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Aircraft equipment problem. Depressurization and emergency descent due to faulty pressure modulating valve.
| Attributes | |
| ACN | 334245 |
| Time | |
| Date | 199604 |
| Day | Thu |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : aba |
| State Reference | FO |
| Altitude | msl bound lower : 14000 msl bound upper : 33000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | B727-200 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise other |
| Route In Use | enroute : other oceanic enroute airway : tncf |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : instrument pilot : commercial pilot : atp |
| Experience | flight time last 90 days : 150 flight time total : 10000 flight time type : 180 |
| ASRS Report | 334245 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 120 flight time total : 15000 flight time type : 9000 |
| ASRS Report | 334071 |
| Events | |
| Anomaly | aircraft equipment problem : critical other anomaly other |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other flight crewa |
| Resolutory Action | flight crew : declared emergency none taken : unable |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
Narrative:
Flight from aruba to boston. In cruise at FL330 about 28 NM north of moloc on A567. Cabin altitude warning horn sounded. Cabin altitude was climbing through 7000 ft. Unable to stop cabin climb or silence warning horn. Initiated an emergency descent to FL140 and notified tncf that we were descending and turning right off of airway. During descent regained control of cabin pressure and leveled at FL140. Notified company operations and ATC that we wished to divert to mco. With cabin pressure controled and stable remainder of flight to orlando was uneventful. Partial pressure loss due to failure of pressure modulating valve. Failure of warning horn silence feature not yet known. 14000 ft was selected as descent target altitude because it is the maximum altitude for en route depressurization as per limitations section of B727 aircraft operating manual. Remainder of flight to orlando was conducted at FL240.
Original NASA ASRS Text
Title: ACFT EQUIP PROB. DEPRESSURIZATION AND EMER DSCNT DUE TO FAULTY PRESSURE MODULATING VALVE.
Narrative: FLT FROM ARUBA TO BOSTON. IN CRUISE AT FL330 ABOUT 28 NM N OF MOLOC ON A567. CABIN ALT WARNING HORN SOUNDED. CABIN ALT WAS CLBING THROUGH 7000 FT. UNABLE TO STOP CABIN CLB OR SILENCE WARNING HORN. INITIATED AN EMER DSCNT TO FL140 AND NOTIFIED TNCF THAT WE WERE DSNDING AND TURNING R OFF OF AIRWAY. DURING DSCNT REGAINED CTL OF CABIN PRESSURE AND LEVELED AT FL140. NOTIFIED COMPANY OPS AND ATC THAT WE WISHED TO DIVERT TO MCO. WITH CABIN PRESSURE CTLED AND STABLE REMAINDER OF FLT TO ORLANDO WAS UNEVENTFUL. PARTIAL PRESSURE LOSS DUE TO FAILURE OF PRESSURE MODULATING VALVE. FAILURE OF WARNING HORN SILENCE FEATURE NOT YET KNOWN. 14000 FT WAS SELECTED AS DSCNT TARGET ALT BECAUSE IT IS THE MAX ALT FOR ENRTE DEPRESSURIZATION AS PER LIMITATIONS SECTION OF B727 ACFT OPERATING MANUAL. REMAINDER OF FLT TO ORLANDO WAS CONDUCTED AT FL240.
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.