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A D10 approach controller has a loss of separation between a GLF4 arriving from byp landing dal and a learjet from cqy landing ads on converging courses.
| Attributes | |
| ACN | 626160 |
| Time | |
| Date | 200408 |
| Day | Sun |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | airport : dal.airport |
| State Reference | TX |
| Altitude | msl single value : 3000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tracon : d10.tracon tower : bwi.tower |
| Operator | general aviation : corporate |
| Make Model Name | Gates Learjet Corp Undifferentiated or Other Model |
| Operating Under FAR Part | Part 91 |
| Flight Phase | descent : intermediate altitude |
| Flight Plan | IFR |
| Aircraft 2 | |
| Controlling Facilities | tracon : d10.tracon |
| Operator | general aviation : corporate |
| Make Model Name | Gulfstream IV |
| Operating Under FAR Part | Part 91 |
| Flight Phase | descent : intermediate altitude |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : approach |
| Qualification | controller : radar |
| Experience | controller military : 4 controller non radar : 4 controller radar : 25 controller time certified in position1 : 12 flight time total : 1000 |
| ASRS Report | 626160 |
| Person 2 | |
| Affiliation | government : faa |
| Function | controller : approach |
| Events | |
| Anomaly | conflict : airborne critical non adherence : required legal separation non adherence : published procedure |
| Independent Detector | atc equipment other atc equipment : radar/mode c other controllera other controllerb other flight crewa other flight crewb |
| Resolutory Action | none taken : detected after the fact |
| Miss Distance | horizontal : 15840 vertical : 0 |
| Supplementary | |
| Problem Areas | ATC Human Performance |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Intra Facility Coordination Failure Operational Error |
Narrative:
Learjet, arriving ads from cqy checked onto my frequency at 5000 ft. A G4, arriving dal from byp checked onto my frequency descending to 5000 ft. These 2 aircraft were 30 mi apart on converging courses. The learjet was heading 310 degrees and a G4 was heading 220 degrees. I descended the learjet to 3000 ft and assigned a heading of 320 degrees. When the learjet was below 4000 ft, I switched him to frequency 124.25, the arrival controller for ads airport. I descended a G4 to 4000 ft. I subsequently descended the G4 to 3000 ft. The learjet passed behind the G4, both at 3000 ft. I think I had 3 mi between them at the point when the G4 crossed in front of the learjet. Even though their courses were diverging at that time, the distance between aircraft subsequently decreased. This is being processed as an operational error even though I had 3 mi between aircraft until their paths diverged. The one thing I could have done to have further insured separation was to have kept the G4 at 4000 ft a bit longer.
Original NASA ASRS Text
Title: A D10 APCH CTLR HAS A LOSS OF SEPARATION BTWN A GLF4 ARRIVING FROM BYP LNDG DAL AND A LEARJET FROM CQY LNDG ADS ON CONVERGING COURSES.
Narrative: LEARJET, ARRIVING ADS FROM CQY CHKED ONTO MY FREQ AT 5000 FT. A G4, ARRIVING DAL FROM BYP CHKED ONTO MY FREQ DSNDING TO 5000 FT. THESE 2 ACFT WERE 30 MI APART ON CONVERGING COURSES. THE LEARJET WAS HDG 310 DEGS AND A G4 WAS HDG 220 DEGS. I DSNDED THE LEARJET TO 3000 FT AND ASSIGNED A HDG OF 320 DEGS. WHEN THE LEARJET WAS BELOW 4000 FT, I SWITCHED HIM TO FREQ 124.25, THE ARR CTLR FOR ADS ARPT. I DSNDED A G4 TO 4000 FT. I SUBSEQUENTLY DSNDED THE G4 TO 3000 FT. THE LEARJET PASSED BEHIND THE G4, BOTH AT 3000 FT. I THINK I HAD 3 MI BTWN THEM AT THE POINT WHEN THE G4 CROSSED IN FRONT OF THE LEARJET. EVEN THOUGH THEIR COURSES WERE DIVERGING AT THAT TIME, THE DISTANCE BTWN ACFT SUBSEQUENTLY DECREASED. THIS IS BEING PROCESSED AS AN OPERROR EVEN THOUGH I HAD 3 MI BTWN ACFT UNTIL THEIR PATHS DIVERGED. THE ONE THING I COULD HAVE DONE TO HAVE FURTHER INSURED SEPARATION WAS TO HAVE KEPT THE G4 AT 4000 FT A BIT LONGER.
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.