Narrative:

Flight was conducted and dispatched from cvg-jan with the following items -- inoperative according to the logbook and MEL: left inboard landing light, automatic mode on the pressurization controller and the right air-conditioning pack OTS thereby limiting our maximum flight cruise altitude to FL250. Proper fuel and passenger loads were boarded and we were flight planned up to FL240. The pressurization controller was operated in standby mode with a manual mode as a backup according to company abnormal procedures. Approximately 75 NM south of bna VORTAC, at night in smooth air, a loud bang noise emanated throughout the cabin along with popping ear sensations had occurred. At that moment, we checked the cabin rate/altitude/differential indications and determined we were losing the cabin pressurization system. We tried to force the outflow valve close in standby mode and then switched to manual, the outflow valve position indicated full close, no other overtemp/bleed valve failure or duct rupture indications were displayed. The cabin altitude continued climbing and we donned our oxygen masks. By establishing communication with ZMP we asked for a lower altitude down to 10000 ft MSL. They cleared us to descend at our discretion and wanted to know if we would declare an emergency. After notifying the passenger, flight attendants and the company we decided to declare an emergency in order to keep jan tower open after hours of XX00 CST. Our arrival occurred approximately XX10 CST, with no further incident and the emergency equipment standing by just in case. Cabin altitude reached a maximum of 11500 ft and passenger oxygen masks were not deployed. We arrived in jan and downed the aircraft for contract maintenance to inspect and remedy whatever caused this situation to occur in the first place. After having remained overnight, we consulted with contract maintenance and the company in atl and decided to ferry the aircraft back to atl. We also researched and found the aft cargo door had been changed several months earlier and found the cargo door seal blown out. We ferried the aircraft unpressurized back to atl with all documentation and approval of our ferry permit. We safely landed in atl.

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Original NASA ASRS Text

Title: AN ACR B737-200 FLC, OPERATING WITH 1 AIR-CONDITIONING AND PRESSURIZATION SYS, HAS THE AFT CARGO DOOR SEAL FAIL AT FL240 LOSING PRESSURIZATION CAPABILITY.

Narrative: FLT WAS CONDUCTED AND DISPATCHED FROM CVG-JAN WITH THE FOLLOWING ITEMS -- INOP ACCORDING TO THE LOGBOOK AND MEL: L INBOARD LNDG LIGHT, AUTOMATIC MODE ON THE PRESSURIZATION CTLR AND THE R AIR-CONDITIONING PACK OTS THEREBY LIMITING OUR MAX FLT CRUISE ALT TO FL250. PROPER FUEL AND PAX LOADS WERE BOARDED AND WE WERE FLT PLANNED UP TO FL240. THE PRESSURIZATION CTLR WAS OPERATED IN STANDBY MODE WITH A MANUAL MODE AS A BACKUP ACCORDING TO COMPANY ABNORMAL PROCS. APPROX 75 NM S OF BNA VORTAC, AT NIGHT IN SMOOTH AIR, A LOUD BANG NOISE EMANATED THROUGHOUT THE CABIN ALONG WITH POPPING EAR SENSATIONS HAD OCCURRED. AT THAT MOMENT, WE CHKED THE CABIN RATE/ALT/DIFFERENTIAL INDICATIONS AND DETERMINED WE WERE LOSING THE CABIN PRESSURIZATION SYS. WE TRIED TO FORCE THE OUTFLOW VALVE CLOSE IN STANDBY MODE AND THEN SWITCHED TO MANUAL, THE OUTFLOW VALVE POS INDICATED FULL CLOSE, NO OTHER OVERTEMP/BLEED VALVE FAILURE OR DUCT RUPTURE INDICATIONS WERE DISPLAYED. THE CABIN ALT CONTINUED CLBING AND WE DONNED OUR OXYGEN MASKS. BY ESTABLISHING COM WITH ZMP WE ASKED FOR A LOWER ALT DOWN TO 10000 FT MSL. THEY CLRED US TO DSND AT OUR DISCRETION AND WANTED TO KNOW IF WE WOULD DECLARE AN EMER. AFTER NOTIFYING THE PAX, FLT ATTENDANTS AND THE COMPANY WE DECIDED TO DECLARE AN EMER IN ORDER TO KEEP JAN TWR OPEN AFTER HRS OF XX00 CST. OUR ARR OCCURRED APPROX XX10 CST, WITH NO FURTHER INCIDENT AND THE EMER EQUIP STANDING BY JUST IN CASE. CABIN ALT REACHED A MAX OF 11500 FT AND PAX OXYGEN MASKS WERE NOT DEPLOYED. WE ARRIVED IN JAN AND DOWNED THE ACFT FOR CONTRACT MAINT TO INSPECT AND REMEDY WHATEVER CAUSED THIS SIT TO OCCUR IN THE FIRST PLACE. AFTER HAVING REMAINED OVERNIGHT, WE CONSULTED WITH CONTRACT MAINT AND THE COMPANY IN ATL AND DECIDED TO FERRY THE ACFT BACK TO ATL. WE ALSO RESEARCHED AND FOUND THE AFT CARGO DOOR HAD BEEN CHANGED SEVERAL MONTHS EARLIER AND FOUND THE CARGO DOOR SEAL BLOWN OUT. WE FERRIED THE ACFT UNPRESSURIZED BACK TO ATL WITH ALL DOCUMENTATION AND APPROVAL OF OUR FERRY PERMIT. WE SAFELY LANDED IN ATL.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.