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A B757-200 at FL340 required use of the deferred inoperative left pack to maintain cabin pressure at assigned altitude. Pack operated normally.
| Attributes | |
| ACN | 578421 |
| Time | |
| Date | 200304 |
| Day | Wed |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | airport : zzz.airport |
| State Reference | US |
| Altitude | msl single value : 34000 |
| Environment | |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | tracon : zzz.tracon tower : zzz.tower |
| Operator | common carrier : air carrier |
| Make Model Name | B757-200 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | other |
| Flight Phase | cruise : level |
| Route In Use | enroute : atlantic |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| ASRS Report | 578421 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| ASRS Report | 578898 |
| Events | |
| Anomaly | aircraft equipment problem : critical maintenance problem : non compliance with mel maintenance problem : improper maintenance non adherence : published procedure non adherence : far |
| Independent Detector | aircraft equipment other aircraft equipment : cabin altitude indicator other flight crewa other flight crewb |
| Resolutory Action | aircraft : equipment problem dissipated flight crew : overcame equipment problem |
| Consequence | other other |
| Factors | |
| Maintenance | contributing factor : manuals contributing factor : schedule pressure performance deficiency : fault isolation |
| Supplementary | |
| Problem Areas | Maintenance Human Performance Flight Crew Human Performance Chart Or Publication Aircraft |
| Primary Problem | Aircraft |
Narrative:
Prior to departure, the left pack was placarded, because it was producing too much hot air. The flight crew was dispatched with FL350 limitation on right pack. Approximately 1 hour into the flight crew, we noticed that the cabin was slowly climbing towards 10000 ft at FL340 with the outflow valve closed, so I elected to reinstate the left pack to avoid doing an emergency descent. The pressure returned to normal, and the pack operated normally, so we continued to the destination uneventfully, using both packs.
Original NASA ASRS Text
Title: A B757-200 AT FL340 REQUIRED USE OF THE DEFERRED INOP L PACK TO MAINTAIN CABIN PRESSURE AT ASSIGNED ALT. PACK OPERATED NORMALLY.
Narrative: PRIOR TO DEP, THE L PACK WAS PLACARDED, BECAUSE IT WAS PRODUCING TOO MUCH HOT AIR. THE FLT CREW WAS DISPATCHED WITH FL350 LIMITATION ON R PACK. APPROX 1 HR INTO THE FLT CREW, WE NOTICED THAT THE CABIN WAS SLOWLY CLBING TOWARDS 10000 FT AT FL340 WITH THE OUTFLOW VALVE CLOSED, SO I ELECTED TO REINSTATE THE L PACK TO AVOID DOING AN EMER DSCNT. THE PRESSURE RETURNED TO NORMAL, AND THE PACK OPERATED NORMALLY, SO WE CONTINUED TO THE DEST UNEVENTFULLY, USING BOTH PACKS.
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.