Narrative:

I was working the local control position on day X. The final controller on position at the time was vectoring aircraft inbound with minimum separation. Just prior to the error I had an aircraft following too close to a heavy jet. When I was in communication with the following aircraft I asked if he saw the preceding aircraft in sight; he said he did and I was able to allow the aircraft to continue his approach. 2 aircraft later I had a B767 followed by an MD80. Looking at my stars display I determined that I had enough spacing and comparable speeds to allow the MD80 to continue the approach. In my opinion I had the required separation at all times. An audit was performed on the date above. It was determined by electronic means that I did not have the required separation and I was accessed an operational error based on the audit. It is my understanding that the people who do these audits use a program that tracks spacing at all times throughout an aircraft's flight. It seems to me that if we as air traffic controllers are being held to this type of precision we should have the equipment that will allow us to maintain what is required of us. The separation was 4.72 mi when the heavy jet was just inside of 1 mi final. That means that; according to management; I should have been able to tell the difference between 5 mi and 4.72 mi on my stars scope. I do not know if those who are reading this have ever looked at a stars scope but they do not provide you with enough resolution to determine this amount of difference; .28 mi!

Related reports:

Google
 

Original NASA ASRS Text

Title: SEA LCL CTLR EXPERIENCED OPERROR ON FINAL INVOLVING WAKE TURB SEPARATION.

Narrative: I WAS WORKING THE LCL CTL POS ON DAY X. THE FINAL CTLR ON POS AT THE TIME WAS VECTORING ACFT INBOUND WITH MINIMUM SEPARATION. JUST PRIOR TO THE ERROR I HAD AN ACFT FOLLOWING TOO CLOSE TO A HVY JET. WHEN I WAS IN COM WITH THE FOLLOWING ACFT I ASKED IF HE SAW THE PRECEDING ACFT IN SIGHT; HE SAID HE DID AND I WAS ABLE TO ALLOW THE ACFT TO CONTINUE HIS APCH. 2 ACFT LATER I HAD A B767 FOLLOWED BY AN MD80. LOOKING AT MY STARS DISPLAY I DETERMINED THAT I HAD ENOUGH SPACING AND COMPARABLE SPDS TO ALLOW THE MD80 TO CONTINUE THE APCH. IN MY OPINION I HAD THE REQUIRED SEPARATION AT ALL TIMES. AN AUDIT WAS PERFORMED ON THE DATE ABOVE. IT WAS DETERMINED BY ELECTRONIC MEANS THAT I DID NOT HAVE THE REQUIRED SEPARATION AND I WAS ACCESSED AN OPERROR BASED ON THE AUDIT. IT IS MY UNDERSTANDING THAT THE PEOPLE WHO DO THESE AUDITS USE A PROGRAM THAT TRACKS SPACING AT ALL TIMES THROUGHOUT AN ACFT'S FLT. IT SEEMS TO ME THAT IF WE AS AIR TFC CTLRS ARE BEING HELD TO THIS TYPE OF PRECISION WE SHOULD HAVE THE EQUIP THAT WILL ALLOW US TO MAINTAIN WHAT IS REQUIRED OF US. THE SEPARATION WAS 4.72 MI WHEN THE HVY JET WAS JUST INSIDE OF 1 MI FINAL. THAT MEANS THAT; ACCORDING TO MGMNT; I SHOULD HAVE BEEN ABLE TO TELL THE DIFFERENCE BTWN 5 MI AND 4.72 MI ON MY STARS SCOPE. I DO NOT KNOW IF THOSE WHO ARE READING THIS HAVE EVER LOOKED AT A STARS SCOPE BUT THEY DO NOT PROVIDE YOU WITH ENOUGH RESOLUTION TO DETERMINE THIS AMOUNT OF DIFFERENCE; .28 MI!

Data retrieved from NASA's ASRS site as of January 2009 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.