument power supply?

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The purpose of a standby instrument power supply is to keep the essential flight instruments powered if the aircraft’s main electrical system fails. In flight, pilots depend on instruments that show attitude, altitude, and airspeed to maintain control and situational awareness. When the primary power sources go offline, the standby power source kicks in to provide power to those critical instruments for a defined period, allowing the pilot to continue flying and safely land. This system is not meant for nonessential systems like entertainment, nor does it power hydraulic actuators during normal operations. It’s typically a self-contained or independent source that ensures basic flight capability even during an electrical failure.