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B737-700 flight crew reported 2 mels that when combined did not provide sufficient bleed air to properly pressurize the aircraft during descent.
| Attributes | |
| ACN | 1603235 |
| Time | |
| Date | 201812 |
| Local Time Of Day | 1801-2400 |
| Place | |
| Locale Reference | ZZZ.Airport |
| State Reference | US |
| Environment | |
| Light | Daylight |
| Aircraft 1 | |
| Make Model Name | B737-700 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Cruise |
| Flight Plan | IFR |
| Component | |
| Aircraft Component | Pressurization System |
| Person 1 | |
| Function | Pilot Not Flying Captain |
| Qualification | Flight Crew Multiengine Flight Crew Instrument Flight Crew Air Transport Pilot (ATP) |
| Experience | Flight Crew Last 90 Days 358 |
| Person 2 | |
| Function | Pilot Not Flying First Officer |
| Qualification | Flight Crew Instrument Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine |
| Experience | Flight Crew Last 90 Days 495 |
| Events | |
| Anomaly | Aircraft Equipment Problem Less Severe Deviation - Procedural MEL Deviation - Procedural Published Material / Policy |
Narrative:
We arrived in ZZZ and swapped to aircraft XXX. This aircraft had two mels; one was the number two engine anti ice cowl valve failed in the open position. The other was the number one engine bleed air shut-off valve (prsov) was closed. This MEL was added in ZZZ as the previous crew made a logbook entry for left engine bleed trip. The number two engine anti-ice valve was locked in the open position and high stage valve was locked closed per MEL sp #30 - ice and rain protection. We were dispatched at FL250. During cruise flight we were directed by ATC to slow to 260 knots. As the throttles moved towards idle; the cabin altitude began to climb at 3000 fpm. I pushed the power up and regained control of the cabin altitude. During descent into ZZZ1; I maintained approximately 1000 fpm descent rate. This maintained control of the cabin altitude. The APU was started and at 17;000 ft; we powered the left pack with the APU. The rest of the descent was normal.
Original NASA ASRS Text
Title: B737-700 flight crew reported 2 MELs that when combined did not provide sufficient bleed air to properly pressurize the aircraft during descent.
Narrative: We arrived in ZZZ and swapped to aircraft XXX. This aircraft had two MELs; one was the number two engine anti ice cowl valve failed in the open position. The other was the number one engine bleed air shut-off valve (PRSOV) was closed. This MEL was added in ZZZ as the previous crew made a logbook entry for left engine bleed trip. The number two engine anti-ice valve was locked in the open position and high stage valve was locked closed per MEL SP #30 - Ice and Rain Protection. We were dispatched at FL250. During cruise flight we were directed by ATC to slow to 260 knots. As the throttles moved towards idle; the cabin altitude began to climb at 3000 fpm. I pushed the power up and regained control of the cabin altitude. During descent into ZZZ1; I maintained approximately 1000 fpm descent rate. This maintained control of the cabin altitude. The APU was started and at 17;000 FT; we powered the left pack with the APU. The rest of the descent was normal.
Data retrieved from NASA's ASRS site 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.