B747 flight crew reported receiving a Fire Warning Bell with no associated EICAS. The overhead panel Main Deck Fire Light was illuminated. The flight crew performed an air turn back and precautionary landing at the departure airport.
Synopsis
B747 flight crew reported receiving a Fire Warning Bell with no associated EICAS. The overhead panel Main Deck Fire Light was illuminated. The flight crew performed an air turn back and precautionary landing at the departure airport.
Narrative
About 20 min after departing ZZZZ; Person A (Captain) and I noticed a high N1 vibrations in engine #2 (up to ~4.4). We were level at FL250. We were having a discussion about contacting the Company about this indication. We were then cleared up to FL310 and initiated the climb. In the climb we noticed the vibrations decreased to ~2 and we decided to see what they did when we leveled at FL310. Around 25;500 ft.; we received a Fire Warning Bell with no EICAS associated. We then checked the overhead panel and saw the Main Deck Fire Illuminated. The associated EICAS was eventually displayed. Person A contacted ATC and stopped the climb at FL260. Person B (3rd seat) got the QRH out and prepared to run the checklist. Person A took over as pilot flying (PF) while I switched to pilot monitoring (PM). Person A [requested priority handling] and asked for an initial vector for a return to ZZZZ. Person A alerted Person C; who came up and was informed of what was going on. Person B started to run the checklist so we donned oxygen masks and made sure we had communication with each other and ATC. We initially stayed at FL260 or descended to FL250; I do not recall. We checked the Environmental Control System (ECS) synoptic to check temperatures but we did not have any indication of high temperature. We also had no smoke in the cockpit. Once we were closer to ZZZZ we descended and extended flaps to 10 and gear in an attempt to burn more fuel. On the descent we had multiple more EICAS Messages and Fire Bells alerting Main Deck Fire. Temps on ECS synoptic stayed the same. We also received ELEC GEN 1 EICAS on descent; which was reset. We prepared for a landing on XXL. Person B ran numbers and referenced QRH for overweight VREF speeds; which matched Flight Duty numbers. Per the QRH we used auto-brakes max. I was communicating with ATC and informed them we would like the fire crew to assess the heat in the cargo hold and to not approach the gear due to overheating brakes. We made an overweight landing on XXL and came to a stop on the runway. Trucks approached us on the runway and it seemed they were hosing the gear with water to cool the brakes. We still had communications with Tower but not the fire crew. Eventually the fire crew boarded the aircraft and checked the entire main deck and upper deck for heat and or fire. We were then towed off the runway. We had conversations with ATC before we were released off the aircraft. Possible cause was the amount of rain water on and around all the cargo on the main deck. It was raining heavily during our time on the ground in ZZZZ for unloading and reloading of the aircraft.
Second reporter narrative
We landed ZZZZ1-ZZZZ under Cat II weather conditions with heavy rain and winds to an uneventful landing. Weather conditions remained the same during our three hour ground time up to our departure time. After a long taxi; we departed Runway XXR 700 Kilos under our (takeoff weight was limited by our max landing weight) limit for ZZZ. The First Officer (FO) had an uneventful takeoff; climb and level off at FL260. I departed the flight deck to change into a cruise shirt as the CA was going on first break. I was to relieve the Captain and take my seat. As I reentered the flight deck; the Crew was monitoring a high engine vibration on #2 and was considering a SATCOM call to Dispatch/Maintenance to discuss. About 5 min later and still in ZZZZ airspace; with me in the observer seat; we received a Main Deck Fire Warning. The flight was now approximately 25 minutes in flight. The Main Deck Fire Warning was not continuous but would cycle on and off. We had no smell or elevated temperatures. I offered to run checklists while the FO was still pilot flying (PF) and the Captain remained as pilot monitoring (PM). We also received an EICAS Advisory - Eng Gen #1. As I worked through the QRH checklists; getting ACARS ATIS; running performance for our weight; the Crew was struggling to communicate with ZZZZ control as the language barrier was very difficult for them to understand our needs. I also messaged Dispatch to advise our intentions. Dispatch asked if we wanted fire assistance and I responded - Yes. We cruised at FL260 for approximately 15 min before we started our descent. The Captain was now the PF. With weather conditions very low; the Captain elected to Cat II auto land to Runway XXL as it was approved to Cat II conditions. We had just landed the same runway earlier so we knew this runway was approved for Cat II. We/crew did not object. I had run performance to Cat II/III and wet runway to ensure we had landing performance. Landing distance required was approximately 9100 ft. and we had approximately 13;100 ft. We made an uneventful flaps 25 (for flap relief protections) landing at approximately 375 kilo tons; 78 Kilo tons over our make landing weight of max limit weight of 296;195 Kilo tons. Touchdown and rollout with Max Auto Brake (per QRH) was very smooth. We were then met by firefighters after stopping on the runway. Over the radio; we asked for aircraft inspection and advised fire crews to remain clear of tires and wheels as they were now showing elevated temperatures. I believe the crew also reviewed the EICAS Brake Temp checklist as they were consulting the Brake Temperature Monitoring System (BTMS) and QRH Brake Cooling charts. As the firefighters approached the airplane I could hear water being sprayed on the aircraft but we did not ask for water. As I opened the L1 door for the firefighters; the main deck cargo was still very wet. I did look outside and could see the wing gear had steam or smoke emitting from the brakes with lots of water in the area. We were not carrying any declared Hazard Materials but were carrying some approved excepted items. After a thorough aircraft search by the firefighters; we stayed on board and waited further instructions. The ZZZZ station manager then met us and asked for us to get towed in which he coordinated. We then ran checklists and was towed to stand XXX. The regulator then came by asked for a Captain statement and checked all crew for licenses and medicals. He also took many pictures of the FP (Flight Plan); manuals and crew and spent time in the flight deck area with another agent. A Flight Operations rep then came by and asked what guidance we used regarding overweight landing and firefighter use of water on the brakes.I believe the extreme full cargo load (cargo was floor to ceiling in all but one pallet position) on the main deck was completely soaked; having too much moisture. There may have been some other water ingress in the L1 floor area as a ramp/load ZZZZ crew member asked for a towel to keep the area dry; may have caused other indications problems. Guidance could include to set cabin altitude to manual 8;000 feet for takeoff to allow for more air passage thru the entire airframe. Once top of climb go back to auto along with the other checklist items. Descent actions may not need to include a cabin altitude adjustment as dry cabin air will more than likely dry off any remaining moisture. Any Boeing service bulletins should also be completed.
More incidents for this aircraft family →
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.