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Controller misjudged closure rate of opposite IFR traffic and issued a descent clearance that resulted in less than standard separation. Operational error.
| Attributes | |
| ACN | 102720 |
| Time | |
| Date | 198901 |
| Day | Sat |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : ott |
| State Reference | MD |
| Altitude | msl bound lower : 29000 msl bound upper : 33000 |
| Environment | |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zdc |
| Operator | common carrier : air carrier |
| Make Model Name | Large Transport, Low Wing, 3 Turbojet Eng |
| Flight Phase | descent other |
| Route In Use | arrival other enroute airway : zdc |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | common carrier : air carrier |
| Make Model Name | Medium Transport, Low Wing, 2 Turbojet Eng |
| Flight Phase | cruise other |
| Route In Use | enroute : direct |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : radar |
| Qualification | controller : radar |
| Experience | controller radar : 11 |
| ASRS Report | 102720 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Events | |
| Anomaly | conflict : airborne less severe non adherence : published procedure non adherence : required legal separation |
| Independent Detector | other controllera |
| Resolutory Action | controller : issued new clearance |
| Consequence | faa : investigated |
| Miss Distance | horizontal : 22800 vertical : 1300 |
| Supplementary | |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Operational Error |
Narrative:
Large transport nebnd, southwest of ott requested descent to FL290. Aircraft was at FL330. I had an mgt at FL310 on J37 westbound at the time and I issued large transport this descent clearance. He was about 25 southwest of ott. At the rate he was traveling I figured I would have at least 5 miles when large transport and mgt westbound passed. However the large transport drifted a little east of course and separation was lost (3.8 miles and 1300').
Original NASA ASRS Text
Title: CTLR MISJUDGED CLOSURE RATE OF OPPOSITE IFR TRAFFIC AND ISSUED A DESCENT CLRNC THAT RESULTED IN LESS THAN STANDARD SEPARATION. OPERATIONAL ERROR.
Narrative: LGT NEBND, SW OF OTT REQUESTED DSCNT TO FL290. ACFT WAS AT FL330. I HAD AN MGT AT FL310 ON J37 WBND AT THE TIME AND I ISSUED LGT THIS DSCNT CLRNC. HE WAS ABOUT 25 SW OF OTT. AT THE RATE HE WAS TRAVELING I FIGURED I WOULD HAVE AT LEAST 5 MILES WHEN LGT AND MGT WBND PASSED. HOWEVER THE LGT DRIFTED A LITTLE E OF COURSE AND SEPARATION WAS LOST (3.8 MILES AND 1300').
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.