Date: 201808
Location: ZZZZ.ARTCC, FO
Flight conditions: VMC
Aircraft: B777-200
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
ATC / advisory: Center ZZZZ
Aircraft component: Hydraulic Syst Reservoir Tank
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: Communication Breakdown; Troubleshooting
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Landed in Emergency Condition
Contributing factors: Procedure; Aircraft; Manuals
Primary problem: Aircraft

Narrative: Almost 3 hours into flight; EICAS displayed a 'HYD Q Low C' message. We ran the checklist; which is advisory only. Quantity was 0.38 in the center system. Over a period of the next hour and a half; the quantity ran down to 0.02. In that time we talked to Dispatch; Maintenance; and ran several scenarios. The hydraulic pressure during this time remained normal; in spite of the fluid loss. There is lots to discuss; but I want to focus on three things.1. My interaction with the Captain was sub-optimal. He was set on the fact that if we completely lost center hydraulics; (and the Dispatcher concurred); he wanted to land [at a suitable alternate]. My position was that the aircraft was designed for the loss of center hydraulics; we were flying normally; and we could proceed safely to [destination airport] (assuming the weather remained good); and could land there without stranding 271 passengers [at the alternate]. There is much more to discuss here. Suffice it to say that I regret that my input; and perhaps how I presented it; was not well received. Eventually; the Captain pretty much shut me out; which was evidenced when we ran the 'C2 HYD Press PRI' checklist; which calls for the C2 electric pump to be turned off. The Captain reached for the C2 air demand pump; and when I told him three times he had the wrong pump; he switched it off anyway. When he realized his error; he then turned off the C2 electric pump. No safety of flight issue; but the interaction had degraded to an extent where clearly my input was not being received. I bring this up only to say this: I had run out of tools to tell the Captain that I felt he (and the Dispatcher) were headed down an unnecessary path of diversion for a non-threatening situation. He mentioned that 'the airplane is 20 years old' and that he wasn't confident that the AIR pumps were rated to run continuously (since that is what they were doing later on when the ELEC C2 pump was switched off with the pressure still good). He mentioned the United Sioux City crash to both the Dispatcher and Maintenance on SATCOM; and later talked about declaring 'MAYDAY' upon arrival; if we made it that far. I felt if I said 'I'm in the red;' I'd be sending the wrong message. I think I understood the problem; but was failing to convince the Captain. I wanted to say something to the effect that HE was in the red; but I had no attention step to drive that home. (And clearly would have been poorly received in this case.) Would it have been safe to land [at the suitable alternate]? Absolutely. But until that decision was made (and we didn't lose the center system completely until much later); I felt it was my duty to try to make a more rational choice. I've talked with some people I know and trust regarding this flight. One pilot described that at another airline that they had an 'ask; suggest; insist' acronym. But since this was much more drawn out; and really wasn't an emergency; the 'insist' step really didn't apply.2. I've mentioned Dispatch. We received erroneous landing data (3;000 feet off); and were told that 'if the pressure drops; it's a land as soon as possible situation.' It was also suggested to 'experiment' with turning on and off pumps to figure out where the leak might be. We didn't do that; and stayed with the checklist. I could go on. Bottom line; I don't think Dispatch should be in the business of telling us to land as soon as possible; particularly since that advice was so wildly off base.3. I think the center checklist could be improved. I'd like to see some revised notes. 'Plan for more time for slower flap and slat operation in secondary electrical mode with the flap handle.' Those added words would have cleared up some system fuzziness. In our scenario; the pressure stayed in normal range for hours despite little or no quantity. The ADP's (Air Turbine-Driven Pumps) cycled on and off. Flight Attendant called up to report a noise near the 3R door. First Officer went back to listen. Turns out it went away when we turned off the ADP's. A note to that effect would have been helpful. (I'm assuming the short operation of the ADP's during landing configuration isn't noticed over the noise of gear and flap extension). The checklist; with the built-in decision tree; was unusable because of the intermittent condition of the pressure. Turning off the ADP's solved that problem. Even after the checklist was run; the green line running through the ELEC C1 pump to the nosewheel steering remained on; then finally went out; leading you to believe maybe in fact you had lost nosewheel steering. (Again; system knowledge after an all night flight can get fuzzy; plus the schematic and the way the malfunction developed was deceptive). A note mentioning that you would get back nose gear steering after about 60 KIAS would have been helpful; which is in fact exactly what occurred. Nevertheless; the Captain insisted on stopping on the runway; and only after some cajoling from the First Officer and I; taxied clear; but yet had us towed to the gate. (Unnecessarily; in my opinion; but certainly his prerogative).4. Finally; though I can't find it now; somewhere in the checklist 'notes' that we reviewed on descent; it mentioned not to fly a NON-ILS procedure. We saw it twice on the lower EICAS. Originally; we'd planned on doing an ILS to Runway XX; but XY became the active; and only the NON-ILS was available. It was VFR; but had it not been; it would have been helpful to know WHY a NON-ILS wasn't permitted.I'd like to mention the dedicated and superb interaction we had with [a] Maintenance Technician; who really did all he could to research some questions we had. As an aside; at one time we could not contact either Dispatch or Maintenance for about an hour through SATCOM; which was annoying. There were no messages indicating a problem. According to Maintenance the next day; an 'O' ring in the center hydraulic control module had failed.




Synopsis: B777-200 First Officer reported low hydraulic center fluid EICAS which resulted in poor CRM; incorrect data from Dispatch; and vague checklist reference.