Date: 201511
Local time of day: 1801-2400
Location: ZZZ.ARTCC, US
Flight conditions: Mixed
Aircraft: B777 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Human factors: Workload; Situational Awareness; Distraction; Communication Breakdown
Second reporter function: Pilot Not Flying; First Officer
Anomaly: Deviation - Speed All Types; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: Aircraft Automation Overrode Flight Crew; Flight Crew Returned To Clearance; Flight Crew FLC Overrode Automation
Contributing factors: Aircraft; Human Factors; Company Policy; Weather
Primary problem: Human Factors

Narrative: My relief first officer working as the pilot monitoring and I both failed to set a hard mach number in VNAV for the Atlantic Crossing.  I was the pilot flying.  Bottom line; we made an error.It had been a very busy and non-normal flight starting at the gate.  There was a last minute aircraft change and dispatch had not told us about it.  They had called [operations] with no answer; as we had been early in planning and left OPS about 1 hour and 10 min prior to scheduled departure.  We were surprised to find a gate change with no aircraft.  Things were very busy getting new paperwork printed at the gate with added maintenance issues. We pushed 13 minutes late after receiving a valid maintenance release.  I had safety concerns for my crew and passengers. We knew we had light to moderate turbulence from Departure all the way to Coast Out at all altitudes FL 290 and above.  We had reports of severe turbulence at FL 370 along our route of flight. I chose to descend from FL 290 to FL 270 and we stayed there until required to climb to FL 370 for the crossing.  I had added fuel for this concern.  We had difficulty getting a clearance and had to use Voice communications.  Our printer was not working; a new issue; and dispatch sent communications to ACARS.  It was very busy the entire time with a lot going on.  I normally have out a paper copy of the Class II NAV/ETOPS Guide in addition to the [tablet].  I did not have the paper copy.  My window mount along with my Co-pilots mount fell three times with broken cup attachments and we held them as necessary.  My flying first officer had his NAV/ETOPS Guide open on his [tablet].  He went on break just prior to our receiving our clearance and climbing for the crossing.  I allowed distractions to keep me from verifying this Class two procedure per SOP; although I had briefed this very thing both in [operations] and on the Aircraft during the preflight check.  I learned after my third break about the Error when briefed by my first officers.  They discovered it while still in Class II airspace.  We were cleared mach .82.  It was likely that when we coasted out or very close to .82; but ended up at .79 enroute.  They sped up to .82 when they noticed it.  ATC; Oceanic never said anything at any time to them.  We were the last flight on that track with no one behind us.  I believe fatigue may have played some part for me having been awake for 16 hours; although two attempts were made to rest for a couple hours during that time period.  I felt fine when coming to work and had stayed at a local hotel the night prior and did not check out until that afternoon.


Second narrative: The event occurred while I was on my designated rest break.  Prior to my break we were trying to request and receive our Oceanic clearance but we were having Controller Pilot Datalink Communications (CPDLC) issues sending our requests; our ACARS printer was inoperative and were in continuous light turbulence with occasional moderate turbulence so there were a lot of distractions going on. After I came back up from my break I asked where the oceanic clearance was I was told that they received it via voice and that it was as assigned. We were planned to arrive over 30 minutes ahead of our normal arrival time so I knew we would be flying slower than normal. Something was bothering me but I couldn't figure it out until I asked the other First Officer if they had chosen to fly at .79M or if that's what they had been assigned. He told me that they had requested and had been cleared to fly at .82M for the crossing. That's when it became apparent that during the distractions with the weather; ACARS; and communication issues with CPDLC that somehow the crossing speed was not entered into the FMC and ECON was the selected speed which was .03M less than cleared. We immediately increased our speed to get back into compliance with our assigned speed. The rest of the flight; descent; and landing were uneventful.We never exceeded any timing issues between any of our crossing points nor were we contacted by HF or CPDLC by ATC querying us on our speed but since we were required to notify ATC when we were more than .02M off of assigned I recommended to the other crew members that they file a [report] as I planned on doing as it was a deviation; although an unintentional one.


Synopsis: The B777 crew forgot to set a hard Mach number for an Atlantic crossing and flew at ECON .79 Mach instead of .82 Mach as cleared.