Date: 201708
Local time of day: 1801-2400
Location: D01.TRACON, CO
Light: Daylight
Aircraft: Small Aircraft; High Wing; 1 Eng; Fixed Gear
Operating under: Part 91
Flight plan: IFR
Flight phase: Initial Approach
ATC / advisory: TRACON D01
Second aircraft: Any Unknown or Unlisted Aircraft Manufacturer
Reporter organization: Government
Reporter function: Approach
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Confusion; Situational Awareness
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Airspace Structure; Human Factors; Procedure
Primary problem: Human Factors

Narrative: I was assigned to split off JeLo; which is a position that is rarely split off from west departure. The CIC and Front Line Manager (FLM) said that I could just plug in and help if it was too busy to split it. I got there and observed that west departure was busy; but handling it. I sat down and set up my scope and scanned the traffic. I saw that there was an aircraft for EIK; an aircraft on final (Aircraft Y). I took a call from BJC Tower saying that 'Aircraft X needs to return to the airport'. I looked and saw Aircraft Y and assumed that's who they were talking about; though he was on final. I told BJC Tower to use the JeLo frequency. I told the west departure controller this and he said? 'You're keeping him? Alright.' I asked about the BJC releases and he gave me the strip of the release; then the proposal strips. At some point he said 'you got it' and I was surprised; because I hadn't been able to call for a briefing.I asked Aircraft Y what he needed; and Aircraft X said he needed vectors to the ILS at BJC. I was looking at Aircraft Y on final. I think I asked him if he needed to be boxed around; but I'm not sure. I issued a left turn to 170. Aircraft X asked about what altitude to maintain. Thinking I was talking to Aircraft Y; I told him 7;000.I called BJC Tower thinking that Aircraft Y was just taking his time starting his turn; letting them know that he would enter their airspace. The BJC Controller questioned me; saying that 'we have this departure coming out'. Thinking that the only problem was Aircraft Y; I said it wouldn't matter. Then I saw Aircraft X just north of BJC. I figured out later; after I saw the strip; that he was coming from BDU. He was beneath the MVA and very close to the BJC departure that had just tagged up. I issued a vector to the west and a climb to 8;000. Once they passed I issued a vector to the southeast.At some point in this west departure flashed Aircraft X to me.I should have insisted on a recorded briefing. I got wrapped up in thinking that the other controller was down the tubes and needed help immediately. This shortcut caused me to miss a vital piece of the picture. I also could have listened to the call signs more carefully.I'm not sure if I made the mental shortcut of saying 'Aircraft X' and thinking I'm talking to Aircraft Y. I'll be very vigilant about that kind of thing.




Synopsis: A D01 TRACON Controller misidentified aircraft with similar sounding call signs and issued a descent and heading to an aircraft below the Minimum Vectoring Altitude and into confliction with departing traffic.