Narrative:

Center clrd us to des so as to cross 30 mi south of cvg at 10000' and 250 KTS. Clearance was read back to center at time of receipt and again when we began our des. Center handed us off to cvg approach when we were passing approximately 14000'. We checked in with approach saying, '(call sign) out of 14000' for 10000',' and approach rogered our call. We then repeated assigned altitude saying, '...one zero thousand.' approach said nothing until we were level at 10000'/30 mi south of cvg. Then approach said, '(call sign) des to 8000' and your assigned altitude should have been 12000', 11000', no, 12000'.' we told approach we had read back 10000' 3 times, twice to him. He said nothing further, and we descended to 8000'. We never did find out if he meant that ind center should have assigned us 12000' (instead of 10000') or if he meant we were assigned 12000' and we descended to wrong altitude. One easy way to solve problems such as this would be to have controllers read back altitude assignments instead of rogering readbacks: ie, ATC: '(call sign) cross 30 south of cvg at 10000'.' aircraft: '(call sign) cross 30 south of cvg at 10000'.' ATC: 'roger, 10000'.' this adds one more reading so if controller gives an assigned altitude, aircraft reads back wrong altitude, controller thinks he heard right altitude, when he gives assigned altitude again, air crew might pick up mistake. Supplemental information from acn 80346: perhaps 2 more digits added to our transponder code which must coincide with controller blip would provide a mechanical backup. This of course would provide more cockpit workload and more cluttering up of the radar screen, but might shortcut human failure with mechanical backup.

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Original NASA ASRS Text

Title: ACR DESCENDED BELOW ALT EXPECTED BY ATC.

Narrative: CENTER CLRD US TO DES SO AS TO CROSS 30 MI S OF CVG AT 10000' AND 250 KTS. CLRNC WAS READ BACK TO CENTER AT TIME OF RECEIPT AND AGAIN WHEN WE BEGAN OUR DES. CENTER HANDED US OFF TO CVG APCH WHEN WE WERE PASSING APPROX 14000'. WE CHKED IN WITH APCH SAYING, '(CALL SIGN) OUT OF 14000' FOR 10000',' AND APCH ROGERED OUR CALL. WE THEN REPEATED ASSIGNED ALT SAYING, '...ONE ZERO THOUSAND.' APCH SAID NOTHING UNTIL WE WERE LEVEL AT 10000'/30 MI S OF CVG. THEN APCH SAID, '(CALL SIGN) DES TO 8000' AND YOUR ASSIGNED ALT SHOULD HAVE BEEN 12000', 11000', NO, 12000'.' WE TOLD APCH WE HAD READ BACK 10000' 3 TIMES, TWICE TO HIM. HE SAID NOTHING FURTHER, AND WE DESCENDED TO 8000'. WE NEVER DID FIND OUT IF HE MEANT THAT IND CENTER SHOULD HAVE ASSIGNED US 12000' (INSTEAD OF 10000') OR IF HE MEANT WE WERE ASSIGNED 12000' AND WE DESCENDED TO WRONG ALT. ONE EASY WAY TO SOLVE PROBS SUCH AS THIS WOULD BE TO HAVE CTLRS READ BACK ALT ASSIGNMENTS INSTEAD OF ROGERING READBACKS: IE, ATC: '(CALL SIGN) CROSS 30 S OF CVG AT 10000'.' ACFT: '(CALL SIGN) CROSS 30 S OF CVG AT 10000'.' ATC: 'ROGER, 10000'.' THIS ADDS ONE MORE READING SO IF CTLR GIVES AN ASSIGNED ALT, ACFT READS BACK WRONG ALT, CTLR THINKS HE HEARD RIGHT ALT, WHEN HE GIVES ASSIGNED ALT AGAIN, AIR CREW MIGHT PICK UP MISTAKE. SUPPLEMENTAL INFORMATION FROM ACN 80346: PERHAPS 2 MORE DIGITS ADDED TO OUR TRANSPONDER CODE WHICH MUST COINCIDE WITH CTLR BLIP WOULD PROVIDE A MECHANICAL BACKUP. THIS OF COURSE WOULD PROVIDE MORE COCKPIT WORKLOAD AND MORE CLUTTERING UP OF THE RADAR SCREEN, BUT MIGHT SHORTCUT HUMAN FAILURE WITH MECHANICAL BACKUP.

Data retrieved from NASA's ASRS site as of August 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.