What happens if the left generator drops offline while all three generators are operating in flight?

When the left generator drops offline while all three generators are operating in flight, the APU (Auxiliary Power Unit) generator automatically switches to power the left side. This action is crucial for maintaining electrical balance and ensuring that critical systems remain operational.

In many aircraft systems, when a primary generator fails, the APU generator is designed to take over the load for the affected bus. This capacity is vital for maintaining power to essential avionics and flight systems, thus enhancing safety and operational stability. The APU serves as a backup power source, and its ability to reroute power to the left side helps prevent a loss of functionality due to the generator failure.

Other options may suggest scenarios where power is lost or alarms are triggered, but the priority is always to maintain power availability and system functionality in the event of a generator failure. This automatic switch by the APU demonstrates the redundancy designed into modern aircraft systems, ensuring that failure of one element does not compromise overall flight safety.