Narrative:

On engine power-up for takeoff the right engine appeared to overboost to just over 42'. On initial climb-out the right engine began shuddering and running rough. Immediately after the rough-running engine; ATC came on the radio and said; 'it appears that your right engine is smoking.' to which I responded that I would need to come back around and land. Tower immediately cleared me to land and asked if I would need the emergency vehicles. I requested that the vehicles be ready just in case. During this conversation I had only reached about 600 feet due to the rough engine; I chose to just stay at that altitude and turned crosswind and then downwind. During the crosswind turn I brought the throttles and props down to climb power (top of the green arcs) to get the overboost under control. Immediately the engine returned to running smoothly and tower reported that the smoke stopped. Because I was low and already on crosswind; and the smoke and rough engine both appeared to have stopped; at that point I elected to concentrate solely on landing the plane safely. I finished the pattern; landed; and taxied back to the gate with no further issues. The emergency vehicles followed me to the gate just in case; and I gave them a brief description of the event after shut-down.

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Original NASA ASRS Text

Title: A C-402 pilot declared an emergency immediately after takeoff due to a rough running and; per the Tower; smoking right engine and returned safely to the departure airport. The immediate symptoms abated after throttling back from takeoff power and the pilot opted not to shut it down.

Narrative: On engine power-up for takeoff the right engine appeared to overboost to just over 42'. On initial climb-out the right engine began shuddering and running rough. Immediately after the rough-running engine; ATC came on the radio and said; 'It appears that your right engine is smoking.' To which I responded that I would need to come back around and land. Tower immediately cleared me to land and asked if I would need the emergency vehicles. I requested that the vehicles be ready just in case. During this conversation I had only reached about 600 feet due to the rough engine; I chose to just stay at that altitude and turned crosswind and then downwind. During the crosswind turn I brought the throttles and props down to climb power (top of the green arcs) to get the overboost under control. Immediately the engine returned to running smoothly and Tower reported that the smoke stopped. Because I was low and already on crosswind; and the smoke and rough engine both appeared to have stopped; at that point I elected to concentrate solely on landing the plane safely. I finished the pattern; landed; and taxied back to the gate with no further issues. The emergency vehicles followed me to the gate just in case; and I gave them a brief description of the event after shut-down.

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.