B767-300 and 300 ER
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Less Severe
Flight Crew Diverted; General Declared Emergency
Aircraft
Well into our transatlantic flight the left engine N1 accelerated multiple times without pilots' input and without throttle movement. Pilots manually reduced power with throttle movement. Dispatch and Maintenance Control were consulted and ultimately the decision was made to divert to a US airport. The left engine produced good thrust; but was inconsistent and required constant attention and frequent readjustment to keep it near the desired power setting. The pilots reviewed appropriate checklists; including possible single engine scenarios in case they would be needed. An emergency was declared and an overweight landing was performed by the Captain at our diversion airport.
A transatlantic B767-300 flight crew heading northeast opted to divert to a mainland airport when the left engine began to make uncommanded N1 increases without accompanying thrust lever movement.