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A controller erred in clearing the wrong aircraft for a descent. The B737-700 then received a TCAS TA and climbed to avoid traffic.
| Attributes | |
| ACN | 696639 |
| Time | |
| Date | 200605 |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : zid.artcc |
| State Reference | IN |
| Altitude | msl bound lower : 38500 msl bound upper : 39000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zid.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | B737-700 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | other |
| Flight Phase | cruise : level |
| Flight Plan | IFR |
| Aircraft 2 | |
| Controlling Facilities | artcc : zid.artcc |
| Make Model Name | Commercial Fixed Wing |
| Flight Phase | cruise : level |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Experience | flight time last 90 days : 215 flight time total : 8000 flight time type : 900 |
| ASRS Report | 696639 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Experience | flight time last 90 days : 190 flight time type : 27 |
| ASRS Report | 696640 |
| Events | |
| Anomaly | conflict : airborne less severe non adherence : required legal separation other anomaly other |
| Independent Detector | aircraft equipment : tcas |
| Resolutory Action | flight crew : took precautionary avoidance action flight crew : returned to assigned altitude |
| Consequence | faa : reviewed incident with flight crew |
| Miss Distance | horizontal : 18000 vertical : 700 |
| Supplementary | |
| Problem Areas | ATC Human Performance |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Operational Error |
Narrative:
In cruise at FL390; ZID issued us a descent to FL360; which the captain read back and set. I verified and repeated the altitude and initiated a descent. At about FL387; a TCAS TA appeared at 1700 ft below us and climbing at about 11 moving to 12 O'clock position. I began to level the aircraft out and stopped the descent at FL385 and we visually acquired the traffic. The captain then queried ATC if we were indeed supposed to be descending to FL360. ATC said; 'no; did you take a clearance for someone else?' the captain replied; 'no; we took our clearance to FL360.' so we climbed back up to FL390. We believe the controller then realized his error because when he gave us a frequency change shortly thereafter; he said that he may have given us a descent when he meant to give a descent clearance to a different company flight on his frequency. There was never a TCAS RA; and the closest that the aircraft got to us was about 700 ft below us and at that time was about 3 mi south of our course. Human error and heavy workload on the part of ATC are the only contributing factors that I can attribute this loss of separation to as the center controller seemed to be busy at the time.
Original NASA ASRS Text
Title: A CTLR ERRED IN CLRING THE WRONG ACFT FOR A DSCNT. THE B737-700 THEN RECEIVED A TCAS TA AND CLBED TO AVOID TFC.
Narrative: IN CRUISE AT FL390; ZID ISSUED US A DSCNT TO FL360; WHICH THE CAPT READ BACK AND SET. I VERIFIED AND REPEATED THE ALT AND INITIATED A DSCNT. AT ABOUT FL387; A TCAS TA APPEARED AT 1700 FT BELOW US AND CLBING AT ABOUT 11 MOVING TO 12 O'CLOCK POS. I BEGAN TO LEVEL THE ACFT OUT AND STOPPED THE DSCNT AT FL385 AND WE VISUALLY ACQUIRED THE TFC. THE CAPT THEN QUERIED ATC IF WE WERE INDEED SUPPOSED TO BE DSNDING TO FL360. ATC SAID; 'NO; DID YOU TAKE A CLRNC FOR SOMEONE ELSE?' THE CAPT REPLIED; 'NO; WE TOOK OUR CLRNC TO FL360.' SO WE CLBED BACK UP TO FL390. WE BELIEVE THE CTLR THEN REALIZED HIS ERROR BECAUSE WHEN HE GAVE US A FREQ CHANGE SHORTLY THEREAFTER; HE SAID THAT HE MAY HAVE GIVEN US A DSCNT WHEN HE MEANT TO GIVE A DSCNT CLRNC TO A DIFFERENT COMPANY FLT ON HIS FREQ. THERE WAS NEVER A TCAS RA; AND THE CLOSEST THAT THE ACFT GOT TO US WAS ABOUT 700 FT BELOW US AND AT THAT TIME WAS ABOUT 3 MI S OF OUR COURSE. HUMAN ERROR AND HVY WORKLOAD ON THE PART OF ATC ARE THE ONLY CONTRIBUTING FACTORS THAT I CAN ATTRIBUTE THIS LOSS OF SEPARATION TO AS THE CTR CTLR SEEMED TO BE BUSY AT THE TIME.
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.