Final answer:
Two aircraft AC generators operating in parallel must have matching frequencies, synchronized phase angles, and identical voltage and phase sequences to ensure proper functionality.
Step-by-step explanation:
When operating two aircraft AC generators in parallel, certain requirements must be met to ensure proper functionality. First, the frequencies and voltages of the generators should match. This can be achieved by adjusting the speed of the generators or using a frequency synchronization system. Secondly, the phase angles of the generators should be synchronized. This can be done by using a phase synchronizing device or adjusting the exciter voltages. Finally, the generators should have the same voltage and phase sequence to avoid any imbalances in the system.