Narrative:

I was the tower controller in charge and training was going on at the local controller position. I was monitoring local. Local got a call from north radar asking if they were talking to a pc-12 and the tower responded 'yes'. The pc-12 had accidentally taken a frequency change meant for another aircraft some time before. The pc-12 was almost on a straight-in about 15 miles out. South radar began to turn a BE40 on the left downwind in front of the pc-12 and then asked local control if they could provide visual separation. The trainee; with only the BE40 in sight replied affirmative and the trainer did not contradict the trainee. I was looking out of the window with a pair of binoculars and had both aircraft in sight. I called north radar (who controls the sequence at ZZZ) and told him to have the BE40 follow the pc-12 as the pc-12 was on a straight-in and significantly faster. North radar replied that the BE40 would follow the pc-12 and I advised local control. South radar never broke the BE40 out and the ojti at local had to immediately call traffic because the pc-12 was significantly faster and was on an intercept course with the BE40. Luckily it was a very clear day and the pc-12 had the BE40 in site. The ojti has to immediately slow the pc-12 and there was about a mile separation when the BE40 crossed the numbers of runway 28. The BE40 did not switch to the tower frequency until 3-4 mile final. I do not know if there was required separation before the request for visual separation was made and there was no possibility that the tower could have provided it given the speed; closure rate and positions of the aircraft. Visual separation between aircraft was the only thing that saved this from what I believed would have; at best; been a near midair collision. I attempted to call the oscic/no in the radar room several times via telephone because ZZZ oscic's have a tendency not to be plugged into the oscic position or forward that line to the position they are at. I never got an answer. After the event the oscic did call the tower to ask what was going on. When I expressed my misgivings about the performance of the radar controllers; I was laughed off; or at least that was my impression. The reason that this report is several days late is because just yesterday I was informed by the radar data controller (an fpl/sits between north and south scopes) that the controller at south radar was instructed by the north radar controller (who controls the sequence) to follow the pc-12 but said (perhaps to himself; or the data controller) that he could make this work and proceeded to cut in front of the pc-12 precipitating the possible separation error/possible near midair collision. I do not know what the oscic was doing at the time except he was 'monitoring' from the west radar scope. Professionally this horrified me. It was the closest that I've seen in my career to an uncontrolled possible near midair collision that I've ever seen on a final. Retraining of the south radar controller in separation standards and ZZZ SOP as to who calls the sequence to the airport. Inquiry as to what role the oscic was taking to ensure separation of the aircraft on final.

Related reports:

Google
 

Original NASA ASRS Text

Title: Tower CIC described a near NMAC event between two arrivals when the RADAR Controller failed to change the sequence recommended by the reporter resulting in the conflict.

Narrative: I was the Tower CIC and training was going on at the Local Controller position. I was monitoring Local. Local got a call from North RADAR asking if they were talking to a PC-12 and the Tower responded 'yes'. The PC-12 had accidentally taken a frequency change meant for another aircraft some time before. The PC-12 was almost on a straight-in about 15 miles out. South RADAR began to turn a BE40 on the left downwind in front of the PC-12 and then asked Local Control if they could provide visual separation. The trainee; with only the BE40 in sight replied affirmative and the trainer did not contradict the trainee. I was looking out of the window with a pair of binoculars and had both aircraft in sight. I called North RADAR (who controls the sequence at ZZZ) and told him to have the BE40 follow the PC-12 as the PC-12 was on a straight-in and significantly faster. North RADAR replied that the BE40 would follow the PC-12 and I advised Local Control. South RADAR never broke the BE40 out and the OJTI at local had to immediately call traffic because the PC-12 was significantly faster and was on an intercept course with the BE40. Luckily it was a very clear day and the PC-12 had the BE40 in site. The OJTI has to immediately slow the PC-12 and there was about a mile separation when the BE40 crossed the numbers of Runway 28. The BE40 did not switch to the tower frequency until 3-4 mile final. I do not know if there was required separation before the request for visual separation was made and there was no possibility that the Tower could have provided it given the speed; closure rate and positions of the aircraft. Visual separation between aircraft was the only thing that saved this from what I believed would have; at best; been a NMAC. I attempted to call the OSCIC/NO in the RADAR room several times via telephone because ZZZ OSCIC's have a tendency not to be plugged into the OSCIC position or forward that line to the position they are at. I never got an answer. After the event the OSCIC did call the Tower to ask what was going on. When I expressed my misgivings about the performance of the RADAR Controllers; I was laughed off; or at least that was my impression. The reason that this report is several days late is because just yesterday I was informed by the RADAR Data Controller (an FPL/sits between North and South scopes) that the controller at South RADAR was instructed by the North RADAR controller (who controls the sequence) to follow the PC-12 but said (perhaps to himself; or the Data Controller) that he could make this work and proceeded to cut in front of the PC-12 precipitating the possible separation error/possible NMAC. I do not know what the OSCIC was doing at the time except he was 'monitoring' from the West RADAR scope. Professionally this horrified me. It was the closest that I've seen in my career to an uncontrolled possible NMAC that I've ever seen on a final. Retraining of the South RADAR Controller in separation standards and ZZZ SOP as to who calls the sequence to the airport. Inquiry as to what role the OSCIC was taking to ensure separation of the aircraft on final.

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.