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B737 captain reports low duct pressure to left pack during climb followed cabin altitude warning at FL340. Crew descends to FL250 and is able to maintain cabin pressure to destination.
| Attributes | |
| ACN | 810368 |
| Time | |
| Date | 200810 |
| Place | |
| Locale Reference | airport : zzz.airport |
| State Reference | US |
| Altitude | msl bound lower : 0 msl bound upper : 34000 |
| Environment | |
| Light | Daylight |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | B737-400 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | climbout : intermediate altitude ground : preflight |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| ASRS Report | 810368 |
| Events | |
| Anomaly | aircraft equipment problem : critical |
| Independent Detector | aircraft equipment other aircraft equipment : cabin alt other flight crewa |
| Resolutory Action | flight crew : overcame equipment problem |
| Supplementary | |
| Problem Areas | Aircraft |
| Primary Problem | Aircraft |
Narrative:
On climb out; we noticed a large split in the duct pressure (R-10; L-50); we continued to climb out and monitor systems. Aircraft appeared to pressurize normally; but the temperature variances from front to back of aircraft were extreme and difficult to control. At cruise altitude; FL340; we were preparing to record the parameters in the maintenance logbook when the altitude warning horn sounded. We donned our oxygen masks; ran qrc checklists; and coordinated lower altitude from ATC. At FL250 we were able to hold the cabin at or below 10000 ft. Due to our location and altitude; we had a difficult time coordinating with dispatch and maintenance. Finally; all of the interested parties agreed to proceed to ZZZ where we landed normally. Better maintenance of aircraft. Improved communication in remote areas.
Original NASA ASRS Text
Title: B737 CAPTAIN REPORTS LOW DUCT PRESSURE TO LEFT PACK DURING CLIMB FOLLOWED CABIN ALTITUDE WARNING AT FL340. CREW DESCENDS TO FL250 AND IS ABLE TO MAINTAIN CABIN PRESSURE TO DESTINATION.
Narrative: ON CLBOUT; WE NOTICED A LARGE SPLIT IN THE DUCT PRESSURE (R-10; L-50); WE CONTINUED TO CLB OUT AND MONITOR SYSTEMS. ACFT APPEARED TO PRESSURIZE NORMALLY; BUT THE TEMP VARIANCES FROM FRONT TO BACK OF ACFT WERE EXTREME AND DIFFICULT TO CTL. AT CRUISE ALT; FL340; WE WERE PREPARING TO RECORD THE PARAMETERS IN THE MAINT LOGBOOK WHEN THE ALT WARNING HORN SOUNDED. WE DONNED OUR OXYGEN MASKS; RAN QRC CHKLISTS; AND COORDINATED LOWER ALT FROM ATC. AT FL250 WE WERE ABLE TO HOLD THE CABIN AT OR BELOW 10000 FT. DUE TO OUR LOCATION AND ALT; WE HAD A DIFFICULT TIME COORDINATING WITH DISPATCH AND MAINT. FINALLY; ALL OF THE INTERESTED PARTIES AGREED TO PROCEED TO ZZZ WHERE WE LANDED NORMALLY. BETTER MAINT OF ACFT. IMPROVED COM IN REMOTE AREAS.
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.