Air carrier flight crew reported receiving a fire warning bell during takeoff roll. The flight crew continued takeoff and returned to the departure airport where the crew evacuated as a precautionary measure after a heat signature on the aircraft was found by airport responders.
Synopsis
Air carrier flight crew reported receiving a fire warning bell during takeoff roll. The flight crew continued takeoff and returned to the departure airport where the crew evacuated as a precautionary measure after a heat signature on the aircraft was found by airport responders.
Narrative
On the takeoff roll; immediately after V1 the fire warning bell sounded with no associated EICAS; master warning light; or fire handle lights. The Captain (CA) was the pilot flying and he continued the take off. I called for rotation at Vr and we got airborne and began the climb out. The fire alarm was sounding continuously. I notified ZZZ tower that we had a problem and to standby. Communication with the CA was challenging because of the volume of the alarm bell. At this point I switched to ZZZ Departure; [requested priority handling] and asked for vectors to the ILS XXL The CA remained the PF as I set up the approach and briefed it. The weather at the time was low overcast and rain. After completing all of the checklists we began the approach. The approach itself was uneventful and we broke out somewhere around 500 ft. We touched down in the landing zone and made a normal rollout. While the alarm bell was still sounding we did not have any secondary indications of a fire so we taxied clear of the runway. Once stopped on taxiway 1; multiple Airport Rescue and Fire Fighting (ARFF) vehicles circled the aircraft and notified us that they did not see any indications of a fire so we continued our taxi to the ramp. However when we turned onto [taxiway] 2 the ARFF Chief said that one of his trucks was seeing heat coming from the cargo compartment so we stopped. After a short period of time the ARFF Chief said they could not determine if a fire was present or not so after we discussed it together as a crew the CA made the decision to evacuate the aircraft. I ran the evacuation checklist and then we exited the aircraft using the emergency reels because no stairs were available.
Second reporter narrative
In rainy and overcast conditions; we departed ZZZ on runway XXL. After V1; the fire bell sounded and continued to sound throughout the flight. The bell could not be silenced and was a definite distraction and hindered communication. There were no other indications of a fire (no EICAS; no engine fire or cargo fire light; etc). We [requested priority handling] and returned to ZZZ via the ILS XXL. After clearing the runway; we began communicating with the ZZZ Fire Depart via VHF. They confirmed that there was no engine fire and instructed us to taxi to the ramp while they followed; we also coordinated the taxi with ZZZ Ground. During the taxi; the fire crew said they were picking up a heat signature from the cargo compartment and couldn't determine if there was a fire; but there was heat. The tower then informed the fire crew of Hazmat onboard including lithium batteries. After discussing it with the fire crew we made the decision to evacuate and the fire crew said to use the ropes. We performed the evacuation procedure in the QRH and exited using the inertial reels. We later made a logbook entry regarding the situation and reports have been filed by me and my FO. There were 3 people onboard the aircraft during this flight; including myself; my FO and a maintenance jump seater.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.