Narrative:

I was working combined sectors. A C560 declared an emergency on departure reaching FL180 10 northeast with smoke in the cockpit. A DHC8 was 5 southeast of the airport on right downwind cleared visual approach to runway xxl. Two other air craft on final were broken out to give the C560 priority. At this time I elected to have the DHC8 continue approach as the C560 was still a ways north of the airport. The DHC8 was told to precede direct the airport and changed to tower frequency. The C560 was given clearance to the airport. When the C560 was a beam airport; was told to expect runway xxr and told about the DHC8. Pilot stated looking for traffic. It was obvious by the pilot's voice that he was stressed and very busy. I was very concern and felt an immediate clearance for approach was needed and the aircraft was cleared for visual approach runway xxr. The C560 started a drastic descent and quick turn to the airport catching me off guard. I was concern about spacing compressing between the 2 aircraft. I ask tower if they could provide visual and they said yes. My mistake was I overlooked that the DHC8 was a large and the C560 was small and tower cannot do this. Realizing that due to terrain and other airspace considerations; both aircraft were allowed to proceed and the emergency aircraft landed safely along with the DHC8. Some factors in my decision. I obviously thought the DHC8 had more than enough room to have required separation. The DHC8 was all ready established on base and breaking him out could have placed aircraft in an unsafe situation reference terrain. Due to terrain; high and often changing MVA's; destiny altitude; turbulence; chop; aircraft did do not descend normally. I did not anticipate that the C560 would perform as he did. Although separation was less than required; it was controlled and the aircraft was not place in unsafe position. Due to the fact that the C560 was a very critical emergency I feel I did what needed to be done. Bottom line; people were back on the ground safely and the aircraft was never placed in unsafe position. Recommendation; do not work these sectors combine as much. I should have broken out the DHC8 at the start; I just thought I had more than safe room and also required separation. I should not have overlooked the weight characteristics of these 2 aircraft. This is complex airspace with little training provided. Bottom line this mistake is on me and I except responsibility; but feel good that it was a safe outcome for all concern.

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Original NASA ASRS Text

Title: TRACON Controller described a 'smoke in the cockpit' emergency event involving a departure returning to the airport that resulted in less than required 'wake' separation with another arrival.

Narrative: I was working combined sectors. A C560 declared an emergency on departure reaching FL180 10 northeast with smoke in the cockpit. A DHC8 was 5 southeast of the airport on right downwind cleared Visual Approach to Runway XXL. Two other air craft on final were broken out to give the C560 priority. At this time I elected to have the DHC8 continue approach as the C560 was still a ways north of the airport. The DHC8 was told to precede direct the airport and changed to Tower frequency. The C560 was given clearance to the airport. When the C560 was a beam airport; was told to expect Runway XXR and told about the DHC8. Pilot stated looking for traffic. It was obvious by the pilot's voice that he was stressed and very busy. I was very concern and felt an immediate clearance for approach was needed and the aircraft was cleared for Visual Approach Runway XXR. The C560 started a drastic descent and quick turn to the airport catching me off guard. I was concern about spacing compressing between the 2 aircraft. I ask Tower if they could provide visual and they said yes. My mistake was I overlooked that the DHC8 was a large and the C560 was small and Tower cannot do this. Realizing that due to terrain and other airspace considerations; both aircraft were allowed to proceed and the emergency aircraft landed safely along with the DHC8. Some factors in my decision. I obviously thought the DHC8 had more than enough room to have required separation. The DHC8 was all ready established on base and breaking him out could have placed aircraft in an unsafe situation reference terrain. Due to terrain; high and often changing MVA's; destiny altitude; turbulence; chop; aircraft did do not descend normally. I did not anticipate that the C560 would perform as he did. Although separation was less than required; it was controlled and the aircraft was not place in unsafe position. Due to the fact that the C560 was a very critical emergency I feel I did what needed to be done. Bottom line; people were back on the ground safely and the aircraft was never placed in unsafe position. Recommendation; do not work these sectors combine as much. I should have broken out the DHC8 at the start; I just thought I had more than safe room and also required separation. I should not have overlooked the weight characteristics of these 2 aircraft. This is complex airspace with little training provided. Bottom line this mistake is on me and I except responsibility; but feel good that it was a safe outcome for all concern.

Data retrieved from NASA's ASRS site as of April 2012 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.