Narrative:

I gave the pilot a clearance to cross 15 mi south of decee at 12000 ft; which he read back perfectly. About 4 mi from the crossing point; the pilot asked to verify the crossing point. I told him it was 15 mi south of decee. When I switched him to approach; he said 'you did give us eight; right?' I told him it was '120' and asked him to say altitude. I had traffic beneath him at 10000 ft. The pilot reported level at 11000 ft climbing back up to 12000 ft. After listening to the tape I learned that when the pilot asked to verify the mileage; which was lengthy and confused; he slipped in these last 2 words: 'at eight.' after reviewing the radar information; it was clear that he leveled off at 12000 ft for 5 updates and then started down. If a pilot is ever questioning a clearance; I would much prefer them to double- or triple-check than not. I could have solved the problem if I would have restated the whole clearance. I didn't because we have had some recent errors in which the controller restated clrncs incorrectly. In the end the controller is always to blame. Our employer expects perfection; but we are all human beings. I expect pilots to be held accountable for their part; but it rarely seems to happen. I turned this one in myself because I thought it was an unsafe situation and they thanked me with an operational deviation in my file and this NASA form.

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Original NASA ASRS Text

Title: ZID CTLR EXPERIENCED OPDEV WHEN FAILING TO HEAR INCORRECT READ BACK ON ASSIGNED DESCENT ALT.

Narrative: I GAVE THE PLT A CLRNC TO CROSS 15 MI S OF DECEE AT 12000 FT; WHICH HE READ BACK PERFECTLY. ABOUT 4 MI FROM THE XING POINT; THE PLT ASKED TO VERIFY THE XING POINT. I TOLD HIM IT WAS 15 MI S OF DECEE. WHEN I SWITCHED HIM TO APCH; HE SAID 'YOU DID GIVE US EIGHT; RIGHT?' I TOLD HIM IT WAS '120' AND ASKED HIM TO SAY ALT. I HAD TFC BENEATH HIM AT 10000 FT. THE PLT RPTED LEVEL AT 11000 FT CLBING BACK UP TO 12000 FT. AFTER LISTENING TO THE TAPE I LEARNED THAT WHEN THE PLT ASKED TO VERIFY THE MILEAGE; WHICH WAS LENGTHY AND CONFUSED; HE SLIPPED IN THESE LAST 2 WORDS: 'AT EIGHT.' AFTER REVIEWING THE RADAR INFO; IT WAS CLR THAT HE LEVELED OFF AT 12000 FT FOR 5 UPDATES AND THEN STARTED DOWN. IF A PLT IS EVER QUESTIONING A CLRNC; I WOULD MUCH PREFER THEM TO DOUBLE- OR TRIPLE-CHK THAN NOT. I COULD HAVE SOLVED THE PROB IF I WOULD HAVE RESTATED THE WHOLE CLRNC. I DIDN'T BECAUSE WE HAVE HAD SOME RECENT ERRORS IN WHICH THE CTLR RESTATED CLRNCS INCORRECTLY. IN THE END THE CTLR IS ALWAYS TO BLAME. OUR EMPLOYER EXPECTS PERFECTION; BUT WE ARE ALL HUMAN BEINGS. I EXPECT PLTS TO BE HELD ACCOUNTABLE FOR THEIR PART; BUT IT RARELY SEEMS TO HAPPEN. I TURNED THIS ONE IN MYSELF BECAUSE I THOUGHT IT WAS AN UNSAFE SITUATION AND THEY THANKED ME WITH AN OPDEV IN MY FILE AND THIS NASA FORM.

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.