Narrative:

A bonanza checked on my frequency about 10 miles prior to my airspace. I had just finished a pretty busy session and aircraft from that session were still in my airspace. I 'rogered' the aircraft and gave them the current altimeter. I went on with other duties; shipping; climbing and descending aircraft. Just prior to the event I was coordinating an inbound with ZZZ1 tower and discussing a release that tower was trying to get off the ground. The focus of the traffic was solely on the west side of the sector. The bonanza was on the east side of the sector all by himself. Shortly after I came off the line with ZZZ1; the bonanza reported a near miss and was questioning what happened. I focused my attention to the aircraft and noticed a transponder code passing underneath the bonanza indicating an altitude of 9;800 ft. I advised the IFR aircraft that it appeared to be a fire fighting aircraft and gave the pilot the number to the center. The pilot reported that he guessed the closest point was 300 ft and X number laterally. We were operating on eram and conflict alert alerted after the two aircraft were all ready passed. I never saw the traffic and did not issue a traffic advisory. The area the IFR aircraft was operating in is an area of known non-radar about 11;000 ft MSL and below. It is possible the transponder code was not displayed on the scope until right near the time of the event; which explains why conflict alert was delayed or did not activate until after they passed. I can not confirm that however because I did not see if the transponder code was displayed prior to the event or not. Something we talk about all the time as controllers is not to focus in. Keep your scan going around the entire sector. Do not glance over aircraft who are all by themselves. Also; better radar coverage would definitely improve safety in that area. Our filters are set at 6;500 ft and we rarely see aircraft at 10;000 ft in that area.

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Original NASA ASRS Text

Title: Enroute Controller described a conflict event between IFR traffic that was handed off; but still in another controllers area; and unknown/unreported VFR traffic apparently participating in fire fighting activities. The reporter listed a RADAR coverage problem that may have contributed to the event.

Narrative: A Bonanza checked on my frequency about 10 miles prior to my airspace. I had just finished a pretty busy session and aircraft from that session were still in my airspace. I 'rogered' the aircraft and gave them the current altimeter. I went on with other duties; shipping; climbing and descending aircraft. Just prior to the event I was coordinating an inbound with ZZZ1 Tower and discussing a release that Tower was trying to get off the ground. The focus of the traffic was solely on the west side of the sector. The Bonanza was on the east side of the sector all by himself. Shortly after I came off the line with ZZZ1; the Bonanza reported a near miss and was questioning what happened. I focused my attention to the aircraft and noticed a transponder code passing underneath the Bonanza indicating an altitude of 9;800 FT. I advised the IFR aircraft that it appeared to be a fire fighting aircraft and gave the pilot the number to the Center. The pilot reported that he guessed the closest point was 300 FT and X number laterally. We were operating on ERAM and Conflict Alert alerted after the two aircraft were all ready passed. I never saw the traffic and did not issue a traffic advisory. The area the IFR aircraft was operating in is an area of known non-RADAR about 11;000 FT MSL and below. It is possible the transponder code was not displayed on the scope until right near the time of the event; which explains why Conflict Alert was delayed or did not activate until after they passed. I can not confirm that however because I did not see if the transponder code was displayed prior to the event or not. Something we talk about all the time as controllers is not to focus in. Keep your scan going around the entire sector. Do not glance over aircraft who are all by themselves. Also; better RADAR coverage would definitely improve safety in that area. Our Filters are set at 6;500 FT and we rarely see aircraft at 10;000 FT in that area.

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.