Narrative:

An operational error has been established between air carrier X and air carrier Y on 2/xx/90 at den because a determination has been made that paragraph 5-73 of the 7110.65F ATC handbook does not apply. The problem arose from a traffic overload situation that was anticipated by myself (working the final radar or AR2 position) and the AR1 (feeder) controller. Given the WX conditions and the amount of arrival traffic, the AR1 controller requested that we utilize simultaneous approach procedures. The supervisor denied the request and left only 2 of us to run the arrs. The request was made 2 more times (and another controller volunteered to open the AR4 position to help but was instructed otherwise) and each time denied by the supervisor. During the busiest time, the AR1 controller stated he was 'losing it' and the supervisor instructed me to 'run them tighter'. Since AR1 was getting overloaded, he descended 3 aircraft below 11000' (against procedure) and handed the aircraft off to me. As a result, I could not fit air carrier X into the sequence for a parallel approach and had to break the aircraft out to fall in behind air carrier Y. Applying the diverging courses rule as I understood it, I positioned air carrier X on a downwind at 8000' behind air carrier Y on a base leg at 8000'. This resulted in a loss of 3 mi lateral separation on 90 degree diverging courses. The supervisor's actions were directly responsible for the traffic overload and the subsequent operational error determination. Supplemental information from acn 136848: I was the supervisor on duty at the time of the incident. I did not decombine operating positions based on information received from ZDV traffic management unit. Therefore, there was 1 feeder controller (AR1) and 1 final controller (AR2). There was no coordinator. I was not only supervising the operation, but was engaged in telephone conversations with user airlines, central flow control facility, and assigning personnel to positions of operation. I was the only supervisor on duty in the TRACON during this time period. WX was marginal/IFR. There are no written guidelines/performance standards regarding the number of aircraft which can be accepted on the runway confign in use. Therefore I was following guidelines used by other supervisory personnel in the past. I had several conversations with center traffic management personnel regarding numbers of arrival aircraft. In spite of my best efforts, the AR1 and AR2 controllers became overloaded with aircraft. The AR2 controller has a history of performance problems, and during a 35 min session leading up to this error, had 3 go arounds, and pulled 2 additional aircraft out of the sequence because of improper spacing. The last aircraft pulled out was air carrier X which he turned into air carrier Y who was on downwind at same altitude, causing the error. I am being listed on the investigation as a contributing factor to the error, because I did not provide controllers assistance when asked. This decision, however, was based on information (numbers of arrival aircraft) which later proved to be inaccurate.

Related reports:

Google
 

Original NASA ASRS Text

Title: ACR X HAD LESS THAN STANDARD SEPARATION FROM ACR Y. SYSTEM ERROR.

Narrative: AN OPERATIONAL ERROR HAS BEEN ESTABLISHED BETWEEN ACR X AND ACR Y ON 2/XX/90 AT DEN BECAUSE A DETERMINATION HAS BEEN MADE THAT PARAGRAPH 5-73 OF THE 7110.65F ATC HANDBOOK DOES NOT APPLY. THE PROBLEM AROSE FROM A TFC OVERLOAD SITUATION THAT WAS ANTICIPATED BY MYSELF (WORKING THE FINAL RADAR OR AR2 POSITION) AND THE AR1 (FEEDER) CTLR. GIVEN THE WX CONDITIONS AND THE AMOUNT OF ARR TFC, THE AR1 CTLR REQUESTED THAT WE UTILIZE SIMULTANEOUS APCH PROCS. THE SUPVR DENIED THE REQUEST AND LEFT ONLY 2 OF US TO RUN THE ARRS. THE REQUEST WAS MADE 2 MORE TIMES (AND ANOTHER CTLR VOLUNTEERED TO OPEN THE AR4 POSITION TO HELP BUT WAS INSTRUCTED OTHERWISE) AND EACH TIME DENIED BY THE SUPVR. DURING THE BUSIEST TIME, THE AR1 CTLR STATED HE WAS 'LOSING IT' AND THE SUPVR INSTRUCTED ME TO 'RUN THEM TIGHTER'. SINCE AR1 WAS GETTING OVERLOADED, HE DESCENDED 3 ACFT BELOW 11000' (AGAINST PROC) AND HANDED THE ACFT OFF TO ME. AS A RESULT, I COULD NOT FIT ACR X INTO THE SEQUENCE FOR A PARALLEL APCH AND HAD TO BREAK THE ACFT OUT TO FALL IN BEHIND ACR Y. APPLYING THE DIVERGING COURSES RULE AS I UNDERSTOOD IT, I POSITIONED ACR X ON A DOWNWIND AT 8000' BEHIND ACR Y ON A BASE LEG AT 8000'. THIS RESULTED IN A LOSS OF 3 MI LATERAL SEPARATION ON 90 DEG DIVERGING COURSES. THE SUPVR'S ACTIONS WERE DIRECTLY RESPONSIBLE FOR THE TFC OVERLOAD AND THE SUBSEQUENT OPERATIONAL ERROR DETERMINATION. SUPPLEMENTAL INFORMATION FROM ACN 136848: I WAS THE SUPVR ON DUTY AT THE TIME OF THE INCIDENT. I DID NOT DECOMBINE OPERATING POSITIONS BASED ON INFO RECEIVED FROM ZDV TFC MGMNT UNIT. THEREFORE, THERE WAS 1 FEEDER CTLR (AR1) AND 1 FINAL CTLR (AR2). THERE WAS NO COORDINATOR. I WAS NOT ONLY SUPERVISING THE OPERATION, BUT WAS ENGAGED IN TELEPHONE CONVERSATIONS WITH USER AIRLINES, CENTRAL FLOW CTL FAC, AND ASSIGNING PERSONNEL TO POSITIONS OF OPERATION. I WAS THE ONLY SUPVR ON DUTY IN THE TRACON DURING THIS TIME PERIOD. WX WAS MARGINAL/IFR. THERE ARE NO WRITTEN GUIDELINES/PERFORMANCE STANDARDS REGARDING THE NUMBER OF ACFT WHICH CAN BE ACCEPTED ON THE RWY CONFIGN IN USE. THEREFORE I WAS FOLLOWING GUIDELINES USED BY OTHER SUPERVISORY PERSONNEL IN THE PAST. I HAD SEVERAL CONVERSATIONS WITH CENTER TFC MGMNT PERSONNEL REGARDING NUMBERS OF ARR ACFT. IN SPITE OF MY BEST EFFORTS, THE AR1 AND AR2 CTLRS BECAME OVERLOADED WITH ACFT. THE AR2 CTLR HAS A HISTORY OF PERFORMANCE PROBLEMS, AND DURING A 35 MIN SESSION LEADING UP TO THIS ERROR, HAD 3 GO AROUNDS, AND PULLED 2 ADDITIONAL ACFT OUT OF THE SEQUENCE BECAUSE OF IMPROPER SPACING. THE LAST ACFT PULLED OUT WAS ACR X WHICH HE TURNED INTO ACR Y WHO WAS ON DOWNWIND AT SAME ALT, CAUSING THE ERROR. I AM BEING LISTED ON THE INVESTIGATION AS A CONTRIBUTING FACTOR TO THE ERROR, BECAUSE I DID NOT PROVIDE CTLRS ASSISTANCE WHEN ASKED. THIS DECISION, HOWEVER, WAS BASED ON INFO (NUMBERS OF ARR ACFT) WHICH LATER PROVED TO BE INACCURATE.

Data retrieved from NASA's ASRS site as of July 2007 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.