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Cpr X descent through occupied altitude had less than standard separation from air carrier Y. System error.
| Attributes | |
| ACN | 208480 |
| Time | |
| Date | 199204 |
| Day | Thu |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : bib |
| State Reference | IL |
| Altitude | msl bound lower : 28000 msl bound upper : 28800 |
| Environment | |
| Flight Conditions | Mixed |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zid |
| Operator | general aviation : corporate |
| Make Model Name | Light Transport, Low Wing, 2 Turbojet Eng |
| Navigation In Use | Other |
| Flight Phase | descent other |
| Route In Use | enroute : direct |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : radar |
| Qualification | controller : radar |
| Experience | controller non radar : 3 controller radar : 1 |
| ASRS Report | 208480 |
| Person 2 | |
| Affiliation | Other |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Events | |
| Anomaly | conflict : airborne less severe inflight encounter : weather non adherence : required legal separation non adherence : published procedure |
| Independent Detector | atc equipment other atc equipment : unspecified |
| Resolutory Action | none taken : anomaly accepted |
| Consequence | faa : investigated |
| Miss Distance | horizontal : 21000 vertical : 400 |
| Supplementary | |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Operational Error |
Narrative:
Cpr X mdw.1.dnv..BW6 -- air carrier Y mem.1.dxv..okk.OXI2.ord mongo 01 2/F18/right dxv..but..obk..nbu. Cpr X was 15 mi west of dnv deviating south direct bwg at FL290. Air carrier Y was 40 mi east of bib northbound deviating west at FL290. Air carrier Y was descended to FL280 and was level. Approximately 5 mins later, cpr X requested FL250. Traffic was 50 mi northeast of pxu at FL250. Cpr X was descended to FL260 not detecting air carrier Y was still in confliction at FL280. The aircraft passed laterally at 4 mi. When conflict alert activated, cpr X was out of FL288 and I then realized the mistake. I also realized the aircraft were already past each other and it was too late to issue turns or reassign altitudes. The reason for the error is my sector was impacted by thunderstorms and I was more concerned about the WX and did not scan completely before descending.
Original NASA ASRS Text
Title: CPR X DSCNT THROUGH OCCUPIED ALT HAD LTSS FROM ACR Y. SYS ERROR.
Narrative: CPR X MDW.1.DNV..BW6 -- ACR Y MEM.1.DXV..OKK.OXI2.ORD MONGO 01 2/F18/R DXV..BUT..OBK..NBU. CPR X WAS 15 MI W OF DNV DEVIATING S DIRECT BWG AT FL290. ACR Y WAS 40 MI E OF BIB NBOUND DEVIATING W AT FL290. ACR Y WAS DSNDED TO FL280 AND WAS LEVEL. APPROX 5 MINS LATER, CPR X REQUESTED FL250. TFC WAS 50 MI NE OF PXU AT FL250. CPR X WAS DSNDED TO FL260 NOT DETECTING ACR Y WAS STILL IN CONFLICTION AT FL280. THE ACFT PASSED LATERALLY AT 4 MI. WHEN CONFLICT ALERT ACTIVATED, CPR X WAS OUT OF FL288 AND I THEN REALIZED THE MISTAKE. I ALSO REALIZED THE ACFT WERE ALREADY PAST EACH OTHER AND IT WAS TOO LATE TO ISSUE TURNS OR REASSIGN ALTS. THE REASON FOR THE ERROR IS MY SECTOR WAS IMPACTED BY TSTMS AND I WAS MORE CONCERNED ABOUT THE WX AND DID NOT SCAN COMPLETELY BEFORE DSNDING.
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.