B737-500
Flight Crew Last 90 Days 215
Troubleshooting; Time Pressure; Situational Awareness; Training / Qualification
Aircraft Equipment Problem Critical
Flight Crew FLC complied w / Automation / Advisory; Flight Crew Overcame Equipment Problem; Flight Crew Returned To Departure Airport; Flight Crew Took Evasive Action; General Flight Cancelled / Delayed; General Maintenance Action
Aircraft
We had tried to land but were unable due to gust front and dust; wind gust to 65 and 3/4 mile in dust. We held for about 20 minutes and Dispatch decided to have us divert. We were cleared back to our departure airport to climb to FL350. I was pilot flying but had given the aircraft to the First Officer so I could talk to ATC; Dispatch; flight attendants and passengers. Climbing out of 30;000 FT we got the Cabin Altitude Warning and noticed the cabin slowly climbing through 10;000 FT. Masks were put on and lower was requested from ATC. We started a decent to FL240 and then to 16;000 FT. The Altitude Warning Checklist was run; and after selecting MAN AC full closed; we got about 3;000 FPM descent on the cabin. I went back to Auto and got a 600 FPM descent. The cabin reached about 12;000 FT but the masks did not drop. We were descending into moderate rain with moderate turbulence and moderate rime ice; and the flight attendants had just asked to get up to do a water service. The First Officer was doing a great job flying while I talked to ATC and ran checklists and ATC was very helpful. We did not declare an emergency; probably should have; but they gave us lower right away and we got the cabin back under control. We never got a pack or bleed trip or controller fail. After we got the cabin below 10;000 FT; we continued with a normal arrival and landing. Maintenance was contacted and a logbook entry was made and the aircraft was taken out of service for inspection. I did learn that Maintenance needs to know the duct pressure from the packs which I did look at and we had pressure but I don't remember how much.
On arrival; I talked to a Chief Pilot and he mentioned a similar pressurization incident occurred in another B737 aircraft a few months back also on a divert.
While climbing through FL300 and returning to the departure airport after a missed approach; a B737-500 pressurization failed but during the descent was recovered using MAN AC so the cabin did not exceed 12;000 FT.