What was found
PBI - FLT 350 - P556 - JUST PRIOR TO STARTING TO DESCEND OUT OF FL 350, CABIN ALTITUDE STARTED CLIMBING. COULD NOT CONTROL PRESSURIZATION. STARTED RAPID DESCENT, MASKS DEPLOYED AT 14,000 FEET CABIN ALTITUDE. P 557 - LT A/C VALVE INOPERABLE IN AUTO AND MANUAL. REF ITEM P557 - SECURED DUCT LT PACK. NO OTHER DEFECTS NOTED. REF MM 21-00-00-501 CABIN PRESSURIZATION CHECKED GOOD. P557 - FOUND DUCT BLOWN OFF LT PACK WATER SEPARATE SECURED DUCT. LEAK CHECK DUCT. OPS CHECKED LT PACK REF MM 21-20-00 A501. (X)