Date: 201508
Local time of day: 1801-2400
Location: ZZZ.TRACON, US
Light: Dusk
Aircraft: HS 125 Series
Operator: Corporate
Operating under: Part 135
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Climb
Airspace: Class C ZZZ
ATC / advisory: TRACON ZZZ
Second aircraft: Skyhawk 172/Cutlass 172
Reporter organization: Government
Reporter function: Approach
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Confusion; Distraction
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Automation Aircraft RA; Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance
Contributing factors: Procedure; Human Factors; Airspace Structure
Primary problem: Procedure

Narrative: Aircraft X was a departure off of ZZZ in a climbing left turn southbound. I radar identified the aircraft off departure end and left the aircraft on the assigned ALT of 3000 feet from tower. Aircraft Y was a VFR aircraft transitioning the departure corridor airspace at 2900-3000 feet on own navigation northwest bound. Aircraft Y had originally requested 3000 feet as the transition altitude. To which I approved when I had no departures off of ZZZ that always climb to 3000 feet on contact. I'm not sure why I approved this altitude because I know it is a conflict. I also had another VFR aircraft at 4500 feet transitioning the same departure corridor.When Aircraft X came off the departure end; in my head I left him at 3000 feet because I knew I had the 4500 feet [traffic] and I told myself that I did what I always do and had Aircraft Y at 3500 feet not at 3000 feet. So I initially I left Aircraft X at 3000 feet and didn't climb the aircraft because 3000 feet should be safe. I went to another pertinent issue that the final controller was yelling across the room coordinating a speed with me and was taking care of that request; I then went back to my departure aircraft and realized that Aircraft Y was not at 3500 feet but at 3000 feet; which was same altitude as Aircraft X. I told Aircraft X to climb without delay and maintain 7000 feet and gave traffic on Aircraft Y. I then gave Aircraft Y traffic on Aircraft X and gave him a wake turbulence call and told him to start to descend immediately. I believe I then went back to Aircraft X; who still had not started to climb and gave another traffic call. The aircraft I felt passed at similar altitudes a lot closer then I would have normally had them. About 3 miles after the above situation; Aircraft X told me that he did have a RA on the VFR aircraft. I was slightly distracted and I was just not 100% on my game. I realize this. I always keep those VFR aircraft at a safe VFR altitude. (3500 feet) and I just don't know why I didn't this time. I will continue to be more vigilant and do what I know is the safest operation.




Synopsis: A TRACON Controller clears a locally departing IFR aircraft and a transitioning VFR aircraft to the same 3000 foot altitude. The Controller issued instructions to expedite separation yet the IFR departure still receives a TCAS RA.