Narrative:

Went through immigration and conducted an aircraft swap. New swapped aircraft experienced maintenance issues from power-up which included no dispatch and front landing gear door opened. Maintenance was called and all was resolved. Pushed back for the second leg; only to be presented with erroneous EICAS messages which included the following : flight ctrl no dis patch; a/T fail; ap fail; avnx modular avionics unit (mau) 3A fail; no dispatch; ads 3 fail; spoiler fault; apm fault; F/D fail FMS 2 fail; stall prot fault; automatic configuration trim fail; yd fault. These messages were presented about 5 times of which were during the start of engine 1 and engine 2; and the shutdown of the APU; and 2 subsequent times. This messages led to a return to gate and a subsequent delay. During this time line maintenance was called to the aircraft and an engine run-up was performed. The aircraft was signed off and returned to service. Pushed from the gate and taxied a second time to the runway. On the takeoff roll after the vr call EICAS messages presented themselves once more along with a master caution. These messages included the following: avnx mau 3B fail; a/T fail; avnx mau 3A fail; ads 3 fail; spoiler fault; datalink 1 fail; engine tla trim fail ads 4 slipcomp fail; FMS 2 fail and automatic configuration trim fail. At the captain's request we advised ATC and proceeded back to the field. After landing; all the previously stated EICAS messages were still all present with the addition of engine 1 and 2 no dispatch; lg no dispatch and flight ctrl no dispatch and 2 circuit breakers on the mau 3 had been tripped. After arrival at the gate; we contacted line maintenance once more; and we were advised that the aircraft was grounded.

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Original NASA ASRS Text

Title: EMB-175 First Officer reported a Modular Avionics Unit 3A and 3B failure causing numerous false EICAS messages. Flight returned to the departure airport.

Narrative: Went through Immigration and conducted an aircraft swap. New Swapped aircraft experienced maintenance issues from power-up which included No Dispatch and front landing gear door opened. Maintenance was called and all was resolved. Pushed back for the second leg; only to be presented with Erroneous EICAS messages which included the following : FLT CTRL NO DIS PATCH; A/T FAIL; AP FAIL; AVNX Modular Avionics Unit (MAU) 3A FAIL; NO DISPATCH; ADS 3 FAIL; SPOILER FAULT; APM FAULT; F/D FAIL FMS 2 FAIL; STALL PROT FAULT; AUTO CONFIG TRIM FAIL; YD FAULT. These messages were presented about 5 times of which were during the start of engine 1 and engine 2; and the shutdown of the APU; and 2 subsequent times. This messages led to a return to gate and a subsequent delay. During this time Line Maintenance was called to the aircraft and an engine run-up was performed. The aircraft was signed off and returned to service. Pushed from the gate and taxied a second time to the runway. On the Takeoff roll after the VR call EICAS messages presented themselves once more along with a master caution. These messages included the following: AVNX MAU 3B FAIL; A/T FAIL; AVNX MAU 3A FAIL; ADS 3 FAIL; SPOILER FAULT; DATALINK 1 FAIL; ENG TLA TRIM FAIL ADS 4 SLIPCOMP FAIL; FMS 2 FAIL AND AUTO CONFIG TRIM FAIL. At the captain's request we advised ATC and proceeded back to the field. After landing; all the previously stated EICAS messages were still all present with the addition of ENG 1 AND 2 NO DISPATCH; LG NO DISPATCH AND FLT CTRL NO DISPATCH and 2 circuit breakers on the MAU 3 had been tripped. After arrival at the gate; we contacted line maintenance once more; and we were advised that the aircraft was grounded.

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.