Date: 201707
Local time of day: 1801-2400
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Light: Night
Aircraft: B777 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb; Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Cargo Equipment
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Second reporter function: Pilot Not Flying; First Officer
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Weight And Balance
Contributing factors: Aircraft; Human Factors; Procedure
Primary problem: Procedure

Narrative: Shortly after takeoff; the cockpit crew received an ACARS message from dispatch advising us that Central Load Planning advised him that we departed with an illegal load. The first officer and I were puzzled since we had definitely received our final weight and balance numbers and takeoff performance message from Company. The dispatcher called me; subsequently; on the Satcom to discuss the situation. The dispatcher conveyed the fact that there was a strong probability that the aircraft had been loaded with containers that were not locked down and the potential for a cargo load shift was possible. We agreed collectively that continuing our flight on an evening that turbulence over the Ocean was probable; was not an option. Dispatch; along with Network Operations; planned a diversion to remedy our cargo loading concern. Thankfully; the departure was uneventful and the weather was clear and rides were smooth. We maneuvered the aircraft 'gingerly' after learning about the possible cargo shift threat. I [advised ATC]; although the aircraft was handling perfectly normally. I had the IRO (International Relief Officer) return to the cockpit for assistance. The aircraft was overweight for landing and so a discussion ensued with dispatch and the 777 fleet [duty manager] concerning landing overweight versus dumping fuel down to maximum landing weight. Although the aircraft had the performance to land overweight and turnaround weight was within limits according to our calculations; the decision was made to dump fuel. We followed procedures to accomplish this and conveyed to dispatch and ATC the appropriate; required reports concerning the fuel dump. We used the Diversion Guide to aid in the planning and coordination of the diversion. Use of the Diversion and subsequent Recovery guides were extremely helpful and practical. I had closely coordinated the diversion with the lead flight attendant. We discussed the nature of the cargo misload and the slight risk of a potential load shift. Load planning had forwarded us a 'worst case' CG change should the entire set of containers slide the 15 feet or so they could have potentially moved. The CG change seemed benign; however; we were aware that possible bulkhead damage could occur. FA (Flight Attendant) and I agreed that no 'brace' signal would be given as the aircraft seemed to fly normally. FA managed the cabin services expertly well; keeping the cabin crew well informed. The passengers seemed to be quite comfortable with the precautionary diversion. All PA announcements were brief and reassuring that the aircraft was operating safely and that our stop was strictly precautionary. (Although there was no chance of us continuing without correcting the container loading issue).I did; however; ask to have the emergency equipment standing by as a precautionary measure. Federal Air Marshals were boarded on our flight. I had the lead flight attendant discretely advise them that this diversion was not security related. The flight landed uneventfully. The issue was corrected and after receiving great support from the [duty manager]; dispatcher; station operations; maintenance; and my fellow crew members; we departed our destination. The flight landed safely only a little hour late.


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


Synopsis: B777 flight crew of a large passenger turbojet reported an issue after takeoff of unsecured cargo pallets. Flight diverted to fix the issue then continued on to its original destination.