Date: 202109
Local time of day: 1201-1800
Location: ZAB.ARTCC, NM
Flight conditions: VMC
Light: Daylight
Aircraft: A321
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Generator Drive
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; First Officer
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Human factors: Training / Qualification; Troubleshooting; Time Pressure; Situational Awareness; Workload; Communication Breakdown; Confusion
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Diverted; Flight Crew Requested ATC Assistance / Clarification; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft; Human Factors; MEL; Procedure
Primary problem: Aircraft

Narrative: Pre-flight document review: Flight Plan indicated extra fuel; cruise at FL320 due to APU use. MEL 24.01a also listed on flight plan.Arriving Captain (CA) briefed me on aircraft status; MEL 24-XX-X for #1 IDG: Requires running APU; Max Altitude 33;000 feet. Otherwise there were no other problems with the aircraft (as reported by CA).Once in cockpit; CA & First Officer (FO) review of MEL 24-XX-X indicated a requirement to (M) c) 'Operator ensures the APU oil quantity if adequate for the intended flight.'* Both CA & FO interpreted this to mean APU Oil quantity check prior to each flight.* CA called Maintenance to ensure and APU oil quantity check was accomplished.* Maintenance came; read the log book & MEL; concluded that an oil quantity check was not required.Pre & post-engine start procedures of MEL were successfully accomplishedDuring departure (approx. 8;000 feet) got 'VENT SKIN VALVE FAULT'; accomplished ECAM procedures (Blower & Extract to OVRD). QRH and Supplemental procedures were reviewed; flight continued.At cruise altitude (FL32;000 feet) we started selecting potential divert fields with adequate runway length; putting fixes and 100 nm rings around. We updated them along the path; and pre-briefed our plan in case of generator failure.Approx 80 NM SW of ZZZ; got 'ELEC GEN 2 FAULT'; with IDG temp high.  Accomplished ECAM procedures; including disconnecting IDG.  Now single generator ops.At this point PM (CA) requested immediate assistance'; nature of problem; and told ATC we were turning toward ZZZ; required vectors for immediate approach & landing. At this point; CA tasked PF (FO) to take ATC comm; descend & set up for ZZZ arrival. FO passed SOB and fuel state.CA briefed Flight Attendants; Passengers; then took back ATC radio duties. Crew set up & briefed ILS XX approach to ZZZ; reviewed non-normal procedures; contacted ZZZ OPS for gate assignment. FO flew arrival and landing to ZZZ Runway XX in VFR conditions.After landing taxied to gate XX; wrote up Generator #2; debriefed to Maintenance personnel.Cause -1. Aircraft was dispatched away from a major maintenance base with an inoperative IDG/Generator.2. MEL does not clearly describe APU oil quantity check (one time; or prior to each flight).3. MEL does not require the opposite side IDG oil level to be checked.4. MEL category B allows too much time. Believe this MEL should only be for a single flight (ferry) to a maintenance base.Suggestions -1. Review MEL 24-XX; rewrite to clearly define oil quantity check requirements. Ensure both APU & other IDG are serviced/checked prior to EACH flight.2. Review Airbus failure data for IDG's; consider re-setting MEL 24 from cat B to single flight only.3. Review maintenance records for this aircraft; specifically the IDG servicing. Determine why/how BOTH IDGs on the same plane can fail within 3 flight legs/2 days. Possibly the units were both serviced at the same time but improperly; or contaminated; or serviced with improper fluid.




Synopsis: A320 Captain reported being dispatched with an MELed IDG and experienced the loss of the APU inflight; causing a diversion due to single generator operations.