Bell Helicopter Textron Undifferentiated or Other Model
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 10
Distraction; Training / Qualification
ATC Issue All Types; Conflict Airborne Conflict; Deviation - Altitude Excursion From Assigned Altitude; Deviation - Speed All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance
Human Factors; Procedure
I was training a developmental on low east. Runway 31 in use. The developmental had released Aircraft X off the seawall and turned the aircraft north bound after departure. (350 heading) which is the heading needed in accordance with the sop. Aircraft Y departed off runway 31 with a Letter of Agreement (LOA) climbout of Runway heading to 2.5 DME the turn right heading 040 at 016 MSL.The developmental did not recognize the speed was such an aggressive overtake by Aircraft Y and climbed Aircraft Y to 040 MSL. I brought it to the developmental attention and he turned Aircraft Y to 130 heading to go behind Aircraft X and stopped Aircraft Y's climb to 030 MSL. (Should've stopped Aircraft Y at 020 MSL.)I was unable to see the altitude of Aircraft X due to overlapping data tags; due to multiple flights working in an area directly above NGP between 065 and 085 MSL. I thought we would have 3 miles or divergence but apparently we didn't.Without taking over every time a developmental makes a bad call; it's difficult to allow someone to learn how to work traffic. I should have stepped in and stopped Aircraft Y at 020 MSL; there were several conversations about Aircraft X prior to this occurrence that prevented insufficient separation with other traffic; with the airspace we have north west of NGP that was the only out. At 5 DME northwest of NGP; Low East (LE) only owns up to 016 MSL so any turns north or west must be pointed out to north radar.
CRP TRACON Instructor reported that while instructing a Developmental an aircraft overtook a helicopter on departure resulting in a loss of separation.