B757 Undifferentiated or Other Model
Flight Crew Last 90 Days 50; Flight Crew Total 10000; Flight Crew Type 1500
Troubleshooting; Workload; Time Pressure
Aircraft Equipment Problem Critical
Flight Crew Diverted; General Declared Emergency
Aircraft
Approximately 1:30 hr in to the flight and level at FL340; we received a LAV SMOKE advisory message with the continuous cabin chime. At the time; I was in the forward lavatory taking a restroom break. This occurred as I was exiting the restroom. I called the First Officer (FO) to return to the flight deck. As I entered; the FO was running the QRH checklist for this item. I immediately grabbed the fire extinguisher in the cockpit and gave it to the Flight Attendant who exited the flight deck. I conversed with the FO and he told me what was going on. We both had our Oxygen masks donned. There was the smell of a burning smoke in the air. Within about 30 seconds I made the immediate decision to divert [back to origin]. I put the aircraft in heading select and made an immediate left turn towards ZZZ. I put direct ZZZ on the FMC legs page and proceeded in that direction. I descended the airplane 500 feet below our cruise altitude of FL340; down to FL335. The autopilot was only banking about 10 degrees; so I disconnected the autopilot and hand flew the airplane into about 25-30 degrees of bank to get the airplane turned around as quickly as possible. I asked the FO to transmit in to the blind on VHF regarding what we were doing. Once I was to the left of our airway and headed to ZZZ; I made the decision to descent the airplane to 10;000 feet and re-engaged the autopilot. I accelerated to just under VMO/MMO (max forward speed); which was approximately 330 KIAS; increasing to 340-345 KIAS as we got lower. As the FO was talking on the radio; I sent a CPDL message to Center telling them we were in an emergency situation; returning to ZZZ; and descending to 10;000 feet. I also sent an ACARS datalink message to company Dispatch advising them of the same. The FO made contact with SFO radio on HF radio and advised them of what we were doing. He continued the Lav Smoke Checklist. Initially he got to a point on the checklist on deploying the oxygen masks which I said not to do. He continued to run through the Smoke Evac Checklist. At a later point in one of the checklists we followed that step. Once down to 10;000 feet; we followed the checklist which directed us to fully open the outflow valve. We descended to 9500 feet prior to doing this. After doing this; the smoke smell dissipated; but was still somewhat there. Going back through the checklist; I made sure all the other items were completed. When we got to the part which advised us to turn off the right pack and wait 2 min; the smoke smell went away a little more. At that point; the FO and I both agreed to leave the left pack off for the remainder of the flight. I also contacted the company via the SAT phone and advised them of what we were doing and what was going on. Throughout the entire descent; I was in contact with the flight attendants and kept asking them to try to locate the source of the smoke; which was my main concern. They had indicated that it was coming from around row 20-25; although they could not locate the exact location. I also advised them to shut off anything electrical in the cabin; including everything in the galley and the entertainment system. The smoke smell in the air had the smell of an electrical burning type smell. I had depowered the utility buses prior to that. Approximately 30 minutes from ZZZ; we noticed that the right engine oil temperature began to raise; going in to the amber band. We then noticed that the right oil pressure had dropped; hovering in and out of the amber band; but not in to the red band. We noticed the oil quantity was down to 10 quarts; hovering between 9-10 quarts; but staying in the white zone the entire time. At that point the FO and I made the joint decision to consider a military airport which was about 15 minutes closer than ZZZ and had a 10;000 foot runway. We were concerned about the right engine failing. About that same time; I received an ACARS datalink message from Maintenance Control stating they saw a spike in our right engine parameters. I established another SAT Comm call with Dispatch and Maintenance Control and discussed the situation. Dispatch advised us that there was no fire/crash rescue equipment at the military airfield and that ZZZ would be a better option. The smoke smell had actually gone down (since we turned off the right pack); and I was comfortable continuing to ZZZ. Dispatch/Maintenance Control also advised us that was the best option. We informed ATC. We continued on to ZZZ and came straight in to ILS runway 7L. Crash / fire rescue was standing by. After landing I came to a stop on the runway and immediately shut down the right engine; which I had briefed that I would do when the FO and I discussed things. I asked the fire truck to keep an eye on the right engine as we taxied to the gate. We taxied perpendicular to the gate and had the tug tow us in. The rest of the flight was uneventful. I then briefed the mechanics on everything that had happened; made the appropriate logbook entry; and contacted the Chief Dispatcher and Operations; and then made a call to the pilot union safety line.
The Captain kept the speed up until about a 10 mile final where we began to configure the aircraft for landing. A normal landing was made and the crash/fire rescue team was there immediately after we stopped straight ahead on the runway. We were checked out by the fire crews and they noticed &quot;steam/smoke&quot; coming from the R engine; the captain and I shut the engine down and we taxied to the ally while the fire crews kept a watchful eye on our R engine. Once abeam our gate; we were towed the rest of the way to the gate.
B757 crew while beginning an Oceanic leg receive LAV SMOKE EICAS at top of climb.  Immediate offset and return to departure airfield is initiated.  While in the descent on the return the smoke begins to dissipate meanwhile their right engine oil pressure begins to drop.