EMB ERJ 145 ER/LR
Flight Crew Air Transport Pilot (ATP)
Situational Awareness
Aircraft Equipment Problem Critical
Flight Crew Landed As Precaution; Flight Crew Returned To Departure Airport; General Maintenance Action
Aircraft; Human Factors
After departure passing through 10;000 we are closely monitoring pack number two since pack number one was MEL'ed. Passing through 16;000 FT we noticed that the plane was not pressurizing and advised ATC we needed to level off at 18;000. At this point cabin rate [altitude] was 6;500 and later turned amber. QRH was consulted to try to recycle pack number two. At this point cabin rate [altitude] was 10;000; called ATC for a lower altitude and to return to departure airport. I did not declare an emergency but asked for priority to the airport. The Flight Attendant was called and at this point she reported a strange noise [in the cabin]. Monitor the cabin rate and notice the problem sooner.
EMB145 Captain reports being dispatched with pack one inoperative and noticing cabin altitude climbing rapidly as the aircraft passes through 16;000 FT during climb. Pack number two has tripped and cannot be reset and flight returns to departure airport.