Narrative:

While working the aforementioned position with a developmental I observed that an error had occurred in my understanding of what the developmental was trying to achieve with sep between 2 aircraft--small transport X, being a 10000' overflt from north to south at the crg VOR, the other air carrier Y descending from 13000 to 6000' arriving a jax northbound. My understanding was errant because I believed small transport X traffic to be on a routing to avoid air carrier Y. Also I believed air carrier Y had been stopped by the developmental at 11000'. As the situation developed we were busy amending another potential conflict between 2 aircraft 15 mi east of crg VOR. When my attention went back to and other aircraft it was obvious my information was wrong. At 3.5 mi from each other I took appropriate action, which turned out to be too late to meet ATC requirements. Although an OJT instrument for the last 8 yrs, this has reaffirmed the basic problem of ensuring both what is actually happening and what your developmental has said and done. Supplemental information from acn 170455: small transport X was on a direct route, southbound at 10000' MSL. Air carrier Y was on a heading inbound to a VOR for an approach to jax at 13000'. With the aircraft approximately 20 mi apart, on converging headings, air carrier Y was issued descent to 6000' MSL, based on projected flight paths and presumed descent rate. Several mins later air carrier Y and small transport X were observed 3 1/2 mi apart, with air carrier Y at 11000' descending. Immediate evasive instructions issued by the ATC's to both aircraft. Both pilots reported other aircraft in sight and passed to within 1 mi and 300' of each other. The small transport X was experiencing a tailwind of up to 40 KTS. Air carrier Y paused descent approaching 10000' to reduce airspeed below 250 KTS. Cause was erroneous planning on ATC's part: failing to consider above factors. ATC was receiving OJT on position at this time. Fpl controller did not have unobstructed view of flight progress strips which would have indicated the problem sooner. Position had another position combined with it and had just been split into 2 radar positions approximately 2 mins prior to incident. This included a detailed position briefing. C/a did not sound. TCAS would have greatly helped.

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Original NASA ASRS Text

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

Narrative: WHILE WORKING THE AFOREMENTIONED POS WITH A DEVELOPMENTAL I OBSERVED THAT AN ERROR HAD OCCURRED IN MY UNDERSTANDING OF WHAT THE DEVELOPMENTAL WAS TRYING TO ACHIEVE WITH SEP BTWN 2 ACFT--SMT X, BEING A 10000' OVERFLT FROM N TO S AT THE CRG VOR, THE OTHER ACR Y DSNDING FROM 13000 TO 6000' ARRIVING A JAX NBND. MY UNDERSTANDING WAS ERRANT BECAUSE I BELIEVED SMT X TFC TO BE ON A RTING TO AVOID ACR Y. ALSO I BELIEVED ACR Y HAD BEEN STOPPED BY THE DEVELOPMENTAL AT 11000'. AS THE SITUATION DEVELOPED WE WERE BUSY AMENDING ANOTHER POTENTIAL CONFLICT BTWN 2 ACFT 15 MI E OF CRG VOR. WHEN MY ATTN WENT BACK TO AND OTHER ACFT IT WAS OBVIOUS MY INFO WAS WRONG. AT 3.5 MI FROM EACH OTHER I TOOK APPROPRIATE ACTION, WHICH TURNED OUT TO BE TOO LATE TO MEET ATC REQUIREMENTS. ALTHOUGH AN OJT INSTR FOR THE LAST 8 YRS, THIS HAS REAFFIRMED THE BASIC PROB OF ENSURING BOTH WHAT IS ACTUALLY HAPPENING AND WHAT YOUR DEVELOPMENTAL HAS SAID AND DONE. SUPPLEMENTAL INFO FROM ACN 170455: SMT X WAS ON A DIRECT RTE, SBND AT 10000' MSL. ACR Y WAS ON A HDG INBND TO A VOR FOR AN APCH TO JAX AT 13000'. WITH THE ACFT APPROX 20 MI APART, ON CONVERGING HDGS, ACR Y WAS ISSUED DSNT TO 6000' MSL, BASED ON PROJECTED FLT PATHS AND PRESUMED DSNT RATE. SEVERAL MINS LATER ACR Y AND SMT X WERE OBSERVED 3 1/2 MI APART, WITH ACR Y AT 11000' DSNDING. IMMEDIATE EVASIVE INSTRUCTIONS ISSUED BY THE ATC'S TO BOTH ACFT. BOTH PLTS RPTED OTHER ACFT IN SIGHT AND PASSED TO WITHIN 1 MI AND 300' OF EACH OTHER. THE SMT X WAS EXPERIENCING A TAILWIND OF UP TO 40 KTS. ACR Y PAUSED DSNT APCHING 10000' TO REDUCE AIRSPD BELOW 250 KTS. CAUSE WAS ERRONEOUS PLANNING ON ATC'S PART: FAILING TO CONSIDER ABOVE FACTORS. ATC WAS RECEIVING OJT ON POS AT THIS TIME. FPL CTLR DID NOT HAVE UNOBSTRUCTED VIEW OF FLT PROGRESS STRIPS WHICH WOULD HAVE INDICATED THE PROB SOONER. POS HAD ANOTHER POS COMBINED WITH IT AND HAD JUST BEEN SPLIT INTO 2 RADAR POSITIONS APPROX 2 MINS PRIOR TO INCIDENT. THIS INCLUDED A DETAILED POS BRIEFING. C/A DID NOT SOUND. TCAS WOULD HAVE GREATLY HELPED.

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.