B767 flight crew reported multiple EICAS messages related to probable air data computer malfunction during cruise. Crew referenced applicable QRH and continued to a normal landing.
Synopsis
B767 flight crew reported multiple EICAS messages related to probable air data computer malfunction during cruise. Crew referenced applicable QRH and continued to a normal landing.
Narrative
After coming back from my crew rest; the Captain briefed me that they experienced an altitude disagree and ran the appropriate QRH. He instructed me to keep an eye on it and to check the books and contact dispatch about RVSM capabilities. I was pilot flying in the FO seat and the Relief Pilot was PM in the Captain seat. We checked with dispatch via satcom voice call to confirm the lack of RVSM capabilities and to have him run the fuel burn if we had to descend out of RVSM Airspace. After disconnecting the call with dispatch; we coordinated with ATC who allowed us to stay at FL340. We kept getting nuisance altitude alerts; so we decided to use the ALTERNATE AIR DATA on the captain side. About 30 minutes later I asked the Relief Pilot to turn off the alternate data to see if the altitude deviation has gotten any worse. When deselecting alternate source we got both an ALT Disagree(500ft difference) and IAS Disagree(.30 Mach difference) EICAS MESSAGE. We reselected the ALTERNATE AIR DATA and continued as normal for about 30 minutes. At that time; the Autopilot disconnected on its own. I started hand flying and chose to disconnect the auto throttles because it was commanding power inputs greater than what was required. We also got the Rudder Ratio and Aileron Lockout EICAS Messages. At this point I suggested waking up the captain and having him come to the flight deck. The Relief Pilot agreed and called the FWD galley to have the captain come up. I also asked the Relief Pilot thoughts on requesting priority handling with ATC. We agreed that notifying ATC was appropriate. At this point the aircraft was extremely sensitive in both the roll and pitch axis and I was worried about entering an Undesired Aircraft State. We ran the associated QRH checklist for both of the items above. The captain returned to the flight deck a few minutes later and I briefed him on what's occurring and the actions we took. At this point he instructed me to continue flying and handle radios as he coordinated with dispatch; Maintenance Control; and the Chief Pilot. I informed ATC at this point of Souls; Fuel on board; and that we currently want to continue on course but that might be changing. I also informed them of the degraded flight controls but that we currently had the ability to maintain altitude and course and would update with any changes. As a crew we discussed diverting but elected that continuing to ZZZ was the best course of action and came up with options if controllability became an issue. We entered an area of turbulence and got a 2000 foot block of airspace and also climbed to smoother air. The captain preformed the TEST briefing with the purser and we started our descent shortly after. The captain set up for the landing and brief the approach and said he was going to do the landing. The captain then took the flight controls and we completed the Decent checklist. We coordinated for direct to the IAF for the ILS XXL in ZZZ and made a normal hand flown approach and landing. We taxied to the gate and parked normally.
Second reporter narrative
CA went on 3rd break. CA's Altimeter started deviating from true Altitude (FO was PF; Route Autopilot engaged; queried ZZZ [ARTCC] for ALT; confirmed 34000). CA side increased deviation followed by ALT DISAGREE EICAS. Ran checklist which lead to selecting CA's ADC switch to ALTERNATE. Notified ZZZ [ARTCC] negative RVSM; They allowed us to stay 34000. After time Autopilot DISCREPANCY EICAS. FO hand flew . Rudder ratio EICAS along with AILERON LOCKOUT EICAS. Ran both checklists. Requested priority handling and got block ALT 33000 to 35000. CA back in seat. Called DISPATCH; Maintenance Control; Chief Pilot. Continued to ZZZ. ATC provided directs and block altitudes all the way in.CA accomplished uneventful landing on XXL. Taxied to the gate.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.