B737-800
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical; Deviation - Altitude Excursion From Assigned Altitude
General Declared Emergency
Procedure; Aircraft
On climb out passing FL230 declared emergency with ATC due to cabin pressurization problem. Requested immediate lower altitude to 10;000 feet. Once at 10;000 feet we continued the arrival with normal approach and landing.
Single pack operation; (inbound write up of hot left pack) complied with MEL direction to bleed APU for rightpack operation during departure. Approximately 3;000 AGL MEL procedure to bleed right engine to right pack. Duct pressure was good and right pack in auto. Climbing through the mid teens we both noted that cockpit temperature seemed to be getting warmer; cooler temperature was selected. (Aircraft cabin/cockpit temperature was already warm due to ground temperature). Level 24;000 we received cabin altitude warning. We donned O2 mask establish com; I descend approximately 300 feet before I declared emergency with ATC. I closed the outflow valve manually. Initial descent to 14;000 feet for mountains; then down below 10;000 feet. The cabin altitude was controlled through descent and outflow valve; the cabin masks were not dropped.
B737-800 flight crew experiences a cabin altitude warning horn passing FL230 after being dispatched with an inoperative pack. Passenger oxygen masks are not deployed and flight is able to continue to destination.