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
A CRJ was inbound on the STAR arrival. An E120 was inbound on the same STAR arrival. I left both aircraft on the approach and descended the CRJ to 090 and the Embraer to 100. I first noticed the CRJ was faster so I knew that aircraft would be #1 and the Embraer was #2. I descended the CRJ to 070 and transferred to Approach Control. Before I transferred communication the CRJ said they have the airport in sight; so I assumed as soon as they checked on with the next controller they would clear him for the visual and they would continue their descent. I then told the Embraer to reduce speed to 210 KTS then maintain 070; he read it back. I soon noticed the CRJ was not descending and the Embraer was catching him. I turned the Embraer to a 030 heading and called the traffic; he called the CRJ in sight but separation was already lost. The Embraer was still told to maintain Visual Separation and vectored across the Final Approach Course and eventually cleared for the Visual Approach. I will make sure the aircraft is at least looking for the person he will eventually be following. Also do not assume what another controller will do. I will watch the speeds of the aircraft and not assume who should be faster. It was too close to bet on the separation working itself out and I should have been more diligent in my efforts to separate the aircraft. I acted too late; so next time I will ensure my separation sooner.
Loss of separation occurred when in-trail separation was allowed to deteriorate below requirements. The reporter acknowledged less than necessary diligence during this occurrence.