Regional Jet 700 ER/LR (CRJ700)
Air Traffic Control Fully Certified
Situational Awareness
ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance
Human Factors
While I was conducting training on the position; my Developmental was vectoring a CRJ-700 at 8;000 for sequencing to the [STAR]. There was a Saab 340 stacked underneath the CRJ-700 at 7;000. A Pilatus PC-12 was an overflight at 8;000 going direct. My Developmental stopped the CRJ-700 at 8;000 from the [STAR] profile descent reference the Saab 340 at 7;000; but got caught up with issuing speed control on arrivals being switched to final; and forgot to turn the CRJ-700. I let the situation go too long before instructing the Developmental to take action. Recommendation; better control of the position. The Developmental is in the late stages of training on this position; working on extended hours and I didn't want to break in. I should have made a mention of the developing situation sooner in a more; 'don't forget about [the PC-12] out there at 8; 000;' providing information only; and still allowing time to take action. It is a tough line when letting a developmental work through tough traffic situations. You don't want to override them; or say something too soon. You want them to recognize the traffic. Being overbearing on the position can work to your disadvantage. But being extremely vigilant is my responsibility and taking action to ensure separation is being maintained is my job. I will be more pro-active in pointing out traffic to the Developmental and taking action sooner.
TRACON Controller providing OJT was late in issuing guidance to the Developmental resulting in a loss of separation.