B747 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Communication Breakdown; Workload; Troubleshooting
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Air Traffic Control Provided Assistance; Aircraft Equipment Problem Dissipated; Flight Crew Diverted; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Landed in Emergency Condition
Aircraft
FO 1(First Officer) and I were flying the first half of the flight. I was operating as PIC. We were relieved north of the islands in vicinity of [VOR]. FO 1 went to the crew bunk and I relaxed in one of the business class seats aft of the cockpit. About an hour and a half after we were relieved; I noticed something had fallen on the floor. That seemed peculiar to me; so I got out of my chair to see what it was. I reached down to pick it up when I noticed warning messages on the EICAS in the cockpit. Then I noticed that CA (Captain) and FO 1 had their oxygen masks on. I immediately went into the bunk room to wake up FO 2. He was getting up as I walked opened his door. Then the oxygen masks dropped. I said; 'They need us in the cockpit.' (The thing I picked up on the floor was the latch/door to one of the PBEs (Personal Breathing Equipment) mounted on the wall aft of the lavatory door)FO 2 quickly made it into the cockpit where he took up the 3rd observer seat; which was where he was situated at the beginning of the flight. I sat next to him in the 4th observer seat; which had no intercom transmitting capability. The first thing I noticed were the warning messages; FIRE MN DK AFT and CABIN ALT; which was now at 25;000 feet. I could hear the intercom and the radios; but I couldn't talk. Shortly after I sat down; CA directed FO 2 to go and open the door to the main deck and see if there was any smoke. He returned in less than half a minute and reported that he didn't see or smell any smoke.At this point the decision was made to proceed to ZZZZ; which was the closest airfield to us; about 250 NM away. I recall that getting communications with [foreign] ATC was difficult at first. We finally made contact and told them we intended to land at ZZZZ. They proceeded to give us vectors to the field. It's worth noting that I was primarily an observer to this whole situation because I didn't have the ability to communicate with the crew nor ATC. Communication between us and the controllers was difficult for a couple of reasons: [The] radio comms were intermittent. Language barrier existed. I believe that everyone (CA; FO 1; and FO 2) at some point attempted to communicate with ATC. Eventually; FO 2 made contact with Dispatch via Satcom. There were also transmissions on VHF and HF frequencies. This lead to a lot of confusion in the cockpit; as nobody was able to hear every transmission and there were constant questions as to 'who said what.' We finally received the weather for ZZZZ and were quickly realizing the landing would be a big challenge. Also; every time we received an update to the weather; the runway braking action changed. It appeared to be trending for the better; but ceiling and visibility were very low; along with blowing snow. They were obviously experiencing a blizzard. CA decided to hold over the field while we processed the information so she could make a decision whether or not to commit to an approach/landing into ZZZZ. At some point; FO 1 mentioned doubling back toward ZZZ which was more than 550 NM away. This is when I decided to dawn the green bottle portable breathing apparatus and make another check of the main deck. I'd never used this device before; so after I dawned the mask; I stayed close to 4th seat oxygen mask until I knew it was working. After 30 seconds; I was reasonably reassured that it was turned on and working properly. I made my way aft of the cockpit and opened the door to the main deck. When I looked down I didn't see any smoke. But this didn't satisfy my curiosity. I wanted to know if there was smoke lingering in the back of the main deck where the EICAS warning message told us it had originated. So I made sure all the main deck lights were on and I climbed down the stairs. I could see all the way to the back of the plane and saw no evidence of a fire or smoke. By the time I got back to the cockpit; I'd been away from my seat for less than two minutes.  I tried to tell FO 2 to tell CA that I went down stairs and saw no smoke. But he was currently engaged on satcom and couldn't hear me anyway. I felt that this critical information needed to be passed; so I took off my oxygen mask and shouted out; 'There is no smoke in the aft cabin! I walked down the stairs and looked all the way back; and I didn't see any smoke!' There was a brief moment of silence as everyone collectively caught their breath. Communication between the crew in the cockpit got much calmer at this point. We had been holding over ZZZZ for at least 20 minutes. Within a couple of minutes after my announcement; the decision was made to proceed to ZZZ; which was approximately an hour and fifteen minutes away. The weather was good there and we all agreed that this was now the best course of action.Enroute to ZZZ; I made one more additional check on the main deck and observed no smoke or evidence of a fire. I communicated this to the crew. Eventually; we began our descent for the approach and I noticed the 'FIRE MN DK AFT' message went away around 12;000 feet. At 10;000 feet cabin altitude we all removed our oxygen masks. We finally landed in ZZZ without incident. Upon landing; we parked on the runway while the crash fire crew inspected the outside then the inside of the plane. They found no evidence of smoke or fire. Suggestions: Know what the weather is for every potential diversion airfield along the route. This will help to determine the immediate direction to travel when 'land as soon as possible' is called for. Understand that wearing of oxygen masks potentially degrades intercom and radio communication.
B747 First Officer reported executing an emergency diversion due to a dual critical component malfunctions.