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ZDV controller experienced operational error when descending aircraft through occupied altitude at FL360.
| Attributes | |
| ACN | 675542 |
| Time | |
| Date | 200510 |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | airport : den.airport |
| State Reference | CO |
| Altitude | msl single value : 36000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zdv.artcc tower : iah.tower |
| 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 | artcc : zdv.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | A320 |
| 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 time certified in position1 : 8 |
| ASRS Report | 675542 |
| 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 |
| Miss Distance | horizontal : 24660 vertical : 500 |
| Supplementary | |
| Problem Areas | ATC Human Performance |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Operational Error |
Narrative:
The crj was at FL370; landing denver; the A320 was en route at FL360. I thought the A320 was at FL340. At XA09:22 I descended the crj to FL350. At XA09:44 I descended another aircraft landing denver to FL370. I then noticed the A320 at FL360. At that time the CRJ7 just started its descent; activating conflict alert. However; the A320 was too close to the CRJ7 (about 6 mi). Turns to the CRJ7 and expeditious descent were not enough to prevent the deviation. For some unexplained reason; I believed the A320 was at FL360. However; from the time I gave a control instruction to the CRJ7 to descend to FL350 and the CRJ7 actually was observed descending was over 40 seconds. If the CRJ7 was shown descending earlier; maybe conflict alert would have activated sooner; allowing me to use vectors sooner.
Original NASA ASRS Text
Title: ZDV CTLR EXPERIENCED OPERROR WHEN DSNDING ACFT THROUGH OCCUPIED ALT AT FL360.
Narrative: THE CRJ WAS AT FL370; LNDG DENVER; THE A320 WAS ENRTE AT FL360. I THOUGHT THE A320 WAS AT FL340. AT XA09:22 I DSNDED THE CRJ TO FL350. AT XA09:44 I DSNDED ANOTHER ACFT LNDG DENVER TO FL370. I THEN NOTICED THE A320 AT FL360. AT THAT TIME THE CRJ7 JUST STARTED ITS DSCNT; ACTIVATING CONFLICT ALERT. HOWEVER; THE A320 WAS TOO CLOSE TO THE CRJ7 (ABOUT 6 MI). TURNS TO THE CRJ7 AND EXPEDITIOUS DSCNT WERE NOT ENOUGH TO PREVENT THE DEV. FOR SOME UNEXPLAINED REASON; I BELIEVED THE A320 WAS AT FL360. HOWEVER; FROM THE TIME I GAVE A CTL INSTRUCTION TO THE CRJ7 TO DSND TO FL350 AND THE CRJ7 ACTUALLY WAS OBSERVED DSNDING WAS OVER 40 SECONDS. IF THE CRJ7 WAS SHOWN DSNDING EARLIER; MAYBE CONFLICT ALERT WOULD HAVE ACTIVATED SOONER; ALLOWING ME TO USE VECTORS SOONER.
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.