B787 flight crew reported wing anti ice system failure during cruise. Flight crew diverted and landed safely.
Synopsis
B787 flight crew reported wing anti ice system failure during cruise. Flight crew diverted and landed safely.
Narrative
We departed ZZZ with a deferred wing anti-ice zone (symmetrical zone pair B slat 5/9). After leveling off; a second zone failed; triggering a 'Wing Anti-Ice Sys' status message on EICAS. We confirmed that it was A Zone slats 5/8. All MAT (Manifold Air Temperature) temperatures were indicating normal; as well as all external temperature readings. After running through the Anti-Ice Wing Checklist (which also populated as a result of this); we climbed to FL380 to avoid any possible icing conditions as per the note in the checklist. From there; we recalled the Relief Pilot to the flight deck and began a conversation between the pilots; Maintenance Control; and Dispatch to determine the best course of action. There was no possibility of an in-air solution and the decision was made to divert. Under the circumstances; the West Coast was not a viable option due to weather. Continuing onward to ZZZZ was also eliminated due to limited resources available for fixing the aircraft. It was determined that ZZZ1 was the best option as we could make it there VFR and they had the maintenance required to fix the issue. We obtained a clearance via CPDLC and proceeded to the airport uneventfully. Upon arrival; we were informed that this would take more time than originally anticipated and that a rescue aircraft was being flown out from ZZZ the next morning; we continued onward to ZZZZ with no issues.
Second reporter narrative
At the last min before the flight they swapped us into this aircraft. It had a wing anti-ice zone written up and it was deferred. After we took off another zone on the same side went out; which caused the whole system to be inoperative; and per the check list we could not go into icing conditions. We called Dispatch and Maintenance Control and opted to go to ZZZ1; as it was foggy/overcast in ZZZ and we would have had to descend down through some clouds in ZZZZ; possibly getting ice. ZZZ was clear and we had maintenance support there.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.