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ZAU controller experienced operational error at approximately FL270 when a descend clearance was issued through occupied altitude.
| Attributes | |
| ACN | 692834 |
| Time | |
| Date | 200604 |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | navaid : vhp.vortac |
| State Reference | IN |
| Altitude | msl bound lower : 27000 msl bound upper : 28000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zau.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | A320 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | descent : intermediate altitude |
| Flight Plan | IFR |
| Aircraft 2 | |
| Controlling Facilities | artcc : zau.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | Regional Jet 200 ER&LR |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise : level |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : radar |
| Qualification | controller : radar |
| Experience | controller radar : 22 controller time certified in position1 : 19 controller time certified in position2 : 6 |
| ASRS Report | 692834 |
| 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 aircraft equipment : tcas other controllera |
| Resolutory Action | none taken : detected after the fact |
| Consequence | faa : investigated |
| Miss Distance | horizontal : 14940 vertical : 900 |
| Supplementary | |
| Problem Areas | ATC Human Performance |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Operational Error |
Narrative:
The air carrier X was at FL280; air carrier Y was at FL270. Air carrier X and air carrier Y were on crossing flight plans. Thinking the air carrier Y was at FL290; I descended the air carrier X to FL240. Air carrier X started to descend and received a TCAS alert. The air carrier X climbed back to FL280. Air carrier Y also received a TCAS alert and started to descend out of FL270. I had just sat down at the sector. This may have been a cause to this situation. To prevent this happening again it would help to have gotten a better mental picture of all traffic before giving a clearance to air carrier X. The conflict alert activated but only after air carrier X left FL280.
Original NASA ASRS Text
Title: ZAU CTLR EXPERIENCED OPERROR AT APPROX FL270 WHEN A DSND CLRNC WAS ISSUED THROUGH OCCUPIED ALT.
Narrative: THE ACR X WAS AT FL280; ACR Y WAS AT FL270. ACR X AND ACR Y WERE ON XING FLT PLANS. THINKING THE ACR Y WAS AT FL290; I DSNDED THE ACR X TO FL240. ACR X STARTED TO DSND AND RECEIVED A TCAS ALERT. THE ACR X CLBED BACK TO FL280. ACR Y ALSO RECEIVED A TCAS ALERT AND STARTED TO DSND OUT OF FL270. I HAD JUST SAT DOWN AT THE SECTOR. THIS MAY HAVE BEEN A CAUSE TO THIS SITUATION. TO PREVENT THIS HAPPENING AGAIN IT WOULD HELP TO HAVE GOTTEN A BETTER MENTAL PICTURE OF ALL TFC BEFORE GIVING A CLRNC TO ACR X. THE CONFLICT ALERT ACTIVATED BUT ONLY AFTER ACR X LEFT FL280.
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.