SR20
Air Traffic Control Fully Certified
Situational Awareness
ATC Issue All Types; Conflict NMAC
General None Reported / Taken
Aircraft; Human Factors; Procedure
A Cirrus called for IFR release off of Runway XXR. The Cirrus was cleared for takeoff. Our IFR departures that take off Runway XX depart to the west and are instructed to 'fly heading 270 Radar vectors to'. The 270 heading puts the aircraft departing Runway XXR in front of the departure path of Runway XXL. A Cherokee requested a left downwind departure off of Runway XXL. The Local Controller issued the IFR traffic departing the parallel runway and cleared him for takeoff. At this point the Cirrus was already rolling on Runway XXR and due to typical performance of both aircraft typically the Cirrus is going to pull away from the Cherokee. I was then relieved from the CIC position and started to conduct my briefing. Once this was completed and I was doing my two minute overlap; a helicopter requested departure from the hospital southbound along the highway. Traffic was issued to the helicopter for the Cherokee on the upwind doing a left downwind departure and he was cleared for takeoff. It was at this point that the Cirrus had started his turn to 270 heading in front of the Cherokee. The Local Controller then told the Cirrus that the Cherokee had him in sight; the pilot of the Cherokee had not said that he had the Cirrus in sight; and to contact Departure. The Cherokee reported to the Tower that the Cirrus had come over top of him at approximately 100 FT. The Cherokee then requested the tail number of the aircraft that cut him off and the Local Controller gave him the Tower Cab number instead so as to discuss it on the telephone when he gets back. At this point I keyed into CIC and said '2 minute overlap complete'. Typical aircraft characteristics of the Cirrus would have it pulling away from the Cherokee. The Local Controller and I had discussed things that could have been done differently which where to delay the Cherokee for departure; tell the Cherokee that the IFR departure off the parallel runway will be turning to a 270 heading once airborne; or advise the Cherokee early left crosswind approved.
Tower Controller described a NMAC between a VFR and IFR departure from parallel runways; the reporter listing IFR departure procedures and unexpected aircraft performance characteristics as contributing to the error.