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Enroute controller experienced loss of separation at FL240 when misjudging the required distance between two aircraft during descent event; automated halo/J ball equipment was not utilized.
| Attributes | |
| ACN | 839853 |
| Time | |
| Date | 200906 |
| Local Time Of Day | 1801-2400 |
| Place | |
| Locale Reference | ZZZ.Airport |
| State Reference | US |
| Environment | |
| Flight Conditions | IMC |
| Light | Dusk |
| Aircraft 1 | |
| Make Model Name | MD-88 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Cruise |
| Flight Plan | IFR |
| Aircraft 2 | |
| Make Model Name | Challenger Jet Undifferentiated or Other Model |
| Operating Under FAR Part | Part 91 |
| Flight Phase | Descent |
| Flight Plan | IFR |
| Person 1 | |
| Function | Enroute |
| Qualification | Air Traffic Control Fully Certified Flight Crew Instrument |
| Experience | Air Traffic Control Radar 2 Air Traffic Control Time Certified In Pos 1 (mon) 6 Air Traffic Control Time Certified In Pos 1 (yrs) 1 Flight Crew Total 3500 |
| Events | |
| Anomaly | ATC Issue All Types |
| Miss Distance | Horizontal 27000 Vertical 900 |
Narrative:
CL60 was at FL250 converging with FL250 traffic. MD88 southbound FL240 passed with what I thought was 5 miles to the east of CL60; so I descended the CL60 from FL250 to FL230 northbound. I did not use a halo/J ball as an aircraft within close proximity had one on it and I assumed I had the separation. Aircraft were already past each other when separation was lost.
Original NASA ASRS Text
Title: Enroute Controller experienced loss of separation at FL240 when misjudging the required distance between two aircraft during descent event; automated halo/J ball equipment was not utilized.
Narrative: CL60 was at FL250 converging with FL250 traffic. MD88 southbound FL240 passed with what I thought was 5 miles to the east of CL60; so I descended the CL60 from FL250 to FL230 northbound. I did not use a halo/J ball as an aircraft within close proximity had one on it and I assumed I had the separation. Aircraft were already past each other when separation was lost.
Data retrieved from NASA's ASRS site as of April 2012 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.