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Following completion of the QRH procedures for a cabin altitude warning horn event; the flight crew of a B737-300 chose to select the standby mode for control of pressurization at the request of maintenance control. Although the system functioned well the flight crew later determined they shouldn't have done so as it was not part of the QRH procedure.
| Attributes | |
| ACN | 905154 |
| Time | |
| Date | 201008 |
| Local Time Of Day | 0601-1200 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Make Model Name | B737-300 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Cruise |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | Pressurization Control System |
| Person 1 | |
| Function | Pilot Not Flying Captain |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Experience | Flight Crew Last 90 Days 152 |
| Person 2 | |
| Function | First Officer Pilot Flying |
| Experience | Flight Crew Last 90 Days 226 Flight Crew Type 4400 |
| Events | |
| Anomaly | Aircraft Equipment Problem Critical Deviation - Procedural Published Material / Policy |
Narrative:
During cruise flight at FL340; we got an intermittent warning horn caused by our cabin altitude reaching 10;000 ft. We complied with the memory items and QRH; descended to FL240; stabilized the cabin at the proper altitude; and notified dispatch of the situation. We completed the QRH page A-15 (cabin altitude warning horn/abnormal pressurization checklist). After things settled down and the cabin was stabilized per the checklist procedure; I was requested by maintenance control through dispatch to select standby on the analog pressurization panel. The standby mode performed perfectly and the cabin altitude remained stable. However; the cabin was being controlled in manual as per the QRH checklist so I think we should have stopped there rather than try another pressurization mode as requested by maintenance control through dispatch. We remained in standby mode for the remainder of the flight with close monitoring. The remainder of the flight was uneventful.
Original NASA ASRS Text
Title: Following completion of the QRH procedures for a Cabin Altitude Warning Horn event; the Flight Crew of a B737-300 chose to select the standby mode for control of pressurization at the request of Maintenance Control. Although the system functioned well the Flight Crew later determined they shouldn't have done so as it was not part of the QRH procedure.
Narrative: During cruise flight at FL340; we got an intermittent warning horn caused by our cabin altitude reaching 10;000 FT. We complied with the memory items and QRH; descended to FL240; stabilized the cabin at the proper altitude; and notified Dispatch of the situation. We completed the QRH page A-15 (Cabin Altitude Warning horn/Abnormal Pressurization Checklist). After things settled down and the cabin was stabilized per the checklist procedure; I was requested by Maintenance Control through Dispatch to select standby on the Analog Pressurization panel. The standby mode performed perfectly and the cabin altitude remained stable. However; the cabin was being controlled in manual as per the QRH checklist so I think we should have stopped there rather than try another pressurization mode as requested by Maintenance Control through Dispatch. We remained in standby mode for the remainder of the flight with close monitoring. The remainder of the flight was uneventful.
Data retrieved from NASA's ASRS site as of April 2012 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.