B737-700 flight crew reported an APU failure during taxi and returned to the gate to deplane.
Synopsis
B737-700 flight crew reported an APU failure during taxi and returned to the gate to deplane.
Narrative
We pushed off gate late due to ATC. Ground Control was saturated; and we were number 40 for taxi. I was communicating with Dispatch about going back to the gate for fuel. We were SET at the time. After approximately 30 minutes; I had just notified Ground we were returning to the gate for more fuel. Suddenly the entire aircraft shook; the #1 source off lite illuminated; and the APU fault light illuminated overhead. As I was looking overhead; I could see the APU auto shutdown and then the APU fire handle illuminated the fire warning bell sounded and the Annunciator Panel Fire lights illuminated. I immediately completed the APU fire memory items. I called for the QRC and QRH.The B FA (Flight Attendant) called and asked what was happening at this time because they felt the aircraft shake severely from the back. Quick conversations took place to ensure everyone's safety and ask if any smoke was in the cabin. No smoke was reported. We called Ground Control where [assistance was requested] and asked for the crash fire and rescue trucks to roll to our position. We confirmed no fire in the APU; taxied to the gate under our own power and deplaned the passengers right away.The FO saw over 900 degrees and climbing. ATC was severely congested; and it was difficult to get a call out for the CFR (Crash Fire Rescue). Ground was reading out what number everyone was; and he was at number 35 when we finally got a radio call out. I asked for a discreet frequency; but Ground said no! I was very close to evacuating the aircraft right there on the tarmac. But the B FA assured me there was no smoke in the cabin. ZZZ Ops was completely no help asking over three times for information on who we were and what gate we wanted to return to. Two ZZZ Chiefs met the aircraft and that was very helpful! Logbook entry was performed back at the gate. All phone calls to Dispatch; Maintenance; Supervisor; and Chief Pilots were completed.
Second reporter narrative
Our flight encountered an indication of an APU fire while still on the ground after pushback from our gate. There were several external factors causing delays out of ZZZ that morning. To start; we were roughly an hour and a half late due to weather in and around ZZZ and the greater region. Our original route from Dispatch and through CPDLC took our flight quite north through the Midwest. We had spoken with Dispatch and worked with them to give us a better route taking us further south and saving us fuel and time. We had contacted Clearance; but the new route had not yet been uplinked to them. We had made the decision to go ahead and push off the gate after hearing that there were 47 aircraft waiting to take off. After pushback there was quite a bit of radio congestion with most aircraft receiving new routing for weather and several departure corridors closing. We were trying to straighten out our routing with Clearance for nearly 30 minutes when we had noticed that we would most likely need to return to the gate for additional fuel. Dispatch had adjusted our minimum takeoff fuel; in hopes we could avoid the need for any additional fuel. Ground began reading off aircraft flight numbers and takeoff position; we were 34th in line. We were trying to coordinate with Ops for a gate; when we heard and felt a loud noise throughout the aircraft. At this time; we had the APU running and providing air to the left pack with the generator online; #1 engine was shut down; #2 engine was running and supplying air for the right pack. The generator on the number #2 engine was online. Suddenly our Master Caution light illuminated; and we had several lights on the electrical panel starting to come on. When I looked up; I noticed an APU fault light with the APU EGT beginning to spike; approaching over 900 degrees Celsius. In that moment we had the fire bell go off and the APU fire handle illuminate. The Captain called for the QRH; as I was getting that out he began to ask the FAs (Flight Attendants) if they saw or smelt smoke in the cabin. They said; No." We ran the QRH and fired the bottle into the APU enclosure and the light when out. At this time Ground was still reading off departure positions to aircraft so it made it difficult to get a word off to [request assistance]. I was finally able to speak with them; only saying we had indications of an APU fire. That asked if we wanted for fire and rescue to be dispatched; to which I said; "Yes." They asked if we were [requesting assistance]; to which I replied; "Yes." At this time; we had Ground Ops trying to bring us in from when we had made contact for additional fuel. We waited until fire trucks had arrived and told us there was no signs of smoke or fire externally. We believed it safe to return to the gate and deplane the passengers. After getting on the gate; we shut down our engine prior to external power being connected leaving the aircraft on emergency power until the door was opened. Everyone was able to deplane safely through the jetbridge door. We spoke with the Fire Chief and answered the questions he had regarding indications we had in the flight deck and what they observed externally.Suggestion: I don't believe this is something that is caused by the Crew or requires change. It does highlight the need to always be prepared to take action on things we train for but don't see on a regular occasion."
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.