Flight Crew Air Transport Pilot (ATP)
Workload; Time Pressure; Situational Awareness
Aircraft Equipment Problem Critical
Flight Crew Returned To Departure Airport; Flight Crew Took Evasive Action; General Maintenance Action
Aircraft
The aircraft on this flight had two MELs; the first was the right pack and the second was the left generator.  The single pack limited our altitude to a maximum of 25;000 feet; and the single generator required us to run the APU for the entire flight. I decided to take the airplane because the weather was good along the entire route. We were also carrying 16;000 lbs of ferry fuel. The flight proceeded normally until we were airborne about an hour when we noticed a Master Caution light illuminated because of an electric problem. We noticed the APU had shut down giving us the Source Off light. The APU was restarted; but the APU Low Pressure light remained illuminated and the APU shut down again. We realized we were down to a single generator and discussed airports to divert to. After talking to dispatch; we decided to come back to the departure airport. I [advised] ATC and told them we were down to a single generator and would be landing overweight. The arrival and landing were uneventful. The First Officer landed the airplane and I taxied to the gate with no further problems.
A B737-800 dispatched with a single generator and pack cruised at FL250 when the APU shutdown. The APU was restarted but shutdown a second time with a low oil pressure warning. The flight returned to the departure airport with a single generator.