EMB ERJ 170/175 ER/LR
Flight Crew Air Transport Pilot (ATP)
Flight Crew Total 1945; Flight Crew Type 945
Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types
Flight Crew FLC complied w / Automation / Advisory
Aircraft
The takeoff and departure were performed normally and without incident. Approximately an hour and a half into the flight while in cruise we received both a master caution and a master warning. There were a large number of EICAS messages that appeared and both the autopilot and auto throttles disconnected. The EICAS messages were present for a few seconds and then they cleared with no action from us; the only message that persisted was YD OFF. Because I was the pilot flying at the time I immediately took control of the aircraft and began to hand fly. When the auto pilot disconnected it took us out of NAV mode and we ended up in ROLL mode. The number 2 FMS had failed and since we were unsure about the accuracy of out navigation we requested a heading from ATC. Because I had taken over control of the aircraft and was hand flying I did not see what all the EICAS messages were. Captain stated that he had seen MAU (Module Avionics Unit) 3A FAIL along with several other messages that seemed to be associated messages. I took over the radios and he ran the QRH procedure for MAU 3A FAIL. After completing the QRH procedure Captain then contacted dispatch via radio to try to get further guidance from maintenance control and the chief pilot. Both dispatch and the chief pilot simply told us to follow the QRH and gave no other guidance or suggestions. Maintenance control also said they couldn't tell us anything more than what we had already told them. At this point both FMS were back online and functioning properly so we were able return to NAV mode and return to our flight plan. ATC did advise us that while we were on a heading we had drifted about a mile and a half north of our filed course. After completing the QRH for MAU 3A FAIL we followed the QRH for AUTO THROTTLE FAIL and reengaged the auto throttles. At this point we were unsure whether or not to reengage the auto pilot because the YD OFF EICAS message was still present and we were unsure about the reaction of the airplane if we tried to engage the auto pilot with the YD OFF. We referenced the QRH procedure for YD OFF however it did not clearly state whether or not we could reengage the yaw dampener. Again at this point since the aircraft we was under control and flying well (and lacking further guidance from company) we decided that the best course of action would simply be to continue flying the aircraft by hand; which I did. At this point we also decided to exit RVSM airspace and descended to FL280. Captain and I then had a discussion about whether or not it was necessary to divert the flight. We both decided that we were comfortable continuing the flight to the destination. We also discussed backup plans and suitable alternate airports along our route of flight and agreed that we would divert if any issues worsened. We did not experience any other issues for the remainder of the flight and after our arrival; Captain contacted dispatch and maintenance control via phone to write up the issue in the maintenance logbook. The on-duty assistant chief pilot was also contacted.Overall I think that we handled the situation well. I biggest issue I felt what that the QRH procedure for YD OFF did not clearly state whether or not the YD could be reengaged during flight. This uncertainty I what lead us to decide to leave the auto pilot off and hand fly the remainder of the flight. Also I was frustrated by the lack of guidance by Dispatch; Maintenance Control and the Assistant Chief Pilot when we contacted the via radio. Rather that helping us determine if we could reengage the YD and auto pilot; and give us guidance on whether to continue the flight or divert all we were told to do was follow the QRH.
EMB-175 First Officer reported multiple system failures with a descent out of RVSM airspace and hand flew the aircraft to the destination airport.