Air carrier crew reported an APU fire while loading at the parked position on the ramp. The crew observed smoke at the tail of the aircraft without cockpit warning; activated fire bottles; then evacuated safely by airstairs.
Synopsis
Air carrier crew reported an APU fire while loading at the parked position on the ramp. The crew observed smoke at the tail of the aircraft without cockpit warning; activated fire bottles; then evacuated safely by airstairs.
Narrative
During the end of preflight after weight balance verification and face to face with mechanic; we were waiting for the last few containers to be loaded; our NOTOC and doing our last briefings. The aircraft was on APU power and APU air with the ground external power disconnected. At approximately XA:33Z the aircraft went down to battery power abruptly as well as emergency power. It was the same looking scenario as if a GPU had dropped of line or an APU had auto shutdown. We had no indications in the cockpit of an APU fire. As were trouble shooting the situation with the loss of APU generator power we started to hear yelling of a possible fire. My First Officer (FO) said that he thought he heard someone say fire from outside the airplane (possibly loaders from the K-loader or cargo compartment area). I asked our jump seater to see if she saw anything outside the airplane or could confirm any type of fire. She said yes. I went back and looked out the L1 door and the tail was smoking. I ran back into the cockpit and said APU Fire checklist as I pulled the APU for handle. We performed the APU Fire checklist and discharged all 3 bottles. We had no indication of whether any of the bottles were extinguishing the fire (because we had no indication of fire to begin with) so we discharged all the bottle in the interest of safety. I called ZZZ ground at the same time and told them we had an APU fire on spot and send Airport Rescue and Firefighting (ARFF) immediately. I then directed everyone off of the airplane; myself; the FO and our jump seater. I turned off the emergency power and battery switch and egress the airplane via the crew stairs with the rest of the crew on board and met down in front of the nose.
Second reporter narrative
While sitting at parking spot in ZZZ on the ramp; our APU did an auto shutdown. Shortly after this happened we heard people yelling fire and then we heard someone say APU fire. We asked our jump seater to step outside and check what was happening. She came back and informed us that the APU was on fire. We ran received no indication but ran the APU fire QRH procedure. We discharged the APU fire bottle; called the fire department on ground; shut down the aircraft; and evacuated using the stairs. When we exited the aircraft we could see the smoke coming from the tail. Once fire and rescue arrived they sprayed fire extinguishing agent on the tail and the temp lowered.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.