What does the Bus Tie switch on the overhead panel do?

The Bus Tie switch on the overhead panel is primarily responsible for tying the left electrical system (LH) essential bus and the right electrical system (RH) essential bus together. This functionality allows for a shared power supply, ensuring that if one side loses power or experiences an electrical fault, the other side can provide power to critical systems. By tying these buses, the aircraft can maintain essential operations and avoid complete loss of electrical power to vital instruments and systems necessary for flight safety.

The correct answer reflects this critical role in providing redundancy and reliability in the aircraft's electrical architecture, which is paramount for normal and emergency operations. Understanding how the Bus Tie switch operates helps pilots and crews manage electrical resources efficiently and maintain control of essential systems even in adverse situations.