Narrative:

We departed [and] upon leveling at 7;000 ft; captain reduced the thrust. I noticed a large split between the left and right engine N1. Captain told me that the left engine would not reduce thrust [and] said that we would likely be declaring an emergency; and returning to [departure airport]. He tested the system by bringing both thrust levers to idle. The right engine spooled down as normal; but the left engine stayed at climb power. In fact; while reducing the thrust; the apr activated on the left engine. This proved that not only did the engine stay at climb power (not an indication issue); but also that the aircraft recognized the thrust difference; and mistakenly believed that the right engine had failed. There was also noticeable yaw when the right engine was at idle. Captain told me to declare an emergency; and inform ATC that we would be returning. We also asked for delay vectors; giving us time to run the appropriate checklist in the QRH. We performed the 'engine - uncommanded acceleration checklist'. This directed me to confirm and reduce the left engine to idle. When this action did not correct the issue; the checklist directed us to confirm and shutoff the left engine. This led us to the 'engine - intentional shutdown checklist'. After completing the QRH checklists; I retrieved the landing data and ATIS information for landing. I called the flight attendant using the emergency switch light. I informed him of our engine shutdown; and that we would be returning. I told him that we decided it should be unnecessary to have the passengers brace; and to not expect an evacuation. I made a PA telling the passengers that due to a mechanical indication; we would have to return to the field. I then called operations to make them aware that we were returning. We landed on the longest runway. The emergency vehicles followed us to the gate; but we required no assistance from them. As we deplaned; maintenance arrived at the aircraft. After we completed the 'shutdown checklist'; captain made sure that both our flight attendant and I were doing fine; and then deplaned behind the passengers to monitor their status as well. With only one ramp agent meeting our aircraft; the passengers waited on the ramp for their carry on bags. I helped retrieve the yellow tag bags so the passengers could go into the terminal. Captain did an outstanding job with the emergency. He remained calm and in control during the flight; assuring that we were completing all required tasks in the appropriate order. Also; upon reaching the gate; it was clear that he cared about the well being of the crew and passengers. Our flight attendant was great with the passengers; he kept everyone in the cabin calm and informed.

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Original NASA ASRS Text

Title: A CRJ-200 left engine would not reduce thrust in response to throttle movement. Engine was shut down in accordance with procedure; an emergency declared; and the flight returned to the departure airport.

Narrative: We departed [and] upon leveling at 7;000 FT; Captain reduced the thrust. I noticed a large split between the left and right engine N1. Captain told me that the left engine would not reduce thrust [and] said that we would likely be declaring an emergency; and returning to [departure airport]. He tested the system by bringing both thrust levers to idle. The right engine spooled down as normal; but the left engine stayed at climb power. In fact; while reducing the thrust; the APR activated on the left engine. This proved that not only did the engine stay at climb power (not an indication issue); but also that the aircraft recognized the thrust difference; and mistakenly believed that the right engine had failed. There was also noticeable yaw when the right engine was at idle. Captain told me to declare an emergency; and inform ATC that we would be returning. We also asked for delay vectors; giving us time to run the appropriate checklist in the QRH. We performed the 'Engine - Uncommanded Acceleration Checklist'. This directed me to confirm and reduce the left engine to idle. When this action did not correct the issue; the checklist directed us to confirm and shutoff the left engine. This led us to the 'Engine - Intentional Shutdown Checklist'. After completing the QRH checklists; I retrieved the landing data and ATIS information for landing. I called the Flight Attendant using the EMER switch light. I informed him of our engine shutdown; and that we would be returning. I told him that we decided it should be unnecessary to have the passengers brace; and to not expect an evacuation. I made a PA telling the passengers that due to a mechanical indication; we would have to return to the field. I then called operations to make them aware that we were returning. We landed on the longest runway. The emergency vehicles followed us to the gate; but we required no assistance from them. As we deplaned; Maintenance arrived at the aircraft. After we completed the 'Shutdown Checklist'; Captain made sure that both our Flight Attendant and I were doing fine; and then deplaned behind the passengers to monitor their status as well. With only one ramp agent meeting our aircraft; the passengers waited on the ramp for their carry on bags. I helped retrieve the yellow tag bags so the passengers could go into the terminal. Captain did an outstanding job with the emergency. He remained calm and in control during the flight; assuring that we were completing all required tasks in the appropriate order. Also; upon reaching the gate; it was clear that he cared about the well being of the crew and passengers. Our Flight Attendant was great with the passengers; he kept everyone in the cabin calm and informed.

Data retrieved from NASA's ASRS site as of July 2013 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.