Narrative:

On right downwind vector to runway 14R at oma while descending from 4000 ft and approaching 3000 ft; first officer (pilot monitoring) alerted captain (pilot flying) of TCAS target closing and climbing quickly 600 ft below. At 400 ft below; captain exercised emergency authority and performed evasive climb. Target came within 300 feet and 1/2 mile. Target was never visually acquired. First officer notified ATC that we were climbing; and ATC responded with traffic call indicating target was a cessna and that he was within one half mile and had visual contact with us. Once clear of traffic; we were cleared for a visual approach to runway 14R for uneventful landing. After landing captain elected to have a conversation with ATC where we learned that the cessna had departed an uncontrolled airfield VFR enroute to oma and that ATC was surprised by the pop-up traffic. Although TCAS provided basic target info; it never gave us either a visual or oral 'traffic' alert or 'RA'. TCAS was written up for maintenance evaluation. It appears that the approach pattern used by oma approach comes dangerously close to a nearby uncontrolled airfield with aircraft departing and arriving VFR and without the knowledge or control of ATC. Suggest review of oma arrival patterns / altitudes to include possibility of conflicts with other airfields.

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Original NASA ASRS Text

Title: Air carrier Captain reported an airborne conflict in the vicinity of OMA with a corporate jet that had departed from a nearby non-towered airport.

Narrative: On right downwind vector to RWY 14R at OMA while descending from 4000 FT and approaching 3000 FT; First Officer (Pilot Monitoring) alerted Captain (Pilot Flying) of TCAS target closing and climbing quickly 600 ft below. At 400 ft below; Captain exercised emergency authority and performed evasive climb. Target came within 300 feet and 1/2 mile. Target was never visually acquired. First Officer notified ATC that we were climbing; and ATC responded with traffic call indicating target was a Cessna and that he was within one half mile and had visual contact with us. Once clear of traffic; we were cleared for a visual approach to RWY 14R for uneventful landing. After landing Captain elected to have a conversation with ATC where we learned that the Cessna had departed an uncontrolled airfield VFR enroute to OMA and that ATC was surprised by the pop-up traffic. Although TCAS provided basic target info; it never gave us either a visual or oral 'Traffic' alert or 'RA'. TCAS was written up for maintenance evaluation. It appears that the approach pattern used by OMA Approach comes dangerously close to a nearby uncontrolled airfield with aircraft departing and arriving VFR and without the knowledge or control of ATC. Suggest review of OMA arrival patterns / altitudes to include possibility of conflicts with other airfields.

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.