Narrative:

While on our descent into london gatwick airport and under radar guidance by approach control received clearance to descend to 13 zero to be at 13 zero by selsi intersection. I started my descent while my first officer read the clearance back to the controller. At 18500 ft our TCASII was activated by 'stop descent' 'stop descent.' as I stopped the descent I automatically started climbing and was forced to overshoot 19000 ft by 400 ft in order to smoothly perform the avoidance maneuver. About the same time that our TCASII was activated a frantic second voice told us to maintain 19 zero and repeated the clearance 3 or 4 times. The WX was VFR and we saw what seemed to be a 320 air bus approaching at our 11 O'clock position. During our descent the controller was giving almost the same instructions/clearance to another aircraft which I assumed to be behind us. I believe the controller confused the radar targets and gave us clearance to descend when he meant to give it to the other aircraft. On landing I contacted the controller supervisor and he informed me that the second voice we heard was probably the instructor controller when he realized the predicament the student controller put us in.

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Original NASA ASRS Text

Title: ACR ON DSCNT HAS TCASII RA TO STOP DSCNT.

Narrative: WHILE ON OUR DSCNT INTO LONDON GATWICK ARPT AND UNDER RADAR GUIDANCE BY APCH CTL RECEIVED CLRNC TO DSND TO 13 ZERO TO BE AT 13 ZERO BY SELSI INTXN. I STARTED MY DSCNT WHILE MY FO READ THE CLRNC BACK TO THE CTLR. AT 18500 FT OUR TCASII WAS ACTIVATED BY 'STOP DSCNT' 'STOP DSCNT.' AS I STOPPED THE DSCNT I AUTOMATICALLY STARTED CLBING AND WAS FORCED TO OVERSHOOT 19000 FT BY 400 FT IN ORDER TO SMOOTHLY PERFORM THE AVOIDANCE MANEUVER. ABOUT THE SAME TIME THAT OUR TCASII WAS ACTIVATED A FRANTIC SECOND VOICE TOLD US TO MAINTAIN 19 ZERO AND REPEATED THE CLRNC 3 OR 4 TIMES. THE WX WAS VFR AND WE SAW WHAT SEEMED TO BE A 320 AIR BUS APCHING AT OUR 11 O'CLOCK POS. DURING OUR DSCNT THE CTLR WAS GIVING ALMOST THE SAME INSTRUCTIONS/CLRNC TO ANOTHER ACFT WHICH I ASSUMED TO BE BEHIND US. I BELIEVE THE CTLR CONFUSED THE RADAR TARGETS AND GAVE US CLRNC TO DSND WHEN HE MEANT TO GIVE IT TO THE OTHER ACFT. ON LNDG I CONTACTED THE CTLR SUPVR AND HE INFORMED ME THAT THE SECOND VOICE WE HEARD WAS PROBABLY THE INSTRUCTOR CTLR WHEN HE REALIZED THE PREDICAMENT THE STUDENT CTLR PUT US IN.

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.