Narrative:

I was riding jump seat sat-iah aircraft in 6/91. We were at cruise altitude, FL240 or FL260, when the aircraft suddenly began to depressurize very quickly. I noticed the cabin vertical speed needle was fully pegged at the top of the scale. The cabin altitude horn went off shortly after that. The passenger O2 masks did not drop automatically. They also failed to drop when the passenger O2 switch was placed in the on position. The amber light did not communication on. The t-handle (continuous flow control manual actuation handle) was pulled and the amber light above the passenger O2 switch did light up and the passenger O2 masks dropped. I did help the first officer manually close the outflow valve to recover the cabin. She was unable to do this because of the pain in her ears. Once I recovered the cabin, she was able to resume her job. The aircraft was safely landed at iah west/O further incident. Supplemental information from acn 180970: when power was retarded to begin the descent, the cabin began a rapid climb. The pressurization was in the automatic mode at this time. Standby was immediately selected. As the cabin continued it's climb, manual was then selected. The rapid decompression checklist was then run, including the deployment of O2 masks. No emergency was declared.

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Original NASA ASRS Text

Title: ACR LGT LOST PRESSURIZATION CTL AT TOD AS THE POWER WAS REDUCTED.

Narrative: I WAS RIDING JUMP SEAT SAT-IAH ACFT IN 6/91. WE WERE AT CRUISE ALT, FL240 OR FL260, WHEN THE ACFT SUDDENLY BEGAN TO DEPRESSURIZE VERY QUICKLY. I NOTICED THE CABIN VERT SPD NEEDLE WAS FULLY PEGGED AT THE TOP OF THE SCALE. THE CABIN ALT HORN WENT OFF SHORTLY AFTER THAT. THE PAX O2 MASKS DID NOT DROP AUTOMATICALLY. THEY ALSO FAILED TO DROP WHEN THE PAX O2 SWITCH WAS PLACED IN THE ON POS. THE AMBER LIGHT DID NOT COM ON. THE T-HANDLE (CONTINUOUS FLOW CTL MANUAL ACTUATION HANDLE) WAS PULLED AND THE AMBER LIGHT ABOVE THE PAX O2 SWITCH DID LIGHT UP AND THE PAX O2 MASKS DROPPED. I DID HELP THE F/O MANUALLY CLOSE THE OUTFLOW VALVE TO RECOVER THE CABIN. SHE WAS UNABLE TO DO THIS BECAUSE OF THE PAIN IN HER EARS. ONCE I RECOVERED THE CABIN, SHE WAS ABLE TO RESUME HER JOB. THE ACFT WAS SAFELY LANDED AT IAH W/O FURTHER INCIDENT. SUPPLEMENTAL INFO FROM ACN 180970: WHEN PWR WAS RETARDED TO BEGIN THE DSNT, THE CABIN BEGAN A RAPID CLB. THE PRESSURIZATION WAS IN THE AUTOMATIC MODE AT THIS TIME. STANDBY WAS IMMEDIATELY SELECTED. AS THE CABIN CONTINUED IT'S CLB, MANUAL WAS THEN SELECTED. THE RAPID DECOMPRESSION CHKLIST WAS THEN RUN, INCLUDING THE DEPLOYMENT OF O2 MASKS. NO EMER WAS DECLARED.

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.