Narrative:

Climbing through FL210, we received a warning of an autopressurization failure and discovered that the cabin altitude was 10000 ft. The captain called for the emergency procedure checklist, but the checklist did not address this event. ATC was advised that we needed an immediate descent to below 10000 ft, and after a 40 degree right turn for traffic below, we were cleared to 9000 ft. The cabin altitude continued to climb at a slow, progressive rate, but not a consistent rate. I followed the appropriate checklist in our company's aom in an attempt to control the cabin pressure manually. The captain made a controled descent on autoplt at initially 3000 FPM and reduced the descent to 2500 FPM. We completed the checklist just prior to leveling off and informed the flight attendant of what had occurred. She informed us that the oxygen masks had deployed and the passenger were using them. We contacted our company and advised we would return to dfw. Other than a shallow descent, we made a normal approach and landing. The captain, and I agree, did not consider it necessary to effect an emergency descent or a full rapid decompression procedure because we did not have a rapid decompression. We also did not put on our own oxygen masks because the cabin altitude did not climb over 13000 ft and we were already descending. Had the cabin altitude climbed dramatically or ATC not allow us to descend, we would have declared an emergency and called for oxygen masks. I feel that the captain was in full control of the situation and at no time was the crew, passenger, or aircraft in jeopardy. Callback conversation with reporter revealed the following information: the reporter stated the aircraft was an embraer 145 and the decompression was caused by a defective electrical connector on the autopressure controller. The reporter said the failure made the pressurization system operate intermittently releasing the cabin pressure gradually. The reporter said the crew oxygen masks were not used as the pressure was not a rapid loss.

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Original NASA ASRS Text

Title: AN EMBRAER 145 IN CLB AT FL210 EXPERIENCED A SLOW INTERMITTENT LOSS OF CABIN PRESSURE CAUSED BY A DEFECTIVE ELECTRICAL CONNECTOR ON THE AUTOPRESSURE CONTROLLER.

Narrative: CLBING THROUGH FL210, WE RECEIVED A WARNING OF AN AUTOPRESSURIZATION FAILURE AND DISCOVERED THAT THE CABIN ALT WAS 10000 FT. THE CAPT CALLED FOR THE EMER PROC CHKLIST, BUT THE CHKLIST DID NOT ADDRESS THIS EVENT. ATC WAS ADVISED THAT WE NEEDED AN IMMEDIATE DSCNT TO BELOW 10000 FT, AND AFTER A 40 DEG R TURN FOR TFC BELOW, WE WERE CLRED TO 9000 FT. THE CABIN ALT CONTINUED TO CLB AT A SLOW, PROGRESSIVE RATE, BUT NOT A CONSISTENT RATE. I FOLLOWED THE APPROPRIATE CHKLIST IN OUR COMPANY'S AOM IN AN ATTEMPT TO CTL THE CABIN PRESSURE MANUALLY. THE CAPT MADE A CTLED DSCNT ON AUTOPLT AT INITIALLY 3000 FPM AND REDUCED THE DSCNT TO 2500 FPM. WE COMPLETED THE CHKLIST JUST PRIOR TO LEVELING OFF AND INFORMED THE FLT ATTENDANT OF WHAT HAD OCCURRED. SHE INFORMED US THAT THE OXYGEN MASKS HAD DEPLOYED AND THE PAX WERE USING THEM. WE CONTACTED OUR COMPANY AND ADVISED WE WOULD RETURN TO DFW. OTHER THAN A SHALLOW DSCNT, WE MADE A NORMAL APCH AND LNDG. THE CAPT, AND I AGREE, DID NOT CONSIDER IT NECESSARY TO EFFECT AN EMER DSCNT OR A FULL RAPID DECOMPRESSION PROC BECAUSE WE DID NOT HAVE A RAPID DECOMPRESSION. WE ALSO DID NOT PUT ON OUR OWN OXYGEN MASKS BECAUSE THE CABIN ALT DID NOT CLB OVER 13000 FT AND WE WERE ALREADY DSNDING. HAD THE CABIN ALT CLBED DRAMATICALLY OR ATC NOT ALLOW US TO DSND, WE WOULD HAVE DECLARED AN EMER AND CALLED FOR OXYGEN MASKS. I FEEL THAT THE CAPT WAS IN FULL CTL OF THE SIT AND AT NO TIME WAS THE CREW, PAX, OR ACFT IN JEOPARDY. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE ACFT WAS AN EMBRAER 145 AND THE DECOMPRESSION WAS CAUSED BY A DEFECTIVE ELECTRICAL CONNECTOR ON THE AUTOPRESSURE CONTROLLER. THE RPTR SAID THE FAILURE MADE THE PRESSURIZATION SYS OPERATE INTERMITTENTLY RELEASING THE CABIN PRESSURE GRADUALLY. THE RPTR SAID THE CREW OXYGEN MASKS WERE NOT USED AS THE PRESSURE WAS NOT A RAPID LOSS.

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.