Master Switch

The main electrical power switch in the cockpit that controls the aircraft electrical system, often split into two halves: a battery switch and an alternator switch. The battery side connects the battery to the electrical bus, providing power for starting and as a backup, while the alternator side enables the engine-driven alternator to charge the battery and power electrical systems in flight. During the starting sequence, the master switch is turned on before engaging the starter. In an electrical fire emergency, the master switch may be turned off to de-energize all electrical systems.