MD-83
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Weight And Balance
Flight Crew Returned To Departure Airport; Flight Crew Landed As Precaution; General Declared Emergency; General Maintenance Action
Aircraft
Before gate departure the aircraft had placards on the Thrust Limit Indicator; autothrottle; and right pack. After takeoff we were unable to pressurize the aircraft. After running the checklist we came to the conclusion the left pack had failed (right pack placarded inoperative). We declared an emergency due to an overweight landing and air return. Before gate departure I felt like we were right on the limit for the number/combination of placarded items; especially after reviewing the aircraft maintenance history. After gate arrival I felt like the entire event would have been much safer had the autothrottle been functioning. There were no pilot deviations from accepted procedures that I am aware of.
MD83 pilot reports being dispatched with the right pack inoperative and discovering airborne that the left pack has also failed. Flight returns to the departure airport for an overweight landing.