Narrative:

It started out as an ordinary flight. Obtained clearance, received clearance for taxi and takeoff, handed over to departure (an en route center facility), radar idented, cleared on course and cleared to climb to 10000 ft. As I'm climbing through 7500 ft, the controller asks me to verify that I'm leveling at 7000 ft. I respond negative, I've got clearance to 10000 ft! However, I immediately throttled back and stopped the climb. I glanced at the altitude pre-select, and it was set at 10000 ft. There was a long moment of silence, after which I announced my intention to descend back down to 7000 ft. Another controller then came on frequency and told me to maintain present altitude. After a short while, I was cleared on up to 8000 ft, and eventually on up to cruise altitude. And I also got a telephone number I was asked to call when I reached my destination. It was obvious that some sort of miscom had occurred. I spoke with a supervisor at the center facility. He had reviewed the tape of the situation, and informed me that the controller issued clearance to 7000 ft. He also stated that I read back 10000 ft. He said that he would have to classify the situation as 'operational error,' but that there were 2 things that really bothered him. From his perspective, he felt the clearance to 7000 ft was very clear, and wondered how I could have heard it as 10000 ft. From my perspective, I had no doubt the clearance was to 10000 ft. This was a situation where both controller and pilot heard what we thought we heard. Supplemental information from acn 535575: departure from jst sbound cleared to 7000 ft due to en route traffic at 8000 ft. The departing traffic (C550) read back 'ten' which was missed. The clearance to 7000 ft was plain and clear using proper phraseology. The readback was slightly rushed using improper phraseology.

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Original NASA ASRS Text

Title: CLE DEP CTLR FAILS TO HEAR READBACK FROM C550 PLT, CLBING TO 10000 FT, WHEN ONLY CLRED TO 7000 FT.

Narrative: IT STARTED OUT AS AN ORDINARY FLT. OBTAINED CLRNC, RECEIVED CLRNC FOR TAXI AND TKOF, HANDED OVER TO DEP (AN ENRTE CTR FACILITY), RADAR IDENTED, CLRED ON COURSE AND CLRED TO CLB TO 10000 FT. AS I'M CLBING THROUGH 7500 FT, THE CTLR ASKS ME TO VERIFY THAT I'M LEVELING AT 7000 FT. I RESPOND NEGATIVE, I'VE GOT CLRNC TO 10000 FT! HOWEVER, I IMMEDIATELY THROTTLED BACK AND STOPPED THE CLB. I GLANCED AT THE ALT PRE-SELECT, AND IT WAS SET AT 10000 FT. THERE WAS A LONG MOMENT OF SILENCE, AFTER WHICH I ANNOUNCED MY INTENTION TO DSND BACK DOWN TO 7000 FT. ANOTHER CTLR THEN CAME ON FREQ AND TOLD ME TO MAINTAIN PRESENT ALT. AFTER A SHORT WHILE, I WAS CLRED ON UP TO 8000 FT, AND EVENTUALLY ON UP TO CRUISE ALT. AND I ALSO GOT A TELEPHONE NUMBER I WAS ASKED TO CALL WHEN I REACHED MY DEST. IT WAS OBVIOUS THAT SOME SORT OF MISCOM HAD OCCURRED. I SPOKE WITH A SUPVR AT THE CTR FACILITY. HE HAD REVIEWED THE TAPE OF THE SIT, AND INFORMED ME THAT THE CTLR ISSUED CLRNC TO 7000 FT. HE ALSO STATED THAT I READ BACK 10000 FT. HE SAID THAT HE WOULD HAVE TO CLASSIFY THE SIT AS 'OPERROR,' BUT THAT THERE WERE 2 THINGS THAT REALLY BOTHERED HIM. FROM HIS PERSPECTIVE, HE FELT THE CLRNC TO 7000 FT WAS VERY CLR, AND WONDERED HOW I COULD HAVE HEARD IT AS 10000 FT. FROM MY PERSPECTIVE, I HAD NO DOUBT THE CLRNC WAS TO 10000 FT. THIS WAS A SIT WHERE BOTH CTLR AND PLT HEARD WHAT WE THOUGHT WE HEARD. SUPPLEMENTAL INFO FROM ACN 535575: DEP FROM JST SBOUND CLRED TO 7000 FT DUE TO ENRTE TFC AT 8000 FT. THE DEPARTING TFC (C550) READ BACK 'TEN' WHICH WAS MISSED. THE CLRNC TO 7000 FT WAS PLAIN AND CLR USING PROPER PHRASEOLOGY. THE READBACK WAS SLIGHTLY RUSHED USING IMPROPER PHRASEOLOGY.

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.