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ARTCC radar controller had less than standard separation with large transport descending through altitude of light transport. System error.
| Attributes | |
| ACN | 91833 |
| Time | |
| Date | 198808 |
| Day | Mon |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : eph |
| State Reference | WA |
| Altitude | msl bound lower : 33300 msl bound upper : 35000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zse |
| Operator | common carrier : air carrier |
| Make Model Name | Large Transport, Low Wing, 2 Turbojet Eng |
| Navigation In Use | Other Other |
| Flight Phase | descent other |
| Route In Use | enroute airway : zse |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | general aviation : corporate |
| Make Model Name | Light Transport, Low Wing, 2 Turbojet Eng |
| Flight Phase | cruise other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : radar |
| Qualification | controller : radar |
| ASRS Report | 91833 |
| Person 2 | |
| Affiliation | government : faa |
| Function | controller : flight data |
| Qualification | controller : radar |
| Events | |
| Anomaly | conflict : airborne less severe non adherence : required legal separation |
| Independent Detector | atc equipment other atc equipment : unspecified other controllera |
| Resolutory Action | other |
| Consequence | Other |
| Miss Distance | horizontal : 27750 vertical : 1700 |
| Supplementary | |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Operational Error |
Narrative:
Large transport X was descending through light transport Y's altitude. I felt that they would pass with greater than 5 mi/2000'. My attention was diverted by a heavy workload in the sector. When I returned my attention to the 2 aircraft I recognized that large transport X and light transport Y were going to pass with less than standard separation unless corrective action was taken. I attempted to instruct large transport X to increase his rate of descent. It took 3 calls to obtain an acknowledgement from the pilot. The aircraft passed with 4.625 mi and 1700'. Supplemental information from acn 91623: r-side descended large transport X for overtaking light transport Y. R-side realized it wasn't working, tried to tell large transport X to expedite, but was blocked by another aircraft. After a couple more attempts pilot acknowledged, but descent wasn't quite fast enough. Sector traffic was very complex with a lot of frequency congestions.
Original NASA ASRS Text
Title: ARTCC RADAR CTLR HAD LESS THAN STANDARD SEPARATION WITH LGT DESCENDING THROUGH ALT OF LTT. SYSTEM ERROR.
Narrative: LGT X WAS DSNDING THROUGH LTT Y'S ALT. I FELT THAT THEY WOULD PASS WITH GREATER THAN 5 MI/2000'. MY ATTN WAS DIVERTED BY A HVY WORKLOAD IN THE SECTOR. WHEN I RETURNED MY ATTN TO THE 2 ACFT I RECOGNIZED THAT LGT X AND LTT Y WERE GOING TO PASS WITH LTSS UNLESS CORRECTIVE ACTION WAS TAKEN. I ATTEMPTED TO INSTRUCT LGT X TO INCREASE HIS RATE OF DSCNT. IT TOOK 3 CALLS TO OBTAIN AN ACKNOWLEDGEMENT FROM THE PLT. THE ACFT PASSED WITH 4.625 MI AND 1700'. SUPPLEMENTAL INFO FROM ACN 91623: R-SIDE DSNDED LGT X FOR OVERTAKING LTT Y. R-SIDE REALIZED IT WASN'T WORKING, TRIED TO TELL LGT X TO EXPEDITE, BUT WAS BLOCKED BY ANOTHER ACFT. AFTER A COUPLE MORE ATTEMPTS PLT ACKNOWLEDGED, BUT DSCNT WASN'T QUITE FAST ENOUGH. SECTOR TFC WAS VERY COMPLEX WITH A LOT OF FREQ CONGESTIONS.
Data retrieved from NASA's ASRS site as of August 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.