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C90 controller experienced operational error at approximately 4500 ft when 2 aircraft he had issued descent clrncs to lost required separation.
| Attributes | |
| ACN | 685713 |
| Time | |
| Date | 200601 |
| Place | |
| Locale Reference | airport : ord.airport |
| State Reference | IL |
| Altitude | msl single value : 4400 |
| Environment | |
| Flight Conditions | IMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tracon : c90.tracon |
| Operator | common carrier : air carrier |
| Make Model Name | Regional Jet 700 ER&LR |
| Operating Under FAR Part | Part 121 |
| Flight Phase | descent : approach |
| Flight Plan | IFR |
| Aircraft 2 | |
| Controlling Facilities | tracon : c90.tracon |
| Operator | common carrier : air carrier |
| Make Model Name | Regional Jet 700 ER&LR |
| Operating Under FAR Part | Part 121 |
| Flight Phase | descent : intermediate altitude |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : approach |
| Qualification | controller : radar |
| Experience | controller military : 4.5 controller radar : 3 controller time certified in position1 : 1 |
| ASRS Report | 685713 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Events | |
| Anomaly | conflict : airborne less severe non adherence : required legal separation |
| Independent Detector | atc equipment : conflict alert other controllera |
| Resolutory Action | controller : issued alert controller : issued new clearance |
| Consequence | faa : investigated |
| Miss Distance | horizontal : 6000 vertical : 800 |
| Supplementary | |
| Problem Areas | ATC Human Performance |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Operational Error |
Narrative:
Aircraft X was level flight at 7000 ft and 170 KTS. Aircraft X was issued a descent clearance to maintain 4000 ft. Aircraft Y was level flight at 10000 ft and 170 KTS. Aircraft Y was then issued a descent clearance to 5000 ft. I then plugged in to receive a position relief briefing. After the briefing was finished; I made a few xmissions and aircraft Y was leaving 6500 ft and aircraft X was leaving 4900 ft. Then next thing I know the conflict alert was going off with aircraft Y at 5400 ft and aircraft X was at 4400 ft about 1 mi apart. Both aircraft were CRJ7's and both aircraft should have descended at the same rate. The 2 aircraft were at the same speed and issued the descent clearance over 3000 ft apart.
Original NASA ASRS Text
Title: C90 CTLR EXPERIENCED OPERROR AT APPROX 4500 FT WHEN 2 ACFT HE HAD ISSUED DSCNT CLRNCS TO LOST REQUIRED SEPARATION.
Narrative: ACFT X WAS LEVEL FLT AT 7000 FT AND 170 KTS. ACFT X WAS ISSUED A DSCNT CLRNC TO MAINTAIN 4000 FT. ACFT Y WAS LEVEL FLT AT 10000 FT AND 170 KTS. ACFT Y WAS THEN ISSUED A DSCNT CLRNC TO 5000 FT. I THEN PLUGGED IN TO RECEIVE A POS RELIEF BRIEFING. AFTER THE BRIEFING WAS FINISHED; I MADE A FEW XMISSIONS AND ACFT Y WAS LEAVING 6500 FT AND ACFT X WAS LEAVING 4900 FT. THEN NEXT THING I KNOW THE CONFLICT ALERT WAS GOING OFF WITH ACFT Y AT 5400 FT AND ACFT X WAS AT 4400 FT ABOUT 1 MI APART. BOTH ACFT WERE CRJ7'S AND BOTH ACFT SHOULD HAVE DSNDED AT THE SAME RATE. THE 2 ACFT WERE AT THE SAME SPD AND ISSUED THE DSCNT CLRNC OVER 3000 FT APART.
Data retrieved from NASA's ASRS site as of January 2009 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.