Date: 202012
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Dawn
Aircraft: A320
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
Aircraft component: APU
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Maintenance; Ground Event / Encounter Ground Equipment Issue
Detector: Person Flight Crew
When detected: Pre-flight
Result: General Release Refused / Aircraft Not Accepted; General Flight Cancelled / Delayed
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: On Date; I was the assigned Captain on Aircraft X. The aircraft had the following MEL:APU shutdown during Engine 1 start action. Reset retry no help; request approval to apply MEL action. Applied MEL action; APU surges / rumbles during MES (main engine start) mode. It can carry both packs normally. When [the] First Officer and I were preflighting the aircraft arrived at the gate; the aircraft had already been completely boarded.  There was no ground air operating. During the preflight; the ground power failed and the entire airplane went dark.  Ramp personnel attempted to reconnect; but the airplane would not accept the power.  The Ramp Supervisor; talking with me through the open aircraft window advised he was going to get a second ground power unit.  Minutes later; with the aircraft still dark ramp [agents] attempted to connected power.  The aircraft powered for just at 30 seconds and went dark again.  The Ramp Supervisor stated the he knew both ground power units are working; yet the aircraft would not accept the power. I contacted the Duty Manager; briefed the situation and stated that I was refusing the aircraft.  He agreed; stating he would back my decision. I contacted the Dispatcher for the flight; who conferenced in Maintenance Control.  I explained the situation and that I was refusing the aircraft - unable to operate.  Maintenance Control stated that with both the APU and ground power not working; The aircraft could not be dispatched; so that technically it was not a refusal. During this call; passengers were becoming agitated and wanting off the dark aircraft.  Flight attendants and gate personnel began de-planing the passengers.  Several were taking video while in the dark airplane with no air. Maintenance arrived at the airplane during the passenger exit and advised they were able to get the power to work; 'the connection was not good.'The Dispatcher called; conferenced Maintenance Control; and we again briefed what I have stated so far in this report.  Both stated that the refusal was completely understandable and advised with questionable contingencies: what happens if the ground power doesn't work in ZZZ; what if it does work during an unplanned divert; etc.  additionally; with passengers filming; said it was the prudent call to refuse the aircraft. The aircraft was powered down so no MRM (maintenance report message) could be sent.




Synopsis: Captain refused aircraft after aircraft would not accept external power with an APU already on MEL.