Narrative:

Descending through about 22000 ft we were asked by ATC to reduce to 270 KTS. Upon retarding both throttles quickly to idle, the cabin began a 1500 FPM climb. I rapidly checked the outflow valve was closed, and asked for power to be increased, to increase the duct pressure. Simultaneously, I told the first officer to start a rapid descent, and he descended the airplane to 12000 ft which was approved by ATC. The cabin altitude climbed to about 12500-13000 ft. The oxygen mask deployed automatically. The oxygen did not begin to flow, because the cabin altitude did not get high enough to start the automatic oxygen flow. The flight was completed to mco. No other problems occurred. ATC was questioned if there were any problems or traffic conflicts. They said no problems.

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Original NASA ASRS Text

Title: ACR MLG EXPERIENCES A FAULTY, SLOW OPERATING OUTFLOW VALVE AND STARTS TO DEPRESSURIZE IN DSCNT WITH THROTTLES CLOSED.

Narrative: DSNDING THROUGH ABOUT 22000 FT WE WERE ASKED BY ATC TO REDUCE TO 270 KTS. UPON RETARDING BOTH THROTTLES QUICKLY TO IDLE, THE CABIN BEGAN A 1500 FPM CLB. I RAPIDLY CHKED THE OUTFLOW VALVE WAS CLOSED, AND ASKED FOR PWR TO BE INCREASED, TO INCREASE THE DUCT PRESSURE. SIMULTANEOUSLY, I TOLD THE FO TO START A RAPID DSCNT, AND HE DSNDED THE AIRPLANE TO 12000 FT WHICH WAS APPROVED BY ATC. THE CABIN ALT CLBED TO ABOUT 12500-13000 FT. THE OXYGEN MASK DEPLOYED AUTOMATICALLY. THE OXYGEN DID NOT BEGIN TO FLOW, BECAUSE THE CABIN ALT DID NOT GET HIGH ENOUGH TO START THE AUTOMATIC OXYGEN FLOW. THE FLT WAS COMPLETED TO MCO. NO OTHER PROBS OCCURRED. ATC WAS QUESTIONED IF THERE WERE ANY PROBS OR TFC CONFLICTS. THEY SAID NO PROBS.

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.