Date: 201502
Local time of day: 1801-2400
Location: GPT.TRACON, MS
Light: Night
Aircraft: Small Aircraft
Flight plan: IFR
Flight phase: Final Approach
Airspace: Class C GPT
ATC / advisory: TRACON GPT
Reporter organization: Government
Reporter function: Approach
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Situational Awareness
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation - Speed All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Separated Traffic
Contributing factors: Human Factors; Procedure
Primary problem: Procedure

Narrative: I came into work to work my first shift back since my two RDO's.  It started just like any day and I had been well rested and ready to work.  The second time I was on position I was working East/West combined up in the tower on the DBRITE.  It was average workload with three same type of aircraft in the radar pattern for GPT and HSA combined along with a VFR and a couple arrivals/departures during the session.  After Aircraft X did a couple approaches at GPT he wanted to go to HSA to complete the RNAV runway 18 full stop.  I cleared him and gave him a vector to set him up for the approach.  I had another aircraft that was holding for the RNAV for 18 over STENN.  I cleared the other aircraft and he began his approach.  The winds had been quite gusty most of the day and the aircraft were going fast on the downwind and then would slow down significantly once the made the turn onto final.  When I gave Aircraft X his turn to final he was going over 200 knots which I expected to die down significantly when established on final.  I also gave him the aircraft in front of him's speed to let him know he would be following traffic and the speed they indicated.  I noticed that he was going through final and asked if he needed a new vector to join.  He said no and it was at that time I noticed the sequence looked like it was not going to work.  I used the distance measuring tool on the ARTS key pack and it looked just over 3 miles and Aircraft X was still 60 knots faster.  I cancelled the approach clearance and gave him a vector of 270 and to maintain 020 for altitude and proceeded to resequencing him.  When I looked at the FALCON to see the exact measurements of how close it was; it seems that I had in between 2.7 and 2.8 miles before he made his turn into the heading given.  When working the DBRITE and having approaches into HSA it is a little harder to measure the exact distances to ensure you have the full mileage you need.  I also underestimated the speed of Aircraft X when he turned onto final as every aircraft had been slowing tremendously when turned onto final.  Do not anticipate speeds based on winds as each aircraft may fly it differently than the other.If you know that it's harder to watch your exact mileage when operating on DBRITE make sure to give extra separation to be sure. If it becomes close go ahead and cancel the approach clearance and act immediately instead of any hesitation.




Synopsis: GPT Controller; while working a radar position; had numerous aircraft of the same type at a couple of different airports. When vectoring one onto final behind another; the Controller had a loss of separation due to the second aircraft's speed.