Narrative:

Beginning our duty day at our departure airport; we accepted a 737-900 aircraft with 3 mels. 21-1G (one pack inop); 21-19I (trim air prsov remains closed) and 32-7B (automatic brake system). The flight was planned at 24;000 feet. Planned fuel load was 20.6. The flight was dispatched with no alternate and 800 lbs. Of extra fuel. Mid-range headwinds and some sigmets for turbulence in the vicinity of mountainous terrain were expected along our route of flight.during taxi out; flight attendants complained of a warm cabin. They called again about 15 minutes into the turbulent flight complaining that a few passengers were getting sick. The next 30 minutes of the flight smoothed out; but the cabin remained warm.approximately 45 minutes into cruise; the captain pilot monitoring (pm) noticed the cabin pressure beginning to climb at 1200 f.p.m. He attempted to control and reverse the climb trend by switching the pressurization mode controller to altn; to no effect. He initiated a descent with ATC; first to 17;000 feet and lower as the situation continued. The captain made one more effort to control the cabin by switching the cabin altitude controller to manual and adjusting the pneumatic outflow valve switch to full close. The cabin continued to depressurize. The cabin altitude warning illuminated. The crew donned our O2 masks and established communications. We followed the [checklist] for pressurization and emergency descent procedures. Since the flight began at a lower cruise altitude than customary; we adjusted for a more gradual descent comfortably allowing the flight crew to catch the cabin at 13;500 feet as we continued down to 11;000 feet. The captain attempted to reach dispatch via the sat phone. The first attempt was unsuccessful. He advised ATC and requested an immediate vector to our closest suitable airport; 40 nautical miles away. We were cleared via right turn direct to our diversion airport. Part of the joint decision to divert hinged on three primary factors: 1) the emergency descent now placed the aircraft into light to moderate turbulence at 11;000 feet. A third call from our 'a' flight attendant indicated that several more passengers were now sick; including some [of] our cabin crew; now seated in their jump seats with sick-sacks in hand. 2) with 1:15 remaining to our original destination; the prospect of scud-running at low altitude with a much higher fuel burn would have placed the crew and passengers in an unnecessarily unsafe position. 3) light snow and cloudy conditions at our original destination meant that; should a go-around have been necessary; minimal fuel would have remained to allow a safe landing. With a suitable airport so close; the decision was easy.

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Original NASA ASRS Text

Title: B737-900 First Officer reported being dispatched with one pack inoperative at FL240. The cabin altitude is noted to be climbing and a descent is initiated. Pressurization cannot be restored and with turbulence at 10000 feet and poor weather at destination; the crew elects to divert to the nearest suitable airport.

Narrative: Beginning our duty day at our departure airport; we accepted a 737-900 aircraft with 3 MELs. 21-1G (One pack inop); 21-19I (Trim air PRSOV remains closed) and 32-7B (Automatic brake system). The flight was planned at 24;000 feet. Planned fuel load was 20.6. The flight was dispatched with no alternate and 800 lbs. of extra fuel. Mid-range headwinds and some SIGMETs for turbulence in the vicinity of mountainous terrain were expected along our route of flight.During taxi out; flight attendants complained of a warm cabin. They called again about 15 minutes into the turbulent flight complaining that a few passengers were getting sick. The next 30 minutes of the flight smoothed out; but the cabin remained warm.Approximately 45 minutes into cruise; the Captain Pilot Monitoring (PM) noticed the cabin pressure beginning to climb at 1200 f.p.m. He attempted to control and reverse the climb trend by switching the pressurization mode controller to ALTN; to no effect. He initiated a descent with ATC; first to 17;000 feet and lower as the situation continued. The captain made one more effort to control the cabin by switching the cabin altitude controller to manual and adjusting the pneumatic outflow valve switch to full close. The cabin continued to depressurize. The CABIN ALT warning illuminated. The crew donned our O2 masks and established communications. We followed the [checklist] for pressurization and emergency descent procedures. Since the flight began at a lower cruise altitude than customary; we adjusted for a more gradual descent comfortably allowing the flight crew to catch the cabin at 13;500 feet as we continued down to 11;000 feet. The captain attempted to reach dispatch via the SAT phone. The first attempt was unsuccessful. He advised ATC and requested an immediate vector to our closest suitable airport; 40 nautical miles away. We were cleared via right turn direct to our diversion airport. Part of the joint decision to divert hinged on three primary factors: 1) The emergency descent now placed the aircraft into light to moderate turbulence at 11;000 feet. A third call from our 'A' flight attendant indicated that several more passengers were now sick; including some [of] our cabin crew; now seated in their jump seats with sick-sacks in hand. 2) With 1:15 remaining to our original destination; the prospect of scud-running at low altitude with a much higher fuel burn would have placed the crew and passengers in an unnecessarily unsafe position. 3) Light snow and cloudy conditions at our original destination meant that; should a go-around have been necessary; minimal fuel would have remained to allow a safe landing. With a suitable airport so close; the decision was easy.

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.