Date: 201507
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Weather elements / visibility: Thunderstorm
Aircraft: B777 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Ramp ZZZ
Aircraft component: Indicating and Warning - APU
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Confusion; Situational Awareness
Second reporter function: Pilot Not Flying; First Officer
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Automation Aircraft Other Automation; Person Flight Crew
When detected: Aircraft In Service At Gate
Result: Aircraft Equipment Problem Dissipated; General Maintenance Action
Contributing factors: Aircraft; Human Factors
Primary problem: Aircraft

Narrative: The First Officer and I completed the Preflight ECL (Electronic Check List). Then proceeded right into the Before Pushback ECL. I then asked the First Officer to call for pushback clearance. At that moment the APU Auto shutdown and automatically discharged the APU Fire bottle due to sensing an APU Fire on the ground with both engines shutdown in the (APU Unattended Mode). The EICAS on the Upper Center Screen displayed a Master Caution (Amber) and had an ECL procedure. There were other multiple EICAS messages. We also heard a short Fire Bell. So short that I almost said was that the fire bell? I also heard the APU Nose Gear horn go off momentarily.The First Officer asked; 'do you want to run the APU ECL' I said yes!! At that moment all screens went blank; except the CA's Displays. The Push-crew (Tug operator) started calling for ready to push. I told him to run back to the tail and see if there was a Fire in the APU. The First Officer at this point was making a PA announcement to the flight attendants and passengers to remain seated; and briefly explained what had happened. I immediately tried to radio call Station OPS on the CA audio Panel since we were only on BATT PWR at that point. Tried multiple attempts. Flt Ops did not answer the radio; so I went to ATC Ramp Push Back Frequency and told them we had a APU Fire indication and to 'Call the Fire Department'--'Call Ops' Tell them we have a possible APU Fire-- need Jet Bridge back up--need Ground PWR plugged back in.The Passenger Cabin at this point was on emergency PWR lighting only. The cabin started to get hot due to over 200 people with no air-conditioning. I then made a backup PA announcement to the passengers saying that the Fire Department was on their way so as to determine if it was an indication problem or actual Fire stay calm and wait for instructions. The push crew finally got back to me and said there was no fire; so at that point I did not order an evacuation. I needed additional indications before I sent people down the slides. I could hear the sirens in the background as the fire trucks approached. I was finally able to get ahold of Flight OPS and informed them of the situation and to PLEASE get some Ground PWR and Air-Conditioning on the Aircraft. Flight Ops just could not handle it. Never did get electricity or air until we left the aircraft. The jet-bridge was brought up; the Fire-Crews boarded the aircraft. I told the First Officer to hold the fort down on the Flight Deck as I was going to assist in the cabin with the crews and the Gate Agent. The Fire Chief said no evidence of fire so I order the Passengers off the aircraft. Once we were deplaned the fire marshal wanted all PWR turned off so we de-powered by turning the Battery switch off.That's just about it. I do have some additional comments though.1.) The Ground Push Crew heard the APU Fire Horn or Fire Bell and did not know or respond in anyway; continued to ask for push clearance2.) There was a communication barrier with the tug driver I had to use slow and concise language.3.) Called OPS Multiple times no response. Had to call ATC Push Authority for Fire Trucks.4.) An unidentified man appeared on my flight-deck. Looked like Technician Ops had airport ID and started asking questions I stopped him and inquired as to who he was; said he was Airport Ops authority.5.) After the PAX and flight attendants were off the aircraft I had Three Maintenance Technician Ops with one in the First Observers seat grilling us on exactly what happened and why was the APU Handle Pulled and Rotated. I asked him if he was a Maintenance supervisor he said no and I wanted to know who he was. Said he was some kind of specialist I can't recall the title or name.6.) Started to Run the APU Shutdown ECL only to have the screens go blank after AC PWR was lost. The First Officer was brilliant and went immediately to the EFB FM-Non normals and found a checklist but it was for in flight only. It did not address our situation on the ground. Later while I was in the cabin assisting the Fire Department the FO was able to get the ECL on the LT Inboard display screen.7.) Approximately 20 minutes later while on Battery PWR the APU Fire Handle on the Over Head Panel illuminated again so the FO Pulled and rotated the APU Fire handle as this was a precautionary step and redundant.8.) My experience on the B777 is still very low and am on [probationary] status. This was only my 4th solo trip on the B777. Transition training was adequate for this event; however it was our combined Airline experience as Professional Airman that was our greatest asset.


Second narrative: [Report narrative contained no additional information.]


Synopsis: B777 flight crew experiences an APU fire indication and automatic shut down just prior to push back. Difficulties communicating with ground personnel and company representatives are reported.