What was found
LEFT BLEED TRIP OFF LIGHT ON AT CRUISE - RESET OK. DUCT PRESSURE SPLIT LT 13 PSI/ RT 37 PSI. ON INITIAL DESCENT RT BLEED TRIPPED. PRESSURIZATION UNCONTROLLABLE. ALT APPROX. 360, CABIN ALTITUDE RISING RAPIDLY TO GREATER THAN 10,000. THE FLIGHT MADE AN EMERGENCY DESCENT AND ALL MASKS DEPLOYED. AN EMERGENCY WAS DECLARED. THE FLIGHT LANDED IN DFW WITHOUT FURTHER INCIDENT. MAINTENANCE REPLACED NR 2 ENGINE BLEED AIR REGULATOR IAW AMM 36-11-03. THE AIRCRAFT WAS GROUNDED. (SEE ALSO SDR'S AALA20170508011, AALA201705119033, AALA201705119035, AALA201705119036, AND AALA201705119037.)