What was found
DURING CRUISE FLIGHT, LT BUS TIE OPEN WARNING FOLLOWED BY LT DC GENERATOR FAIL WARNING. CAPTAIN LOST HEADSET AUDIO WHICH IS POWERED FROM LT GENERATOR BUS. THIS OCCURRENCE CAUSED LOSS OF COMMUNICATION BETWEEN COCKPIT CREW AT A TIME CREW COORDINATION IS CRITICAL. COMMUNICATION IS LOST DUE TO LOSS OF DC BUS POWER. SUBMITTER STATES BUS TIE PROTECT DEVICES TEND TO BE OVERLY SENSITIVE IN OPERATION.