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 operations 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 navigation/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 navigation/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.

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Original NASA ASRS Text

Title: 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.

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.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.