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37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
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After receiving a cabin altitude warning horn during cruise flight, a B737 flight crew donned oxygen masks, declared emergency, and began an emergency descent. During the descent, the flight crew received a TCASII RA for traffic which they had in sight. The flight diverted and subsequent maintenance inspection revealed a forward outflow valve stuck in the open position. The valve was MEL'ed and the flight continued to the destination.
| Attributes | |
| ACN | 326081 |
| Time | |
| Date | 199601 |
| Day | Fri |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : mmj |
| State Reference | PA |
| Altitude | msl bound lower : 33000 msl bound upper : 33000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Dusk |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Flight Phase | cruise other |
| Route In Use | enroute airway : zob |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | common carrier : air carrier |
| Make Model Name | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Flight Phase | cruise other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 180 flight time total : 8000 flight time type : 2800 |
| ASRS Report | 326081 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 200 flight time total : 11500 flight time type : 3000 |
| ASRS Report | 326086 |
| Events | |
| Anomaly | aircraft equipment problem : critical conflict : airborne less severe |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified |
| Resolutory Action | flight crew : declared emergency other |
| Consequence | Other |
| Miss Distance | horizontal : 9600 |
| Supplementary | |
| Primary Problem | Aircraft |
Narrative:
After being in cruise flight for approximately 15 mins, the cabin altitude warning horn sounded. Both pilots noticed the cabin altitude approaching 10000 ft and climbing at about 500 FPM. An emergency was declared to ZOB and a descent initiated. TCASII had traffic at 12 O'clock. The captain had the other aircraft in sight during the initial descent and through the 'clear of conflict.' we turned approximately 30 degrees to the right followed by an RA to 'climb' and an immediate 'clear of conflict.' oxygen masks had been donned and all emergency checklists completed. We continued the descent to 10000 ft then continued to 8000 ft and diverted to pit. The emergency was secured and the flight to pit was uneventful. Callback conversation with reporter revealed the following information: the B737-200 flight crew canceled the emergency equipment while inbound to the airport. There was no follow-up investigation from the FAA or further inquiry from ATC. Maintenance inspection discovered the forward outflow valve was stuck in the open position. The outflow valve was MEL'ed and the flight continued at an altitude less than the aircraft was certified for to the scheduled destination. Supplemental information from acn 326086: had visual on a wbound B737 company traffic and ZOB said we came within 1.6 NM.
Original NASA ASRS Text
Title: AFTER RECEIVING A CABIN ALT WARNING HORN DURING CRUISE FLT, A B737 FLC DONNED OXYGEN MASKS, DECLARED EMER, AND BEGAN AN EMER DSCNT. DURING THE DSCNT, THE FLC RECEIVED A TCASII RA FOR TFC WHICH THEY HAD IN SIGHT. THE FLT DIVERTED AND SUBSEQUENT MAINT INSPECTION REVEALED A FORWARD OUTFLOW VALVE STUCK IN THE OPEN POS. THE VALVE WAS MEL'ED AND THE FLT CONTINUED TO THE DEST.
Narrative: AFTER BEING IN CRUISE FLT FOR APPROX 15 MINS, THE CABIN ALT WARNING HORN SOUNDED. BOTH PLTS NOTICED THE CABIN ALT APCHING 10000 FT AND CLBING AT ABOUT 500 FPM. AN EMER WAS DECLARED TO ZOB AND A DSCNT INITIATED. TCASII HAD TFC AT 12 O'CLOCK. THE CAPT HAD THE OTHER ACFT IN SIGHT DURING THE INITIAL DSCNT AND THROUGH THE 'CLR OF CONFLICT.' WE TURNED APPROX 30 DEGS TO THE R FOLLOWED BY AN RA TO 'CLB' AND AN IMMEDIATE 'CLR OF CONFLICT.' OXYGEN MASKS HAD BEEN DONNED AND ALL EMER CHKLISTS COMPLETED. WE CONTINUED THE DSCNT TO 10000 FT THEN CONTINUED TO 8000 FT AND DIVERTED TO PIT. THE EMER WAS SECURED AND THE FLT TO PIT WAS UNEVENTFUL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE B737-200 FLC CANCELED THE EMER EQUIP WHILE INBOUND TO THE ARPT. THERE WAS NO FOLLOW-UP INVESTIGATION FROM THE FAA OR FURTHER INQUIRY FROM ATC. MAINT INSPECTION DISCOVERED THE FORWARD OUTFLOW VALVE WAS STUCK IN THE OPEN POS. THE OUTFLOW VALVE WAS MEL'ED AND THE FLT CONTINUED AT AN ALT LESS THAN THE ACFT WAS CERTIFIED FOR TO THE SCHEDULED DEST. SUPPLEMENTAL INFO FROM ACN 326086: HAD VISUAL ON A WBOUND B737 COMPANY TFC AND ZOB SAID WE CAME WITHIN 1.6 NM.
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.