What was found
DURING THE CRUISE PHASE, AIRCRAFT N336QT DISPLAYED THE WARNING MESSAGE "CAB PR EXCESS CAB ALT," ACCOMPANIED BY A LOSS OF CABIN PRESSURIZATION. IN RESPONSE TO THIS SITUATION, THE CREW DECIDED TO RETURN TO THE DEPARTURE STATION, MIA. DURING THE FAULT ISOLATION PROCEDURE, THE AIRCRAFT’S SELF-DIAGNOSTIC SYSTEMS WERE INTERROGATED, AND IT WAS DETERMINED THAT THE PACKS HAD BEEN TURNED OFF DUE TO A FAULT CAUSED BY THE SMOKE DETECTOR (120WU), WHICH WAS SUBSEQUENTLY REPLACED. SMOKE DETECTOR ON/OFF