Date: 201603
Local time of day: 0001-0600
Location: ZZZZ.Airport, FO
Light: Night
Aircraft: B777-200
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
ATC / advisory: Center ZZZZ
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Physiological - Other; Communication Breakdown; Situational Awareness; Time Pressure; Troubleshooting
Second reporter function: Pilot Not Flying; First Officer
Anomaly: Aircraft Equipment Problem Less Severe; Flight Deck / Cabin / Aircraft Event Illness / Injury; Inflight Event / Encounter Other / Unknown
Detector: Person Flight Attendant
When detected: In-flight
Result: Flight Crew Took Evasive Action; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Landed in Emergency Condition; Flight Crew Returned To Departure Airport; General Maintenance Action; General Physical Injury / Incapacitation
Contributing factors: Procedure; Staffing; Human Factors; Aircraft
Primary problem: Aircraft

Narrative: Forty-four minutes after takeoff purser advised that four passengers and three flight attendants in the aft cabin had similar symptoms of dizziness and light-headedness. Information was second-hand; and purser said he would seek more information first-hand and call us back. When he called back; he said that more flight attendants now had the symptoms; and that he experienced the same symptoms when he walked toward the aft cabin. He said that there was no smoke and no odor. I instructed the First Officer to fly the airplane and talk to ATC; and to reverse course for return to our departure airport. The language barrier with ATC was a significant impediment to receipt of a timely clearance. With northbound traffic behind us; I decided not to initiate the turn without a clearance. Eventually; we received clearance direct to the airport. I instructed the purser to wake the relief pilot. We donned oxygen masks and established communications. We notified Dispatch via ACARS. Another flight in the vicinity assisted by communicating our situation to Dispatch; as well.During the above events; we accomplished the Smoke; Fire or Fumes checklist; 'Wait 2 minutes...' I waited longer than two minutes because; with no smoke or smell to begin with; the only indication of fume reduction would be improvement of the symptoms; and I decided that the greater time lag of human symptom improvement warranted an increased waiting time prior to decision. After approximately five minutes; the purser reported general improvement in symptoms; so we chose the 'fumes decreasing' checklist option; leaving the left pack and all fans off; and proceeded immediately into the Smoke or Fumes Removal checklist. After completing that checklist; we returned to the Smoke; Fire or Fumes Supplemental Information; and found that it applied primarily to electrical fire/smoke; with little applicability to our fumes situation. I made P/A announcements periodically to reassure the passengers and keep them informed. We spoke with Dispatch on SatCom to ensure arrangements at the station; and then; at the First Officer's recommendation; accomplished the Emergency Landing checklist and the Overweight Landing checklist. We made a normal approach and landing at 498;000 pounds; approximately eight percent above max landing weight. We used max reverse thrust and rolled to the end of the runway to minimize brake energy. The highest brake temperature we saw some time after landing was 1.9; with an average of approximately 1.5. Because our situation was stable; we turned off the runway at the end for the ARFF inspection; to avoid causing a runway closure. As it turned out; that attempt was futile; as the airport was closed after our arrival anyway; by policy.Communication with the ARFF personnel was problematic. During descent; we had queried ATC regarding the communication capabilities of the ARFF personnel. Even then; the language barrier was a significant impediment to communication; with conflicting information on that subject from two different ATC controllers. In the end; we found that the ARFF personnel communicate in the native language to tower on a separate frequency; and then tower translates to us on the ATC frequency. Much was lost in translation. Tower reported to us that ARFF saw smoke from the bottom of our still-running right engine. Despite the likelihood that this was only the oil breather; and in an abundance of caution; we shut down the right engine and pulled the fire switch. We did not discharge the fire extinguisher. Tower told us that ARFF reported that the smoke stopped immediately when we shut the engine down. After some time; tower then reported to us that ARFF saw smoke from our left engine; so we repeated the shutdown on the left side; pulling the fire switch but not discharging the extinguisher. Tower also reported that ARFF had seen 'sparkles' near the top of our left engine; but they had stopped when we shut the engine down. At that point; with the APU Bleed valve closed and the left pack off per abnormal procedure; there was no air coming into the cabin; but the moderate outside temperature kept the passengers comfortable. I considered the fact that we were cooking the avionics with the Equipment Cooling Fan selected off per the abnormal procedures. I considered the likelihood that the Equipment Cooling Fan was causing the fumes to be very low; so I turned the EQUIP COOLING switch back on to avoid damage to the avionics and possible loss of communications. After some delay; we were towed to a hardstand. All passengers deplaned normally via airstairs; except the wheelchair passengers; who deplaned via a lift truck. No passengers required unusual assistance; to my knowledge. The FO and F/B were extremely helpful throughout the events; contributing suggestions; ideas; observations; etc.; that made the outcome materially better. I made all appropriate logbook entries; including fumes; overweight landing; reported engine smoke and 'sparkles.' No discrepancies were found by maintenance. The aircraft was returned to service.Under [this country's] law; it is an infraction to cause the closure of an airport; and the police are required to file a report. They interviewed me for approximately 1.5 hours; and then produced a declaration for me to sign; written in their native language. I declined; and called the Accident/Incident Hotline. The attorney counseled me that it is their country; and their rules; and the best course of action would be to have an agent translate the declaration word-for-word; and sign it when it is revised for accuracy to my satisfaction. The police agreed to this process. Agents were very helpful in this regard. There were numerous errors in the original document - the result of the language barrier and not any bad intent on the part of the police. It took another hour to sort out the exact wording of the declaration; and then I signed it. They claimed it would be illegal for them to provide a copy to me. They made a copy of my passport and ID for their records. I finally left the airport almost five hours after landing. Scheduled to fly out that night. Difficulty sleeping. Called in fatigued. Flight rescheduled to following morning.This is the third idiopathic cabin fumes event for our 777 fleet in a short period of time; resulting in costly diversions; degraded passenger service; and possible legal/financial liability. Per discussion with [Maintenance]; these events are high-visibility; but determining the source has proven to be an intractable problem. No discrepancies are found; and the fumes do not repeat on subsequent flights. Possibilities range from intermittent oil seal leaks; to bad terrorism; to mass hysteria. The events don't fit the terrorism profile; although it can't be ruled out. Based upon my debrief with the flight attendants; I don't believe that mass hysteria was a factor in this event - I believe their symptoms were real. That leaves aircraft maintenance.The post-flight FIM task 21-00-00 assigned to these airplanes looks for smoke and odors; and is aimed more toward electrical smoke events. Because these fume events are smokeless and odorless; that FIM task is inadequate/inappropriate/futile; and is essentially a weak method to pencil-whip the airplane back into the air; for lack of a better idea. According to [Maintenance]; Boeing is aware; but not helpful. Analysis of the recent spike in events should be undertaken. One method to proactively attack the problem might be to provision each airplane with simple sealed bottles that can be opened to trap suspected toxic cabin fumes; for later lab analysis. In addition; a protocol involving chemical analysis of bleed air; pack air; cabin air; etc.; needs to be developed; so the cause of these problems can be identified.


Second narrative: [Report narrative contained no additional information.]


Synopsis: B777 flight attendants and passengers in the aft cabin reported dizziness and light headedness while at cruise with no associated smoke or odor. The flight crew commanded a return to the departure airport which was complicated at all stages by a language barrier.