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The pilots of a B747 observed an outflow valve fault during climb; but elected to continue the climb due to workload and considering the previous maintenance history. When they received a cabin altitude warning; they requested a lower altitude and attempted to remedy the issue per the flight manual. This was unsuccessful; so they dumped fuel and returned to the departure airport.
| Attributes | |
| ACN | 1110069 |
| Time | |
| Date | 201308 |
| Place | |
| Locale Reference | ZZZZ.Airport |
| State Reference | FO |
| Environment | |
| Flight Conditions | VMC |
| Aircraft 1 | |
| Make Model Name | B747 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Initial Climb |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | Pressurization Outflow Valve |
| Person 1 | |
| Function | Pilot Flying Captain |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Person 2 | |
| Function | First Officer Relief Pilot |
| Experience | Flight Crew Last 90 Days 105 Flight Crew Total 7257 Flight Crew Type 137 |
| Events | |
| Anomaly | Aircraft Equipment Problem Critical |
Narrative:
Climbing through 3;000 ft; we received an outflow valve left EICAS message. This had been written up several times in the past; and it appeared to be a nuisance message because the pressurization was operating normally when we looked at it. Because of this fact and the high workload after departure; I elected to delay running the procedure for a few minutes. Immediately after climbing through 10;000 ft; we received a cabin altitude warning. We immediately requested and were given clearance to 8;000 ft. We ran the appropriate checklist and were unable to regain control of either outflow valve in auto. Manual worked as expected. The cabin altitude did not exceed 11;300 ft. We returned to [the departure airport] for repair after dumping approximately 120;000 pounds of fuel.
Original NASA ASRS Text
Title: The pilots of a B747 observed an outflow valve fault during climb; but elected to continue the climb due to workload and considering the previous maintenance history. When they received a cabin altitude warning; they requested a lower altitude and attempted to remedy the issue per the flight manual. This was unsuccessful; so they dumped fuel and returned to the departure airport.
Narrative: Climbing through 3;000 FT; we received an Outflow Valve L EICAS message. This had been written up several times in the past; and it appeared to be a nuisance message because the pressurization was operating normally when we looked at it. Because of this fact and the high workload after departure; I elected to delay running the procedure for a few minutes. Immediately after climbing through 10;000 FT; we received a Cabin Altitude warning. We immediately requested and were given clearance to 8;000 FT. We ran the appropriate checklist and were unable to regain control of either outflow valve in Auto. Manual worked as expected. The cabin altitude did not exceed 11;300 FT. We returned to [the departure airport] for repair after dumping approximately 120;000 pounds of fuel.
Data retrieved from NASA's ASRS site as of July 2013 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.