Date: 201701
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Light: Daylight
Aircraft: B777 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
Aircraft component: Aeroplane Flight Control
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: First Officer; Relief Pilot; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Troubleshooting; Communication Breakdown
Second reporter function: Pilot Not Flying; First Officer
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Hazardous Material Violation; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Aircraft In Service At Gate
Result: Flight Crew Returned To Gate; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Company Policy; Procedure; Human Factors
Primary problem: Human Factors

Narrative: During preflight I noticed a status message of FLIGHT CONTROL SYSTEM. The flying First Officer was busy; so with his concurrence I called it in to Maintenance.Two mechanics came on board very soon after that; followed by two more; plus a passenger who was a 777 maintenance bigwig. The First Offers left the cockpit because there was no room; but the Captain remained.The mechanics couldn't get the message to clear by resetting the Maintenance Access Terminal (MAT) computer. Finally; they isolated the problem to either the right flaperon being out of alignment; or to its Power Control Unit (PCU). They decided to attempt a manual fix by aligning the edges of the flaps. This seemed to work; the status message cleared up.During this lengthy repair; the passengers were deplaned to avoid a tarmac/extensive delay. While waiting for the cockpit mechanics to find a solution; a junior mechanic approached me and mentioned that he thought one of the starboard tires was flat; but that the senior mechanics in the cockpit had said; 'the tires frequently look like that.' He was concerned enough about it to approach me; I agreed that we should take a look at it. The other First Officer had already done the walk-around and hadn't seen anything amiss.At about this time; Customer Service told us they'd need to close the doors on our gate for about 15 minutes to accommodate an arriving international flight that needed to deplane passengers through the secure area. So we were locked in; the junior mechanic left (I think) with the cockpit group; and it slipped my mind to go check the tire with him.After the flap issue was fixed; the passengers were reboarded and we taxied out with about 1+40 remaining on our Critical Crew Off (CCO).On taxi out; we received our first final Dangerous Goods (DG) statement. What caught my attention on this DG was the large assortment of items. Usually we only get dry ice. But this one had codes I hadn't seen before; encompassing explosive materials; corrosive agents; and radioactive items. I told the Captain that we had a variety of DG on board; and that the first action items were; in general; to use 100% O2 and be ready for a possible explosive or rapid decompression. He acknowledged that.Approaching Runway; we were cleared to position and hold.As the Captain lined up the plane; we received a communication message that said; 'Potential problem with your DG load. Call dispatch/Operations for resolution.' (I'm paraphrasing because I can't recall the exact wording.)We taxied clear of the runway and called Operations. They told us to taxi to the gate and that they were going to remove some DG and rearrange baggage around some other DG pallets/boxes.The Captain told Operations at that time that we would require more fuel; and needed the jetway brought up for the fueling process and to have the International Relief Officer (IRO) do a walk around.Dispatch sent a message advising us of a possible CCO extension. We declined any and all extensions. The flight attendants were going to time out by now; so they (the flight attendants) began working with their Scheduler on whether to extend their duty day or not.As we pulled into the gate; we realized that Operations wasn't going to bring the jetway up. The Captain immediately radioed Operations; and the discussion began.The Company repeatedly declined to put the jetway up; we speculated that it was because then the flight attendants could exit the aircraft; and replacement flight attendants would have to be brought in.The Captain was adamant that the jetway be brought up for the safety of the passengers/crew on board during refueling. Station Operations refused.In response to the walk around issue; Station Operations stated that we weren't required to do a walk around. He said; 'It's in your own manual' and quoted a page number from a manual. (This is; of course; incorrect. It's not required if you divert to a station with no ability to deplane. This was not a diversion; and we had the means to deplane.)They decided to defer action on the walk around discussion because (1) the Captain was deeply involved in getting the jetway up for passenger safety/refueling; and (2) it seemed that we would time out on CCO issues. (Had we ended up taking the aircraft; the crew would have insisted on a walk around.)At this point the fueler informed everyone that he was not allowed to refuel the airplane unless a cabin door were opened for the passengers to egress if necessary.Finally; the jetway was positioned and the door was opened.Two Flight Operation Managers; retired pilots; came on board. They were extremely helpful and supportive of the Captain and the crew; and I really appreciated their efforts.After fueling began; we realized that we had limited CCO time left. Our original CCO was XA:40 and there was no way to close up the plane; run checklists; get a Maintenance Release Document (MRD) and final paperwork; taxi to the runway; and get airborne in the few minutes remaining.Once fueling was complete; Operations said they had completed all their DG rearranging. We never saw a cargo door open; though; and were unsure about how they fixed their problems.The Duty Manager then called and talked with the Captain about how he had plenty of time with his CCO; insisting that our CCO time was XC:40. This was the CCO time if we extended the two hours. We had already messaged back when we cleared the runway and said we were unable to extend. But the Duty Manager kept pushing the Captain; saying that we had 'high revenue cargo and passengers' on board.The Duty Manager sounded angry and told the Captain at one point that if he had just buttoned up the plane and left; we wouldn't even be having this CCO discussion; we'd be airborne. The Duty Manager kept getting our times wrong and assumed we would extend for two hours; even after the Captain told him repeatedly that we had declined to do so under the LOA.It was finally apparent even to the Duty Manager that we were going to expire on CCO time. The crew desk reassigned all of us to various trips.


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


Synopsis: B777 aircrew reported that while at the gate prior to departure they encountered a mechanical problem requiring maintenance action. In addition there were issues with hazardous material in the cargo hold. Flight departed the gate; but returned after the cargo issue was discovered just prior to takeoff. Pilots timed out on their projected duty time and were taken off the trip and reassigned.