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A B737-800 flight crew experienced cabin pressure difficulties in descent. A normal approach and landing followed.
| Attributes | |
| ACN | 801848 |
| Time | |
| Date | 200808 |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : zzzz.artcc |
| State Reference | FO |
| Altitude | msl single value : 30000 |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | B737-800 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | descent : approach |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : relief pilot |
| ASRS Report | 801848 |
| Events | |
| Anomaly | aircraft equipment problem : critical |
| Independent Detector | aircraft equipment other aircraft equipment : cabin altitude warning other flight crewa other flight crewa |
| Resolutory Action | flight crew : overcame equipment problem |
| Supplementary | |
| Problem Areas | Aircraft |
| Primary Problem | Aircraft |
Narrative:
During descent at approximately FL300; cabin altitude warning sounded. Throttles at idle. Duct pressure was 20-25 psi; cabin differential was 4 psi; and cabin altitude was at 10000 ft. Outflow valve indicated closed. Backed up outflow indication by going to manual and held/toggled the valve closed. No change in pressurization; the cabin still held at 10000 ft. While doing this we first completed red box items and told ATC of pressurization problem and requested altitude below 10000 ft and was cleared to 7000 ft still out over water and terrain was not a factor. Cabin altitude stayed at 10000 ft throughout the descent. Warning horn stopped once we were below 10000 ft. Manually opened outflow valve so the cabin would descend with the aircraft. Approach and landing uneventful.
Original NASA ASRS Text
Title: A B737-800 FLT CREW EXPERIENCED CABIN PRESSURE DIFFICULTIES IN DSCNT. A NORMAL APCH AND LNDG FOLLOWED.
Narrative: DURING DSCNT AT APPROX FL300; CABIN ALT WARNING SOUNDED. THROTTLES AT IDLE. DUCT PRESSURE WAS 20-25 PSI; CABIN DIFFERENTIAL WAS 4 PSI; AND CABIN ALT WAS AT 10000 FT. OUTFLOW VALVE INDICATED CLOSED. BACKED UP OUTFLOW INDICATION BY GOING TO MANUAL AND HELD/TOGGLED THE VALVE CLOSED. NO CHANGE IN PRESSURIZATION; THE CABIN STILL HELD AT 10000 FT. WHILE DOING THIS WE FIRST COMPLETED RED BOX ITEMS AND TOLD ATC OF PRESSURIZATION PROB AND REQUESTED ALT BELOW 10000 FT AND WAS CLRED TO 7000 FT STILL OUT OVER WATER AND TERRAIN WAS NOT A FACTOR. CABIN ALT STAYED AT 10000 FT THROUGHOUT THE DSCNT. WARNING HORN STOPPED ONCE WE WERE BELOW 10000 FT. MANUALLY OPENED OUTFLOW VALVE SO THE CABIN WOULD DSND WITH THE ACFT. APCH AND LNDG UNEVENTFUL.
Data retrieved from NASA's ASRS site as of May 2009 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.