Date: 201212
Local time of day: 0001-0600
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Aircraft: B757 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: AC Generator/Alternator
Component problem: Failed
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight; Taxi
Result: Flight Crew Landed in Emergency Condition; Flight Crew Diverted; General Maintenance Action
Contributing factors: Human Factors; Aircraft
Primary problem: Human Factors

Narrative: After taxi out for departure. the right engine generator failed.  Followed the checklist; notified Maintenance Control; and Dispatch.  Returned to the gate to perform HMG generator test and check oil in the APU so as to defer aircraft with right generator inop.  I agreed to accept deferral and fly aircraft to ZZZ with IFR WX thinking if I had to fly a CAT III autoland. I was legal to go.  A Mechanic showed up and started to perform the test to verify the HMG was working.  He spent over 45 minutes without a checklist to test the HMG.  I asked what circuit breaker he pulled and he replied it was the HMG control CB.  He said that's the CB he pulls on B767s.  Later another Mechanic showed up and questioned why the HMG [Hydraulic Moter Generator] CB was pulled.  They left and came back with a copy of the test procedure from their manual.  They pulled a different CB and tested the HMG; which passed successfully. Then they asked me to de-power the entire aircraft to reset some relays.  We departed 2 hours late.  Thirty minutes after departure at FL360 50 nm west of ZZZ1 the APU flamed out.  We restarted and it flamed out again.  We contacted Dispatch and elected to divert to ZZZ1 since ZZZ was down to 1/4 mile vis; and 200 foot ceiling.  Also directed by checklist and dispatch to divert to nearest suitable airport.  Notified flight attendants; passengers; etc.  Completed all checklist; and diversion guide.  Obtained overweight landing data for ZZZ1 from Dispatch.  Landed normally and taxied to the gate.  Met with three mechanics; and observed them at the APU area.  The Mechanic said he found the APU filler cap was not secured; oil was leaking everywhere; and the chip detector was loose.  They found the APU to only have two quarts of oil remaining.  That is why the APU flamed out.  The next day we were to ferry the aircraft with the right gen still deferred using the APU.  It took over 2.5 hours to get the aircraft released from Maintenance.  There was a conflict between the two maintenance departments. They couldn't agree on how or who should defer it.  I got everyone involved trying to get a resolution.  I finally went into the Maintenance Office and asked; 'What seems to be the problem?'  The same Mechanic we dealt with the day before said there was no problem; and that we had the opportunity to take the aircraft yesterday.  Also; there wasn't anything he could do to help us.  He denied that the APU cap was off yesterday even though he made the entry in the log book; and showed us that it was indeed off. Maintenance Control finally sent the release and we departed.




Synopsis: B757 Captain experiences a generator failure during taxi out and returns to the gate for maintenance.  The generator is MEL'd and the flight is dispatched with the APU running and its generator connected to the right bus. Enroute the APU fails and flight diverts to the nearest suitable airport.