Narrative:

While en route at FL210, ATC cleared me to expedite to FL180 as this would begin my initial descent for landing at ind. I acknowledged this instruction and began my descent immediately. About 10 seconds later while descending through FL207, ATC gave me a climb to FL210. His instruction was in a hurried and somewhat urgent tone of voice as if he had made an error in my initial clearance or had just discovered that he needed me back at FL210 for the time being. I acknowledged 'ok, climb back to 210 for xyz.' I thought it was strange to change my INS like that, yet the controller was very busy and his tone of voice kept me from verifying this clearance a second time to make sure. I felt my acknowledgement would be heard and if I was in error, ATC would correct me upon hearing my readback. Several mins later, while still at FL210, ATC called 'xyz, are you expediting to 180,' or 'xyz, are you level at 180?' (I don't recall exactly which). I told him I was level at FL210 as I understood he had told me to climb back up after I had initially started down. ATC said he thought I had picked up a clearance for a different aircraft. I told him I thought I had heard my north# preceding the climb instruction, and that I had acknowledged the instruction I thought was for me. I feel there were several ways this occurrence could have been prevented. 1) if I did answer another aircraft's instructions, my readback should have been heard by the controller and I could have been corrected. I feel he many have been too busy to hear my readback. 2) if the controller had noticed my climb back to FL210, he could have queried me and straightened the situation out then. Again, I assume he was too busy to monitor my altitude, even though he originally wanted me to hurry to FL180. 3) I should have double-checked what I heard, even though I was 99.9% sure the climb back to FL210 was for me. Perhaps I did miss the north# on the instruction I thought was for me. That was my 1 mistake. This occurrence has taught me that even if a controller is very busy, double-check any instruction that seems a little out of the ordinary and non-standard.

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Original NASA ASRS Text

Title: CONFUSION OVER CLRNC. DEVIATION FROM CLRNC.

Narrative: WHILE ENRTE AT FL210, ATC CLRED ME TO EXPEDITE TO FL180 AS THIS WOULD BEGIN MY INITIAL DSNT FOR LNDG AT IND. I ACKNOWLEDGED THIS INSTRUCTION AND BEGAN MY DSNT IMMEDIATELY. ABOUT 10 SECS LATER WHILE DSNDING THROUGH FL207, ATC GAVE ME A CLB TO FL210. HIS INSTRUCTION WAS IN A HURRIED AND SOMEWHAT URGENT TONE OF VOICE AS IF HE HAD MADE AN ERROR IN MY INITIAL CLRNC OR HAD JUST DISCOVERED THAT HE NEEDED ME BACK AT FL210 FOR THE TIME BEING. I ACKNOWLEDGED 'OK, CLB BACK TO 210 FOR XYZ.' I THOUGHT IT WAS STRANGE TO CHANGE MY INS LIKE THAT, YET THE CTLR WAS VERY BUSY AND HIS TONE OF VOICE KEPT ME FROM VERIFYING THIS CLRNC A SECOND TIME TO MAKE SURE. I FELT MY ACKNOWLEDGEMENT WOULD BE HEARD AND IF I WAS IN ERROR, ATC WOULD CORRECT ME UPON HEARING MY READBACK. SEVERAL MINS LATER, WHILE STILL AT FL210, ATC CALLED 'XYZ, ARE YOU EXPEDITING TO 180,' OR 'XYZ, ARE YOU LEVEL AT 180?' (I DON'T RECALL EXACTLY WHICH). I TOLD HIM I WAS LEVEL AT FL210 AS I UNDERSTOOD HE HAD TOLD ME TO CLB BACK UP AFTER I HAD INITIALLY STARTED DOWN. ATC SAID HE THOUGHT I HAD PICKED UP A CLRNC FOR A DIFFERENT ACFT. I TOLD HIM I THOUGHT I HAD HEARD MY N# PRECEDING THE CLB INSTRUCTION, AND THAT I HAD ACKNOWLEDGED THE INSTRUCTION I THOUGHT WAS FOR ME. I FEEL THERE WERE SEVERAL WAYS THIS OCCURRENCE COULD HAVE BEEN PREVENTED. 1) IF I DID ANSWER ANOTHER ACFT'S INSTRUCTIONS, MY READBACK SHOULD HAVE BEEN HEARD BY THE CTLR AND I COULD HAVE BEEN CORRECTED. I FEEL HE MANY HAVE BEEN TOO BUSY TO HEAR MY READBACK. 2) IF THE CTLR HAD NOTICED MY CLB BACK TO FL210, HE COULD HAVE QUERIED ME AND STRAIGHTENED THE SITUATION OUT THEN. AGAIN, I ASSUME HE WAS TOO BUSY TO MONITOR MY ALT, EVEN THOUGH HE ORIGINALLY WANTED ME TO HURRY TO FL180. 3) I SHOULD HAVE DOUBLE-CHKED WHAT I HEARD, EVEN THOUGH I WAS 99.9% SURE THE CLB BACK TO FL210 WAS FOR ME. PERHAPS I DID MISS THE N# ON THE INSTRUCTION I THOUGHT WAS FOR ME. THAT WAS MY 1 MISTAKE. THIS OCCURRENCE HAS TAUGHT ME THAT EVEN IF A CTLR IS VERY BUSY, DOUBLE-CHK ANY INSTRUCTION THAT SEEMS A LITTLE OUT OF THE ORDINARY AND NON-STANDARD.

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.