Date: 201711
Local time of day: 1801-2400
Location: D01.TRACON, CO
Flight conditions: VMC
Aircraft: Small Transport
Operator: Air Taxi
Operating under: Part 135
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Climb
Airspace: Class B DEN
ATC / advisory: Tower DEN
Second aircraft: Large Transport; Low Wing; 2 Turbojet Eng
Reporter organization: Government
Reporter function: Departure
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Training / Qualification; Situational Awareness; Confusion
Second reporter function: Local
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Automation Aircraft TA; Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Took Evasive Action
Contributing factors: Human Factors; Procedure; Airspace Structure
Primary problem: Procedure

Narrative: Tower requested approval to put Aircraft X on a 150 heading. I approved it. Shortly after Aircraft X took off 17R and right next to him appeared Aircraft Y departing the parallel left runway. I assumed the tower would call to amend their plan; but Aircraft X turned left. They were very close very fast; and I thought there could be no way that Local Control didn't see it and I didn't want to distract Local Control at such a critical time.But the planes just stayed right next to each other. I tried to call to get them to turn away; and there was someone else talking on the frequency. I got off the line. I tried to call again and I saw Aircraft X turning left. I got off the line again. I didn't think of it at the time; but I could have called the other Local Control or tried to call the Cab Coordinator; or had the Supervisor do it.


Second narrative: This was a configuration I had never worked before and took a second prior to getting the position to make sure my bearings were correct with departure procedures. The departures were set up by the Traffic Management to be RNAV correctly assigned the correct parallel runways. For the safety event I initially cleared Aircraft X for departure off runway 17R on a 185 heading. I had departures holding short of behind that aircraft whose first RNAV fix was GOROC which would not give degree divergence off the end of the runway. I coordinated a 150 heading with the Departure Controller to get divergence with the departures behind Aircraft X.Around the same time; Aircraft Y was cleared for takeoff off runway 17L to the first RNAV fix RAYDR. A direct conflict with the 150 heading of Aircraft X. Being this was my first time working this configuration I had continuously thought of the 135 heading off the left runway and to be sure that I did not assign the normal first RNAV fix; GISTT; for departures. While I was thinking that; I had it in my head that Aircraft Y would be going out on the 135 heading and my 150 heading for Aircraft X would have sufficient separation. However; Aircraft Y was on the SID slipped my mind. When I noticed the targets merging on the display I questioned the assigned headings and noticed 300 ft altitude difference. By this time; Aircraft X and Aircraft Y had crossed flight paths. I issued Aircraft Y the 135 heading I thought they were on and reiterated the 150 to Aircraft X. I then issued an immediate left 360 to Aircraft X and turned them back to a 180 heading. The pilot of Aircraft Y declared a near miss. There was another flight departing runway behind Aircraft Y on the 135 heading. I stopped that aircraft at 7000 ft to avoid the conflict ahead. I thought all through training and even as a certified controller that mixing RNAV for higher performance aircraft and headings for lower performing aircraft is not a good mix. Headings allow for too many variables and give the potential for situations like this.


Synopsis: DEN Tower Controller; D01 TRACON Controller; and a flight crew reported a NMAC between aircraft departing on parallel runways.