Troubleshooting; Distraction; Human-Machine Interface
Aircraft Equipment Problem Critical
Flight Crew Diverted; General Maintenance Action; General Declared Emergency
Aircraft
During cruise we noticed the aircraft yaw to the left twice for no [apparent] reason. As we looked for any clues on the third time it yawed the Captain noticed that the N1 on Engine 1 surged to about 70%; and the thrust levers were set in the detent in the cruise thrust setting; around 90%. We noticed this the third and fourth time it happened; and also noticed that the ignition kicked on momentarily; and then the N1 returned to the FADEC calculated setting in the cruise setting. These events lasted for about 5 seconds each. On the fifth surging event; the N1 decreased significantly; the ignition did not kick on; and the FADEC alternated from B to A. At this point; we were already contacting Dispatch and Maintenance. We briefed for a single engine approach and landing and discussed alternates. Dispatch advised us to proceed to a diversion airport that suited them; so we declared an emergency and deviated there. We did not end up shutting down the engine. We briefed the approach and landing and there were no further disruptions or Engine 1 events during the rest of the flight. On the landing; EICAS message 'E1-2 No Dispatched' and 'E1 Short Dispatch' appeared.The threats of this event included task saturation (executing an unplanned emergency landing and diversion) as well as trying to figure out the best course of action to respond to this engine abnormality. I believe the Captain and I did a good job executing this diversion and emergency landing. When we landed; Maintenance told us that this aircraft has had a history of FADEC issues; and that there have been unavailable parts. If this is true; I would highly recommend to the company that we fix the underlying problems with FADECs the first time whenever possible rather than simply 'defer' them or 'clear' them. I also appreciate very much our Dispatcher and his rapid response and coordination with this event.
When their left engine initiated repeated surges of lowered N1 the flight crew of an EMB-145 conferred with Dispatch and Maintenance and opted to declare an emergency and divert for maintenance attention.